This invention relates to fluid connections for medical devices and, in particular, to pneumatic connectors for small-bore tubing that conducts a fluid such as a liquid or a gas .

Numerous medical devices use pneumatic tubing to conduct fluids such as liquids or gases to or from a patient . A saline bag may be connected to an IV needle to administer pharmaceutical compounds to a patient, for example . Tubing may be needed to connect a patient mask to an instrument which measures the patient ' s respiratory gases or supplies oxygen to the patient . Another instance which requires pneumatic tubing is a non-invasive blood pressure monitor . For periodic monitoring at the bedside, an inf latable pressure cuff is wrapped around the arm of the patient . The pressure cuff is coupled by pneumatic tubing to a non-invasive blood pressure monitor . Periodically the blood pressure monitor will inflate the cuff around the arm of the patient, then slowly allow the pressure of the cuff to be released as the systolic and diastolic pressure levels are measured. Blood pressure cuffs come in a variety of different sizes . When a different size cuff is needed, the current cuff and its tubing are disconnected from a length of tubing attached to the blood pressure monitor and the tubing of a di fferent cuff is connected to the monitor ' s tubing . Generally a longer section of tubing extends from the blood pressure monitor and terminates at connector which mates with the connector on the tubing of the blood pressure cuff . When the connectors are coupled together, the two tubing sections are j oined in a fluid-tight connection that will not leak under the pressure of cuff inflation . In some cases the blood pressure cuff and its length of tubing are only used with a single patient . When the patient ' s blood pressure is no longer being monitored the pressure cuff and its short length of tubing and connector may be discarded.

Blood pressure cuffs are divided into two general classes , neonatal and adult, each class comprising multiple sizes, from the smallest neonatal to the largest adult . The automated blood pressure monitoring industry supports numerous types of connectors for adult size cuf fs . For neonatal patients the "Slip Luer" connector has gained widespread acceptance . But it is important that the connector used for neonatal cuffs be di fferent from any connector used for adult cuffs , as the monitor hose and algorithm are di fferent for neonatal monitoring . Safety concerns have been raised about the use of the Luer connector in blood pressure monitoring since Luer connectors are also used in IV lines, and misconnections of a non-invasive blood pressure monitor to an IV tube have been reported. Accordingly the present invention provides a different type of connector which replaces the Luer connector for use in neonatal blood pressure monitoring . Implementations of the connector of the present invention can be used in other medical and non-medical applications requiring a pneumatic connection . In accordance with the principles of the present invention, a pneumatic connector is described which utilizes a dome and cavity connection as the pneumatic interface . Mating male and female connectors with this pneumatic interface may be coupled together and released by a simple quarter- turn . Each connector has a mating coupling mechanism which holds the coupled connectors together when engaged. A detent mechanism which provides a tactile sensation when the connector is engaged may also be used . The dome and cavity connection obviates the need for an 0-ring seal commonly required by standard pneumatic connectors . In the drawings :

FIGURE 1 illustrates the pneumatic tubing of a monitoring instrument coupled to a blood pressure cuff by a pneumatic connector of the present invention .

FIGURE 2 is an enlarged view of the male connector of a pneumatic connector of the present invention .

FIGURE 3 is an enlarged view of the female connector of a pneumatic connector of the present invention .

FIGURE 4 illustrates the quarter-turn connecting of a pneumatic connector of the present invention .

Referring first to FIGURE 1 , a monitoring instrument 10 is shown connected by pneumatic tubing sections 12 and 14 to a blood pressure cuff 16. The inflatable cuff 16 is generally wrapped around the upper arm of a patient and held securely with overlapping hook-and-loop fasteners . A relatively short section 14 of small-bore flexible tubing is fastened to the cuff 16 and provides air to inflate a bladder within the cuff . The tubing section 14 terminates at a pneumatic connector 20 .

Another, generally longer, section of tubing 12 is coupled at one end to an inflation port 8 of the monitoring instrument 10 . The tubing section 12 terminates at a pneumatic connector 40 . The monitoring instrument shown in this example i s one which monitors a number of bodily functions such as the patient ' s ECG, heart rate, and CO ₂ , among other functions . The patient ' s recent blood pressure measurement is shown on the second line of the display 6 of the monitor, which is 120/ 80 in this example . Zn typical use, the monitoring instrument is set to take a measurement periodically at predetermined intervals . At each interval the monitoring instrument wi ll inflate the cuff 16 through the tubing sections 12, 14 until the blood vessels in the upper arm are occluded. The inflation pressure is then gradually bled of f until normal blood flow returns , and, using the oscillometric method, the monitoring instrument calculates the systolic and diastolic blood pressure levels from mean and other arterial pressure measurements taken over the inflation cycle . The measurements are recorded and stored by the monitoring instrument and the most recent reading is displayed on the monitor display 6.

