CLOSED-SYSTEM SUCTION CATHETER ASSEMBLIES
This invention relates to closed-system suction catheter assemblies.
Suction catheter assemblies may be used to remove secretions from within a tracheal tube or the respiratory passages of a patient. They are also used in other applications. Suction catheter assemblies may be of the closed-system kind in which the catheter is enclosed within a flexible envelope. Such assemblies have a manifold at the patient end with a sliding seal through which a suction catheter can be advanced and withdrawn. The flexible envelope is joined at one end to the manifold and encloses the catheter along its length. The other end of the envelope and the catheter are joined with a rear, machine end housing including a suction control valve and a connector. The connector connects the catheter to a suction source and the valve enables the clinician to control the suction applied by the catheter.
Examples of closed-system suction catheter assemblies are described in US5269768, US5300043, US4569344, US4638539, US4872579, US5167622, US5779687, US5325850, US5490503, US5419769, US5460613, US5349950, GB2394761, GB2400160, US6109259, US6227197, EP801577B, W096/09082, EP1239907B, EP1478424B, US6588427, EP1620148B, US2004/0221852, EP1911482A, EP1795217A, US2007/0282250, W02007/143502, US2008/0188833, US6227200, US6543451, EP1239909B, US6602219, EP1347798, W002/49680, US6609520, WO/055143, US6805125, US6923184,
US7021313, US7191782, W02004/101045, US7263997, W02004/103448, WOOO/15276, EP637257B, EP1113835B, EP1210957A, EP1237612B, US7152603, EP1267957B, US6978783, US2004/0007236, US2005/0211253, US2005/0211245, US2005/0235987, US7059322, W02004/032817, US2008/0135051, US4836199, US4850350,
US4967743, US5025806, US5083561, US5220916, US5215522, US5255676, US5277177, US5309902, US5333606, US5343857, US5487381, US5513628, US5791337, EP1343552A, WO02/49699, US6612304, EP1322371A, WO02/28463, US6629530, W002/051485, US6769430, EP1330284, WO02/36191, US6886561, W02004/034946, US7188623, W02006/014431, US7341059, W02005/094925, W02006/103233, W02007/030388, W02009/003135, US4838255, US5107829, US5133345, US5642726, US6702789, US7458955, US7273473, US5139018, US4327723, US4515592, US6099519, EP695556B, US5065754, US5730123, US5207220, US5309903, US7086402, US7597686, US7726315, WOl 1020985, WO2021/079079, W02020/178540 and GB2468946. Closed system suction catheters are available from various manufacturers including Smiths Medical, Kimberley Clark, Covidien and Viasys.
One problem with conventional closed-system suction catheter assemblies arises from the sliding seal in the patient end coupling. The length of the suction catheter and the outer envelope are chosen so that, when the suction catheter is pulled rearwardly to its full extent, the tip of the catheter projects a short distance through the sliding seal into the patient end manifold. This has the advantage that the ensuring that the tip of the catheter is aligned with the opening in the seal and also prevents the envelope being inflated by gas pressure in the patient manifold. Previous closed system catheter assemblies may, therefore, be manufactured and stored in this state, with the catheter extending through the sliding seal. The problem with this is that the relatively soft nature of the plastics material from which the catheter is extruded and the relatively tight interference fit exerted by the seal (needed to resist the positive pressure from the ventilator) means that the catheter is deformed by contact with the seal and takes on a permanent set in the form of a shallow indented annular groove or channel. This is unsightly and gives a poor feel as the catheter is advanced and retracted through the seal and during passage through the airway. Another disadvantage is that the indented groove weakens the tip of the catheter, which can be so severe, especially after repeated use and in small diameter catheters, that the tip of the catheter on the patient side of the groove detaches from the main part of the catheter and can enter the patient’s airway. This problem is exacerbated when the catheter is exposed to elevated temperatures such as during sterilization or storage.
It is an object of the present invention to provide an alternative closed-system suction catheter assembly.
