Infants and children with an abnormality in their airway and lungs often require procedures to further investigate their lungs and improve their breathing. A very common way to do this is a flexible bronchoscopy. During the anaesthesia for this procedure, the anaesthetist delivers oxygen and monitors the adequacy of the child’s breathing. In this situation both the respiratory physician and the anaesthetist share the child’s airway for both delivery of oxygen and for placement of a small telescope to directly view the anatomy within the airway and lungs. It is impractical for the anaesthetist to place a breathing tube into the airway for delivery of oxygen as this obstructs the view.
It is not uncommon for the oxygen levels in the blood to fall (hypoxaemia) during these procedures. The procedure may need to be interrupted to correct this which can potentially compromise the safety of the child, prolong the procedure, increase exposure to anaesthetic agents and affect the success of the procedure. The interruptions are necessary as hypoxaemia remains the primary cause of anaesthetic-related death and morbidity. A recent anaesthetic audit showed that nearly a third of children undergoing flexible bronchoscopy procedures experienced low oxygen levels one or more times during the procedure.
Associate Professor Susan Humphreys, Queensland Children’s Hospital
Professor Britta Regli von Ungern-Sternberg, Perth Children’s Hospital
Professor Kristen Gibbens, Child Health Research Centre, The University of Queensland
The project was awarded $A89,999 (including scholarship) through the ANZCA research grants program for 2022.
The method which the anaesthetist chooses to give the oxygen to the child may help to prevent the occurrence of low oxygen levels. Traditionally anaesthetists have delivered oxygen via face mask or airway device which is placed inside the mouth above the voice box part of the airway at flow rates of up to 6 litres per minute. The research team investigated a new mode of oxygen delivery called Nasal High Flow. In Nasal High Flow, warm humidified oxygen is delivered to the airway via nasal cannulae, at a rate determined by the child’s weight. For example, Nasal High Flow can be delivered at rates of 2L/kg/min. Therefore, a 10kg infant would receive 20 litres per minute. Matching the flow delivered to the patient’s breathing allows the anaesthetist to deliver oxygen to the child at the required concentration. Recent studies have demonstrated Nasal High Flow is an effective alternative technique for oxygen delivery that can be safely used in infants and children with abnormal airways.
To date there have been no large-scale studies evaluating Nasal High Flow in comparison to other oxygenation techniques during flexible bronchoscopy in children. Therefore, the aim was to compare the two techniques using a randomised controlled trial in infants and children during flexible bronchoscopy. If Nasal High Flow reduces the risk of low oxygen levels, this has the potential to both improve the safety and the success of these procedures.
The outcomes were chosen to assess the feasibility of implementation of this trial, in two clinical settings, specifically in its recruitment and adherence to the protocol. it was found that the current high-flow protocol requires further education among both anaesthetic and respiratory physician teams to ensure successful implementation.
This protocol to compare the use of nasal high-flow with standard facemask/LMA oxygenation is likely feasible in its current form, however, clinical teams require significant training before trial start to increase acceptability of the technique clinically and in managing these cases with NHF.
A publication of the protocol can be found in Pilot and Feasibility Studies.
Flexible bronchoscopy insufflated and high-flow nasal oxygen pilot trial (BUFFALO protocol pilot trial)
S Humphreys, A Schibler, T Williams, S Spall, T Pham, T Atkins, V Goyal, ...Pilot and Feasibility Studies 10 (1), 45.
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