Effect of cannula size on oxygen saturation during nasal high flow therapy in newborns

Abstract

Background: Noninvasive respiratory support with nasal high flow (NHF) as an alternative to continuous positive airway pressure (CPAP) is commonly used in neonates who require supplemental O₂ to maintain arterial blood O₂ saturation (SpO₂). It has been shown that upsizing the high flow nasal cannula (HFNC) interface increases pressure during NHF and the beneficial role of positive airway pressure in respiratory failure is well known.

Objectives: To compare an effect of smaller (S) and larger (L) HFNC on SpO₂ in newborns with respiratory failure requiring NHF with supplemental O₂ as a standard therapy protocol.

Methods: In a prospective crossover study of 24 neonates with mean gestational age 36.4 ± 1.97 weeks, 2 types of HFNC with NHF 8 L/min were randomly assigned to 2 groups with 3 periods (30 min/period) in the following sequences L-S-L or S-L-S. The fraction of inspired oxygen (FiO₂) was set at the start of the first period to maintain SpO₂ between 90% and 94%. Apart from SpO₂, transcutaneous CO₂ and O₂ as well as respiratory frequency and effort using inductance plethysmography were measured. Each period was assessed by a fixed effects analysis of variances.

Results: NHF therapy via the L interface resulted in higher SpO₂ than via the S interface (92.2% vs. 91.3%) with a difference of 0.90 (CI 0.271 - 1.529), p = 0.006, at the same FiO₂. Individual actual and mean LOESS profile plots demonstrated the difference in SpO₂ throughout all 3 study periods. The secondary outcomes did not change significantly.

Conclusion: Enlarged prongs in the HFNC interface led to higher SpO₂, indicating an improved gas exchange that can be related to increased positive airway pressure.