According to one aspect of the present invention there is provided a closed-system suction catheter assembly of the kind having a suction catheter, a patient end fitting with a wiper seal through which the forward, patient end of the catheter can be advanced and retracted, a machine end fitting to which the rear end of the catheter is attached, and a flexible envelope enclosing the catheter and attached at its rear end with the machine end fitting, the forward end of the envelope being attached with the patient end fitting by means of a longitudinally-displaceable connection that is displaceable from a rear position relative to the patient end coupling in which the patient end tip of the catheter can be withdrawn through the rear wiper seal and a forward position in which the patient end tip of the catheter extends through the wiper seal and cannot be withdrawn through the rear of the wiper seal.
The longitudinally displaceable connection is preferably a sliding connection, such as a collar, and may be arranged to be retained in the forward position once displaced to this position so that the patient end tip of the catheter cannot thereafter be withdrawn rearwardly through the wiper seal. The patient end coupling preferably includes guide means on the machine side of the wiper seal to guide insertion of the patient end tip of the catheter through the wiper seal when the catheter is advanced forwardly.
A closed-system suction catheter assembly according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a side elevation view of the assembly;
Figure 2 is an enlarged sectional side elevation view of the patient end of the assembly in a storage state; and
Figure 3 is an enlarged sectional side elevation view of the patient end of the assembly in a state for use.
With reference first to Figure 1, the assembly has a rear, machine end fitting 1 with a ribbed, tapered male coupling 2 at its rear end adapted to receive one end of suction tubing 3 fitted on the coupling. Other forms of suction coupling are also available. The machine end fitting 1 includes some form of conventional valve 4 that the user can actuate to control suction applied to the machine end of a flexible, plastics suction catheter 5, which is fixed with the forward end of the machine end fitting. The catheter 5 extends forwardly to a patient end fitting or manifold 10. The catheter 5 is enclosed along its length between the machine end fitting 1 and the patient end fitting 10 within a flexible plastics envelope or sleeve 11, which is fixed at opposite ends to the forward end of the machine end fitting 1 and to the real end of the patient end fitting 10 respectively. In use, the patient end fitting 10 assembly is connected to the machine end of a tracheal tube 12 or other airway and the catheter 5 is manipulated through the envelope 11 to advance it forwardly through the patient end fitting and down the bore of the tracheal tube.
As so far described the assembly is conventional.
Figures 2 and 3 show the interior of the patient end fitting 10 with Figure 2 showing the condition after manufacture, during storage and before use. The patient end fitting 10 has a main housing or manifold 100 of generally cruciform or T-shape configuration with a patient end, female coupling 101 at one end having an internal tapered surface 102 adapted to make a sealing fit on the outside of a conventional 15mm male connector 103 fitted in the machine end of the tracheal tube 12. Other machine end connectors could be used. The opposite, machine end 104 of the manifold 100 has a tapered region 105 towards its patient end, which continues as an outer region with an external cylindrical region 106. An annular stop ring 107 projects outwardly of the manifold 100 between the tapered region 105 and the cylindrical region 106. The stop need not be a complete ring but could just be a single projection. The outer surface of the manifold 100 also has a locking surface 108 in the form of a shallow annular groove or channel adjacent the stop ring 107 on its machine side. Internally, the manifold 100 is moulded at its machine end with a guide surface in the form of a tapered formation 109 extending along about half the length of the cylindrical region 106. The tapered formation 109 varies in diameter from about twice the external diameter of the catheter 5 at its machine end to a diameter just greater than that of the catheter at its opposite, patient end. The cylindrical region 106 also includes within it a wiper seal 110 extending internally across the diameter of the region just forwardly of the tapered region 105. The wiper seal 110 is in the form of a flat disc of a flexible, resilient material having a small diameter hole 111 centrally through which the catheter 5 can be extended. In this way the edge of the hole 111 makes a close, sliding, sealing interference fit with the outside of the catheter 5. Other forms of sliding seal, such as a duckbill valve, could be used.
