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

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.

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 cmH₂O and PaCO₂ was >45 cmH₂O; 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.

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.

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