Bain’s circuit (Mapelson D) by Zikrullah mallick

bain circuit

1. Bains circuit ( Mapelson D) Dr.zikrullah mallick

2. Breathing system An assembly of components,which connect the patients airway to the anaesthetic machine creating an artificial atmosphere,from and into which the patient breathes.

3. CLASSIFICATION Bidirectional flow Afferent reservoir systems Mapelson A Mapelson B Mapelson C Efferent reservoir system Mapelson D Mapelson E Mapelson F Bain’s system

4. Bain’s circuit They have a 6 mm diameter tube as afferent and carries fresh gas from machine end to patient end Reservoir bag is attached to efferent limb which is a wide bore corrugated tube

5. APL valve is placed near the reservoir bag In bain’s modification afferent and efferent limbs are coaxially place Inner tube 6mm Outer tube 22 mm Length 180 cm

6. Bain’s circuit

7. During inspiration fresh gas from machine, reservoir bag and corrugated tube flow to the tube During expiration, fresh gas to the system at the patient and expired gas gets continuously mixed with fresh gas as it flows back into corrugated tube and reservoir bag

8. Once the system is full, the excess gas is vented to the atmosphere through the APL valve during expiratory pause fresh gas continues to flow and fill the proximal portion of corrugated tube while mixed gas is vented through the valve During next inspiration, patient breaths fresh gas and mixed gas

9. During inspiration the patient gets ventilated with fresh gas flow from the machine, corrugated tube and reservoir bag During expiration the expired gas gets mixed with the fresh gas that is flowing into the system at patient end During expiratory pause the fresh gas continues to enter the system and pushes the mixed gas towards reservoir bag

10. When next ventilation is initiated patient gets ventilated with the gas in the corrugated tube. As the pressure in the system increases APL valve opens and contents of reservoir bag are released into the atmosphere

11. FGF requirement Spontaneus : 1.5 to 3 times minute ventilation (100 to 300 ml/kg/min) Controlled : 1 to 2 times minute ventilation

12. Test for Mapelson D By occluding the patient end and closing APL valve, pressurizing the system Open the APL valve Bag deflates easily

13. Tests for BAINS system Occlude the inner tube at the patient end after setting a low flow oxygen If the inner tube is intact the flow meter indicator will fall

14. Pethick test Activate oxygen flush and observe the bag Venturi effect caused by high flow oxygen at the patient end will create a negative pressure at the outer tube Bag deflates

15. Advantages Can be used in controlled / spontaneous respiration Adults and paediatrics Portable, light weight Scavenging of exhaled gases

16. Hazards Accidental disconnection of inner tube from machine end Double back itself and cause obstruction to fresh gas flow