The manifold 100 is completed by two gas ports 120 and 121 projecting laterally in opposite directions between the patient end coupling 101 and the machine end 104 of the manifold. Both ports 120 and 121 open into the interior of the manifold 100. In operation, one of the ports 120 is connected to a gas supply tube and the other is connected to a gas return tube (neither shown) so that ventilation gas can be supplied to the tracheal tube 12 via the patient end manifold 100. In some ventilation systems where the same tube is used to supply and return gas it would only be necessary to use one of the ports, the other being capped closed or omitted.
The patient end of the envelope 11 is attached with the patient end fitting 10 by means of a longitudinally displaceable connection provided by a sliding collar 130 fitted in a telescoping fashion on the outside of the machine end 104 of the manifold 100. The collar 130 is cylindrical and has a circular section with an internal diameter that is a close sliding fit on the outside of the machine end 104 of the manifold 100. The rear, machine end of the collar 130 is sealingly attached to the forward, patient end of the envelope 11 by means of a mounting ring 131 embracing the collar on top of the envelope so that the envelope is sealingly attached to the collar. The mounting ring could be held by frictional engagement or by bonding. The collar 130 is displaceable from a rear position relative to the patient end fitting 10 to a forward position. The collar 130 also has a locking formation 132 at its forward, patient end, such as in the form of an inwardly-projecting lip. Other locking formations could be used. The collar 130 need not have a circular section providing it is a close sealing fit with the outside of the manifold
When the assembly is first made the sliding collar 130 is in the rear position shown in Figure 2 where it extends rearwardly beyond the rear end of the manifold 100 with just its forward end in contact with the rear, outside end of the manifold. In this position the patient end of the suction catheter 5 is located in the region of the tapered guide 109 to the rear of the wiper seal 110. In this state the catheter 5 does not extend through the wiper seal 110.
The assembly is stored in this state. When the assembly is to be used on a patient it is put into the condition shown in Figure 3 by sliding the collar 130 forwardly, in the patient direction, to a forward position as far as it will go, as limited by engagement with the ring stop 107. When the collar 130 is in this position its locking formation 132 engages in the locking groove 108 on the manifold 100 so that the collar cannot be subsequently slid back. Although it is preferable for the collar 130 to be locked in its forward position it is not essential for it to have any locking means. The length of the envelope 11 and of the suction catheter 5 are selected such that when the collar 130 is moved to this forward position it straightens and tightens the envelope causing the tip of the suction catheter to move forwardly through the wiper seal 110. The tapered guide surface 109 on the machine side of the seal 110 helps guide the tip of the catheter 5 centrally through the opening 111 of the wiper seal, which stretches to receive the catheter. The suction catheter 5 can then be advanced in the normal way by gripping through the envelope 11 until the tip of the catheter is positioned in the desired location in the tracheal tube 12 for suctioning. Suction is applied using the suction control valve 4 on the machine end fitting 1. When suctioning has been completed the catheter 5 is pulled back in so that its tip is again in the manifold 100 and extending through the wiper seal 110. Because the collar 130 is locked in the forward position the overall length of the envelope 11 (including the collar) is shorter than that of the catheter 5. This prevents the patient end tip of the catheter 5 being inadvertently drawn back through the wiper seal 110. The outside of the catheter 5, therefore, remains engaged by the seal 110, thereby preventing ventilator pressure inflating the envelope 11.
Although the catheter is engaged by the wiper seal during use it is not engaged during storage, which can be for months or years, so any deformation caused by the seal is minimal compared with conventional closed-system suction catheter assemblies. Also, the movement out and in of the manifold during each use means that there will be small differences in the locations at which the seal contacts the catheter each time it is withdrawn, thereby spreading out the loading and further reducing damage to the catheter.
The present invention can be applied to various different forms of suction catheter assembly, such as those having a dual lumen catheter and those having provision for irrigation in the patient end fitting. The invention is not limited to suction catheter assemblies for use with tracheal tubes but could be used with other tubes requiring suction.