Table 2. Characteristics, laboratory parameters and outcomes of non-obese, obese and morbidly obese patients admitted to intensive care unit during the first pandemic wave of influenza A(H1N1)pdm09.
| Parameter | Non–obese (n = 100) | Obese* (n = 73) | P–value | Non–morbidly obese (n = 150) | Morbidly obese+ (n = 23) | P–value |
| Age (years) (Mean, SD) | 48.4 (16.2) | 43.4 (13.7) | 0.035 | 47.5 (15.4) | 38.6 (12.5) | 0.009 |
| Height (centimetres) (Mean, SD) | 169.6 (9.0) | 170.2 (9.7) | 0.69 | 170.4 (9.0) | 166.5 (10.4) | 0.06 |
| Weight (kilograms) (Mean, SD) | 70.4 (13.2) | 114.5 (27.1) | <0.0001 | 80.86 (19.8) | 142.26 (28.9) | <0.0001 |
| BMI (kg/m2) (Mean, SD) | 24.4 (3.5) | 39.7 (9.9) | <0.0001 | 27.7 (5.7) | 51.4 (9.7) | <0.0001 |
| APACHE II score (Median, IQR) | 17 (14–23) | 15 (12–19) | 0.029 | 17 (13–23) | 15 (12–19) | 0.45 |
| APACHE III score (Median, IQR) | 56 (43–80) | 48.5 (37–65) | 0.012 | 55 (43–73) | 41.5 (37–50) | 0.012 |
| Glasgow coma score (Mean, SD) | 13.4 (3.2) | 13.5 (3.3) | 0.94 | 13.5 (3.1) | 13.2 (3.7) | 0.66 |
| Temperature (OC) (Mean, SD) | ||||||
| High | 38.1 (1.3) | 38.3 (1.1) | 0.44 | 38.1 (1.2) | 38.5 (1.3) | 0.20 |
| Low | 36.2 (1.2) | 36.5 (0.8) | 0.14 | 36.2 (1.1) | 36.8 (1.0) | 0.006 |
| Mean arterial pressure (mmHg)(Mean, SD) | ||||||
| High | 99.4 (17.6) | 102 (15.4) | 0.37 | 100 (16.7) | 102 (17.1) | 0.71 |
| Low | 63.3 (10.3) | 68.8 (12.9) | 0.003 | 65.3 (11.8) | 67.8 (11.0) | 0.36 |
| Heart rate (beats/minute) (Mean, SD) | ||||||
| High | 114 (20.2) | 109 (20.0) | 0.19 | 113 (20.5) | 106 (17.4) | 0.16 |
| Low | 77.9 (15.9) | 78.4 (19.3) | 0.84 | 77.9 (17.7) | 79.6 (14.7) | 0.66 |
| Respiratory rate (respirations/minute) | ||||||
| High (Median, IQR) | 30 (22–38) | 28 (20–34) | 0.09 | 30 (22–37) | 22 (19–30) | 0.007 |
| Low (Median, IQR) | 14 (12–18) | 15 (12–18) | 0.16 | 14 (12–18) | 15 (12–16) | 0.66 |
| Hemoglobin (g/dL) (Median, IQR) | ||||||
| High | 11.9 (10.2–13.3) | 12.2 (10.4–13.5) | 0.26 | 12 (10.2–13.4) | 12 (10.4–13.6) | 0.69 |
| Low | 10.5 (9.0–12.0) | 11.7 (9.5–12.7) | 0.026 | 10.9 (9.0–12.3) | 11.6 (9.5–12.8) | 0.22 |
| White cell (x109/L) (Median, IQR) | ||||||
| High | 11.8 (6.4–19.3) | 8.4 (6.0–12.1) | 0.016 | 10.9 (6.2–16.2) | 7.6 (5–9.5) | 0.02 |
| Low | 8.5 (4.1–13) | 6.2 (4.4–8.4) | 0.05 | 7.3 (4.5–12.0) | 6.4 (4.2–7.5) | 0.09 |
| Platelet count (x 109/L) (Mean, SD) | ||||||
| High | 243 (132) | 242 (118) | 0.95 | 249 (132) | 201 (65) | 0.11 |
| Low | 208 (115) | 208 (100) | 0.98 | 212 (114) | 183 (62) | 0.28 |
| Creatinine (µmol/L) (Median, IQR) | 83 (59–146) | 89.5 (66–152) | 0.57 | 91 (66–154) | 76.5 (50–100) | 0.13 |
| Urea (mmol/L) (Median, IQR) | 7.6 (3.9–12.3) | 6.2 (3.7–12.3) | 0.45 | 7.9 (3.9–13.1) | 4.5 (3.5–6.4) | 0.029 |
| Albumin (g/L) (Median, IQR) | 26 (22–29) | 29 (25.5–32.5) | 0.0002 | 27 (23–31) | 29 (27–32) | 0.09 |
| Bilirubin (µmol/L) (Median, IQR) | 6 (4–10) | 8 (5–13) | 0.37 | 6.5 (4–11) | 8.5 (5–11) | 0.87 |
| Glucose (mmol/L) (Mean, SD) | 10.2 (5.6) | 9.4 (3.4) | 0.29 | 9.8 (5.0) | 9.7 (3.7) | 0.88 |
