The invention relates to medical apparatus for monitoring one or more physiological conditions of a patient and in particular to medical apparatus for measuring medical data related to a physiological condition of a patient when the patient is in a pressurised chamber. The invention further relates to a battery module for providing power to a medical apparatus and/or other apparatus in a pressurised chamber. The invention further relates to kit of medical apparatus for measuring medical data related to a physiological condition of a patient when the patient is in a pressurised chamber and a power supply and a kit for delivering power within a pressurised chamber.

Background

Hyperbaric pressurised chambers offer a high oxygen, slightly higher than atmospheric pressure environment. These are used extensively for medical and other therapeutic purposes such as hyperbaric oxygen therapy and can be used, for example for the treatment of decompression sickness ("the bends") and gas embolism. Typically, hyperbaric chambers operate from 1 -6 bar and or have greater than 21 % oxygen, this being the partial pressure oxygen in air. Treatment sessions or dives can last 1 -6 hours for example during which time it is preferred that the patient is monitored.

Saturation pressurised chambers typically allow divers to work at depth for long periods and may comprise living chamber, transfer chamber and decompression chamber. Typical saturation pressurised chambers operate at 1 to 45 bar (0 to 450 meters of sea water MSW) with a gas mixture of 98% helium and 2% oxygen.

There are no wall sockets and no mains supply in pressurised chambers. Lights are hard wired through chamber walls. Some of the newer chambers are being built with dc supply, but only on specific instruction from chamber purchaser i.e. there is no routine provision of power inside the chamber. In order to use electrical equipment and in particular portable medical apparatus within a pressurised chamber there is a requirement to provide 'safe' power.

Providing electrical apparatus particularly medical apparatus can be problematic in the unusual and even extreme environments of pressurised chambers. In pressurised chambers in general and in both types of chambers described above, sparks and open flames must necessarily be avoided to maintain safety. The International Marine Contractors Association (IMCA) issues guidance on "Battery Packs in Pressure Housings" "Prevention of Explosions during Battery Charging in relation to Diving Systems" and "Use of Battery operated equipment in Hyperbaric Conditions". Specifically explosive decompression due to helium ingress should be avoided; battery power sources should use cells no larger than AA size NIMH rechargeable or their physical equivalent in non - rechargeable form (500mA/hr).

The inventors have developed a medical apparatus for measuring medical data comprising a medical data gathering module, a microprocessor, a medical data handling module for buffering transfer of medical data between the medical data gathering module and the microprocessor located within a unitary housing such as a personal computer housing or laptop housing. This is described further in co-pending international patent application PCT/GB2010/000564, the contents of which are hereby incorporated by reference.

US5621299 KRALL describes a rechargeable battery power supply with load sensing selectable output voltage and a wrist rest. WO03/O3898O DOSS and WO03/O38981 MACDONALD describe a dual input AC/DC battery operated power supply.

US5421340 STANGA describes a compact, portable critical care unit for hyperbaric and recompression chambers.

JP2004103483 KIMURA SOLECTRON describes a battery pack for monitoring voltages in sub units.

Typically, desktop personal computers require ac input. Typically laptop (Li-ion) batteries require ac input or use lithium ion rechargeable batteries. Laptop Li-ion batteries typically offer capacities of 5000mAh and offer running times of 3-6 hours depending on power usage, however these are not suitable for use in pressurised chambers. In particular, Li-ion batteries are not suitable for usage in pressurised chambers such as hyperbaric or saturation chambers, due to their composition. In the event of a fire or explosion, lithium is volatile upon contact with water.

All cells (also termed batteries) are an energy source and if short circuited can generate ignition through sparking or overheating. Certain cells can emit gases upon charging and/or short circuit. Different types of cell have differing gas emissions for example, lithium cells emit hydrogen gas when charging, nickel cadmium batteries emit oxygen. Lithium cells have a terminal voltage of 3.7 volts whereas AA cells have a terminal voltage of 1 .2 - 1.5 volts depending on the fuel cell chemistry. The capacity of AA cells is much lower than that of lithium cells at 2800mAh. There is therefore a problem of providing sufficient capacity at the correct voltage using AA cells alone. Laptops typically have a battery management board for managing and monitoring battery temperature and remaining capacity and for predicting "remaining time" at current power usage. However this is battery specific and there is therefore the problem of monitoring the remaining power in a battery rated for pressurised chambers.

In addition, there is the problem of providing sufficient running time, too short and the swap out rate for battery replacement is too frequent to be practicable for pressurised chambers, too long and the battery capacity introduces extra, unacceptable risk in having large amounts of energy available that could cause high currents or other faults resulting in the risk of sparks, heating, fire and explosions in the event of a short circuit or other failure which is not acceptable for pressurised chambers. It should further be noted that NimH batteries have a slower charging rate with a charging requirement of capacity C x 1/10 (charging to full capacity in 10 hours) compared to lithium ion batteries with a charging requirement of capacity, C x ½ (charging . to full capacity C in 2 hours). There is therefore the problem of providing sufficient running time in pressurised chambers compared to the re-charge time required (typically outside pressurised chambers) so that excessive downtime is avoided.

There is further a need to provide a power supply for a laptop, or other computing device, and for a medical apparatus incorporating a laptop or other computing device (such as that described in PCT/GB2010/000564).

There is further a need to provide a power supply for other types of portable equipment, such as certain mp3 and mp4 players, portable mobile telephones and so on, that meets the criteria of working, withstanding and being safe in the unusual and extreme environments of pressurised chambers such as hyperbaric and saturation chambers.

The present invention seeks to alleviate one or more of the above problems.

Statements of the Invention The invention relates to apparatus for measuring medical data in a pressurised chamber comprising: a computing device, the computing device comprising at least nn _P mc-Hirai Hata gathering module; and, a battery module for powering the computing device. The invention further relates to apparatus for computing in a pressurised chamber comprising a computing device and a battery module for powering the computing device. The apparatus further relates to a battery module for use in a pressurised chamber, and to a method of measuring medical data in a pressurised chamber.

In a first aspect of the invention there is provided apparatus for measuring medical data in a pressurised chamber comprising: a computing device, the computing device comprising at least one medical data gathering module; and, at least one battery module for powering the computing device, the battery module comprising: at least two battery packs in parallel; each battery pack comprising at least one individual cell rated for use in a pressurised chamber, such as a hyperbaric chamber and/or saturation chamber; each battery pack further comprising at least one first resettable fuse in series with the at least one individual cell; whereby charging of one battery pack by another is substantially prevented within the battery module.

In a second aspect of the invention there is provided apparatus for computing in a pressurised chamber comprising: a computing device, and at least one battery module for powering the computing device, the battery module comprising: at least two battery packs in parallel; each battery pack comprising at least one individual cell rated for use in a pressurised chamber, such as a hyperbaric chamber and/or saturation chamber; each battery pack further comprising at least one first resettable fuse in series with the at least one individual cell, whereby charging of one battery pack by another is substantially prevented within the battery module.

In a third aspect of the invention there is provided a battery module for delivering power within a pressurised chamber comprising: at least two battery packs in parallel; each battery pack comprising at least one individual cell rated for use in a pressurised chamber, such as a hyperbaric chamber and/or saturation chamber; each battery pack further comprising at least one first resettable fuse in series with the at least one individual cell, whereby charging of one battery pack by another is substantially prevented within the battery module.

Thus, the use of individual cells parses the energy provided within the pressurised chamber into individual quantities each within an individual cell.

