Background
Methods
Multivariable analyses
Control for confounding to verify differences in mortality risk in ARDS patients
University hospital | Non-university hospital | ||
---|---|---|---|
(n = 87) | (n = 111) |
p value | |
Age (years) | 59.0 (16.2); 63 (47–72) | 62.8 (15.9); 65 (52–74) | 0.10 |
Sex, male/female | 62 (71.3)/25 (28.7) | 80 (72.1)/31 (27.9) | 0.9 |
BMI (kg/m2) | 26.0 (4.9); 25.7 (23.2–27.7) | 26.9 (6.2); 26.0 (23.1–29.4) | 0.34 |
BMI categories | |||
< 18.5/<25.5/<30.0/≥30.0 kg/m2
| 3 (4.5)/28 (41.8)/28 (41.8)/8 (11.9) | 5 (4.7)/39 (36.8)/41 (38.7)/21(19.8) | 0.6 |
SAPS II at ICU admission | 45.2 (17.2); 42 (32–58) | 48.7 (20.4); 48 (37–62) | 0.21 |
Main problem, medical/surgical | 48 (55.2)/39 (44.8) | 69 (62.2)/42 (37.8) | 0.32 |
ARDS origin, pulmonary/ extrapulmonary | 65 (78.3)/18 (21.7) | 79 (72.5)/30 (27.5) | 0.36 |
Late onset of ARDSa
| 35 (40.2) | 28 (25.2) | 0.02 |
Onset of ARDS: day after initiation of mechanical ventilation | 1 (0-5) | 0 (0-2) | 0.02 |
PaO2/FiO2 (mmHg) | 157 (124-186) | 149 (114-179) | 0.29 |
Dynamic complianceb (ml/mbar; ml/mbar/kg PBW) | 39 (29–55); 0.58 (0.44–0.79) | 33 (24–43); 0.52 (0.39–0.67) | 0.006; 0.04 |
Reason for initiation of mechanical ventilation (only presented when different between groups)c
| |||
Postoperative acute respiratory failure | 19 (21.8) | 12 (10.8) | 0.03 |
Acute respiratory failure after aspiration | 2 (2.3) | 12 (10.8) | 0.02 |
Complications until the onset of ARDS | |||
Sepsisc
| 41 (47.1) | 38 (34.2) | 0.07 |
Pneumoniac
| 43 (49.4) | 44 (39.6) | 0.17 |
Cardiovascular failure | 63 (72.4) | 71 (64.0) | 0.21 |
Renal failure | 26 (29.9) | 32 (28.8) | 0.87 |
Coagulopathy | 23 (26.4) | 8 (7.2) | <0.001 |
Liver failure | 11 (12.6) | 2 (1.8) | 0.002 |
Metabolic acidosis | 8 (9.2) | 13 (11.7) | 0.57 |
Respiratory acidosis | 18 (20.7) | 23 (20.7) | 1.0 |
Barotrauma | 14 (16.1) | 13 (11.7) | 0.37 |
Results
Variable | Univariable analysisa
| Multivariable analysisb
| ||
---|---|---|---|---|
Odds ratio (95% CI) |
p value | Odds ratio (95% CI) |
p value | |
Factors related to patients’ baseline factors | ||||
Sex | 0.068 | |||
Male | 1.82 (0.96–3.46) | |||
Female | 1 | |||
SAPS II at ICU admission | 0.005 | |||
≤40 | 1 | |||
40–59 | 2.09 (1.03–4.22) | |||
≥60 | 3.69 (1.64–8.29) | |||
Factors related to individual patient management | ||||
FiO2 (0.1 increments) | 1.79 (1.35–2.38) | <0.001 | 1.62 (1.17–2.24) | 0.004 |
Driving pressurec (1 cmH2O increments) | 1.17 (1.08–1.26) | <0.001 | 1.10 (1.02–1.20) | 0.016 |
Use of vasoactive drugs (2 consecutive days) | 2.01 (1.00–4.02) | 0.049 | ||
Factors developing during mechanical ventilation | ||||
Liver failure | 7.85 (2.24–27.55) | 0.001 | 6.93 (1.68–28.59) | 0.007 |
Renal failure | 4.15 (2.25–7.64) | <0.001 | 3.46 (1.59–7.55) | 0.002 |
Metabolic acidosis | 3.29 (1.48–7.29) | 0.003 | 2.94 (1.03–8.27) | 0.043 |
pHa | 0.001 | |||
Acidosis (<7.35) | 4.09 (1.90–8.77) | |||
7.35–7.45 | 1 | |||
Alkalosis (>7.45) | 1.17 (0.55–2.47) | |||
Lowest PaO2/FiO2 (mmHg) | 0.009 | |||
≤100 | 3.08 (1.38–6.85) | |||
100–150 | 2.53 (1.26–5.10) | |||
>150 | 1 | |||
Factors related to the setting of care | ||||
Non-university hospital | 2.10 (1.17–3.75) | 0.013 | 2.89 (1.31–6.38) | 0.008 |
University hospital | 1 | 1 |
Odds ratio for hospital mortality of ARDS patients in non-university hospitals vs university hospitals | |||
