The invention also relates to a method for the operation of such a moisture-heat exchanger unit.

Field of the Invention For patients being treated in respirator or another similar breathing assistance, it has been known for a long time to provide a moisture-heat exchanger in the pipe that connects the patient to the respirator. By the fact that the filter in such a moisture-heat exchanger absorbs moisture from the exhalation air and desorbs it to the inhalation air, moisture and heat carried by the same are brought back to the patient. Thereby, it is avoided that the patient becomes dry in throat and airways.

However, there are situations where such a moisture-heat exchanger involves drawbacks. Such an example is when the patient needs supply of pharmaceutical preparation of such a type that is supplied in the form of an aerosol. Here, the pharmaceutical preparation consists of a substance dissolved in a liquid, usually water, where the water is converted into mist in a nebulizer before it is supplied to the patient.

Frequently, it concerns the treatment of an anaesthetized patient.

If such an aerosol is supplied to a patient connected to a respirator via a moisture-heat exchanger, the same will absorb the aerosol. This entails that the supply of the pharmaceutical preparation becomes uneven and uncontrolled and involves the risk of the moisture-heat exchanger becoming clogged.

In order to avoid this, it is common to disconnect the moisture-heat exchanger from the respirator and then connect the patient to the supply of aerosol. Upon finalized supply, the moisture-heat exchanger is reconnected to the patient and the respirator. This becomes fairly intricate and involves the risk of faulty manipulation and contamination.

Therefore, devices and methods have been developed to facilitate this switch of the connection of the patient to treatment equipment.

By US 5,505, 768, a moisture-heat exchanger arranged in a housing is previously known, where the housing has one connection for the patient pipe and one connection to the respirator. The housing has two compartments located next to each other, and in the normal position the filter is located in the one of the same where the connections are.

When the patient is to be treated with aerosol pharmaceutical preparation, the filter is displaced to the other department of the housing. Thereby, a free passage through the first department of the housing is provided, so that the supply of aerosol does not become obstructed by the filter.

This device becomes relatively intricate to operate and ungainly by the fact that it is required that the filter has to be moved when the type of treatment is to be switched.

Furthermore, by EP 1192 968, a device is previously known having a moisture- heat exchanger in the pipe between respirator and patient and with a bypass pipe being arranged for enabling supply of aerosol without passage through the filter of the moisture- heat exchanger. With one end thereof, the bypass pipe is connected to the pipe between the respirator and the moisture-heat exchanger and with the other end thereof to the pipe between the moisture-heat exchanger and the patient. In the latter connection, a valve is arranged and that may be controlled so that the flow goes either through the moisture-heat exchanger or through the bypass pipe.

The same device becomes relatively complicated by the fact that it is composed of a system of components comprising the moisture-heat exchanger, the valve and the bypass pipe, which components have to be connected in the correct way by an operative person.

Furthermore by WO 02/26306 a device is previously known where the filter thereof can be by-passed when supplying gas for treatment. This is accomplished by reciprocating valve means, which results in a relatively complicated construction and in addition requires valving function on the inlet as well as the outlet side.

The object of the present invention is, against this background, to provide a simple solution to enable switch between breathing assistance only and supply of aerosol pharmaceutical preparation, and thereby obviate the disadvantages associated with previously known devices and methods in this area.

Summary of the Invention According to the first aspect of the invention, the object set-up has been attained by the fact that a moisture-heat exchanger unit of the kind defined in the preamble of claim 1 comprises the special features in that the moisture-heat exchanger unit comprises a rotary valve arranged in the housing for the provision of two alternative flow paths of the air through the housing, a first flow path entailing that the air flows through the filter and a second flow path entailing that the air flows through the housing without flowing through the filter.

Thanks to the fact that the moisture-heat exchanger unit itself allows alternative flow paths, the need for an external bypass pipe and a special external valve for the control of the flow is eliminated. Furthermore, the invented device entails that the filter can be kept in one and the same position during the various types of treatment. In addition, since the valve is a rotary valve, switch-over can be achieved by a simple rotary motion, with the risk of faulty operation being very small. Hence, the invented device becomes extraordinarily simple and easy to operate with minimal risk of malpractice. Moreover, by virtue of the few and simple components required, it becomes inexpensive to manufacture.

According to a preferred embodiment, the two flow paths are concentrically arranged in relation to each other.

This entails that the unit can be made compact and that the flow paths can be established at very small changes of direction.

According to an additional preferred embodiment, the filter is arranged in the radially outer flow path.

Normally, the flow path through the filter requires a larger flow passage area than the free flow passage area. By locating the filter farthest out, thereby the unit will be possible to be made with a smaller diameter than in opposite arrangements. This is because of hydromechanics reasons it is not possible to have too a small spacing between the walls of the flow path.

