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

Abstract

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, 2021, to September 1, 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 non-invasive respiratory support (NRS) were enrolled. Clinical features and tidal changes in esophageal and nasal pressure were recorded on admission and 24 h 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 (R² = 0.88, p < 0.001) and 24 h apart (R² = 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 h remained significant even after splitting the study population according to the type of NRS (high-flow nasal cannulas [R² = 0.79, p < 0.001] or non-invasive ventilation [R² = 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.

Trial registration: NCT03826797 . Registered October 2016.

Keywords: Acute respiratory failure; COVID-19; Endotracheal intubation; Esophageal pressure swings; Inspiratory effort; Nasal pressure swings; Non-invasive Mechanical ventilation; Respiratory monitoring; Self-inflicted lung injury.

Fig. 1

A Simultaneous positioning of esophageal catheter for ΔP_es assessment and nasal plug made of hypoallergenic foam ear plug equipped with a 16 Gauge polyurethane intravenous cannula for ΔP_nos measurements. The contralateral nostril was kept open. B, C Simultaneous assessment of ΔP_nos and ΔP_es during unsupported spontaneous breathing, showing in phase waveforms with a 196 ms time latency of ΔP_nos over the onset of inspiratory effort captured by ΔP_es. D, E Simultaneous assessment of ΔP_nos and ΔP_es, showing decremental inspiratory effort after NIV placement

Fig. 2

Pearson’s R showing correlation between ΔP_es and ΔP_nos at baseline (A), when all patients were assisted with HFNC (R² = 0.88, p < 0.001), and at 24 h (B, R² = 0.94, p < 0.001), with most patients receiving NIV. At both time points ΔP_es and ΔP_nos showed strong correlation

Fig. 3

Histogram bars illustrating the distribution of ΔP_es/ΔP_nos ratio at baseline and at 24 h. The ratio was not different between baseline and 24 h (p = 0.41)