| First author [ref.] | Year | Country | Study design | Interface | Received NIV | NIV failure | Transmission among HCW# | Mortality | Observations |
| Kaufman [21] | 2009 | Australia | Multicentre, prospective cohort (n=3) | Face mask | 0 | 100% | No | ||
| Perez-Padilla [22] | 2009 | Mexico | Retrospective, multicentre cohort (n=98) | Face mask | n=18 (IMV: n=12) | Yes | n=7 | 22 HCW were treated with oseltamivir None were hospitalised None of the secondary infections among HCW were severe | |
| Rello [23] | 2009 | Spain | Multicentre cohort (n=32) | Face mask | n=8 (33%) | 75% | No | n=8 | 24 (75.0%) required IMV |
| Djibre [28] | 2009 | France | Case 1: pregnant | Face mask | 1 | 0% | No | 0 | Pregnancy population |
| Kumar [24] | 2009 | Canada | Prospective, observational, multicentre cohort (n=168) | Face mask | n=55 (33%) | 85% | No | 136 (81.0%) patients received IMV | |
| DomÍnguez-Cherit [31] | 2009 | Mexico | Prospective, observational, multicentre cohort (n=58) | Face mask | 0 | 0 | No | 0 | |
| Miller [29] | 2009 | USA | Monocentre, observational cohort (n=47) | Face mask | n=13 (3%) | 85% | No | 17% | Severe ARDS with MOF in the absence of bacterial infection was a common clinical presentation |
| Li [26] | 2010 | China | Retrospective, monocentre cohort (n=75) | Face mask | n=33 (44%) | n=10 (30%) | No | 10% | |
| Koegelenberg [30] | 2010 | South Africa | Monocentre, observational cohort (n=19) | Face mask | n=6 (66%) | 66.6% | No | n=13 (68.4%) | |
| Winck [36] | 2010 | Portugal | Case report (n=1) | Face mask | n=1 | 0 | No | ||
| Esquinas [37] | 2010 | International NIV Network Survey | Prospective, international, observational cohort | Face mask | No | ||||
| Hajjar [38] | 2010 | Brazil | Monocentre cancer patients, observational study cohort (n=8) | Face mask | n=8 (50%) | n=5 (62.5%) | No | 100% | Cancer patients highlight the severity of the H1N1 pandemic in this vulnerable population and the urgent need to establish specific protocols of care and management strategies designed to face this healthcare challenge |
| Louriz [40] | 2010 | Morocco | Observational, prospective, multicentre cohort (n=186) | Face mask | n=10 | n=10 (100%) | 30% | ||
| Adigüzel [32] | 2010 | Turkey | Observational, monocentre cohort (n=19) | Face mask | Nasal cannula: n=4 (21.1%) | No | First study to include nasal cannula | ||
| Nin [39] | 2011 | Spain | Multicentre, observational, prospective cohort (n=96) | Face mask | n=43 (45%) | 77% | No | 50% global | High mortality, primarily due to refractory hypoxia |
| RÍos [25] | 2011 | Argentina | Face mask | n=49 (28%) | 94% | No | |||
| Liu [43] | 2011 | China | Retrospective, observational, monocentre cohort (n=62) | Face mask | n=23 | n=3 | No | n=4 (6.5%) | Hypoxaemia, MOF, and a requirement for IMV |
| Timenetsky [46] | 2011 | Brazil | Prospective, observational, monocentre cohort (n=14) | Face mask | 85.7% | 58.4% | No | 2.1% | |
| Grasselli [45] | 2011 | Italy | Prospective, observational, monocentre cohort (n=19) | Face mask | n=13 | n=11 | No | Frequent IMV | |
| Belenguer-Muncharaz [47] | 2011 | Spain | Retrospective, observational, monocentre cohort | Face mask and helmet | n=10 | 0 | No | 0 | First study to use a helmet and a face mask |
| Masclans [48] | 2012 | Spain | Prospective, observational, multicentre registry cohort | Face mask | n=177 | n=105 (59.32%) | No | 0 | Best outcome in low APACHE II and SOFA, no vasopressor, lower chest radiograph quadrants and shorter ICU stay |
| Zhang [33] | 2012 | China | Retrospective, observational, monocentre cohort (n=394, including 1 pregnant subject) IMV (n=186) | Face mask | n=83 | n=45 (24.32%) | No | n=24 (28.91%) | Pregnancy population |
HCW: healthcare workers; IMV: invasive mechanical ventilation; ARDS: acute respiratory distress syndrome; MOF: multi-organ failure; APACHE II: Acute Physiology and Chronic Health Evaluation II; SOFA: Sequential Organ Failure Assessment; ICU: intensive care unit. #: instances of transmission of influenza A H1N1 among HCW.