In a fourth aspect there is provided a method of measuring medical data in a pressurised chamber comprising: providing an apparatus according as described herein; powering the computing device and medical data gathering module using the battery module; gathering medical data using the medical data gathering module. In a fifth aspect there is provided a power supply comprising at least one battery module, optionally also comprising a battery module support housing, such as an attachment, having at least one cavity for receiving at least one battery module, and at least one battery module.

Any one or more features from the example embodiments described below and elsewhere herein may be used in any one or more of the aspects of the invention.

Each battery pack may comprise at least two individual cells in series. One or more or each at least one battery module may be separate from the computing device, such as within a separate housing.

The computing device may have a dc input terminal for receiving power from an ac supply via an ac/dc adaptor and one or more or each at least one battery module may comprise a suitable number and arrangement of individual cells to provide a suitable dc input to the dc input terminal for powering the computer device.

The at least one first settable fuse in each battery pack may be a resettable fuse comprising a polymeric positive temperature coefficient thermistor.

Each at least one first resettable fuse may act as a thermal fuse and may be in thermal contact and/or in direct contact with at least one individual cell within the battery pack.

One or more or each at least one battery module may comprise a secondary resettable fuse in series with the at least two battery packs.

The holding current of at least one first resettable fuse in each battery pack may be 3 amps and/or the trip current may be 6 amps; and/or at least one second resettable fuse in series with the at least two battery packs may be provided having a holding current of 6 amps and/or a trip current of 12 amps.

The individual cells may be nickel metal hydride (NiMH) AA size batteries.

One or more or each battery pack may comprise 9, 12 or 16 individual cells.

Two or three battery packs may be provided, each may comprise 16 NiMH AA size individual cells in series with one another and with the at least one first resettable fuse.

One or more or each battery module may comprise a low battery monitoring circuit and at least one low battery indicator circuit for providing an indication when the voltage across the battery packs falls below a first threshold voltage or comprises a low battery monitory circuit and two or more low battery indicator circuits for providing an indication when the voltage across the battery pack falls below a first threshold voltage.

One or more or each at least one battery module may comprise an autoshut off circuit for switching off the power output from one or more or each at least one battery module when the voltage across the battery packs falls below a second threshold voltage. The autoshut off circuit may comprise a hysteresis component, such as a resister, so that the power output from one or more or each at least one battery module switches on when the voltage across battery pack rises above a third threshold voltage and the third threshold voltage is greater than the second threshold voltage or the third threshold voltage may be greater than both the first threshold voltage and the second threshold voltage, when a low battery indicator circuit is provided.

At least two individual cells may be provided within one, each or more battery packs. The individual cells may be thermally insulated from one another or thermally insulated from one another by the provision of thermal insulation therebetween. Thermal insulation between individual cells is provided and may comprise intumescent material.

The autoshut off circuit may comprise a solid state relay for switching the power output from the battery module on and off.

One or more or each at least one battery module may comprise a low battery timer circuit for providing a pulsed indicator signal and further in which only tantalum capacitors are used within the low battery timer circuit.

One or more or each at least one battery module may comprise a nominal 19v dc output.

One or more or each at least one battery module may comprise a universal serial bus (USB) rated power output.

Two or more battery modules may be provided in parallel whereby one battery module can be swapped out and replaced by a replacement battery module without interrupting power being supplied to the computing device.

An auxiliary static battery module may be provided in parallel with the at least one battery module whereby one or all battery modules can be swapped out and replaced by a replacement battery module without interrupting power being supplied to the computing device.

Two or more identical battery modules may be provided in parallel.

A battery module support housing, such as an attachment, having one or more, preferably two, cavities each for accommodating a battery module may be provided wherein the outer size and shape of a battery module is sized and shaped to cooperate with the inner size and shape of a cavity so that a battery module can be slotted into the cavity. The battery module support housing accommodating the battery module(s) may be of approximately the size and shape of a computing device such as a laptop and/or may form a platform on which a computing device, such as a laptop can be placed.

One or more or each battery module may comprise a non-leak proof housing and/or vents to facilitate gas ingress and egress.

At least one medical data gathering module may comprise a motor and the motor may be a brushless motor.

The medical data handling module may be arranged to gather and store data in at least one predetermined group of data and the at least one microprocessor may be arranged to retrieve data from the medical data handling module in one or more multiples of the at least one predetermined group of data. The predetermined group of data may be N bits of data and/or T1 seconds worth of data. The medical data handling module may be arranged to gather N bits of data every T1 seconds from the least one medical data gathering module and store the sampled bits of data in the predetermined group of data. The computing device may comprise a wireless communication circuit for communicating wirelessly with remote networks and/or devices.

The computing device may comprise hardware and/or software adapted to provide a low battery indicator for monitoring and for indicating the voltage delivered to the computing device from the at least one battery module. The apparatus may comprise two or more battery modules in parallel for providing power and a battery module switching circuit to enable switching of power between modules, whereby a partially depleted battery module may be switched off allowing time for it to recover. This switching circuit may comprise a control function for switching the battery modules on and off in accordance with a predetermined protocol depending upon factors which may include one or more of the following: the time since last full recharge of the battery module, rate of depletion of battery module, remaining power of the battery module, and current delivered by the battery module. The switching circuit may comprise one or more solid state switches.

The method may comprise storing and/or transmitting the medical data via the wireless communication circuit of the comprising device. Several embodiments of the invention are described and any one or more features of any one or more embodiments may be used in any one or more aspects of the invention as described above.

Brief Description of the Invention The present invention will now be described, by way of example only, with reference to the following figures. In the figures, like reference numerals refer to like referenced features.

Figure 1 shows a perspective, exploded view of apparatus for measuring medical data in the form of desk top personal computer according to an example embodiment of a first aspect of the invention. Figure 2 shows perspective, front and rear views of apparatus for measuring medical data in the format of an adapted laptop computer according to an example embodiment of a first aspect of the invention.

Figure 3 shows a perspective, rear, cutaway view of apparatus for measuring medical data in the form of an alternative laptop computer according to an example embodiment of the first aspect of invention.

Figure 4 shows a schematic functional block diagram of apparatus according to an example embodiment of a first aspect of the invention.

Figure 5 shows a schematic block diagram of various components for ECG and BP measurements, and interconnections via data handling module interface and internal computer address bus according to an example embodiment of a first aspect of the invention. A spirometer head and a universal serial bus (USB) connector for it are also shown according to an example embodiment of a first aspect of the invention.

Figure 6 shows a perspective view of apparatus according to a first aspect of the invention comprising apparatus for measuring medical data in the form of a laptop and a battery module for the laptop.

Figure 7 shows a perspective, exploded view of a housing for a battery module according to an example embodiment of a first and further aspects of the invention.

Figure 8 shows a perspective exploded view of a corner section of a housing for a battery module according to an example embodiment of a first and further aspects of the invention. Figure 9 shows side, cross sectional and perspective views of a housing for a laptop according to a further example embodiment of a first and further aspects of the invention.

Figure 10 shows a perspective view of a battery module according to a further example embodiment of a first and further aspects of the invention. Figure 1 1 shows a perspective cutaway view of the battery module of Figure 10.

Figure 12 shows a perspective, cutaway view of a printed circuit board (PCB) mounting board for use in the battery module of Figure 10.

Figure 13 shows a circuit diagram of a battery module in an example embodiment according to a first and further aspects of the invention and in particular shows the control circuit for the battery module. Figure 13 also shows a perspective view of a battery module control panel and various sockets and connectors according to an example embodiment of a first and further aspects of the invention.

