Table 2.
Clinical characteristics of latent class analysis–defined patterns of acute respiratory distress syndrome onset
| Characteristic | Class I: Early Onset (n = 98) | Class II: Late Onset (n = 76) | Class III: Latest Onset (n = 15) | P Value |
|---|---|---|---|---|
| Demographics | ||||
| Age, yr | 38 (22–50) | 34 (23–48) | 38 (21–53) | 0.986 |
| Sex, % male | 77/97 (79%) | 58/76 (76%) | 12/15 (80%) | 0.926 |
| Race | 0.567 | |||
| African American | 41/97 (42%) | 38/74 (51%) | 7/15 (47%) | |
| White | 53/97 (55%) | 35/74 (47%) | 7/15 (47%) | |
| Asian | 2/97 (2%) | 1/74 (1%) | 1/15 (7%) | |
| Other race | 1/97 (1%) | 0/74 (0%) | 0/15 (0%) | |
| Severity of illness | ||||
| ISS | 25 (20–32) | 25 (19–29) | 21 (18–29) | 0.419 |
| AIS thorax (0–5) | 3 (2–4) | 3 (0–3) | 2 (0–3) | <0.001 |
| AIS head and neck (0–5) | 2 (0–3) | 2 (1–4) | 3 (0–4) | 0.272 |
| AIS face (0–5) | 0 (0–2) | 0 (0–2) | 1 (0–2) | 0.817 |
| AIS abdomen (0–5) | 2 (0–3) | 2 (0–4) | 0 (0–3) | 0.308 |
| AIS extremities (0–5) | 2 (1–3) | 2 (1–3) | 1 (0–3) | 0.551 |
| AIS external (0–5) | 1 (0–1) | 1 (0–1) | 0 (0–1) | 0.118 |
| APACHE III w/o ABG | 59 (50–71) | 58 (47–73) | 58 (48–74) | 0.821 |
| Etiology of injury | ||||
| Blunt | 72/98 (74%) | 56/76 (74%) | 10/15 (67%) | 0.846 |
| Penetrating | 26/98 (26%) | 20/76 (26%) | 5/15 (33%) | |
| Pulmonary contusion | 39/98 (40%) | 24/75 (32%) | 3/15 (20%) | 0.276 |
| Substance history | ||||
| Alcohol use | 12/74 (16%) | 9/60 (15%) | 3/14 (21%) | 0.846 |
| Current smoker | 23/58 (40%) | 21/54 (39%) | 5/13 (39%) | 0.995 |
| Initial assessment | ||||
| Lowest SBP, ED or OR | 78 (68–98) | 90 (80–104) | 90 (80–102) | 0.003 |
| Temp max, ED, °C | 36.3 (35.5–36.8) | 36.5 (35.9–36.6) | 35.9 (35.0–36.6) | 0.740 |
| Initial Hgb, mean | 12.2 ± 2.1 | 12.4 ± 2.2 | 12.7 ± 2.1 | 0.586 |
| Initial WBC | 12 (8.4–18.8) | 12.5 (8.2–16.6) | 16.2 (9.7–21.4) | 0.579 |
| Initial Cr | 1.1 (0.9–1.3) | 1.1 (0.9–1.3) | 1.0 (0.9–1.3) | 0.756 |
| Interventions | ||||
| Intravenous fluids, L | 5.0 (2.3–8.0) | 3.5 (2.0–7.5) | 5.9 (3.0–8.1) | 0.384 |
| RBC, units* | 4 (0–9) | 2 (0–6) | 1 (0–6) | 0.011 |
| RBC, transfusion* | 70/98 (71%) | 42/76 (55%) | 8/15 (53%) | 0.062 |
| FFP, units | 1 (0–4) | 0 (0–3) | 2 (0–4) | 0.470 |
| Mortality | 23/98 (24%) | 19/76 (25%) | 3/15 (20%) | 0.966 |
Definition of abbreviations: ABG = arterial blood gas; AIS = Abbreviated Injury Scale; APACHE = Acute Physiology and Chronic Health Evaluation; Cr = creatinine; ED = emergency department; FFP = fresh frozen plasma; Hgb = hemoglobin; ISS = Injury Severity Score; OR = operating room; RBC = red blood cells; SBP = systolic blood pressure; Temp max = maximal temperature; WBC = white blood cells; w/o = without.
Values represent median and interquartile range, mean ± standard deviation, or number and percentage. Distributions of continuous variables were compared using a Kruskal–Wallis test or analysis of variance test as appropriate, and categorical variables were compared using a Pearson chi-square test or Fisher’s exact test.
Packed RBC transfusion was considered a continuous variable based on number of units transfused during resuscitation and a dichotomous categorical variable distinguishing subjects transfused from those who required no transfusion.