In accordance with the principles of the present invention the sections of tubing 12, 14 are pneumatically coupled by a connector 18 which includes the two mating connectors 20 and 40 . The male connector 20, which is located at the end of the cuff tubing section 14 in this example, is shown in the enlarged view of FIGURE 2 . The male connector 20 includes a dome 22 with a fluid aperture 24 extending as a channel through the dome, through the body 36 of the connector, through a hose barb 26 to the proximal end 28 of the connector . I t is the purpose of the dome 22 to form a fluid-tight connection of the fluid aperture 24 when the male and female connectors are connected together as shown in FIGURE 1 . The body 36 of the male connector is not symmetrical ( is asymmetric) in four directions, that is , it is not square or circular for the reasons described below . The hose barb 26 will provide a fluid-tight connection to the hose or small bore tubing which is slipped over the barb to connect the connector to tubing . The male connector 20 has two arms 30a and 30b which will align with shoulders on the female connectors when the two connectors are coupled together . The distal surfaces 32a and 32b of the undercuts of the arms 30a and 30b are slightly tapered in the axial direction of the connector so that the mating arms and shoulders will pull the male and female connectors tightly together and compress the dome 22 in a fluid-tight fit when the two connectors are coupled together . The outer proximal surfaces of the undercuts contain ribs 34a and 34b which travel in mating channels in the female connector as the two connectors are coupled together . To prevent over-rotation when connecting the male and female connectors together, the ribs 34a and 34b of the male connector encounter stops in the female connector when the male and female connectors are fully engaged and coupled together .

The female connector 40 is shown in an enlarged view in FIGURE 3. At the proximal end ( top) of the female connector 40 is a cavity extension 41 with a cavity 42 which is sized and shaped to mate with the dome 22 of the male connector . In a constructed embodiment the cavity 42 is s lightly smaller than the dome 22 so that the dome is slightly compressed in the cavity when the male and female connectors are coupled together, thereby providing a good fluid- tight fit . At the bottom of the cavity 44 is a fluid aperture 44 which is in line with the fluid aperture 24 of the male connector when the male and female connectors are coupled together . The fluid aperture 44 extends as a channel through the body 46 of the female connector 40, through the hose barb 48 at the proximal end of the female connector, and to the proximal end 50 of the female connector . The body of the female connector has a similar cross-axial shape as the male connector, which is generally oval in this example . The female connector 40 has shoulders 52a and 52b which align with the distal arms 30a and 30b of the male connector when the two are coupled together . When engaged, the arms 30a and 30b of the male connector 20 fit into undercuts 54a and 54b of the female connector . The undercuts 54a and 54b of the female connector are similarly slightly tapered to pull the male and female connectors tightly together when j oined . Above the undercuts 54a and 54b are channels 56a and 56b (not visible in FIGURE 3 ) in which the ribs 34a and 34b of the male connector travel as the two connectors are joined together . The ribs 34a and 34b of the male connector encounter stops 58a and 58b at the ends of the channels when the male and female connectors are fully engaged .

In this example the male and female connectors also have an optional detent mechanism which provides a tactile sensation as the male and female connectors become fully engaged . In this example the female connector 40 has a small groove or depression 60a extending axial Iy between the undercut 54a and the channel 56a . A similar groove 60b (not visible in

FIGURE 3) is present on the other side of the female connector between undercut 54b and channel 56b . As the two connectors come into full engagement, the grooves 60a and 60b engage small projections extending from the walls of the undercuts of the arms 30a and 30b j ust above the ribs 34a and 34b . As the male and female connectors come into full engagement the projections snap into the grooves, producing a slight tactile sensation or clicking sound. Whether one or both of the sensation and sound are produced is controlled by the fabricator of the connectors by the characteristics of the design of the proj ections and grooves .

The male and female connectors 20 and 40 are coupled together by holding them in asymmetrical opposition with the dome 22 axially aligned with the cavity 42 as shown by arrows 70a and 70b in FIGURE 4 . The dome 22 of the male connector 20 is inserted into the cavity 42 of the female connector 40 and the two connectors are pressed together . The two connectors are then rotated in opposite directions as indicated by the arrows 72a and 72b . The outwardly extending wings of the cavity extension 41 will then be rotated into the undercuts of the arms 30a and 30b of the male connector 20 and the arms 30a and 30b are rotated into the undercuts 54a and 54b of the female connector 40 . The taper of the undercuts aids in pulling the two connectors snugly together . The ribs 34a and 34b of the male connector 20 are thereby moved into the channels 56a and 56b of the female connector 40 until the ribs contact the stops 58a and 58b of the female connector . At this point the detent mechanism 60 , 62 , if present, will snap together and produce its designed cl icking sound or tactile sensation . The two connectors are now securely joined together with the fluid apertures 24 , 44 aligned and sealed by the compression of the dome 22 in the cavity 42 . When coupled in this manner the asymmetrically shaped bodies 36, 46 of the two connectors are now symmetrically aligned as shown in FIGURE 1 .

The connectors are preferably formed of a polymeric material , preferably by injection molding . In a constructed embodiment the male connector was made of nylon and the female connector was made of polysulfone, although alternate materials may be used for either or both connectors . In the constructed implementation the male connector 20 which is attached to the pressure cuff 16 is formed of a s lightly softer material than the female connector

40 . This material difference enables the dome 22 of the male connector to better compress when fitted into the more rigid cavity 42 of the female connector, and the arms 30a, 30b to slightly compress under the compression of the taper of the undercuts of the arms 30 and the undercuts 54a, 54b of the female connector . It has been found that repeated connection and disconnection of the connectors can cause wear of the small projections of the detent mechanism, which is more likely when the male connector is made of a softer material . However, in the example of FIGURE 1 the pressure cuff 16, its hose line 14 , and its male connector 20 are a disposable part, whereas the hose line 12 for the monitoring instrument 10 and its female connector 40 are reusable . The wear of the male connector 20 in this example is thus of little consequence as the part is disposed of after its use with the patient is discontinued . Correspondingly, wear of the female connector of the harder material is negligible, and i ts usable life of repeated connection and disconnection is extended by the material difference .