According to an additional preferred embodiment, the valve comprises a first unit and a second unit rotatable in relation to each other and adjacent to each other, which first unit comprises an even number of sections distributed in the circumferential direction, each section comprising a wall member and an opening, where in every second section the opening is situated radially outside the wall member and in every second section the opening is situated radially inside the wall member, and which second unit comprises an even number of portions distributed in the circumferential direction, where every second portion consists of a fully covering wall and every second consists of an opening.

Such a construction of the valve is a simple and handy solution for distributing the flow to either of two concentric flow paths.

According to an additional preferred embodiment, the number of sections is eight or greater and the number of portions equal to the number of sections, and each section and each portion being of substantially triangular shape and each opening and each wall member being of substantially triangular or trapezoidal shape.

By having a relatively great number of sections and portions, an efficient and evenly distributed distribution is attained in the circumferential direction.

According to an additional preferred embodiment, each of said units is of conical shape.

Thereby, walls are obtained that are obliquely directed in the direction of flow, which decreases the flow resistance of the valve.

According to the second aspect of the invention, the object set-up has been attained by the fact that a method of the kind defined in the preamble of claim 7 comprises the particular measures of directing the flow of the tidal air by means of a rotary valve through the housing to either of two flow paths through the housing, where one of them entails that the air is directed to flow through the filter and the other entails that the air does not flow through the filter.

According to preferred embodiments of the invented method, the same is exercised while using the invented device.

By means of the invented method, advantages of the type corresponding to what has been stated above for the invented device and preferred embodiments of the same are gained.

The invention is explained closer by the appended detailed description of advantageous embodiments of the same, reference being made to the appended drawing figures.

Brief Description of the Figures Figure 1 is a longitudinal section through a first embodiment example of the invention.

Figure 2 is a section through a first detail in the device in figure 1.

Figure 3 is a section through a first detail in the device in figure 1.

Figures 4 and 5 illustrate co-operation between the details in figures 2 and 3 in two different positions.

Figures 6 and 7 are perspective views of additional embodiment examples of the invention.

Figure 8 is an exploded view of the device according to figure 6.

Figure 9 is a perspective view from the inside of the housing of a detail in figure 8 illustrating a first valve position.

Figure 10 is a perspective view corresponding to that of figure 14 but illustrating a second valve position.

Figure 1 is a longitudinal section through a schematic illustration of an embodiment example of the invention. The housing is composed of a first member 42 and a second member 43, each of which is connected to a respirator 6 and a patient pipe 7, respectively, by means of an opening 46 and 47, respectively. The housing members 42 and 43 are rotatable in relation to each other, and in the right housing member 43, the filter 44 is arranged. The same is formed as a hollow cylinder having a through hole 45.

A first plate 48 is fixedly connected to the housing member 42, and a second plate 49 is fixedly connected to the housing member 43. Each plate is provided with openings arranged so that when the plates are in a first rotational position in relation to each other, a flow path through the filter 44 is formed while flow through the central hole 45 is blocked. in a second rotational position, the openings end up in such a position that a flow path through the central hole 45 is formed while the flow through the filter 44 is blocked. How the openings in the plates 48,49 are arranged for the achievement of the same alternative flow paths is seen in figures 2 and 3.

Figure 2 is a section through the plate 48 in the left housing member 42. The plate 48 is composed of eight portions, each of which constituting a segment of 45°. Every second portion 50 entirely consists of a wall constituting a part of the plate. Every second portion 51 substantially consists of an opening.

Figure 3 is a corresponding section through the plate 49 in the right housing member 43. The plate 49 is composed of eight sections, each of which constituting a segment of 45°. Every second section 52 is composed of a radially inner part that consists of a wall 54 and a radially outer part that consists of an opening 55. Every second section 53 is composed of a radially inner part that consists of an opening 56 and a radially outer part that consists of a wall 57.

In a first rotational position, the plates 48, 49 are located so that the portions 51 and the sections 52 cover each other and the portions 50 and the sections 53 cover each other. Thereby, a pattern of overlapping openings and walls arises, which is illustrated in figure 4, where the shaded parts indicate wall. Hence, flow path is established through the radially outer the part, i. e. , through the filter 44 (figure 1).

In a second rotational position, 45° from that illustrated in figure 4, the plates 48, 49 are located so that the portions 51 and the sections 57 cover each other and the portions 50 and the sections 52 cover each other. Thereby, a pattern of overlapping openings and walls arises, which is illustrated in figure 5, where the shaded portions indicate wall. Hence, flow path is established through the radially inner part, i. e. , through the hole 45 (figure 1).

The plates 48 and 49 may advantageously be replaced by conical elements having the corresponding orientation of openings and wall members. Figures 6-10 illustrate different examples of such an embodiment.