Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause severe pneumonia requiring invasive mechanical ventilation [1], in the context of atypical acute respiratory distress syndrome (ARDS) [2]. The magnitude of the epidemic places an unprecedented pressure on intensive care units (ICUs), making avoidance of intubation a critical issue. Supplemental oxygen is the first-line treatment of ARDS. When escalation is needed, pre-intubation approaches carry the risk of delaying intubation and increasing mortality [3]. Noninvasive ventilation (NIV) is not recommended [4] but high-flow nasal oxygen (HFNO) may decrease the need for intubation without impacting mortality [4, 5]. Mostly because of an early negative report [6], continuous positive airway pressure (CPAP) remains largely undocumented in ARDS. In SARS-CoV-2 pneumonia, evidence-based guidelines are lacking [7] but CPAP could prove useful [8]. In this context, on 20 March, 2020, the French learned society for respiratory medicine circulated a clinical management algorithm derived from the Italian experience and suggesting the use of CPAP in SARS-CoV-2 patients requiring oxygen escalation [8]. This algorithm was implemented in our department on 24 March, 2020, in a context of limited HFNO availability and environmental contamination concerns. We designed this retrospective study to evaluate the impact of the CPAP strategy on intubation rate. We compared the period immediately before the algorithm implementation (11-23 March, 2020) with the period immediately after (24 March to 8 April), testing the hypothesis that CPAP can avoid intubation in patients with severe forms of SARS-CoV-2 pneumonia over the first week of their management. This observational study with short-term historical controls was conducted in the 25-bed pulmonology unit of a 1600-bed university hospital (Pitié-Salpêtrière, Paris, France). It was approved by the institutional review board of the French learned society for respiratory medicine (CEPRO2020-024). Patients were informed of the use of their anonymised data and given the opportunity to refuse it.

The use of a mouthpiece to measure ventilatory flow with a pneumotachograph (PNT) introduces a major perturbation to breathing (“instrumental/observer effect”) and suffices to modify the respiratory behavior. Structured light plethysmography (SLP) is a non-contact method of assessment of breathing pattern during tidal breathing. Firstly, we validated the SLP measurements by comparing timing components of the ventilatory pattern obtained by SLP vs. PNT under the same condition; secondly, we compared SLP to SLP+PNT measurements of breathing pattern to evaluate the disruption of breathing pattern and breathing variability in healthy and COPD subjects. Measurements were taken during tidal breathing with SLP alone and SLP+PNT recording in 30 COPD and healthy subjects. Measurements included: respiratory frequency (Rf), inspiratory, expiratory, and total breath time/duration (Ti, Te, and Tt). Passing-Bablok regression analysis was used to evaluate the interchangeability of timing components of the ventilatory pattern (Rf, Ti, Te, and Tt) between measurements performed under the following experimental conditions: SLP vs. PNT, SLP+PNT vs. SLP, and SLP+PNT vs. PNT. The variability of different ventilatory variables was assessed through their coefficients of variation (CVs). In healthy: according to Passing-Bablok regression, Rf, TI, TE and TT were interchangeable between measurements obtained under the three experimental conditions (SLP vs. PNT, SLP+PNT vs. SLP, and SLP+PNT vs. PNT). All the CVs describing “traditional” ventilatory variables (Rf, Ti, Te, Ti/Te, and Ti/Tt) were significantly smaller in SLP+PNT condition. This was not the case for more “specific” SLP-derived variables. In COPD: according to Passing-Bablok regression, Rf, TI, TE, and TT were interchangeable between measurements obtained under SLP vs. PNT and SLP+PNT vs. PNT, whereas only Rf, TE, and TT were interchangeable between measurements obtained under SLP+PNT vs. SLP. However, most discrete variables were significantly different between the SLP and SLP+PNT conditions and CVs were significantly lower when COPD patients were assessed in the SLP+PNT condition. Measuring ventilatory activity with SLP preserves resting tidal breathing variability, reduces instrumental observer effect and avoids any disruptions in breathing pattern induced by the use of PNT-mouthpiece-nose-clip combination.

In amyotrophic lateral sclerosis (ALS), respiratory muscle weakness leads to respiratory failure. Non-invasive ventilation (NIV) maintains adequate ventilation in ALS patients. NIV alleviates symptoms and improves survival. In 2006, French guidelines established criteria for NIV initiation based on limited evidence. Their impact on clinical practice remains unknown. Our objective was to describe NIV initiation practices of the main French ALS tertiary referral centre with respect to guidelines. In this retrospective descriptive study, 624 patients followed in a single national reference centre began NIV between 2005 and 2013. We analysed criteria used to initiate NIV, including symptoms, PaCO, forced vital capacity, maximal inspiratory pressures and time spent with SpO <90% at night. At NIV initiation, 90% of patients were symptomatic. Median PaCO was 48 mmHg. The main criterion to initiate NIV was 'symptoms' followed by 'hypercapnia' in 42% and 34% of cases, respectively. NIV was initiated on functional parameters in only 5% of cases. Guidelines were followed in 81% of cases. In conclusion, despite compliance with French guidelines, the majority of patients are treated at the stage of symptomatic daytime hypoventilation, which suggests that NIV is initiated late in the course of ALS. Whether this practice could be improved by changing guidelines or increasing respiratory-dedicated resources remains to be determined.