amir salah modern anaesthetic machine modern anaesthetic machine 2 of 4

AMIR SALAH

MODERN ANAESTHETIC MACHINE

2 of 4

CLASSIFICATION OF BS I. MODE OF RESPIRATION 1. Spontaneous : patient use his own muscles of

respiration ; this needs neuronal and muscle power

2.Controlled :This needs no resistance to ventilation which can be achieved by means of : MR, central inhibition (anaesth,opioid,illness) or adaptation or cooperation in ICU patients.

II.RATE OF FGF 1. Low FGF : < ½ MV or < alveolar v. 2. High FGF := or > MV

III.REBREATHING 1.Total rebreathing. 2.Partial rebreathing. 3.No rebreathing.

IV. OPEN OR CLOSED 1. Open : Insufflation ? 2. Semi-open : Open-drop ansth.? 3. Semi-closed :Mapleson ? 4. Closed.

V. VALVES AND RESERVOIR PRESENCE 1. No valve or reservoir bag 2. Single adjustable spill valve and

reservoir bag 3. In addition one or more unidirectional valves ,this group can be categorized

into : With CO2

Without CO2

V. MAPLESON’S CIRCUITS In 1954 Mapleson described and analyzed

five different semi-closed anaesthetic systems and are designated A,B,C,D,E. Willis and co-workers added the F system to the five original in 1975

In this systems there is a steady flow of FGF supplying a variable and cyclical tidal

flow,in order to reach NO REBREATHING by alternating its components. Which are ?

Components of Mapleson’s

1. Breathing tubes.2. Fresh Gas Inlet.3. Adjustable Pressure-Limiting Valve (APL) Pressure Relief Valve ;Pop-Off Valve 4.Reservoir Bag (Breathing Bag).

1.Breathing tubes

Corrugated black (elephant tubing) BT made of rubber (reused) or plastic (disposable) with large diameter (22mm) creates a low resistance pathway which maintains its internal lumen patent when angled acutely.

BT volume must be more than peak inspiratory flow(30L/min) or in combination with bag.

2.Fresh Gas Inlet

The relative position of FGI is a key differentiating factor in Mapelson’s performance.

FGI is in the beginning of “A” and in the end of others.

3.Adjustable pressure-limiting valve APL valve present near patient in Mapleson’s

A,B,C and on the other end in D,E,F. If the gas flow is greater than the combined

uptake of the patient and circuit compliance ,so the excess gas must be allowed to go out through APL valve controlling the pressure buildup.

The exiting gas enter the operating room or preferably a scavenging system.

The APL valve should be fully open during spontaneous respiration. Assisted and controlled ventilation require positive pressure during inspiration to expand lungs. Partial closure of the APL valve limits gas exit, permitting positive pressure during bag compression

APL VALVE

Unidirectional ValveAMBU

4.Reservoir Bag It presents in the beginning of “A” and at the

end of the rest except “E” without. RB has elastic characteristics up to 5 K

pascal(60 cmH2O).It is designed to increase in compliance as volume increase .Three distinct phases are recognized in RB filling

1. full of 3 L capacity 2.Pressure rises to a peak press.

3.Plateau pressure This ceiling effect helps to protect the lungs if

APL valve is left in close position. A danger of RB is the possibility of bag material

to be sucked across inlet to prevent this a metal or a plastic basket is fitted into the connector.

function of RB1. It allows BS to meet peak inspiratory

flows that are greater than FGF.2. It allows manual artificial ventilation.3. monitors respiration in spontaneous vent4. It allows testing for FGF and circuit leak5. Increases compliance of system if there

is an obstruction to the outflow.