unidirectional valves

1. 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.

3. VALVE TERMINOLOGY
 VALVE 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.

4.  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.

5.  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.

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.

8.  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.

9. 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.

10. VALVES DESIGNED FOR
SPONTANEOUS VENTILATION
 During 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.

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.

13. SPECIFIC VALVES
 AMBU:
- 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.

15. 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.
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.
1.

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

17. AMBU E VALVE
 CLASS:
- sp/controlled.
- Construction: transparent plastic with inlet coloured
blue .
- Contains two moulded shutters – for inh. & exh.

19.  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.

20.  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.

21. AMBU E2 VALVE
 CLASSIFICATION: 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 .

23.  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.

24.  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.

25. 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.

26. FINK VALVE
 CLASSIFICATION: 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.

29.  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.

30.  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.

31. - 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.

32.  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.

33.  CARE & CLEANING:
- Can be disassembled ,washed with water & can be
autoclaved.

34. FRUMIN VALVE
 CLASSI: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.

36.  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.

37.  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.

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

39. LAERDAL VALVE
 CLASSI: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.

42. - 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.

43.  CARE & CLEANING:
- Can be disassembled,cleaned with water,chemicals
,can be autoclaved.

44. LEWIS – LEIGH VALVE
 CLASSI: 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.

46.  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.

47. - 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.

48. RUBEN VALVE
 CLASSI: 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.

50. - 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.

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

52.  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 .

53. STEPHEN – SLATER VALVE
 CLASSI: 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.

55. - -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.

56.  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.

57. HEIDBRINK VALVE
 APL 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.

58.  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.

60. Hazards of unidirectional valves
1. External occlusion
2. Internal occlusion

61. Advantages of unidirectional valves
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
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

62. Disadvantages of unidirectional valves
1.
2.
3.
4.
5.
6.
7.
8.
9.
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

63. Disadvantages of unidirectional valves
10. No standardisation among the valves
11. More dead space in some valves in pediatric patients
12. Fresh gas flow must be matched to minute volume.