NON RETURN VALVES (UNIDIRECTIONAL VALVES)<br />Dr.P.N.REDDY<br />DEPT.OF ANESTHESIOLOGY <br />NARAYANA MEDICAL COLLEGE<br />NELLORE<br />
Introduction <br />Useful in resuscitation equipment.<br />Remote areas where CO2 absorption not available.<br />Non rebreathing valve:<br />- It directs the FGF to the patient & releases expired air to atmos. Or to a scavenging system.<br />
VALVE TERMINOLOGY<br />VALVE BODY ASSEMBLY:<br /><ul><li>It is a housing with associated internal parts including one or more movable parts which opens,shuts or partially obstructs one or more parts.</li></ul>VALVE SEAT:<br />- 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.<br />
PATIENT PORT:<br /><ul><li>It is the part attached to the mask or ET tube.It has female 15mm with a concentric 22mm connector.</li></ul>EXHALATION PORT:<br />A channel through which exhaled gas escape to atm. Or scavenging system after passing through the valve.<br />
POSITIONAL VALVE:<br /><ul><li>It is one which must remain horizontal as it requires gravity to close it completely.</li></ul>NON POSITIONAL VALVES:<br />- It is closed by elastic tension or rubber or spring & may be used in any position.<br />
FLAP VALVE:<br />It is one in which movable part is made of flexible material & it is secured at its centre or by its edge.<br />FISH MOUTH VALVE:<br />- Its a valve in which two flaps approximate at midpoint. <br />
The flow of gases in one direction causes the flaps open like a fish mouth.Reversal of flow prevents retrograde flow.<br />
DISC VALVE:<br /><ul><li>Consists of flat disc made of plastic or metal.It is held in position by gravity or by a spring.</li></ul>MUSHROOM VALVE:<br />- It is a hollow balloon like device which when inflated occludes the opening.<br />
CLASSIFICATION OF VALVES<br /> BASED ON MECHANICAL CHARACTERISTICS:<br /><ul><li>Like presence or absence of springs,rubber flaps & knife edge etc.</li></ul>BASED ON FUNCTIONAL CLASSIFICATION <br /><ul><li>Like spontaneous ,controlled or both.
In spontaneous respiration pressure inside the valve is negative whereas in controlled ventilation it is positive.</li></li></ul><li>VALVES DESIGNED FOR SPONTANEOUS VENTILATION<br />During inspiration ,negative pressure closes the expiratory valve .<br />During expiration,positive pressure opens the exh. Valve.<br />If this used for controlled ventilation,exp.port must be closed during inspiration.<br />
VALVES DESIGNED FOR CONTROLLED VENTILATION<br />Duriung insp. Positive pressure opens the inlet valve & closes the exh. Port.<br />During exp. Gases escape through the exp.port.<br />If spontaneous ventilation is allowed pt. breathes atm. Air .<br />These valves are used for resuscitation purpose.<br />
VALVES DESIGNED FOR BOTH SP/CONTROLLED VENTILATION<br />Also called Automatic non rebreathing valves.<br />In these valves exh.port is closed & insp.port is opened whether it is spont. Or controlled.<br />During exh. Air escapes through unblocked exh.port & insp.port is blocked to prevent rebreathing.<br />
SPECIFIC VALVES<br />AMBU:<br /><ul><li>Classification : controlled resp.
The movable part consists of yellow plastic disc which is held on to the seat by a spring.
Locating pin centres the disc.</li></li></ul><li>
AMBU contd..<br />FUNCTION:<br />When bag is squeezed, the force of gas pushes the disc against seat B closing the exh. port & allowing gas to flow to pt.<br />During exh. The pressure on the bag side falls & the spring pushes the disc onto seat A.<br />Gases escape through exh.port.<br />If pt.breathesspont. Air enters through exh.part.<br />
AMBU contd..<br />CARE & CLEANING:<br />- it can be opened & cleaned.<br />- Guiding pin must be inserted properly.<br />
AMBU E VALVE<br />CLASS:<br /><ul><li>sp/controlled.
Construction: transparent plastic with inlet coloured blue .
Contains two moulded shutters – for inh. & exh.</li></li></ul><li>
FUNCTION:<br /><ul><li>-VE pressure during insp. Closes the exh. shutter& gas is drawn through inlet shutter.
