Breathing circuit

A child undergoing general anaesthesia is breathing spontaneously using the Jackson- Rees modification of the Ayres T-Piece. Respiratory rate is 20/min and tidal volume is 75 ml. What is the minimum fresh gas flow required to prevent rebreathing?

• 750 ml/min

• 1500 ml/min

• 2250 ml/min

• 4500 ml/min

During general anaesthesia administered through a circle system, the soda lime absorbent is exhausted. No fresh soda lime is available for use. Which of the following is the most appropriate next step to prevent hypercapnia in this patient?

• Decreasing the dead space of the circle system

• Increasing the fresh gas flow

• Increasing tidal volume

• Switching to spontaneous ventilation

During induction of anesthesia, a patient is breathing isoflrane from a semiclosed circle absorber system. The temperature-compensated vaporizer is set to deliver isoflurane 1.5%. Which of the following will result in the lowest inspired concentration of isoflurane?

• Doubling the length of circle system hoses

• Changing from rubber to plastic breathing hoses

• Decreasing fresh gas flow

• Exhaustion of soda lime

The Bain Circuit

• Provides nearly identical delivered and inspired anesthetic concentrations

• Has the fresh gas flow inlet near the reservoir bag

• Is a non-rebreathing circuit at any fresh gas flow rate

• Is most efficient during spontaneous ventilation

Which Mapleson breathing circuit permits the LEAST amount of fresh gas inflow to prevent rebreathing during spontaneous ventilation?

• A

• B

• C

• D

• E

Which of the following is a characteristic of soda lime and Baralyme carbon dioxide absorption canisters used in circle systems?

• Calcium carbonate is a major end product

• Calcium dioxide absorption cools the anesthetic gases

• Flushing the canister with oxygen for six hours will regenerate 50% of the spent Baralyme

• Gases lose water vapour as they pass through the canisters

In a 5-kg child, the end-tidal carbon dioxide tension is 35 mmHg during spontaneous ventilation through Mapleson D system. Which single change is most likely to increase this value?

• Decreasing fresh gas flow

• Increasng respiratory minute volume

• Removing the reservoir bag

• Substituting larger bore tubing

During general anaesthesia, a patient’s spontaneous ventilation is manually assisted with a fresh gas flow of 5 L/min. A sudden malfunction of the pressure-relief (pop-off) valve of circle absorption system occurs, and the valve cannot be opened. The next appropriate next step is to

• Change to a smaller reservoir bag

• Increase total fresh gas flow

• Control ventilation manually

• Switch to mechanical ventilatory mode

A 32-year old woman is anesthesized for suboccipital craniotomy. During positioning, the capnograph shows an abrupt decrease in the slope of the expiratory upstroke. Which of the following is the most likely cause?

• Incompetent expiratory valve

• Incompetent neuromuscular block

• Kinked endotracheal tube

• Tracheal extubation

Two reasons that a circle system can cause increased inspired CO2 are:

• Absorbent granules exhausted and inadequate flow of fresh gas

• Absorbent granules exhausted and Low fresh gas flows

• Low fresh gas flows and faulty unidirectional valve

• Low fresh gas flows and use of Nitrous oxide