1. NON RETURN VALVES (UNIDIRECTIONAL VALVES) Dr.P.N.REDDY DEPT.OF ANESTHESIOLOGY NARAYANA MEDICAL COLLEGE NELLORE
2. Introduction Useful in resuscitation equipment. Remote areas where CO2 absorption not available. Non rebreathing valve: - It directs the FGF to the patient & releases expired air to atmos. Or to a scavenging system.
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6. FLAP VALVE: It is one in which movable part is made of flexible material & it is secured at its centre or by its edge. FISH MOUTH VALVE: - Its a valve in which two flaps approximate at midpoint.
7. The flow of gases in one direction causes the flaps open like a fish mouth.Reversal of flow prevents retrograde flow.
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11. VALVES DESIGNED FOR CONTROLLED VENTILATION Duriung insp. Positive pressure opens the inlet valve & closes the exh. Port. During exp. Gases escape through the exp.port. If spontaneous ventilation is allowed pt. breathes atm. Air . These valves are used for resuscitation purpose.
12. VALVES DESIGNED FOR BOTH SP/CONTROLLED VENTILATION Also called Automatic non rebreathing valves. In these valves exh.port is closed & insp.port is opened whether it is spont. Or controlled. During exh. Air escapes through unblocked exh.port & insp.port is blocked to prevent rebreathing.
16. The movable part consists of yellow plastic disc which is held on to the seat by a spring.
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18. AMBU contd.. FUNCTION: When bag is squeezed, the force of gas pushes the disc against seat B closing the exh. port & allowing gas to flow to pt. During exh. The pressure on the bag side falls & the spring pushes the disc onto seat A. Gases escape through exh.port. If pt.breathesspont. Air enters through exh.part.
19. AMBU contd.. CARE & CLEANING: - it can be opened & cleaned. - Guiding pin must be inserted properly.
29. It is mixture of FGF & air. During controlled venti.,during insp. Insp.shutteroccludes the exp. Channel & gases go to the pt. During exh.insp. Shutter closes & gases go out.
30. EVALUATION: - RESISTANCE: not available. - DEAD SPACE: 10ml. - BACK FLOW: 9%. CARE & CLEANING: - It can be disassembled ,cleaned with soapwater or sterilizing solution.parts can be boiled or autoclaved.
31. AMBU HESSE It is similar to ambu E2 valve but bigger in size. EVALUATION: - resistance :0.2 -0.9 cmH2O. - Back flow :7.3% of TV.
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35. This space can communicate to the atm.through a vent. At the top of the valve an adjustable knob which is connected to rotating disc. Knob turned max. counterclockwise,pressure tube communicates with the space above the diaphragm& vent to atm. Is closed.
36. If the knob is turned clockwise disc closes the pressure tube & vent. At an intermediate position vent & pressure tube are partially closed . FUNCTION: - spont: knob is turned clockwise ,insp.-ve pressure opens the insp.flap valve & closes the exp.flap valve.
73. Sticking of bobbin & exh.valve.CARE & CLEANING: - Cleaned by flushing with soap water,chemicalsolutins. Deteriorates when exposed to heat . - Can be gas sterilised .
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75. Has 2 rubber flaps each secured by a shaft at centre .FUNCTION: - insp. –ve pr opens the inh. Flap valve allowing the gas to the pt.
89. Advantages of unidirectional valves CO2 Absorption system avoided Light weight Compact Mobile Inexpensive Simple Minute volume can be estimated Less dead space, less resistance, less rebreathing Composition of delivered and inspired gas is same Better feel of lungs
90. Disadvantages of unidirectional valves Large volumes of inspired mixture leading to O.T. pollution Higher cost , Explosion Noisy and sticky valves Some times two hands may be needed to ventilate Cleaning and sterilisation is some what difficult Valves must be located near the patient possible disconnection of E.T.tube Increased resistance with higher flows Some rebreathing can occur Some difficulty to use with scavenging systems
91. Disadvantages of unidirectional valves No standardisation among the valves More dead space in some valves in pediatric patients Fresh gas flow must be matched to minute volume.