Back flow: 9% of TV.</li></li></ul><li>AMBU E2 VALVE<br />CLASSIFICATION: SPONT/CONTROLLED.<br />Construction: clear plastic body with 1 shutters.<br />No exhalation shutter.<br />FUNCTION:<br />- -ve pressure during inh. Opens inh. Shutter & also air is drawn from exh. Channel .<br />
It is mixture of FGF & air.<br />During controlled venti.,during insp. Insp.shutteroccludes the exp. Channel & gases go to the pt.<br />During exh.insp. Shutter closes & gases go out.<br />
EVALUATION:<br />- RESISTANCE: not available.<br />- DEAD SPACE: 10ml.<br />- BACK FLOW: 9%.<br />CARE & CLEANING:<br />- It can be disassembled ,cleaned with soapwater or sterilizing solution.parts can be boiled or autoclaved.<br />
AMBU HESSE<br />It is similar to ambu E2 valve but bigger in size.<br />EVALUATION:<br />- resistance :0.2 -0.9 cmH2O.<br />- Back flow :7.3% of TV.<br />
FINK VALVE<br />CLASSIFICATION: SPONT/CONTROLLED.<br />CONSTRUCTION:body made of metal.<br /><ul><li>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.</li></li></ul><li>
This space can communicate to the atm.through a vent.<br />At the top of the valve an adjustable knob which is connected to rotating disc.<br />Knob turned max. counterclockwise,pressure tube communicates with the space above the diaphragm& vent to atm. Is closed.<br />
If the knob is turned clockwise disc closes the pressure tube & vent.<br />At an intermediate position vent & pressure tube are partially closed .<br />FUNCTION:<br />- spont: knob is turned clockwise ,insp.-ve pressure opens the insp.flap valve & closes the exp.flap valve.<br />
<ul><li>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.</li></li></ul><li>During exh.pr in the inlet dec. ,inh.flap closes ,diaphragm goes up,exh.flap opens.<br />EVALUATION:<br /><ul><li>DEAD SPACE:11.5CC
RESISTANCE:0.5-8cmH2O.</li></li></ul><li>CARE & CLEANING:<br /><ul><li>Can be disassembled ,washed with water & can be autoclaved.</li></li></ul><li>FRUMIN VALVE<br />CLASSI:spont/contr.<br />CONSTRUCTION:<br /><ul><li>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.</li></li></ul><li>
FUNCTION:sp.venti.<br /><ul><li>During insp.theinsp.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.</li></li></ul><li>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).<br />During exh. The pr at inlet drops soalso in the M valve & insp.valve is closed & gases go out.<br />
During exh.fish mouth valve closes ,gas escapes through exh.port.
contr. Same as above.</li></ul>EVALUATION:<br /><ul><li>RESISTANCE:0.3-2.8CMH2O.</li></li></ul><li>CARE & CLEANING:<br />- Can be disassembled,cleaned with water,chemicals ,can be autoclaved.<br />
LEWIS – LEIGH VALVE<br />CLASSI: sp/contr.<br />CONSTRUCTION:<br /><ul><li>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.</li></li></ul><li>
FUNCTION:<br /><ul><li>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.</li></li></ul><li><ul><li>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.</li></li></ul><li>RUBEN VALVE<br />CLASSI: sp/contr.<br />CONSTRUCTION:<br /><ul><li>Clear plastic body with metal fittings .
BACKLEAK – 30CC WITH 500ML TV.</li></li></ul><li>DISADVANTAGES:<br /><ul><li>With prolonged & repeated use,exp.leaf may curl & allow air dilution.</li></ul>CARE & CLEANING:<br /><ul><li>Can be washed ,gas sterilised .
Rubber valves should not be autoclaved or boiled.</li></li></ul><li>HEIDBRINK VALVE<br />APL valve, exp valve or pop off valve.<br />It allows expired air and surplus gases to go out without permitting entry of outside air even during –ve phase.<br />The pr required to open valve must be low.<br />It should not allow spont collapsing of R bag.<br />
CLASSI: spont/contr.<br />CONSTRUCTION: <br /><ul><li>Metal structure with a disc & spring .
Small grub screws & a groove prevents falling of the valve.</li></li></ul><li>
Hazards of unidirectional valves<br />External occlusion<br />Internal occlusion<br />
Advantages of unidirectional valves<br />CO2 Absorption system avoided<br />Light weight <br />Compact<br />Mobile<br />Inexpensive<br />Simple<br />Minute volume can be estimated<br />Less dead space, less resistance, less rebreathing<br />Composition of delivered and inspired gas is same<br />Better feel of lungs<br />
Disadvantages of unidirectional valves<br />Large volumes of inspired mixture leading to O.T. pollution<br />Higher cost , Explosion <br />Noisy and sticky valves<br />Some times two hands may be needed to ventilate<br />Cleaning and sterilisation is some what difficult<br />Valves must be located near the patient possible disconnection of E.T.tube<br />Increased resistance with higher flows<br />Some rebreathing can occur<br />Some difficulty to use with scavenging systems<br />
Disadvantages of unidirectional valves<br />No standardisation among the valves<br />More dead space in some valves in pediatric patients<br />Fresh gas flow must be matched to minute volume.<br />