Figure 14 shows a schematic functional block diagram of the control circuit of a battery module including auto-shut off and alarm circuits of the battery module according to an example embodiment of a first and further aspects of the invention.

Figure 15 shows a close up view of the control circuit of a battery module including the auto- shut off and alarm circuit of Figure 13.

Figure 16 shows a close up perspective view of a combined medical data gathering interface module for a laptop according to an example embodiment of the first aspect of the invention. Figure 17 shows a perspective view of the combined interface of Figure 16 illustrating its U shaped cross-section.

Figure 18 shows the combined medical data gathering interface module of Figure 16 mounted on a rear panel of a laptop base.

Figure 19 shows a pattern for an alternative combined medical data gathering interface module for a laptop prior to holding into a U-shaped cross section.

Figure 20 shows a perspective, view of apparatus for measuring medical data according to the first aspect of the invention immediately prior to being tested in a pressurised chamber.

Figure 21 shows a front view of the operation panel of the pressurised chamher nf Finum ?n Figure 22 shows the indicated percentage (%) of "power left" gas gauge of a laptop computer and actual voltage of a battery pack when powering a laptop computer.

Figure 23 shows the actual voltage and current when powering a laptop computer via the laptop's DC input jack (terminal). Figure 24 shows the range of pressure and oxygen (0 ₂ ) levels for electrical equipment undergoing a hyperbaric "dive" test regime.

Figure 25 shows the range of pressures and oxygen (0 ₂ ) levels for electrical equipment undergoing a saturation "dive" test regime.

Figure 26 shows the range of pressures and oxygen (0 ₂ ) level for electrical equipment undergoing a hatch test for saturation "dive" test.

Figure 27 shows a perspective view of a laptop base 16B attached to a battery module 40 using a battery module support housing in the form of an attachment according to a further aspect of the invention.

Figure 28 shows a perspective view of an example embodiment of a battery module support housing in the form of attachment 200 for attaching a battery module 40 to a laptop, and a battery module 40.

Figure 29 shows a schematic plan view of a further example embodiment of the invention having two (typically identical) battery modules 40 connected in parallel to power the portable computing device 16, here a portable medical computing laptop 16 having medical data gathering modules located therein (not shown).

Figure 30 shows perspective and cross-sectional views of a battery module support housing 200 in the form of a tray with two slots for housing two battery modules 40.

Figure 31 shows a schematic circuit diagram of a further example embodiment of a battery having two battery modules 40', 40" according to the invention which can be swapped out individually one at a time or together and an optional static auxiliary battery module 340, so both the battery modules 40', 40" can be swapped over at the same time without loss of power. Detailed Description of the Invention

In developing existing types of technology for new applications, different design considerations need to be taken into account. Sometimes, when other ways of implementing existing types of technology to meet the different design considerations has failed to provide a suitable solution, use of new and off the shelf components in a new way can be a creative approach to adopt. The present invention has adopted such an approach in one or more embodiments and aspects of the invention.

A NiMH battery pack comprising 12 NiMH AA size cells in series was used to replace a laptop's internal rechargeable battery. The NiMH battery pack provided a voltage of 12 x 1.2v = 14.4v which is approximately equivalent to the voltage of 4 x 3.7v 14.8v provided by the lithium ion laptop battery to the laptop. The actual voltage across the NiMH cells was monitored over time. The laptop's on screen 'gas gauge' remaining power indicator was also monitored over time. The results are shown in Figure 22.

The 'gas gauge' battery capacity indicator showed a steady drop up to 65 minutes and then a rapid decrease between 65 and 70 minutes. However, the actual voltage across the AA cells was relatively constant falling linearly from 14.65v at 15 minutes to 13.59v at 70 minutes.

Thus the 'gas gauge' battery capacity indicator provided by the manufacturer's battery management board for the laptop does not accurately reflect the status of the replacement

NiMH cells. Thus, simply replacing the lithium ion cells of a laptop with sufficient AA cells does not provide a solution to the problem of powering portable apparatus within pressurised chambers. Further, a number of AA cells required to provide the nominal laptop voltage is unlikely to fit within the laptop battery compartment.

The inventors have developed a medical apparatus incorporating a laptop and power supply that is suitable for use inside pressurised chambers, such as hyperbaric and saturation chambers. The solution to the problem of powering portable computing and/or medical apparatus and other portable apparatus in pressurised chambers and of providing a suitable power supply for pressurised chambers is provided by the invention according to the first and further aspects.

Figure 1 shows a medical apparatus 10 for measuring medical data related to one or more physiological conditions of a patient comprising a desktop personal computer 12 and a combined medical data gathering and handling module 14 within a unitary housing. Figure 2 shows a further embodiment of medical apparatus 10 comprising a laptop 16 incorporating a medical data gathering module 18. Figure 3 shows yet a further embodiment of medical apparatus 10 comprising an alternate medical data gathering module 20 positioned on a rear wall of a base of a laptop 16.

Figure 4 shows a schematic view of medical apparatus 10 comprising one or more medical data gathering modules 24, a medical data handling module 26, an internal serial bus 28, optionally one more patient contacting hardware 22, and a personal computer platform 30 (such as a microprocessor and associated motherboard). It will be understood that whilst the first aspect of the invention will be described with respect to a laptop, it could be used with other computing devices such as a desktop computer, computing pad or other portable computing apparatus. In one preferred embodiment the invention is implemented using a laptop computer.

The description herein refers to a laptop computer however, it is to be understood that other computing devices may be used such as desktop computers, computing pads and other portable computing devices unless the context requires otherwise.

Figure 5 shows an ECG medical data gathering module 24A and a blood pressure medical data gathering module 24B. A field programmable gate array (FPGA) interface 26 provides a medical data handling module that handles medical data prior to it being transferred to the microprocessor (not shown) of the computing device via address bus 28. Further details of this embodiment of the invention can be found in PCT/GB2010/00564 incorporated herein.

Figure 6 shows a laptop computer 16 and an associated battery module 40 according to an example embodiment of a first aspect of the invention. Referring to Figures 7 and 8, battery module 40 comprises a substantially planar housing 42 having a substantially planar lid 44 and base 46. Typically the height of battery module 40 is 16mm or around 16mm. The lid 44 and base 46 both have a shallow sided u-shaped cross section and these are held together at corners via angle brackets 48. Thus, housing 42 is not air tight to allow easy ingress and egress of gases, such as helium during pressurisation and depressurisation. Further ventilation holes (not shown) may be provided.

Figure 9 shows an optional additional side wall 50 and associated support struts 52 that may be used in an alternative embodiment of a base of a laptop, such as the base 16B of laptop seen in Figure 27. Figures 10 and 1 1 show a rectangular shaped battery module 40 of generally planar construction. Strips of non-slip material 41 may be placed along one or more edges of the housing 42 of the battery module 40. The planar construction of battery module 40, and optional non-slip material 41 , allows a laptop to be securely located on its upper surface. The housing 41 typically comprises 2mm thick aluminium sheet. Thus, the housing of battery module 40 is preferably of sufficiently robust construction to withstand an individual cell heating up due to short circuit and/or rupturing due to heat and/or leaking battery contents inside the housing of the battery module 40 without causing further damage, e.g. to adjacent equipment inside the pressurised chamber.

Typically the battery module 40 is of shape and dimensions to match that of a laptop, optionally with a mechanism for attaching securely to a laptop. An attachment for the battery module and the laptop, such as that seen in Figure 28 and 30, may be used as will be described in more detail later. The battery module 40 may be of dimensions around A4 size or around 30cm x 38cm, so as to fit through a typical hatch of a pressurised container.