| C-reactive protein (mg/L) (Median, IQR) | ||||||
| On admission to hospital | 100 (63–210) | 106 (49–189) | 0.71 | 115 (62–210) | 67 (44–140) | 0.08 |
| On admission to ICU | 113 (65–225) | 110 (65–190) | 0.47 | 112 (67–213) | 87 (51–200) | 0.39 |
| pH (Mean, SD) | 7.3 (0.2) | 7.3 (0.1) | 0.10 | 7.3 (0.2) | 7.4 (0.1) | 0.19 |
| HCO3 (mmol/L) (Mean, SD) | 21.8 (7.0) | 24.5 (6.2) | 0.013 | 22.2 (6.6) | 27.6 (6.2) | 0.0004 |
| PaO2 (mmHg) (Median, IQR) | 75 (63–95) | 70 (60–90) | 0.26 | 75 (63–95) | 67 (50–79) | 0.034 |
| FIO2 (mmHg) (Mean, SD) | 0.7 (0.3) | 0.8 (0.3) | 0.13 | 0.7 (0.3) | 0.9 (0.2) | 0.002 |
| PaCO2 (mmHg) (Median, IQR) | 41 (34–49) | 44 (37–54) | 0.08 | 44.1 (14.8) | 54.1 (18.8) | 0.006 |
| Influenza subtype – no. (%) | ||||||
| Pandemic (H1N1) 2009 | 83 (83%) | 62 (85%) | 0.84 | 125 (83%) | 20 (87%) | 1.00 |
| Seasonal A/H3N2 | 11 (11%) | 6 (8%) | 0.61 | 15 (10%) | 2 (9%) | 1.00 |
| Seasonal A/H1N1 | 1 (1%) | 0 | 1.00 | 1 (1%) | 0 | 1.00 |
| Untyped | 5 (5%) | 5 (7%) | 0.74 | 9 (6%) | 1 (4%) | 1.00 |
| Influenza syndrome – no. (%) | ||||||
| Viral pneumonitis/ARDS | 43 (44%) | 43 (61%) | 0.029 | 71 (49%) | 15 (68%) | 0.09 |
| Concurrent bacterial pneumonia | 15 (15%) | 9 (13%) | 0.64 | 21 (14%) | 3 (14%) | 0.92 |
| Exacerbation of airflow limitation | 17 (18%) | 12 (17%) | 0.95 | 26 (18%) | 3 (14%) | 0.62 |
| Mechanical ventilation – no. (%) | 64 (64%) | 46 (63%) | 1.00 | 92 (61%) | 18 (78%) | 0.16 |
| Duration of mechanical ventilation(days) (Median, IQR) | 5 (0–11) | 8 (1–7) | 0.06 | 5 (0–12) | 9.5 (3–14) | 0.18 |
| ECMO – no. (%) | 4 (4%) | 7 (10%) | 0.21 | 7 (5%) | 4 (17%) | 0.04 |
| Vasopressor – no. (%) | 36 (42%) | 26 (42%) | 0.96 | 53 (42%) | 9 (45%) | 0.78 |
| Renal replacement therapy – no. (%) | 10 (11%) | 8 (13%) | 0.79 | 16 (12%) | 2 (10%) | 0.76 |
| Length of stay (days) (Median, IQR) | ||||||
| ICU | 6.8 (2.5–13.0) | 10.2 (3.0–20.4) | 0.13 | 7.8 (2.5–14.9) | 11.2 (4.5–19.2) | 0.15 |
| Excluding those that died | 6.8 (3.7–12.3) | 11.9 (3.9–23.3) | 0.017 | 8.9 (3.7–15.2) | 12.1 (8.5–19.8) | 0.07 |
| Hospital | 15.1 (7.6–27.3) | 17.2 (8.3–32.3) | 0.43 | 15.4 (7.5–30.4) | 17.2 (8.3–35.2) | 0.61 |
| Death – no. (%) | ||||||
| In ICU | 15 (17%) | 3 (5%) | 0.02 | 16 (12%) | 2 (10%) | 0.74 |
| In hospital | 18 (20%) | 4 (6%) | 0.016 | 20 (15%) | 2 (9%) | 0.48 |
| Median household income/week(AUD) (Mean, SD) | 1075 (264) | 1012 (210) | 0.10 | 1052 (249) | 1026 (209) | 0.64 |
| SEIFA score (Mean, SD) | 978 (80) | 976 (70) | 0.86 | 978 (78) | 971 (64) | 0.67 |
| SEIFA rank (Mean, SD) | 1099 (725) | 1060 (666) | 0.72 | 1105 (695) | 934 (723) | 0.28 |
Definitions of abbreviations: APACHE = Acute Physiology, Age, and Chronic Health Evaluation; ARDS = Acute respiratory distress syndrome; AUD = Australian dollar; BMI = Body mass index (calculated as weight in kilograms divided by height in metres squared); ECMO = Extracorporeal membrane oxygenation; ICU = Intensive care unit; IQR = Interquartile range; SD = Standard deviation; SEIFA = Socioeconomic indexes for areas.
*
Obese BMI ≥30 kg/m2.
+
Morbidly obese BMI ≥40 kg/m2.