NON RETURN VALVES (UNIDIRECTIONAL VALVES)

Dr.P.N.REDDYDEPT.OF ANESTHESIOLOGY

NARAYANA MEDICAL COLLEGENELLORE

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.

VALVE TERMINOLOGYVALVE BODY ASSEMBLY:- It is a housing with associated internal parts

including one or more movable parts which opens,shuts or partially obstructs one or more parts.

VALVE SEAT:- It is a surface usually annular,with an opening

which maybe partially or completely obstructed by a movable part to direct or obstruct the flow.

PATIENT PORT:- It is the part attached to the mask or ET

tube.It has female 15mm with a concentric 22mm connector.

EXHALATION PORT:A channel through which exhaled gas escape to

atm. Or scavenging system after passing through the valve.

POSITIONAL VALVE:- It is one which must remain horizontal as it

requires gravity to close it completely.NON POSITIONAL VALVES:- It is closed by elastic tension or rubber or

spring & may be used in any position.

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.

The flow of gases in one direction causes the flaps open like a fish mouth.Reversal of flow prevents retrograde flow.

DISC VALVE:- Consists of flat disc made of plastic or

metal.It is held in position by gravity or by a spring.

MUSHROOM VALVE:- It is a hollow balloon like device which when

inflated occludes the opening.

CLASSIFICATION OF VALVES BASED ON MECHANICAL

CHARACTERISTICS:- Like presence or absence of springs,rubber

flaps & knife edge etc.BASED ON FUNCTIONAL CLASSIFICATION - Like spontaneous ,controlled or both.- In spontaneous respiration pressure inside

the valve is negative whereas in controlled ventilation it is positive.

VALVES DESIGNED FOR SPONTANEOUS VENTILATIONDuring inspiration ,negative pressure closes

the expiratory valve .During expiration,positive pressure opens the

exh. Valve.If this used for controlled ventilation,exp.port

must be closed during inspiration.

VALVES DESIGNED FOR CONTROLLED VENTILATIONDuriung 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.

VALVES DESIGNED FOR BOTH SP/CONTROLLED VENTILATIONAlso 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.

SPECIFIC VALVESAMBU:- Classification : controlled resp.- Construction: Body is clear plastic or metal.- Contains 2 seats .- The movable part consists of yellow plastic

disc which is held on to the seat by a spring.- Locating pin centres the disc.

AMBU contd..FUNCTION:1. When bag is squeezed, the force of gas

pushes the disc against seat B closing the exh. port & allowing gas to flow to pt.

2. During exh. The pressure on the bag side falls & the spring pushes the disc onto seat A.

3. Gases escape through exh.port.4. If pt.breathes spont. Air enters through

exh.part.

AMBU contd..CARE & CLEANING: - it can be opened & cleaned.- Guiding pin must be inserted properly.

AMBU E VALVECLASS:- sp/controlled.- Construction: transparent plastic with inlet

coloured blue .- Contains two moulded shutters – for inh. &

exh.

FUNCTION:- -VE pressure during insp. Closes the exh.

shutter& gas is drawn through inlet shutter.- During contro. Venti. Positive pressure opens

insp. Shutter & occludes exh.shutter.- During exp. Insp. Shutter collapses & exp.

Shutter opens.

If there is overflow both shutters open & vent the gases out.

EVALUATION:- Resistance : 0.6 – 0.25.- Dead space: 10ml.- Back flow: 9% of TV.

AMBU E2 VALVECLASSIFICATION: SPONT/CONTROLLED.Construction: clear plastic body with 1

shutters.No exhalation shutter.FUNCTION:- -ve pressure during inh. Opens inh. Shutter &

also air is drawn from exh. Channel .

It is mixture of FGF & air.During controlled venti.,during insp.

Insp.shutter occludes the exp. Channel & gases go to the pt.

During exh.insp. Shutter closes & gases go out.

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.

AMBU HESSEIt is similar to ambu E2 valve but bigger in

size.EVALUATION:- resistance :0.2 -0.9 cmH2O.- Back flow :7.3% of TV.

FINK VALVECLASSIFICATION: SPONT/CONTROLLED.CONSTRUCTION:body made of metal.- A flexible diaphragm is positioned above the

exh.port.- A pressure tube leads from the inlet side of

the insp.flap valve to the space above the diaphragm.

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. counterclock wise,pressure tube communicates with the space above the diaphragm& vent to atm. Is closed.

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.

- During exh.insp.valve is closed by exhaled

gas & it escapes through exh.port.

- Cotn.ventilation:knob turned fully counter

clockwise bag squeezes the pr in the inlet inc.

& it is transmitted to the space above the

diaphragm & it is pushed on to the exp.flap.

Gases go to the pt.

During exh.pr in the inlet dec. ,inh.flap closes ,diaphragm goes up,exh.flap opens.

EVALUATION:- DEAD SPACE:11.5CC- BACK FLOW: NO- RESISTANCE:0.5-8cmH2O.

CARE & CLEANING:- Can be disassembled ,washed with water &

can be autoclaved.

FRUMIN VALVECLASSI:spont/contr.CONSTRUCTION:- Consists of a clear plastic body containing

rubber or silicon insp. flap & an inflating rubber valve which covers the exh.port.

- A pr channel connects the mushroom valve with inlet.

FUNCTION:sp.venti.

