Impact of low dose inhaled nitric oxide treatment in spontaneously breathing and intubated COVID-19 patients: a retrospective propensity-matched study

Abstract

The benefit of Inhaled nitric oxide (iNO) therapy in the setting of COVID-19-related ARDS is obscure. We performed a multicenter retrospective study to evaluate the impact of iNO on patients with COVID-19 who require respiratory support. This retrospective multicenter study included COVID-19 patients enrolled in the SCCM VIRUS COVID-19 registry who were admitted to different Mayo Clinic sites between March 2020 and June 2022 and required high-flow nasal cannula (HFNC), non-invasive ventilation (NIV), or invasive mechanical ventilation (IMV). Patients were included in the ‘spontaneously breathing’ group if they remained non-intubated or were initiated on an HFNC (± NIV) before intubation. Patients who got intubated without prior use of an HFNC (± NIV) were included in the ‘intubated group.’ They were further divided into categories based on their iNO usage. Propensity score matching (PSM) and inverse propensity of treatment weighting (IPTW) were performed to examine outcomes. Among 2767 patients included in our analysis, 1879 belonged to spontaneously breathing (153 received iNO), and 888 belonged to the intubated group (193 received iNO). There was a consistent improvement in FiO2 requirement, P/F ratio, and respiratory rate within 48 h of iNO use among both spontaneously breathing and intubated groups. However, there was no significant difference in intubation risk with iNO use among spontaneously breathing patients (PSM OR 1.08, CI 0.71–1.65; IPTW OR 1.10, CI 0.90–1.33). In a time-to-event analysis using Cox proportional hazard model, spontaneously breathing patients initiated on iNO had a lower hazard ratio of in-hospital mortality (PSM HR 0.49, CI 0.32–0.75, IPTW HR 0.40, 95% CI 0.26–0.62) but intubated patients did not (PSM HR: 0.90; CI 0.66–1.24, IPTW HR 0.98, 95% CI 0.73–1.31). iNO use was associated with longer in-hospital stays, ICU stays, ventilation duration, and a higher incidence of creatinine rise. This retrospective propensity-score matched study showed that spontaneously breathing COVID-19 patients on HFNC/ NIV support had a decreased in-hospital mortality risk with iNO use in a time-to-event analysis. Both intubated and spontaneously breathing patients had improvement in oxygenation parameters with iNO therapy but were associated with longer in-hospital stays, ICU stays, ventilation duration, and higher incidence of creatinine rise.