Table 2.
Randomization, Outcomes, Treatment Difference, and Baseline Characteristics by Quartiles of Individualized Treatment Effect Estimates in the Validation Cohort
| Validation Cohort (n = 544) | Quartile 1 (n = 136) | Quartile 2 (n = 136) | Quartile 3 (n = 136) | Quartile 4 (n = 136) | P Value* | |
|---|---|---|---|---|---|---|
| Preintubation patient characteristics | ||||||
| Age, yr | 58 (44 to 69) | 60.50 (48 to 70) | 59 (46.75 to 69) | 57.50 (45 to 71) | 53.50 (41 to 64.50) | 0.047 |
| Male | 336 (61.8) | 92 (67.6) | 87 (64.0) | 82 (60.3) | 75 (55.1) | 0.18 |
| Black | 104 (19.1) | 34 (25.0) | 20 (14.7) | 21 (15.4) | 29 (21.3) | 0.10 |
| BMI | 26.8 (23.0 to 31.3) | 25.6 (23.8 to 30.3) | 26.9 (23.5 to 30.0) | 25.8 (21.2 to 30.9) | 28.1 (22.3 to 37.8) | 0.053 |
| SpO2 | 100 (97 to 100) | 100 (95.5 to 100) | 100 (97 to 100) | 99 (97 to 100) | 100 (97 to 100) | 0.52 |
| FiO2 | 0.40 (0.21 to 0.70) | 0.66 (0.36 to 1.00) | 0.40 (0.21 to 0.66) | 0.33 (0.21 to 0.66) | 0.39 (0.21 to 0.66) | <0.001 |
| SBP | 133 (114 to 154) | 139.50 (123 to 161) | 137.50 (118 to 157) | 133 (113 to 152) | 123 (104 to 141) | <0.001 |
| Receiving vasopressors | 64 (11.8) | 20 (14.7) | 13 (9.6) | 15 (11.0) | 16 (11.8) | 0.61 |
| Glasgow Coma Scale score | 10 (7 to 14) | 9 (4 to 13) | 10 (6 to 14) | 11 (7 to 14) | 11 (7 to 15) | 0.006 |
| APACHE II score | 17 (12 to 22) | 19.50 (15 to 25.25) | 16 (12 to 20.50) | 15 (11 to 19) | 18 (12.50 to 20.50) | <0.001 |
| Primary diagnosis of trauma | 76 (14.0) | 24 (17.6) | 11 (8.1) | 16 (11.8) | 25 (18.4) | 0.042 |
| Active medical conditions | ||||||
| Gastrointestinal tract hemorrhage | 49 (9.0) | 4 (2.9) | 13 (9.6) | 16 (11.8) | 16 (11.8) | 0.034 |
| Acute encephalopathy | 362 (66.5) | 94 (69.1) | 91 (66.9) | 93 (68.4) | 84 (61.8) | 0.57 |
| Hypoxemic respiratory failure | 176 (32.4) | 59 (43.4) | 34 (25.0) | 42 (30.9) | 41 (30.1) | 0.01 |
| Hypercarbic respiratory failure | 67 (12.3) | 14 (10.3) | 14 (10.3) | 22 (16.2) | 17 (12.5) | 0.41 |
| Characteristics of the intubation procedure | ||||||
| Difficult airway characteristic | ||||||
| Obesity† | 54 (9.9) | 6 (4.4) | 7 (5.1) | 9 (6.6) | 32 (23.5) | <0.001 |
| Other difficult airway characteristic‡ | 78 (14.3) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 78 (57.4) | <0.001 |
| Preoxygenation method | ||||||
| Standard nasal cannula | 150 (27.6) | 41 (30.1) | 40 (29.4) | 30 (22.1) | 39 (28.7) | 0.42 |
| High-flow nasal cannula | 52 (9.6) | 13 (9.6) | 12 (8.8) | 18 (13.2) | 9 (6.6) | 0.31 |
| Nonrebreather mask | 267 (49.1) | 52 (38.2) | 67 (49.3) | 75 (55.1) | 73 (53.7) | 0.023 |
| Bag mask, no ventilation | 54 (9.9) | 12 (8.8) | 20 (14.7) | 12 (8.8) | 10 (7.4) | 0.18 |
| Bag mask, ventilation | 70 (12.9) | 21 (15.4) | 11 (8.1) | 16 (11.8) | 22 (16.2) | 0.17 |
