Prone ventilation in H1N1 virus-associated severe acute respiratory distress syndrome: A case series.

BACKGROUND: Management of H1N1 viral infection-associated acute respiratory distress syndrome (ARDS) has primarily been focused on lung protective ventilation strategies, despite that mortality remains high (up to 45%). Other measures to improve survival are prone position ventilation (PPV) and extracorporeal membrane oxygenation. There is scarcity of literature on the use of prone ventilation in H1N1-associated ARDS patients.

METHODS: In this retrospective study, all adult patients admitted to medical intensive care unit (ICU) with H1N1 viral pneumonia having severe ARDS and requiring prone ventilation as a rescue therapy for severe hypoxemia were reviewed. The patients were considered to turn prone if PaO2 /FiO2 ratio was <100 cmH2 O and PaCO2 was >45 cmH2 O; if no progressive improvement was seen in PaO2 /FiO2 over a period of 4 h, then patients were considered to turn back to supine. Measurements were obtained in supine (baseline) and PPV, after 30-60 min and then 4-6 hourly.

RESULTS: Eleven adult patients with severe ARDS were ventilated in prone position. Their age range was 26-59 years. The worst PaO2 /FiO2 ratio range on the day of invasive ventilation was 48-100 (median 79). A total of 39 PPV sessions were done, with a range of 1-8 prone sessions per patient (median three sessions). Out of the 39 PPV sessions, PaO2 /FiO2 ratio and PaCO2 responder were 38 (97.4%) and 27 (69.2%) sessions, respectively. The median ICU stay and mechanical ventilation days were 15 (range: 3-26) and 12 (range: 2-22) days, respectively. The common complication observed due to PPV was pressure ulcer. At ICU discharge, all except two patients survived.

CONCLUSION: PPV improves oxygenation when started early with adequate duration and should be considered in all severe ARDS cases secondary to H1N1 viral infection.