- During insp.the insp.valve is opened & fresh air

drawn towards the pt.

- Normal resting position of the M valve seals off

the exp.port.

- During inadequate gas flow the –ve pr during

insp. Collapses the M valve & exp.port is also

opened & atm.air is drawn in.

During contr.venti. The pr in the inlet & M

valve is same but as the area of M valve is

more it seals off the exp.valve(prmultiplied by

area).

During exh. The pr at inlet drops soalso in

the M valve & insp.valve is closed & gases go

out.

EVALUATION:- RESISTANCE:1.5CMH2O.- No back leak.CARE:- It can be disassembled,cleaned & can be gas

sterilised.

LAERDAL VALVECLASSI:spont/contr.CONSTRUCTION:- It is a clesr plastic body & yellow rubber

insp.fish mouth valve with a circular flange .- A circular exh.flap valve occludes the

exh.port.FUNCTION: SP.- During insp. Fish mouth valve allows air to go

to the pt.

- exh. Flap prevents inh.of room air.- During exh.fish mouth valve closes ,gas

escapes through exh.port.- contr. Same as above.EVALUATION:- RESISTANCE:0.3-2.8CMH2O.

CARE & CLEANING:- Can be disassembled,cleaned with

water,chemicals ,can be autoclaved.

LEWIS – LEIGH VALVECLASSI: sp/contr.CONSTRUCTION:- Consists of a clear plastic body with a

chimney which can be rotated by 90degrees.- This changes the position of exh.valve seat at

the bottom of the chimney.- A disc type valve is located at the top of the

exh.chimney.

FUNCTION:- Spont. vent: if flap valve is rotated counter

clockwise ,insp.gas goes to the pt. Disc valve prevents fresh air entry to th pt .During exp.flap valve seat & gas goes to the chimney.

- Contr.venti: chimney is rotated clockwise 90degrees,the flap valve can seat on either the ridge or the body or lower edge of chimney.

- During insp. Flap valve blocks exh.valve, gas goes to the pt.

- During exp.the flap valve seats on the ridge of the body allowing the gas to the chimney & gas goes out through disc valve.

- During overflow – both valves are opened.

RUBEN VALVECLASSI: sp/contr.CONSTRUCTION:- Clear plastic body with metal fittings .- Blue- inlet .- Red -patient- Gold -outlet.- Inside the body ,a spool shaped piston held on

to a seat A by a spring.

- A disc type valve is near the exh.port.FUNCTION:- CONTR.VENTI – during insp. The piston is

pushed to right against seat B .- Gas enters the pt.- Exp.valve prevents the rush of atm.air.- During exp. ,as the pr drops the spring

pushes the piston against the seat A & exp.valve opens.

Spont.vent: - exp. Valve will not be there .- Pt. takes atm air.EVALUATION:- RESISTANCE: 0.8-1CMH2O.- Back leak :5%.- Dead space : 9ml.

DISADVANTAGES:

- Clicking noise.

- Sticking of valve in insp. Position.

- Sticking of bobbin & exh.valve.

CARE & CLEANING:

- Cleaned by flushing with soap water,chemical solutins.

Deteriorates when exposed to heat .

- Can be gas sterilised .

STEPHEN – SLATER VALVECLASSI: spont.CONSTRUCTION:- Valve body made of metal.- 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.

- -ve pr keeps the exh.flap closed.- Exp. -- posi pr opens the exp. Valve & closes

the insp flap.EVALUATION:- RESISTANCE – 1.75CMH2O.- DEADSPACE – 10CC.- BACKLEAK – 30CC WITH 500ML TV.

DISADVANTAGES:- With prolonged & repeated use,exp.leaf may

curl & allow air dilution.CARE & CLEANING:- Can be washed ,gas sterilised .- Rubber valves should not be autoclaved or

boiled.

HEIDBRINK VALVEAPL valve, exp valve or pop off valve.

It allows expired air and surplus gases to go out

without permitting entry of outside air even during

–ve phase.

The pr required to open valve must be low.

It should not allow spont collapsing of R bag.

CLASSI: spont/contr.CONSTRUCTION: - Metal structure with a disc & spring .- Disc rests on a “knife edge” seating.- It has a stem to ensure proper position.- Clockwise closure ,anticlockwise open.- Screw down fully closes the valve.- Small grub screws & a groove prevents

falling of the valve.

Hazards of unidirectional valves

1.External occlusion

2.Internal occlusion

Advantages of unidirectional valves1. CO2 Absorption system avoided

2. Light weight 3. Compact4. Mobile5. Inexpensive6. Simple7. Minute volume can be estimated8. Less dead space, less resistance, less

rebreathing9. Composition of delivered and inspired gas is

same10.Better feel of lungs

Disadvantages of unidirectional valves1. Large volumes of inspired mixture leading

to O.T. pollution2. Higher cost , Explosion 3. Noisy and sticky valves4. Some times two hands may be needed to

ventilate5. Cleaning and sterilisation is some what

difficult6. Valves must be located near the patient

possible disconnection of E.T.tube7. Increased resistance with higher flows8. Some rebreathing can occur9. Some difficulty to use with scavenging

systems

Disadvantages of unidirectional valves

10.No standardisation among the valves11.More dead space in some valves in pediatric

patients12.Fresh gas flow must be matched to minute

volume.

Thank u.