Along a side wall 50 of the battery module 40 is an on/off switch 58. Further along the same side wall 50, a green LED 61 is provided as an "on" indicator light, a red LED 22 is provided as a low battery indicator light, a 10A fuse 64 is provided for the battery module, a charger input socket 66 for charging the battery module 40 is provided and, in one example embodiment, a second or alternate power output, here a USB rated voltage output socket 68 is provided. Referring briefly to Figure 31 , a series of LEDs may be provided on each battery module 40 to indicate the capacity remaining in the module (and so capacity drop over time) by displaying a reducing number of lit LEDs over time on the housing of the battery module itself. For example, the LEDs may be on a rear, exposed wall of the or each battery module 40. Along a rear wall 51 of the battery module 40, a dc output cable 69 (typically a 19v dc output) is provided for powering electrical apparatus such as a laptop computer or a medical apparatus comprising a laptop computer. Thus, the control indicator functions and power output functions of the battery module 40 are provided alongside 50 or rear 51 walls of the battery module housing 42. Therefore, in this example embodiment, uppermost and lowermost surfaces of battery module housing 42, which are substantially planar, are left free to act, respectively, as a platform for location of a laptop thereon and a base for supporting the battery module itself.

Referring to Figure 1 1 , a base 46 of battery module 40 is shown. Three battery packs 54, each typically having 16 individual cells 55 are shown. The three battery packs are wired in parallel as will be shown in more detail in Figure 13. The individual cells 55 within a battery pack 54 are wired together in series for example by spot welding.

Typically, at least two battery packs 54 are provided each having at least one or preferably more individual cells 55. The battery packs preferably have the same n ^{, ,mhQr nf} individual cells 55 to reduce the possibility of one pack trying to charge another. In this example embodiment three battery packs 54 are provided; housing the same number of cells (16).

A printed circuit board (PCB) 56 is provided within the battery module 40 comprising a battery module control circuit for controlling battery packs 54, and the one or more outputs for the battery module in a safe manner in a pressurised chamber. This is described in more detail with respect to Figure 13. Typical location of the PCB 56 within a battery module 40 is shown in Figure 29.

Figure 12 shows how PCB 56 is attached to base 46 of battery module 40. Referring now to Figure 13, the control circuit for the battery module 40 is shown along with battery packs 54A, 54B, and 54C. The control circuit is typically mounted on PCB 56 (not shown) within the housing of the battery module 40. Battery module 40 comprises, in this example embodiment, three battery packs 54, labelled 54A, 54B, 54C. Each battery pack 54A, 54B, 54C comprises 16 NiMH cells. In this example embodiment, cells of size AA are provided each providing 1.2v each (not shown). Where multiple individual NiMH cells are provided, these are in series with one another within each battery pack. Sixteen NiMH cells nominally provide 19.2v (16x1.2v) as the output from each battery pack 54A, 54B, 54C. Each battery pack 54A, 54B, 54C also includes a first resettable fuse 72 in series with the one or more individual cells in the battery pack. Typically, first resettable fuses 72 have a hold current, which is the maximum current the device will pass without tripping and a trip current (typically higher than the hold current), which is the minimum current at which the device will trip. Thus, the first resettable fuses 72 help prevent damage caused by harmful current surges or faults. After the current surge or fault is removed the resettable fuse resets. Typically the resettable fuse is a polymeric positive temperature coefficient device such as a Polyfuse ^® or a Polyswitch ^® with a hold current of 3 amps and trip current of 6 amps.

The battery packs 54A, 54B, 54C are in parallel with one another. These battery packs should balance one another and each provide the same voltage to the control circuitry and load. However, if for some reason these are out of balance, for example if one battery pack is fully charged and one is partly or fully discharged, then the full battery pack can attempt to charge the discharged one(s). This could result in very high current flow and unwanted heat generation and even discharge of gases developing during charging. Providing individual resettable fuses to each battery pack substantially prevents one battery pack from charging another. Nevertheless, the ability of the fuses to reset once the fault condition is removed allows the apparatus to continue being used. This is particularly helpful in .no cr- oc measuring medical data in a pressurised chamber, as the chambers are relatively inaccessible and the data being collected may be health and even life critical.

A number of battery packs are provided to enhance the capacity and hence the running time of the battery module. Hence a series of 16 NiMH AA cells may have a capacity of 2800 mAH and deliver nominally 19.2v. Two identical such battery packs in parallel would have 5600mAH capacity, and three would have 8400mAH, providing a realistic running time of 1-6 hours and typically 2-4 hours for a computing device such as a laptop or medical apparatus incorporating a laptop and at least one medical data gathering module.

Providing at least one first resettable fuse in series with at least one, two or more, individual cells 55 in the battery packs 54 is a first stage in addressing the problem of how to convert individual cells rated for use in pressurised chambers to a battery module suitable for safe use in a pressurised chamber and, particularly, for safely powering power hungry electronic devices in a pressurised chamber and more particularly for safely powering critical equipment such as apparatus for measuring medical data in a pressurised chamber. The control circuit of Figure 13 here in this example embodiment further comprises an on/off switch 58 in series with battery packs 54 and a main circuit second resettable fuse 74. Typically, second resettable fuse 74 has a 6 amp hold current and a 12 amp trip current. Other values of hold current and trip current may be considered depending upon the size of the battery packs and intended purpose of the battery module 40. A further 10 amp auto fuse 64 is also provided in series to offer overall back up over current protection. The output from battery packs 54 is delivered to a dc output jack 69. Thus where 16x1.2v NiMH AA individual cells are used in each battery pack, a nominal 19.2v is provided to dc jack 69. This is the expected dc voltage for laptop computers from an ac source. Typically, the laptops do not expect an ac source (via a transformer) to be intermittent and therefore typically there is no provision within the laptop for monitoring this dc supply.

Thus, the inventors have appreciated that it is important to monitor, independently from the laptop, the voltage of the battery packs and prevent these being completely drained and that it is also important to have an indication, in one example embodiment of the invention, of when the apparatus monitoring medical data may cease to function. Therefore there is a further problem of how to safely monitor the battery packs to indicate their remaining capacity. Further, there is a problem of how to provide an indication of remaining battery capacity that does not excite undue panic in persons within the isolated environment of a pressurised chamber, especially if medical data is being measured, for example on an injured person within the isolated (e.g. isolated from medical staff) environment of a pressurised chamber.

Alternatively or in addition, as a further precautionary measure, the medical apparatus, for example laptop 16, may be adapted to monitor the voltage at its dc input (which is equivalent to the terminal voltage of the battery module(s) 40) using internal software. This additional monitoring of input voltage (equivalent to battery module terminal voltage) may be incorporated into the medical data gathering module software. This voltage monitoring may be done by providing the dc input voltage as an input to, for example, an FPGA (field programmable gate array) interface module 26, as seen in Fig 5, containing software for the medical data gathering module(s) and then monitoring the input voltage. This is so that the software in use for monitoring medical data, can also be used to alert the user to a change in battery situation, such as a low battery situation. Further details of the FPGA can be seen in co-pending international patent application PCT/GB2010/000564.

In further embodiments of the invention the circuit of the battery module comprises an on indicator circuit 60, an autoshut off circuit 70, a first comparator circuit 80, a low battery indicator timer circuit 90 and a low battery indicator 100.

Referring now on Figures 13, 14 and 15, the on indicator circuit 60 comprises a green LED 61 and resistor on the power output line to the load. The first comparator circuit 80 comprises a comparator having a first input reference voltage V-i ^ref , typically equal to 5v, from a first zener diode 102. The first input reference voltage V, ^ref goes to the negative input (-ve) of the comparator 80 at pin 2.