| Etomidate given for induction | 408 (75.0) | 101 (74.3) | 101 (74.3) | 103 (75.7) | 103 (75.7) | 0.98 |
| Neuromuscular blockade with rocuronium | 339 (62.3) | 89 (65.4) | 87 (64.0) | 80 (58.8) | 83 (61.0) | 0.68 |
| Straight laryngoscope blade or missing | 54 (9.9) | 22 (16.2) | 11 (8.1) | 4 (2.9) | 17 (12.5) | 0.002 |
| Direct laryngoscopy on initial attempt | 145 (26.7) | 37 (27.2) | 38 (27.9) | 43 (31.6) | 27 (19.9) | 0.17 |
| Operator had critical care specialty training§ | 176 (32.4) | 46 (33.8) | 45 (33.1) | 46 (33.8) | 39 (28.7) | 0.77 |
| Prior intubations using a bougie | 10 (5 to 20) | 20 (12 to 36) | 10 (5 to 20) | 8 (3 to 15) | 5 (2 to 15) | <0.001 |
| Randomized to bougie | 273 (50.2) | 62 (45.6) | 75 (55.1) | 63 (46.3) | 73 (53.7) | 0.27 |
| Primary outcome: successful intubation on the first attempt, overall | 435 (80.0) | 119 (87.5) | 112 (82.4) | 109 (80.1) | 95 (69.9) | 0.003 |
| In bougie group | 209 (76.6) | 56 (90.3) | 61 (81.3) | 48 (76.2) | 44 (60.3) | |
| In stylet group | 226 (83.4) | 63 (85.1) | 51 (83.6) | 61 (83.6) | 51 (81.0) | |
| Average treatment effect | ||||||
| Difference in incidence of the primary outcome between bougie group and stylet group, % (95% CI)ǁ | −6.8 (−13.9 to 0.2) | 5.2 (−7.2 to 17.6) | −2.3 (−16.6 to 12.0) | −7.4 (−22.4 to 7.6) | −20.7 (−37.0 to −4.4) | 0.022¶ |
Definition of abbreviations: APACHE II = Acute Physiology and Chronic Health Evaluation II; BMI = body mass index; CI = confidence interval; SBP = systolic blood pressure; SpO2 = saturation of peripheral oxygen.
Data are presented as median (interquartile range) or n (%) unless otherwise noted. Missing values: BMI, 25 (4.6%); APACHE II score, 3 (0.6%); SpO2 at induction, 11 (2.0%); SBP at induction, 10 (1.8%); highest FiO2 in prior hour, 8 (1.5%); Glasgow Coma Scale score, 3 (0.6%).
Testing for a difference across quantiles using Kruskal-Wallis and chi-square tests.
As listed in the electronic health record at baseline.
Other difficult airway characteristics include: vomiting; witnessed aspiration; upper gastrointestinal bleeding; epistaxis or oral bleeding; upper airway mass, infection, or trauma; head and neck radiation; limited neck mobility; limited mouth opening; history of obstructive sleep apnea; or other.
Reference: emergency medicine, anesthesia, or other.
The average treatment effect and 95% CI for each quartile is a summary measure of the individualized treatment effects for all patients in the quartile. CIs for the individual treatment effect estimates for individual patients in the quartile could exclude 0.0 (no difference), even when the CIs for all patients in the quartile included 0.0 (no difference).
Likelihood ratio test P value for interaction term between predicted individualized treatment effect and treatment.