Table 1.
Baseline characteristics of patients before and after propensity matching
| Characteristic | Overall cohort (n = 547) | Propensity-matched cohort (n = 302) | ||||
|---|---|---|---|---|---|---|
| iNO users (n = 216) | Non-users (n = 331) | P value | iNO users (n = 151) | Non-users (n = 151) | P value | |
| Age, years | 61 ± 17 | 64 ± 16 | 0.07 | 63 ± 17 | 62 ± 16 | 0.59 |
| Female sex, n (%) | 66 (30.6) | 114 (34.4) | 0.34 | 48 (31.8) | 50 (33.1) | 0.81 |
| ARDS severity | ||||||
| Moderate, n (%) | 105 (49) | 208 (63) | 0.001 | 82 (54) | 74 (49) | 0.36 |
| Severe, n (%) | 111 (51) | 123 (37) | 69 (46) | 77 (51) | ||
| Body-mass index, kg/m2 | 23.3 ± 4.7 | 21.9 ± 3.9 | <0.001 | 22.7 ± 4.7 | 22.7 ± 4.0 | 0.95 |
| Cause of ARDS, n (%) | ||||||
| Pneumonia | 167 (77.3) | 258 (78.0) | 0.52 | 121 (80.1) | 122 (80.8) | 0.93 |
| Non-pulmonary sepsis | 32 (14.8) | 47 (14.2) | 20 (13.3) | 19 (12.6) | ||
| Acute interstitial pneumonia | 11 (5.1) | 10 (3.0) | 7 (4.6) | 5 (3.3) | ||
| Multiple transfusion | 1 (0.5) | 5 (1.5) | 1 (0.7) | 2 (1.3) | ||
| Others | 5 (2.3) | 11 (3.3) | 2 (1.3) | 3 (2.0) | ||
| Renal function | ||||||
| Creatinine, mg/dL | 1.1 (0.8–1.6) | 1.1 (0.8 − 1.8) | 0.75 | 1.1 (0.8 − 1.6) | 1.0 (0.8 − 1.7) | 0.83 |
| Creatinine clearance, mL/min | 57.0 (35.5 − 82.2) | 48.3 (31.0 − 70.2) | 0.01 | 55.2 (35 − 81) | 53.8 (33.3–81.5) | 0.97 |
| AKI stage 1, n (%) | 57 (78) | 91 (79) | 39 (81) | 42 (84) | ||
| AKI stage 2, n (%) | 9 (12) | 13 (11) | 0.98 | 5 (10) | 4 (8) | 0.91 |
| AKI stage 3, n (%) | 7 (10) | 11 (10) | 4 (8) | 4 (8) | ||
| Shock, n (%) | 91 (42.1) | 117 (35.4) | 0.11 | 56 (37.1) | 56 (37.1) | 1.00 |
| SAPS II | 49.9 ± 15.1 | 49.8 ± 14.7 | 0.95 | 49.9 ± 14.2 | 50.2 ± 15.2 | 0.89 |
| Lung injury score, total score | 11.4 ± 1.9 | 10.95 ± 1.9 | 0.005 | 11.3 ± 1.8 | 11.5 ± 1.8 | 0.46 |
| FiO2 | 0.9 (0.6–0.9) | 0.7 (0.6–1.0) | <0.001 | 0.8 (0.6–1.0) | 0.8 (0.6–1.0) | 0.96 |
| PaO2/FiO2 | 96 (68 − 134) | 123 (84–181) | <0.001 | 104 (74–143) | 99 (66 − 140) | 0.45 |
| PEEP, cm H2O | 8.9 ± 3.6 | 8.1 ± 3.0 | 0.002 | 8.3 ± 3.4 | 8.7 ± 3.2 | 0.35 |
| Tidal volume, mL/pBW | 8.7 ± 1.9 | 8.5 ± 2.0 | 0.23 | 8.7 ± 1.9 | 8.6 ± 2.0 | 0.82 |
| pH | 7.38 ± 0.10 | 7.39 ± 0.09 | 0.35 | 7.39 ± 0.10 | 7.40 ± 0.08 | 0.66 |
| PaO2, mmHg | 82.0 ± 33.2 | 94.2 ± 43.4 | <0.001 | 83.9 ± 35.0 | 80.9 ± 32.0 | 0.45 |
| PaCO2,mmHg | 37.5 ± 10.4 | 37.1 ± 10.5 | 0.67 | 37.4 ± 9.9 | 37.3 ± 8.7 | 0.97 |
| HCO3 -, mmol/L | 22.0 ± 5.1 | 22.5 ± 5.6 | 0.27 | 22.3 ± 5.2 | 22.5 ± 4.7 | 0.66 |
| Static respiratory compliance, mL/cm-H2O | 29.6 ± 12.8 | 29.7 ± 13.1 | 0.92 | 29.0 ± 12.4 | 30.2 ± 13.7 | 0.45 |
| Plateau pressure, cm H2O | 28 ± 6.8 | 26 ± 7.3 | 0.03 | 27 ± 6.1 | 27 ± 7.9 | 0.70 |
| Driving pressure (cm H2O) | 18.8 ± 6.4 | 18.2 ± 6.6 | 0.35 | 18.5 ± 5.6 | 18.5 ± 7.1 | 0.95 |
| Mean airway pressure, cm H2O | 15.7 ± 4.3 | 14.5 ± 3.9 | 0.002 | 15.0 ± 4.1 | 15.2 ± 3.8 | 0.62 |
| Duration of mechanical ventilation, days | 11 (6–20) | 12 (7–24) | 0.09 | 12 (6–22) | 12 (6–21) | 0.93 |
Data are expressed as the mean ± standard deviation or median (interquartile range) unless otherwise specified. Detailed variables used in the propensity score model are listed in Additional file 1: Table S1. Abbreviations: ARDS acute respiratory distress syndrome, AKI acute kidney injury, iNO inhaled nitric oxide, PEEP positive end-expiratory pressure, pBW predicted body weight, SAPS Simplified Acute Physiology Score