A multitrim potentiometer 106 provides a second indicator voltage V _tap to the positive input (+) of the comparator 80 at pin 3. The voltage across multitrim potentiometer 106 and hence the "tapped off" voltage V _tap falls as the voltage from the battery packs 54 falls. When this voltage results in V _tap being less than V-i ^ref , the output of the comparator 80 switches from being negative (passing V _tap to output pin 1 ) to being positive (passing V ^ef to output pin 1 ) so that the output goes high. This switches on low battery timer circuit 90. In one example embodiment, this may be arranged to occur when the battery pack voltage falls to 16v from the nominal voltage of 19.2v. The low battery timer circuit 90 comprises a timer 1 16 (a 555 timer). The timer 1 16 is powered when its input is high into an astable mode. This turns on the panel red LED 62 (which flashes) and produce a short beep from a speaker 63 in low battery indicator circuit 100. A diode across a timing resistor (here a 10k resistor) produces a signal with a short mark/space ratio (½ second on and 10 seconds off) and further during the ½ second beep, the red LED 62 goes off. Thus, in one embodiment, the invention provides a low battery signal having a short mark to space ratio e.g. ½:10 (= 1 :20). A mark to space ratio of 1 : 10 to 1 :40 is preferred as these are quite different from the usual mark to space ratios of physiological signals (e.g. 1 breath per second is 1 : 1 mark to space ratio and 60 beats per minute is 1 beat per second i.e. 1 :1 mark to space ratio).

This ½ second on and 10 seconds off indicator system, and further having the beep sound for ½ second and the LED switch off for the same ½ second, is an unusual non-physiologically related signal which is not easy to confuse with physiological signals. This assists in avoiding confusion with physiological alarms which may be present in the medical data measuring components and/or in the medical data gathering module itself.

Tantalum capacitors 1 18 are used instead of electrolytic capacitors to avoid the problem of collapse and/or leakage of electrolyte from the electrolytic capacitors which would be undesirable in a pressurised chamber. Referring briefly to Figures 30 and 31 , here an alternative embodiment of the invention is shown having two identical battery modules arranged in parallel with one another (and arranged in battery module support housing 200 in a removable manner) so one can be swapped out for a fresh (fully charged) battery module 40 when it is depleted without switching off the computing device 16 to which it is connected. Typically each battery module 40', 40" is provided with two battery packs 54 in parallel as described elsewhere herein. Optionally an auxiliary static battery module 340 is hard wired into battery module support housing 200 so both battery modules 40', 40" can be removed and replaced without immediate loss of power from computing device 16. For example, the optional auxiliary battery 340 may have a capacity of 5 minutes for powering computing device 16. Also, shown in Figure 31 is an optional additional low battery indicator circuit 256 provided in each of battery modules 40 ', 40". Thus, in one example embodiment, each battery module 40', 40" is provided with an additional low battery indictor circuit 256.

Each battery module 40', 40" is preferably provided with two indicators: a green LED indicator ("on" indicator circuit 60) to show that the battery power output is "on" and that power is present at the connector, and a red LED indicator ("low battery indicator" circuit 100) to indicate that the battery is becoming depleted and that replacement of the battery is required. Further battery charge indication is provided in additional indicator circuit 256 with an LED bar graph. The bar graph consists of several LEDs e.g. 5 LEDs, 3 green and 2 are red. LED bar graph driver IC LM3814 is used to drive the LEDs over the required range of battery capacity, full charge results in all 5 LEDs being illuminated. As the battery voltage drops from 20 volts to the cut off point of 16 volts the display will illuminate fewer LEDs until just a single red led is illuminated. Returning to Figure 13, 14 and 15 , the autoshut off circuit 70 comprises a voltage regulator 105, here providing a regulated voltage of 12v, a second comparator 108 receiving a second reference voltage V ₂ ^ref from zener diode 102. Typically second reference voltage V ₂ ^ref is lower than first reference voltage V-i ^ref provided to first comparator 80, so that as the battery pack voltage falls, the first event is activation of the first comparator circuit 80 to activate the timer circuit 90 and indicator circuit 100 and the second event is activation of the autoshut off circuit 70 by means of second comparator 108.

Second reference voltage V ₂ ^ref is provided to the negative (-) input (pin 6) of second comparator 108. The voltage tapped from the settable multitrim potentiometer 106 is delivered to the positive (+) input pin 5 of second comparator 108. As the battery voltage falls, say to 16v, the "tapped" voltage V ^tap from multitrim potentiometer 106 falls below that of the reference voltage V ₂ ^ref . Thus, the voltage output V ₂ ^0Ut of the second comparator 108 changes from positive in which V ₂ ^0Ut is high to low.

Autoshut off circuit 70 further comprises a second voltage regulator 1 12 (here a 5 volt regulator) and a solid state relay 1 14 that receives the voltage across the battery pack(s) at pin 3.

Initially, when the battery pack(s) are fully charged, at say 19v, then the positive input at pin 5 to second comparator 108 is higher than V ₂ ^ref at the negative input (pin 6) and the output of the comparator V ₂ ^0Ut is high. This is passed to the voltage regulator 1 12. The voltage regulator 112 then delivers 5v to the relay 1 14 (here a VN05N) which switches on, passing the battery pack (s) voltage (Vcc) to the LOAD. The battery pack(s) voltage falls, say to 16.5v, then the positive input at pin 5 falls below that of the reference voltage V ₂ ^ref , and the output of the comparator 108 goes low. This is passed to the voltage regulator 1 12. Thus, no voltage is passed to the input (pin 2) of the solid state relay 1 14. To prevent the input to the solid state relay floating, it is pulled to the ground rail via a resistor (not labelled) connected to the input of pin 2 of solid state relay 1 14. Thus, the input of the solid state relay 1 14 goes to ground and the relay is switched off (as it requires a suitable voltage e.g. 5 volts from the voltage regulator to switch it on). Thus the voltage from the battery pack(s) is switched off and prevented from powering the LOAD. This autoshut off feature addresses the problem of the increase in current to maintain power supplied (power = voltage x current) as the voltage from the battery pack(s) falls. This voltage drop increases the risk of current overload and heating due to higher current which is undesirable in the environment of a pressurised chamber. This increase in current is avoided as the autoshut off circuit switches off as the battery voltage falls (typically below a second threshold voltage) and the current rises.

When the load is removed the battery pack(s) may recover slightly. A resistor 1 10 feeds back from the output of comparator 108 to the positive input of comparator 108 so that a higher voltage is required to switch the relay 1 14 back on following autoshut off. EXAMPLE

Ohms law shows that as the battery voltage drops during the discharge, to maintain the same power, the current increases. At 19 volts the current required to power the laptop is about 1.2 amps, as the battery voltage reaches 16 volts the current rises to about 2 amps. At some point, the autoshut off circuit activates to switch off automatically, before the current gets too high. It is generally considered that a Ni-MH battery is fully charged at 1 .2 volt and is flat when the voltage is about 1 volt. Thus, in one example embodiment to make a suitable battery pack that will provide 19 volts, a 16 cell battery pack was used.

The capacity of the AA cells is 2800mAH. A single string of 16 cells would power a laptop for a little over 1 hour. In an example embodiment the battery module will have 3 battery packs, each battery pack being a string of 16 AA cells in series. The 3 battery packs are connected in parallel to increase the battery capacity of the battery module to over 3 hours.

