Helmet CPAP to treat hypoxic pneumonia outside the ICU: an observational study during the COVID-19 outbreak

Abstract

Background: Respiratory failure due to COVID-19 pneumonia is associated with high mortality and may overwhelm health care systems, due to the surge of patients requiring advanced respiratory support. Shortage of intensive care unit (ICU) beds required many patients to be treated outside the ICU despite severe gas exchange impairment. Helmet is an effective interface to provide continuous positive airway pressure (CPAP) noninvasively. We report data about the usefulness of helmet CPAP during pandemic, either as treatment, a bridge to intubation or a rescue therapy for patients with care limitations (DNI).

Methods: In this observational study we collected data regarding patients failing standard oxygen therapy (i.e., non-rebreathing mask) due to COVID-19 pneumonia treated with a free flow helmet CPAP system. Patients' data were recorded before, at initiation of CPAP treatment and once a day, thereafter. CPAP failure was defined as a composite outcome of intubation or death.

Results: A total of 306 patients were included; 42% were deemed as DNI. Helmet CPAP treatment was successful in 69% of the full treatment and 28% of the DNI patients (P < 0.001). With helmet CPAP, PaO2/FiO2 ratio doubled from about 100 to 200 mmHg (P < 0.001); respiratory rate decreased from 28 [22-32] to 24 [20-29] breaths per minute, P < 0.001). C-reactive protein, time to oxygen mask failure, age, PaO2/FiO2 during CPAP, number of comorbidities were independently associated with CPAP failure. Helmet CPAP was maintained for 6 [3-9] days, almost continuously during the first two days. None of the full treatment patients died before intubation in the wards.

Conclusions: Helmet CPAP treatment is feasible for several days outside the ICU, despite persistent impairment in gas exchange. It was used, without escalating to intubation, in the majority of full treatment patients after standard oxygen therapy failed. DNI patients could benefit from helmet CPAP as rescue therapy to improve survival.

Trial registration: NCT04424992.

Keywords: Coronavirus pneumonia; Covid-19; Helmet continuous positive airways pressure CPAP; Noninvasive ventilation; Positive end expiratory pressure PEEP.

Conflict of interest statement

AC has a patent and received consultancy fees from Flowmeter for a topic possibly related to this article; GB has a patent and received consultancy fees from Flowmeter, lecturing fees from Dimar SRL and Intersugical SPA for a topic possibly related to this article; GF received lecturing fees from Dimar SRL. Other authors have no COI to disclose no conflict of interest.

Figures

Fig. 1

PaO2/FiO2 ratio increase with helmet CPAP therapy. The number of patients showing severe and moderate-to-severe gas exchange impairment is reduced shortly after start of helmet CPAP therapy (P < 0.001 by Chi-Square, panel a). PaO2/FiO2 ratio increase was higher among patients showing a more severe gas exchange impairment (P < 0.001 for helmet CPAP effect and for its interaction with severity class by RM Anova, panel b)

Fig. 2

C-reactive protein levels and gas exchange impairment severity. C-reactive protein levels were not associated with gas exchange impairment severity during standard oxygen therapy (grey boxes, P = 0.088 by Anova). Patients showing a persistently severe gas exchange impairment despite helmet CPAP treatment (i.e., non-responders), showed higher levels of C-reactive proteins (white boxes, P = 0.009 by Anova). Boxes represent median and 25–75 percentiles; filled circles represent 5th and 95th percentiles

Fig. 3

Treatment outcome among patients with or without limitations of care. Helmet CPAP therapy resulted effective in the majority of patients without any limitation of care (Full treatment). Helmet CPAP represented a valuable rescue therapy for patients who had failed standard oxygen therapy and had a Do Not Intubate (DNI) order

Fig. 4

oxygenation improvement with helmet CPAP therapy. PaO2/FiO2 ratio increased with helmet CPAP therapy both in successful (Hospital discharge) and failure (intubated or non survivors) patients (P < 0.001 for CPAP effect). Patients in the successful treatment group showed a higher oxygenation response to CPAP (P = 0.002 for interaction between CPAP effect and Outcome by RM Anova)

Fig. 5

Helmet CPAP failure at 28 days. Probability of helmet CPAP failure at 28 days is presented stratifying the same population of patients depending on PaO2/FiO2 ratio measured either during standard oxygen (panel a) or during helmet CPAP (panel b). While a PaO2/FiO2 ratio below 100 mmHg with standard oxygen therapy is a weak predictor of failure (50% probability), showing the same oxygenation impairment during helmet CPAP is associated with a high probability of failure (80%, P < 0.001 by Log Rank for both)