Nasal pressure swings as the measure of inspiratory effort in spontaneously breathing patients with de novo acute respiratory failure

Background- Excessive inspiratory effort could translate into self-inflicted lung injury, thus worsening clinical outcomes of spontaneously breathing patients with acute respiratory failure (ARF). Although esophageal manometry is a reliable method to estimate the magnitude of inspiratory effort, procedural issues significantly limit its use in daily clinical practice. The aim of this study is to describe the correlation between esophageal pressure swings (ΔP es ) and nasal (ΔP nos ) as a potential measure of inspiratory effort in spontaneously breathing patients with de novo ARF. Methods- From January 1 st , 2021 to September 1 st , 2021, 61 consecutive patients with ARF (83.6% related to COVID-19) admitted to the Respiratory Intensive Care Unit (RICU) of the University Hospital of Modena (Italy) and candidate to escalation of noninvasive respiratory support (NRS) were enrolled. Clinical features and tidal changes in esophageal and nasal pressure were recorded on admission and 24 hours after starting NRS. Correlation between ΔP es and ΔP nos served as primary outcome. The effect of ΔP nos measurements on respiratory rate and ΔP es was also assessed. Results- ΔP es and ΔP nos were strongly correlated at admission (R 2 =0.88, p<0.001) and 24 hours apart (R 2 =0.94, p<0.001). The nasal plug insertion and the mouth closure required for ΔP nos measurement did not result in significant change of respiratory rate and ΔP es . The correlation between measures at 24 hours remained significant even after splitting the study population according to the type of NRS (high-flow nasal cannulas [R 2 =0.79, p<0.001] or non-invasive ventilation [R 2 =0.95, p<0.001]). Conclusions- In a cohort of patients with ARF, nasal pressure swings did not alter respiratory mechanics in the short term and were highly correlated with esophageal pressure swings during spontaneous tidal breathing. ΔP nos might warrant further investigation as a measure of inspiratory effort in patients with ARF.