The battery module will shut down when the battery voltage reaches in one embodiment, 16 volts and the laptop will simply switch off. In an example embodiment to provide the user with an indication of low battery condition, the battery module will have a 'battery low' red LED and an audible alarm, the nature of the alarm is intended to be of low urgency and will not occur at an interval that may be confused with a physiological event, it is desirable that a short bleep (500ms) occurs every 10 seconds.

To provide a battery that is safe, extensive use of resettable fuses is made. These have a holding current specification and a cut-off current specification. In a preferred example embodiment 3 amp Polyfuses ^® are placed at the positive terminal of each battery pack 54 and optionally positioned so that they lie on top of the battery pack. The 3 amp Polyfuses ^® prevent the battery current from becoming excessive, the 3 amp Polyfuse ^® will go high resistance if the current reaches 6 amps. Also the Polyfuse ^® , as it lies preferably adjacent e.g. on top of, a battery pack 54, acts as a thermal fuse, if the Polyfuses ^® temperature reaches 100°C, the resistance again goes high limiting the current flow.

Preferably, a 6 amp Polyfuses ^® is also placed at the output of the parallel battery pack. Preferably there is a 10 amp automotive fuse to provide an overall fuse for the (typically for each) battery module.

The battery pack terminal voltage is monitored and the output of the battery pack is switched through a solid state relay (solid state relay is preferred as it is not affected by ambient pressure, and as it does not have contacts, thus the potential for a spark is eliminated). Early research into hyperbaric instrumentation identified electrolytic capacitors as a possible component that may be affected by pressure, electrolytic capacitors are basically a roll of the dielectric material that is then placed in a tiny can, under pressure the capacitance of the component may change and also rupture of the can may occur. Tantalum Capacitors are preferred in all circuits. The circuit that monitors the battery voltage and provides the low battery alarm preferably uses an LM293 dual comparator IC as a first comparator 80. The reference voltage is provided by a 5v zener diode (low battery) and a 4.8v zener diode (auto shut-off).

Circuit Description

The terminal voltage of the battery packs 54 in parallel after a full charge may be 20 volts, this will drop to a working voltage of 19.6 soon after a load is applied and then deliver the majority of its energy at this voltage, when the battery becomes flat the voltage will drop from the working voltage of 19.6 v. Figures 13 shows the circuit used to provide a low battery alarm and an auto shut off of the battery module.

The circuit is described further. The first comparator 80 (e.g. the dual comparator IC LM293) is used as it is specified to work at up to 36 volts rails, it is however regulated to 12 volts using a 12v voltage regulator 70L12. The reference voltages to the two comparators 80, 108 are supplied by the two zener diodes, irrespective of the battery terminal voltage the voltage across the zeners is clamped at 5v and 4.8 respectively. The 100k multi-turn trim potentiometer across the battery provides a voltage that will drop as the battery discharges. Setting the trim potentiometer sets the low battery alarm and auto shut-off points. In this example it is required that the battery module supply to the load is switched off when the battery terminal voltage reaches 16 volts. The second comparator 108 is used to provide the autoshut off feature of autoshut off circuit 70. With a fully charged battery the voltage at pin 5 of second comparator 108 is set to 5.5 volts, this is greater than the 4.8 at the inverting input pin 6 and the output at pin 7 is high (12v). The solid state relay VN05N requires a 5v input to turn it on, 78L05 voltage regulator acts as a voltage converter, dropping the 12v comparator output to 5v, the resistor to ground (10k) at pin 2 of the VN05N acts to pull down the relay input. With a 5v input to pin 2 of the VN05N the battery voltage is switched through to the load.

As the battery terminal voltage continues to drop the input to the second comparator 108 pin 5 drops. When this input goes below the reference voltage supplied by the 4.8v zener, the output pin 7 goes low and the relay is turned off. The resistor 1 10 connected between pin 7 and pin 5 provides hysteresis and prevents the relay from switching on as the battery terminal voltage rises when the load is removed. A fully charged battery is required to turn the relay back on again.

The first comparator 80 is used to provide a low battery alarm. The reference voltage to this comparator (pin 3) is a 5v zener diode and the variable input (pin 2) again drops as the battery discharges. Pin 1 of the comparator 80 of low battery circuit 70 is low when the battery terminal voltage is above the low battery threshold, and hence the sounder circuit has no supply. When the comparator switches, the output goes high and powers the 555 timer 1 16. The timing components are selected to produce a short beep (500ms) every 10 second when the 555 circuit 1 16 operates in astable mode. The nature of the low battery alarm is designed so as to not be confused with physiological events such as heart rate etc, the red panel LED blinks to indicate low battery also.

Consider the comparators as two separate devices, even though these may be in a dual package. The battery terminal voltage is across a multiturn 100K potentiometer and this 'tapped off voltage' is fed to both comparators and will fall as the battery discharges. The 1st event occurs as the 'tapped off voltage" becomes less than the 5v zener ref voltage, which is rock steady at 5v as long as the battery voltage is above 5v.

Comparator circuits allow the bigger input signal to be passed. The two inputs to a comparator integrated circuit are marked with a + and - respectively, inverting and non- inverting inputs.

Pin 3 is the + and pin 2 is -, output is pin 1. If the voltage on the + is greater than the voltage on the - then the + is passed, if the voltage on the - is greater than the voltage on the +, then - is passed. With a fully charged battery, the voltage on pin 2 (-ive or inverting input) should be higher than the 5v fixed zener input to pin3 (+ive or non-inverting input), if the negative input is greater that the positive then the output pin 1 is low.

As the battery reaches 16.5 volts the 'tapped off' ref voltage to pin 2 goes below the 5v zener ref and the output at pin 1 goes high (pin 1 ), this high voltage powers the 555 timer in an astable mode to turn on the panel red LED and produce a short beep every 10 seconds. The diode across the second timing resistor produces a signal with a very short mark/space ratio (1/2 sec on 10 sec off) and during the ½ second beep the red LED goes off.

The battery continues to give up its energy from 16.5 down to 16v and during this period the beep & red LED continue. Then the 2nd event of switching the load off occurs. Unlike the 1st event comparator 80, the output of which is switched high to power the 555 at the low battery point, the 2nd event comparator's (108) output is high (relay on) until the battery tap-off V _tap goes below the 2nd zener at 4.8v. When this occurs the output goes low and the relay is switched off, switching off power to the LOAD.

A resistor lies in series with the smoothing 10uF tantalum capacitor across the rails of the timer 555 and provides a current limit to the tantalum capacitor. The 100uF tantalum capacitor will have a saw tooth wave as the 555 operates.

Should one battery pack be replaced with another fully charged pack then the full battery pack will attempt to charge the flat ones and very high currents could flow (10's of amps). The 3 amp Polyfuse ^® 72 is in series with each block of individual cells 55 in series with one another in a battery pack 54 to prevent this high battery pack to battery pack current flow.

Where two or more (preferably identical) battery modules are provided in parallel (such as 40' and 40" in Figure 31 ), diodes 265 may be provided to prevent charging of one battery module by another in the event of an imbalance such as a fully charged and less than fully charged battery module being in use together. The 6 amp Polyfuse ^® 74 acts as an overall battery module output limit. The 1 0 Amp automotive fuse is there to blow in the event of an output short.

Typically, the first resettable fuses 72 associated with the battery packs 40 may also be placed in thermal contact with their respective battery pack 54. For example, each first resettable fuse 72 may be laid on top of their respective battery pack 54. This is because resettable fuses comprising polymeric positive temperature coefficient devices such as Polyfuse® or Polyswitch® are temperature sensitive and go to high resistance at high temperature typically at 100°c. Thus the self-resetting fuses 72 can operate as a thermal fuse providing a dual function both as a current sensitive resettable fuse and as a thermal fuse.

