Table 1. Baseline characteristics of patients admitted to intensive care unit during the first pandemic (H1N1) 2009 influenza wave of 2009.
| Characteristic | All patients (n = 173) | Patients with A(H1N1)pdm09 only (n = 145) |
| Age – years | ||
| Median | 46 | 47 |
| IQR | 34–84 | 34–55 |
| Female sex – no. (%) | 95 (55%) | 73 (50.3%) |
| Pregnant – no. (%) | 22 (12.7%) | 20 (13.8%) |
| Ethnicity – no. (%) | ||
| Caucasian | 130 (75.1%) | 106 (73.1%) |
| Aboriginal or Torres Strait Islander | 13 (7.5%) | 11 (7.6%) |
| Maori or Pacific Islander | 6 (3.5%) | 6 (4.1%) |
| Asian | 5 (2.9%) | 5 (3.4%) |
| Other | 19 (11%) | 17 (11.7%) |
| Body mass index (kg/m2) – no. (%) | ||
| <25 | 56 (32.4%) | 45 (31%) |
| 25–30 | 44 (25.4%) | 38 (26.2%) |
| ≥30 | 73 (42.2%) | 62 (42.8%) |
| ≥40 | 23 (13.3%) | 20 (13.8%) |
| Co-morbidities – no. (%) | ||
| Diabetes | 23 (13.3%) | 21 (14.5%) |
| Chronic lung disease | 61 (35.3%) | 53 (36.6%) |
| Chronic heart disease | 26 (15%) | 23 (15.9%) |
| APACHE II score | ||
| Median | 16 | 16 |
| IQR | 13–23 | 12–23 |
| APACHE III score | ||
| Median | 56 | 55 |
| IQR | 43–73 | 42–73 |
| Mechanical ventilation – no. (%) | 110 (63.6%) | 107 (73.8%) |
| ECMO – no. (%) | 11 (6.4%) | 11 (7.6%) |
| Vasopressor support – no. (%) | 62 (35.8%) | 52 (35.9%) |
| Renal replacement therapy – no. (%) | 18 (10.4%) | 13 (9%) |
| Corticosteroids – no. (%) | 75 (43.4%) | 63 (43.4%) |
| Hydrocortisone | 62 (35.8%) | 50 (34.5%) |
| Methylprednisolone | 13 (7.5%) | 13(9%) |
| Influenza subtype | ||
| A(H1N1)pdm09 | 145 (83.8%) | 145 (100%) |
| Seasonal A/H3N2 | 17 (9.8%) | – |
| Seasonal A/H1N1 | 1 (0.6%) | – |
| Untyped | 10 (5.8%) | – |
| Influenza syndrome – no. (%) | ||
| Viral pneumonitis/ARDS | 86 (49.7%) | 76 (52.4%) |
| Concurrent bacterial pneumonia | 24 (13.9%) | 17 (11.7%) |
| Exacerbation of airflow limitation | 29 (16.7%) | 23 (15.9%) |
| Length of stay – days | ||
| ICU | ||
| Median | 8.38 | 8.6 |
| IQR | 2.8–16.4 | 2.8–17.9 |
| Hospital | ||
| Median | 15.6 | 16.2 |
| IQR | 8.0–30.5 | 7.5–31.2 |
| Death – no. (%) | 22 (12.7%) | 22 (15.2%) |
Definition of abbreviations: IQR = Interquartile range; BMI = Body mass index (calculated as weight in kilograms divided by height in metres squared); APACHE = Acute Physiology, Age, and Chronic Health Evaluation; ECMO = Extracorporeal membrane oxygenation; ARDS = Acute respiratory distress syndrome; ICU = Intensive care unit.