Transnasal humidified rapid insufflation ventilatory exchange for oxygenation of children during apnoea: a prospective randomised controlled trial
This is a prospective, single-centre randomised controlled trial of using high-flow nasal canulae to safely prolong apnoea in children aged 1-6 years (10-20kg) scheduled for elective surgery using neuromuscular blockade. Patients were randomly allocated to three groups:
- Low-flow 100% oxygen 0.2mL/kg/min
- High-flow 100% oxygen at 2L/kg/min
- High-flow 30% oxygen at 2L/kg/min
All patients were subjected to a period of apnoea under standardised conditions until one of three predefined criteria were met; desaturation <95%, transcutaneous CO2 (tcCO2), or 10 minutes. Patients (i.e. family) were blinded to group allocation but theatre staff could not practically be blinded. Sample sizes and randomization were adequately specified and appropriate. The primary outcome was the time until any of the termination criteria were met. Secondary outcomes were the rate of rise of tcCO2 and safety outcomes.
No difference in median apnoea time was shown between low-flow 100% oxygen and high-flow 100% oxygen groups, both were about 7 minutes. Median apnoea time for the high-flow 30% oxygen group was shorter at about 3 minutes. There was no difference in the rate of rise of tcCO2 between any group.
This study addresses a useful question; can the use of high-flow nasal canula safely prolong the time to desaturation during apnoea in children after induction of anaesthesia, in a manner similar to that seen using THRIVE in adults? This would be handy when anaesthetising babies since they desaturate more quickly and have less reserve than adults due to their tendency for atelectasis, their low FRC and their higher relative oxygen consumption. While the use of humidified high-flow nasal canulae is well established in neonatal and paediatric intensive care, it has not yet found an established role in elective paediatric anaesthesia.
A relevant publication by Humphreys et al. last year showed that (in a similar population) the time to desaturation during apnoea was prolonged with the application of high-flow 100% oxygen, compared with a control group in room air alone. The current study shows a similar prolongation; however, this was seen equally with the application of 100% oxygen at both high- and low-flows, and NOT with the application of high-flow 30% oxygen. A control group of apnoea in room air was not included. Both studies agree that there is no difference in the rate of rise of transcutaneous CO2 across any group. Similarly, other recent studies have also demonstrated that the application of nasopharyngeal oxygen during apnoea for intubation prolongs the time to desaturation (Windpassinger M et al, Steiner JW et al).
This study is fairly well designed. However, for a study design of 60 patients, 93 families refused consent, which may have introduced selection bias. Also, the use of median in the results of this study is unusual and suggests the data were skewed (although the whisker plots look symmetric). Skewed data could arise due to use of 10 minutes as a somewhat arbitrary termination criterium, which was reached by both 100% oxygen groups, consequently masking a meaningful difference between these groups. The study would be strengthened by the inclusion of a room air control group. The population studied appears to be well suited to daily practice for paediatric anaesthetists in Australia.
Take Home Message
The administration of supplementary oxygen – not the use of high-flow nasal canulae per-se – prolongs the time to desaturation during apnoea after the induction of anaesthesia in children aged 1-6 years (10-20kg).
Reviewed by: Bae Corlette