In addition to one or more of the safeguards described herein to prevent a single individual cell causing a consequential effect on neighbouring cells and equipment, a further safeguard may be provided. A thermal barrier may be provided between each individual cell 55. Thermal insulator material may be provided as a thermal barrier between each cell. Such material may comprise intumescent material.

For safety reasons, it is preferred to not charge any battery modules 40 in the pressurised chamber. An external programmable battery charger is preferred. One or two supplementary battery modules 40, of identical specification to the original battery module 40, may be provided per laptop or medical apparatus comprising a laptop so as to enable an extended (C/10) charging regime outside the pressurised chamber, whilst the laptop or medical apparatus continues to be powered inside the pressurised chamber.

The battery module may optionally comprise a USB rated power output 68 powered from the output of relay 1 14 via a suitable current limited voltage regulator, here a 5v, 500mA voltage regulator 115. Thus, in a further aspect of the invention the battery module can be adapted to provide a USB standard power source for electrical equipment to use in pressurised chambers.

Figure 16 shows a further medical data gathering module 120 for use in the first aspect of this invention. The medical data gathering module in this example embodiment comprises an interface module 120 having a number of sockets and connectors for associated circuitry within an adapted laptop 16 (seen in Figure 18). The medical data gathering module 120 comprises a u-shaped bar (see Figure 17) mounted on a rear wall of the laptop base. Typically a medical data gathering module comprises an interface having one or more sockets and/or connectors and associated circuitry for gathering one or more kinds of medical data. Here a number of different sockets and/or connectors are provided mounted on an interface module comprising a single frame (u-shaped bar 120) and associated circuitry is located within laptop 16. Thus whilst each socket and/or interface and associated circuits could each be viewed as a medical data gathering module in its own right, for the sake of convenience in the discussion herein these can be viewed as a combined medical data gathering module. Nevertheless it is to be understood that any one or more individual medical data gathering modules may be used or a combined medical data gathering module having two or more medical data gathering functions may be used. Examples of modules for use as individual and/or combined medical data gathering modules include one or more of an electrocardiogram (ECG) data gathering module; a blood pressure (BP) data gathering module; spirometry (lung data) data gathering module; pulse oximetry data gathering module; skin temperature data gathering module; both invasive and non- invasive blood pressure data gathering module; retinal testing data gathering module; ultrasound data gathering module; dermatology screening (image capture) data gathering module; imaging, tissue and/or wound care data gathering module; video endoscopy data gathering module; video for remote consultants data gathering module; video conference data gathering module; audio data gathering module; scaliometer (height) data gathering module; foetal heart Doppler ultrasound and/or audio acquisition and/or analysis data gathering module; weighing scales data gathering module; imaging data gathering module; capnography (end tidal; C0 ₂ partial pressure of C0 ₂ in respiratory gases) data gathering module; e-stethoscope data gathering module; otoscope data gathering module; dental scope data gathering module, iriscope data gathering module; Doppler/ultrasound data gathering module.

To provide a blood pressure (BP) data gathering module, a pump is used to inflate a cuff around a patient's limb. This can be problematic in the unusual environments of pressurised chambers in general and hyperbaric and saturation pressurised chambers in particular. The pumps typically used in BP apparatus require a motor, and motors can create sparks due to their brushes. Therefore in a further embodiment of the invention, a blood pressure data gathering module is provided with a brushless motor such as those available from NIDEC, USA.

Thus, in one example embodiment at least, the inventors provide a combination of new and off shelf components, and provide an apparatus and associated battery module uniquely adapted for the unusual environments of pressurised chambers such as hyperbaric and saturation chambers.

Referring to figures 16 to 19 in more detail, combined medical data gathering interface module 120 is here in the form of an interface and has a pulse oximetry ribbon cable 126, an ECG cable socket 128, a temperature thermistor socket 130 comprising a phono jack 132 and a blood pressure pneumatic connector 134. Apertures 136 are provided in U-shaped bar 122 for mounting the connectors and sockets 124 to 134 thereon. U-shaped bar 122 is formed flat and folded along line 138.

Referring now to figure 20, an apparatus 140 for measuring medical data in a pressurised chamber is shown. Apparatus 140 comprises a specially adapted laptop ^{1 K h inn t lQ et} one medical data gathering module for example a combined medical data gathering module having multiple medical data gathering module functions thereon, and a battery module 40 (hidden from view beneath the laptop 16). Various medical data gathering cables 146 are shown emerging from combined medical data gathering module 120. The apparatus 140 is ready for testing in a pressurised testing chamber 142 which can be operated under a variety of conditions including hyperbaric and saturation environments. A "dummy" patient 144 is connected up to the medical data gathering devices and/or modules.

Figure 21 shows a control panel 150 for pressurised testing chamber 140. The control panel 150 has a screen 152 which shows an image of the equipment under test inside the chamber. A pressure gauge 154 illustrates the pressure inside the chamber here 450msw (meters of seawater) equivalent to 45 bar. A control panel screen 158 shows the pressure level in the chamber 160, the temperature 162, the humidity 164, the percentage oxygen 166, the C0 ₂ in parts per million and the supply of pressure 170 e.g. from gas bottles supplying the chamber.

In one aspect, the problem of controlling the interaction of one or more cells, when one is fully charged so that these do not charge another group of one or more cells that is depleted, is avoided or reduced. In a further aspect two or three battery modules are provided in a kit, optionally with an apparatus for measuring medical data comprising a laptop or other computing device as described herein, so that electrical equipment or apparatus for measuring medical data can continue to be used whilst the battery modules are swapped out of the pressurised chamber for re-charging (typically at a low e.g. C/10 charge rate).

Figure 23 shows the actual voltage and current available to a laptop during use over time, powering the laptop via its dc input terminal. It is of note that the voltage dips near the end of the battery pack(s) capacity and this correlates with an increase in current. The battery module of the present invention has been designed to develop an alarm condition when the battery voltage drops to a first threshold value (say 16.5v) and to automatically switch off at second (lower) threshold voltage (say 16v) before this dramatic voltage dip. This arrangement avoids the extra risk associated with running circuits at increasing current values in the unique environment of a pressurised chamber.

Figure 24 shows the pressure level variation 172 from 0 to around 18 meters of seawater (equivalent to 1.8 bar) at a variety of oxygen levels from around 4% to around 24.5% in a hyperbaric chamber test routine (a simulated "dive").

Figure 25 shows the pressure level variation 172 in steps from atmosphere up to 450 meters of seawater (equivalent to 45 bar) and oxygen level around 2.5% in a saturation chamber test routine (a simulated saturation "dive"). Figure 26 shows the pressure level variation in a simulated hatch test going from atmosphere to 450 meters of seawater (45 bar) and a reduction of 0 ₂ from around 20% to around 2%, in a few seconds.

Apparatus 140 according to a first aspect of the invention as tested under the conditions shown in figures 24 to 26 operated correctly. Further the apparatus 140 was used to gather simulated medical data from patient 144. Software controlling the medical device gathering modules data (as described in co-pending international patent application PCT/GB2010/000564) was used to gather and process medical data.

