Oxygen delivery devices

Low flow systems means low FiO₂

• True

• False

When tidal volume is decreased, the FiO₂ in a variable performance device is decreased if all other parameters remain constant.

• True

• False

In high flow devices, the FiO2 increases with increased minute ventilation in the patient

• True

• False

A 4 year old child is in PACU following hernia repair under general anaesthesia with caudal analgesia. He was well preoperatively except for history of mouth breathing and snoring. Grade 1 tonsillar enlargement is evident on oral examination. He requires supplemental oxygen in the postoperative period. Which of the following is incorrect choice?

• Nasal prongs

• Simple face mask

• Wafting oxygen near mouth via oxygen tubing

A 50 year old lady underwent laparoscopic cholecystectomy under general anaesthesia. She is transferred to PACU and requires oxygen supplementation. A simple face mask is attached. Flow rate is adjusted to 2 l/min which improved the SpO2 from 93% to 100%. The above management is appropriate in this patient.

• True

• False

In air entrainment devices, as the FiO₂ increases, the air:oxygen entrainment ratio _______

• increases

• decreases

• no change occurs

A non-rebreathing mask has the following features

• No valves

• Always has 4 valves

• Has 1 expiratory and 2 inspiratory valves

• Has 1 inspiratory and 2 expiratory valves

A 40 year old lady in the preoperative holding area awaiting emergency laparotomy for intestinal obstruction has a tidal volume of 350ml and a respiratory rate of 35 cycles per minute. Her room air saturation is 85%. Which of the following is the most appropriate choice for her?

• Simple face mask at 15 l/min

• Non-rebreathing bag with reservoir bag at 15 l/min

• Nasal canula at 4 L/min

• 60% Venturi mask

Calculate the FiO₂ reaching the patient when fresh gas flows of 5 l/min of air and 3 l/min of oxygen are administered via a closed system (no leaks).

• 0.3

• 0.4

• 0.5

• 0.6

Which of the following results in a higher FiO₂ in a Venturi device?

• Large cross-sectional area for oxygen and small air entrainment port

• Small cross-sectional area for oxygen and large air entrainment ports

• Increased minute ventilation in the patient

• Increase in total gas flows