Retrospective Evaluation of the Correlation Between Pa2:FiO2 and SpO2 Ratios in Dogs Undergoing High-Flow Nasal Cannula Oxygen Therapy.

Background: In veterinary medicine, high-flow nasal cannula oxygen therapy (HFNT) has gained popularity in managing hypoxemic respiratory failure, bridging the gap between conventional oxygen therapy and mechanical ventilation. The SpO₂:FiO₂ (SF) ratio could be useful in assessing oxygenation impairment in dogs undergoing HFNT. The current study aimed to determine whether the SF ratio correlates with the PaO₂:FiO₂ (PF) ratio in dogs undergoing HFNT.

Key findings: A total of 30 data pairs with concurrent SpO₂ and PaO₂ measurements were identified from 19 dogs treated with HFNT from two university veterinary teaching hospitals. PF and SF ratios were measured when PaO₂ fell between 74 and 129 mm Hg. The median SF and PF ratios were 186 (interquartile range: 97-243) and 168 (interquartile range: 108-297), respectively. SF ratios were strongly correlated with PF ratios (rho = 0.86 [95% confidence interval: 0.73-0.93], P < 0.001, weighted r = 0.89 [95% confidence interval: 0.74-0.96]).

Significance: Preliminary results suggest a statistically significant positive correlation between SF and PF ratios in dogs treated with HFNT. This study provides data that can be used to calculate appropriate sample sizes for subsequent studies investigating the specific SF ratios corresponding with the PF ratios as the criteria for assessing hypoxemia.