High-flow nasal cannula does not improve lowest SpO2 but prolongs safe apnoea time

Lowest SpO₂ during the first intubation attempt was the primary outcome, while secondary ones were incidence of SpO₂ falling below 90 percent and safe apnoea time.

During the first intubation attempt, the median lowest SpO₂ was 100 percent in both groups. The intervention group had a lower incidence of SpO₂ falling below 90 percent compared to the control group (15.5 percent vs 22.6 percent; adjusted relative risk, 95 percent confidence interval [CI], 0.37‒1.25). [Ann Acad Med Singap 2022;51:149-160]

In post hoc quantile regression analysis, the first quartile of lowest SpO₂ during the first intubation attempt was higher by 5.46 percent (95 percent CI, 1.48‒9.45; p=0.007) in the intervention group.

“Our study showed that HFNC was safe compared to our usual care,” the researchers said, noting that the safety of HFNC use in RSI had been duplicated in other existing literature. [Intensive Care Med 2019;45:447-458]

“Pending availability of more evidence, HFNC can be considered as a useful alternative in selected patients with contraindications to noninvasive ventilation (NIV), given its safety profile and better tolerance,” they added.

Positive pressure ventilation using NIV is an acceptable alternative strategy to improve SpO₂ for intubation. NIV appears superior to conventional oxygenation therapy in preoxygenation, but its use may be limited if patients are obtunded, have emesis, or are unable to tolerate face masks, according to the researchers. [EClinicalMedicine 2019;13:112-119; Crit Care Med 2019;47:e340-348]

HFNC, unlike NIV, allows apnoeic oxygenation during intubation without additional maneuvers, but studies compared these two have produced inconsistent results.

In a 2019 study on 313 participants, neither of the two modalities reduced the risk of severe hypoxia during intubation. However, a 2016 study suggested a potential synergistic benefit in combining NIV with HFNC. [Lancet Respir Med 2019;7:303-312; Intensive Care Med 2016;42:1877-1187]

“Nevertheless, combining the use of both NIV and HFNC has its problems of inadequate mask seal due to obstruction from the HFNC nasal cannula, as well as increase in procedural complexity and healthcare costs due to using two oxygen delivery devices,” the researchers said. “This may not be adequate given current dearth in evidence for this oxygenation method.”