Figure 27 shows a laptop base 16B attached securely to a battery module 40 so that it does not move with respect to the battery module. Indeed it may be arranged that the laptop cannot be moved without also moving the battery module 40 supplying power to it. Such an arrangement is shown in Figure 28, which here also allows the battery module 40 to be easily swapped out without moving the laptop 16 (not shown). These advantages are provided by battery module support housing in the form of an attachment 200. Attachment 200 comprises a multipurpose panel 202 which functions as a roof for a battery module cavity 204, and as a platform on which the laptop 16 (not shown) can rest. The battery module cavity 204 is formed by two or three side walls 206 and panel 202. The battery can be slid into place within the cavity in the direction of arrow A. A positive locking mechanism that "clicks" when the battery is in place may be provided. A shaped protrusion 210, here a rectangular box shaped protrusion, may be provided to locate attachment 200 in the empty recess of the laptop battery compartment (not shown). It may be sized and shaped to match the empty battery compartment. A U-shaped channel 220 may be provided for engaging with the base of a laptop. A lever 230 may be provided which is slid into place to hold the laptop base in place in position on top of panel 202. A lock 232 may be provided. Together the shaped protrusion 210, the U-shaped channel 220, and the lever 230 hold the laptop base securely in position on top of panel 202 within attachment 200.

Figure 29 shows a schematic plan view of a further example embodiment of the invention having two (typically identical) battery modules 40 connected in parallel in for example battery module support housing 200 (not shown). Figure 30 shows a suitable battery module support housing 200 in the form of a tray with two slots for housing two battery modules 40. Referring now to Figures 29 and 30, a battery module support housing 200 for receiving identical battery modules 40', 40" is shown having two identical cavities 204 in the form of rectangular slots sized and shaped to receive and accommodate the housing of battery modules 40', 40"with a small gap in between (here 2mm). Typically battery modules 40', 40" are slotted into cavities 204 in the direction of the arrows as shown. The upper and lower portions 42, 44 of the housing of battery modules 40', 40" is sized to fit within the cavities 204 and enable connection of connector parts (254a, and 254b), on the battery module and on the battery module support housing 200, of a connector 254. Typically connector part 254b is located in a distal end component 252 of support housing 200 and connection is made to it when the battery module is inserted into a suitable position within cavity 204.

Similarly on battery insertion, the 'power' pins 262 make connection (being longer) before the 'control' pins 264 make a connection and switch on the battery power output.

In this case, support housing 200, may be fixedly attached to the computing device, and/or may be substantially planar so as to serve as a platform for locating beneath computing device 16.

The support housing 200 houses two battery, modules 40', 40" alongside one another. Each battery module 40,' 40" has two identical battery packs 54A, 54B of 16 AA NimH batteries serially connected, a circuit board 56 for housing the control circuits and a rear connector panel for easy access to switches, fuses. The LED bar graph display is typically located on the rear panel of each battery module 40, for example near on/off switch 58. The LED bar graph display allows a quick visual reference of the remaining power (as the battery module voltage falls). The battery module main on/off switch 58 may be recessed (in a recess) to assist avoiding accidental switch on or off. The two battery modules 40', 40" are connected in parallel with one another.

Each battery module 40', 40" incorporates a 3 Amp Polyfuse to limit the current from each of the battery packs 54A, 54B, and a control circuit mounted on a PCB 56 also housed within the battery module 40', 40".

The battery power is routed from the PCB 56 (immediately after the connection between the PCB 56 and the battery packs 54) and is connected to the On/Off switch. From the On/Off switch, the power is routed through a user replaceable 10 Amp automotive fuse. From the automotive fuse, the power is routed to a 6 Amp Polyfuse before returning to the PCB.

The NiMH cells have a charged terminal voltage of 1 .2 volts and a capacity of around 2300 mAH. The terminal voltage of a 16 cell pack 54A, 54B is 19.2 volts. The two parallel packs 54A, 54B in each battery module 40', 40" provide a capacity of 4600 mAH, providing an overall capacity with both battery modules 40', 40" inserted of 9200 mAH. Referring also to Figure 31 , it is preferable that the battery power contacts are volt-free, whilst the batteries are being inserted and/or being removed. This is because if the power contacts were to be broken under load, an arc would potentially be generated.

The use of 'break before make' contacts within the connector 254 achieves this. The control signal to the solid state relay within the battery module 40', 40" (which is at a low energy 5v level) is routed to the connector 254 and immediately back to the battery module PCB 56, if the battery is not inserted into the battery tray (support housing 200), the electronic battery switching is disabled.

The 'power' pins 262 in the connector 254 are longer than the 'control' pins 264, so upon battery removal the 'control' pins 264 will break connection before the 'power' pins, turning the battery off (switching off the battery module 40', 40") before the 'power' pins 262 break, producing a volt-free disconnection.

Figure 31 shows a schematic circuit diagram of a further example embodiment of a battery having two battery modules 40 according to the invention which can be swapped out individually one at a time or together and an optional static (i.e. hardwired) auxiliary battery module 340. Auxiliary battery module 340 has an on indicator circuit 60', an autoshut off circuit 70', a low battery comparator circuit 80', a low battery timer circuit 90' and a low battery indicator circuit 100' and a single battery pack 54' having 16 individual cells (AA NiMh cells) and a 3A polyfuse 72' in series. The wireless capability of the laptop 16 of apparatus 140 and a computer network were used to communicate with a remote computer from within the chamber. The remote computer was located several hundred miles away and the apparatus 140 gathered medical data within the pressurised chamber and transmitted the data to that remote computer.

Thus the various aspects of the present invention described herein provide a safe solution to the problem of power delivery in pressurised chambers, to the problem of safely gathering medical data within pressurised chambers and the problem of transmitting data, especially medical data, from within pressurised chambers, to, for example, a remote location. Further, by separating the energy required by electrical equipment and medical apparatus for use within a pressurised chamber into individual cells, each individually rated for use in a pressurised chamber, each "lump" of energy within each individual cell has insufficient energy capacity to ignite a neighbouring cell or other components even if its whole energy capacity were released over a very short period. Furthermore by providing a dc output, for example rated to the dc input of a laptop, or a laptop forming a medical apparatus, then one or more battery module(s) can be very easily swapped out for a replacement, as it is external to the laptop's housing.

Further in the embodiment in which two or more battery modules are provided, these can be swapped out one at a time (a "hot swappable" feature) without losing power to the equipment such as a portable computing device, personal computer, laptop or apparatus for measuring medical data. A remaining, removable battery module can still power the equipment during the swap of the other removable battery module.

A further variation may be envisaged as a result of this hot swappable feature. For example in a further embodiment, in which two or more battery modules are provided (typically in parallel) a battery module switching circuit is also provided to enable switching of power between battery modules whereby when a fully charged battery module is inserted, a partially depleted battery module may be switched off allowing time for it to recover preserving battery life. Indeed, during use, battery modules may be switched off in turn to allow recovery time and preserve battery life. This switching circuit may comprise a control function for switching the battery modules on and off in accordance with a predetermined protocol depending upon factors which may include one or more of the following: the time since last full recharge of the battery module, rate of depletion of battery module, remaining power of the battery module, and current delivered by the battery module. The switching circuit may comprise one or more solid state switches. For example, a situation may arise if one battery module is partially depleted and one near fully depleted, the near fully depleted battery module may be replaced with a fully charged battery module. To conserve battery life and give the partially depleted module a rest, the battery module switching circuit may enable power delivery to be switched to the fully charged battery module, the partially depleted battery module being switched off, allowing the partially depleted battery module time to recover. This switching feature may be enabled by provision of, for example, voltage comparator circuit(s) (optionally located in distal end components 252) and/or one or more solid state switches (for example located in each battery module) to control of voltage delivery from each battery module 40.