---|---|---|---|
n
a
| Odds ratio multivariable |
p value | |
Multivariable analysis with all potential confounders | 128 | 2.8 (1.1–7.1) | 0.035 |
Excluding SAPS II | 137 | 2.7 (1.1–6.6) | 0.032 |
Excluding BMI | 142 | 3.5 (1.5–8.4) | 0.004 |
Excluding compliance | 151 | 2.4 (1.1–5.5) | 0.037 |
Excluding SAPS II, BMI | 151 | 3.4 (1.5–7.7) | 0.005 |
Excluding compliance, SAPS II | 164 | 2.4 (1.1–5.4) | 0.028 |
Excluding compliance, BMI | 174 | 3.5 (1.7–7.6) | 0.001 |
Excluding compliance, SAPS II, BMI | 189 | 3.3 (1.6–6.7) | 0.001 |
University hospital (n = 87; 592 days of mechanical ventilation) | Non-university hospital (n = 111; 599 days of mechanical ventilation) |
p value | |
---|---|---|---|
Ventilatory parameters averaged over the first week after ARDS onset, mean (SD); median (IQR) | |||
Driving pressurea (cmH2O) | 15.7 (5.1); 15 (13–19) | 16.3 (4.7); 16 (13–19) | 0.40 |
Driving pressure when FiO2 > 0.4 and PEEP ≥ 5 (cmH2O)b
| 15.1 (4.4); 16 (12–19) | 17.0 (5.0); 18 (14–20) | 0.02 |
PEEP (cmH2O) | 10.1 (4.2); 10 (7–13) | 8.4 (3.9); 8 (6–11) | 0.005 |
PEEP when FiO2 > 0.4 and PEEP ≥ 5 (cmH2O)b
| 11.7 (4.7); 10 (8–15) | 9.7 (3.7); 9 (7–12) | 0.005 |
PEEP categories, n (%) | |||
≤5 cmH2O | 11 (12.6) | 24 (21.8) | 0.05 |
≤10 cmH2O | 41 (47.1) | 58 (52.7) | |
≥11 cmH2O | 35 (40.2) | 28 (25.5) | |
Tidal volume (ml/kg PBW) | 8.9 (2.0); 8.6 (7.6–10.0) | 8.9 (2.4); 8.7 (7.6–10.0) | 0.99 |
Plateau pressure (cmH2O) | 26.4 (5.8); 27 (23–31) | 25.3 (5.4); 25 (22–28) | 0.18 |
Plateau pressure categories, n (%) | |||
≤30 cmH2O | 54 (70.1) | 89 (86.4) | 0.007 |
>30 cmH2O | 23 (29.9) | 14 (13.6) | |
Compliancec (ml/mbar; ml/mbar/kg PBW) | 42 (32–54); 0.62 (0.49–0.80) | 38 (29–48); 0.59 (0.45–0.73) | 0.06; 0.23 |
Respiratory frequency (breaths/min) | 20 (16–22) | 18 (13–22) | 0.17 |
FiO2
| 0.44 (0.40–0.54) | 0.48 (0.41–0.57) | 0.07 |
PaO2 (mmHg) | 91 (84–105) | 92 (78–107) | 0.64 |
PaO2/FiO2 (mmHg) | 208 (169–250) | 194 (155–248) | 0.19 |
PaCO2 (mmHg) | 42 (38–47) | 42 (37–48) | 0.91 |
pHa | 7.41 (7.36–7.45) | 7.42 (7.36–7.46) | 0.59 |
Days with ventilatory mode during the first week after ARDS onset, n (% of all days of mechanical ventilation) | <0.001 | ||
Biphasic intermittent positive airway pressure | 281 (47.5) | 271 (45.2) | 0.44 |
Pressure controlled ventilation | 69 (11.7) | 111 (18.5) | 0.001 |
Pressure support ventilation | 105 (17.7) | 75 (12.5) | 0.01 |
SIMV + pressure support ventilation | 31 (5.2) | 41 (6.8) | 0.24 |
SIMV | 24 (4.1) | 10 (1.7) | 0.01 |
Volume-controlled ventilation (assist/control) | 28 (4.7) | 15 (2.5) | 0.04 |
Non-invasive ventilation | 31 (5.2) | 38 (6.3) | 0.41 |
Other | 9 (1.5) | 7 (1.2) | 0.60 |
Not specified | 14 (2.4) | 31 (5.2) | 0.01 |
Days applying adjunctive therapies, n (% of all days of mechanical ventilation); median (IQR) | |||
Prone positioning or rotation bed, all days | 44 (7.4) | 22 (3.7) | 0.005 |
Sedatives all days, duration/patient (days) | 439 (74.2); 12 (7–21) | 411 (56.8); 5 (2–10) | 0.03; <0.001 |
Neuromuscular blocking agents, all days | 11 (1.9) | 7 (1.2) | 0.33 |
Incidence | Incidence rate | ||||
---|---|---|---|---|---|
University hospital (n = 87) | Non-university hospital (n = 111) | University hospital (n = 87) | Non-university hospital (n = 111) | ||
n
a (%) |
n
a (%) |
