Objective: Severe respiratory failure is a well-recognized complication of pH1N1 influenza infection. Limited data regarding the efficacy of rescue therapies, including high-frequency oscillatory ventilation and extracorporeal membrane oxygenation, have been previously reported in the setting of pH1N1 influenza infection in the United States.
Design: Retrospective, single-center cohort study.
Setting: Pediatric, cardiac, surgical, and medical intensive care units in a single tertiary care center in the United States.
Patients: One hundred twenty-seven consecutive patients with confirmed influenza A infection requiring hospitalization between April 1, 2009, and October 31, 2009.
Interventions: Electronic medical records were reviewed for demographic and clinical data.
Measurements and main results: The number of intensive care unit admissions appears inversely related to age with 39% of these admissions <20 yrs of age. Median duration of intensive care unit care was 10.0 days (4.0-24.0), and median duration of mechanical ventilation was 8.0 days (0.0-23.5). Rescue therapy (high-frequency oscillatory ventilation or extracorporeal membrane oxygenation) was used in 36% (12 of 33) of intensive care unit patients. The severity of respiratory impairment was determined by Pao²/Fio² ratio and oxygenation index. High-frequency oscillatory ventilation at 24 hrs resulted in improvements in median Pao²/Fio² ratio (71 [58-93] vs. 145 [126-185]; p < .001), oxygenation index (27 [20-30] vs. 18 [12-25]; p = .016), and Fio2 (100 [70-100] vs. 45 [40-55]; p < .001). Extracorporeal membrane oxygenation resulted in anticipated improvement in parameters of oxygenation at both 2 hrs and 24 hrs after initiation of therapy. Despite the severity of oxygenation impairment, overall survival for both rescue therapies was 75% (nine of 12), 80% (four of five) for high-frequency oscillatory ventilation alone, and 71% (five of seven) for high-frequency oscillatory ventilation + extracorporeal membrane oxygenation.
Conclusion: In critically ill adult and pediatric patients with pH1N1 infection and severe lung injury, the use of high-frequency oscillatory ventilation and extracorporeal membrane oxygenation can result in significant improvements in Pao²/Fio² ratio, oxygenation index, and Fio². However, the impact on mortality is less certain.