p value | Rate/1000 daysb (analyzed daysc) | Rate/1000 daysb (analyzed daysc) | |
Sepsis | 8/46 (17.4) | 3/73 (4.1) | 0.02 | 12 (671) | 5 (653) |
Pneumonia | 17/44 (38.6) | 13/67 (19.4) | 0.03 | 30 (570) | 21 (609) |
Cardiovascular failure | 11/24 (45.8) | 12/40 (30) | 0.20 | 38 (289) | 28 (423) |
Liver failure | 7/76 (9.2) | 3/109 (2.8) | 0.09 | 6 (1139) | 3 (972) |
Renal failure | 15/61 (24.6) | 11/79 (13.9) | 0.11 | 16 (942) | 15 (755) |
Coagulopathy | 13/64 (20.3) | 8/103 (7.8) | 0.02 | 13 (966) | 9 (916) |
Metabolic acidosis | 7/79 (8.9) | 8/98 (8.2) | 0.87 | 6 (1159) | 9 (911) |
Respiratory acidosis | 16/69 (23.2) | 9/88 (10.2) | 0.03 | 17 (995) | 11 (795) |
Barotrauma | 2/23 (2.7) | 0/98 (0) | 0.18 | 2 (1099) | 0 (849) |
University hospital (n = 87) | Non-university hospital (n = 111) |
p value | |
---|---|---|---|
Tracheostomy | 0.16 | ||
Tracheostomy after ARDS onset/nontracheostomized patients until ARDS onset | 33/76 (43.4) | 20/102 (19.6) | 0.001 |
Tracheostomy, percutaneous /surgical/not specified | 29 (87.9)/3 (9.1)/1 (3.0) | 11 (55.0)/8 (40.0)/1 (5.0) | 0.01 |
Days to tracheostomy after ARDS onset | 10 (4–13) | 4 (2–11) | 0.10 |
Main weaning method | 0.16 | ||
Daily spontaneous weaning trial | 12 (19.7) | 25 (34.7) | |
Gradual reduction of ventilatory support | 45 (73.8) | 43 (59.7) | |
Not specified | 4 (6.6) | 4 (5.6) | |
Extubation | |||
Extubation | 42/86 (48.8) | 63/107 (58.9) | 0.16 |
Reintubation within 48 h | 17/42 (40.5) | 16/53 (25.4) | 0.10 |
Non-invasive ventilation after extubation; reintubation thereafter | 23/42 (54.8); 10 (43.5) | 27/63 (42.9); 12 (44.4) | 0.23; 0.95 |
Duration of mechanical ventilation (days) | 16 (9–29) | 8 (3–16) | <0.001 |
After ARDS onset | 13 (6–23) | 6 (3–14) | <0.001 |
Survivors | 14 (9–25) | 7 (3–14) | <0.001 |
Length of ICU stay (days) | 19 (12–34) | 10 (5–23) | <0.001 |
After initiation of mechanical ventilation | 19 (11–34) | 10 (5–24) | <0.001 |
After ARDS onset | 15 (9–31) | 8 (4–18) | <0.001 |
Survivors | 19 (13–35) | 13 (5–24) | 0.003 |
Length of hospital stay (days) | 31 (17–46) | 21 (9–41) | 0.007 |
After initiation of mechanical ventilation | 26 (14–42) | 15 (6–34) | 0.002 |
After ARDS onset | 23 (11–37) | 14 (4–28) | 0.005 |
Survivors | 32 (19–53) | 24 (14–41) | 0.077 |
University hospital | Non-university hospital |
p value | |
---|---|---|---|
Number of hospitals | 18 (22.5) | 62 (77.5) | |
Number of participating ICUs | 33 (34.7) | 62 (65.3) | |
Beds per hospital | 1275 (1189–1444) | 367 (280–526) | <0.001 |
Beds per ICU | 13 (10–16) | 9 (7–12) | 0.001 |
ICU size category | |||
< 5/<8/ <14/ ≥14 beds per ICU | 4 (12.1)/3 (9.1)/9 (27.3)/17 (51.5) | 18 (29)/21 (33.9)/18 (29)/5 (8.1) | <0.001 |
Total number of all ICU beds | 465 (43.2) | 612 (56.8) | |
ICU specialization | <0.001 | ||
Surgical/medical | 6 (18.2) | 41 (66.1) | |
Medical | 8 (24.2) | 6 (9.7) | |
Surgical | 16 (48.5) | 15 (24.2) | |
Neurological | 3 (9.1) | 0 | |
Number of all ICU patients | 2994 (39.7) | 4546 (60.3) | |
Patients per ICU | 74 (51–106) | 74 (49–98) | 0.47 |
Patients per ICU bed | 5.8 (4.4–8.0) | 7.7 (5.2–9.6) | 0.04 |
Number of ventilated patients | 558 (54.3) | 470 (45.7) | |
Ventilated patients per ICU | 14 (8–23) | 6 (4–10) | <0.001 |
Ventilated patients per ICU bed | 1.0 (0.7–1.5) | 0.7 (0.5–1.0) | 0.002 |
% ventilated patients in all ICUs | 19 (12–27) | 10 (6–15) | <0.001 |