Table 2.
Characteristics of the Intubation Procedure.
| Characteristic | Bag-Mask Ventilation (N = 199) |
No Ventilation (N = 202) |
Relative Risk or Mean Difference (95% Cl) |
|---|---|---|---|
| Before induction | |||
| Preoxygenation method — no. (%)* | |||
| Bag-mask device | 79 (39.7) | 22 (10.9) | 3.65 (2.37 to 5.60) |
| Bilevel positive airway pressure† | 32 (16.1) | 48 (23.8) | 0.68 (0.45 to 1.01) |
| High-flow nasal cannula‡ | 23 (11.6) | 41 (20.3) | 0.57 (0.36 to 0.91) |
| Non-rebreather mask | 54 (27.1) | 62 (30.7) | 0.88 (0.65 to 1.20) |
| Standard nasal cannula‡ | 17 (8.5) | 24 (11.9) | 0.72 (0.40 to 1.30) |
| No preoxygenation | 3 (1.5) | 7 (3.5) | 0.44 (0.11 to 1.66) |
| Preoxygenation with positive pressure — no. (%)§ | 132 (66.3) | 111 (55.0) | 1.21 (1.03 to 1.42) |
| Oxygen saturation at induction¶ | |||
| Median (IQR) — % | 99 (95–100) | 99 (96–100) | −0.6 (−1.4 to 0.3)‖ |
| <92% — no./total no. (%) | 27/194 (13.9) | 17/198 (8.6) | 1.62 (0.91 to 2.88) |
| Median systolic blood pressure at induction (IQR) — mm Hg | 122 (105–142) | 123 (107–140) | 0.0 (−5.5 to 5.6)‖ |
| New vasopressor before induction — no./total no. (%) | 27/197 (13.7) | 29/200 (14.5) | 0.95 (0.58 to 1.54) |
| Oxygenation and ventilation between induction and intubation | |||
| Bag-mask ventilation between induction and laryngoscopy to prevent hypoxemia — no. (%)** |
198 (99.5) | 5 (2.5) | 40.20 (16.91 to 95.53) |
| Bag-mask ventilation between induction and intubation for any indication — no. (%)†† |
198 (99.5) | 44 (21.8) | 4.57 (3.52 to 5.93) |
| Supplemental oxygen between induction and laryngoscopy — no.(%)‡‡ |
199 (100) | 157 (77.7) | 1.29 (1.20 to 1.39) |
| After induction§§ | |||
| Median time from induction to laryngoscopy (IQR) — sec | 98 (65–135) | 72 (52–120) | 13.8 (−1.1 to 28.6)‖ |
| Median time from laryngoscopy to intubation (IQR) — sec | 42 (25–72) | 45 (30–71) | −11.5 (−30.5 to 7.5)‖ |
| Median time from induction to intubation (IQR) — sec | 158 (110–218) | 130 (90–191) | 7.7 (−15.6 to 31.0)‖ |
| Video laryngoscope as initial device — no. (%) | 71 (35.7) | 65 (32.2) | 1.11 (0.84 to 1.46) |
| Successful intubation on first attempt — no. (%) | 167 (83.9) | 162 (80.2) | 1.05 (0.95 to 1.15) |
| Use of bougie — no. (%) | 33 (16.6) | 44 (21.8) | 0.76 (0.51 to 1.14) |
More than one method could be used in each patient.
In patients receiving bilevel positive airway pressure, inspiratory and expiratory settings were determined by the operator.
Among the patients with high-flow nasal cannula, flow rates were up to 70 liters per minute of humidified oxygen. Among those with standard nasal cannula, flow rates were 6 liters per minute or less of nonhumidified oxygen.
Preoxygenation with positive pressure was defined as the use of a bag-mask device, bilevel positive airway pressure, or high-flow nasal cannula.
Additional details regarding oxygen saturation at induction are provided in Table S7 and Figure S2 in the Supplementary Appendix.
The mean difference is indicated in this category.
The receipt of bag-mask ventilation by five patients in the no-ventilation group was considered to be a protocol violation. Additional details on protocol violations are provided in Table S9 in the Supplementary Appendix.
Therapeutic bag-mask ventilation was allowed in the no-ventilation group after a failed attempt at laryngoscopy or in patients with an oxygen saturation of less than 90%.
Supplemental oxygen in the bag-mask group was provided by means of bag-mask ventilation. Supplemental oxygen in the no-ventilation group was provided by means of a non-rebreather mask or a nasal cannula. Details are provided in Table S10 in the Supplementary Appendix.
Data regarding the time from induction to laryngoscopy were missing for 15 patients (3.7%): 8 in the bag-mask ventilation group and 7 in the no-ventilation group; from laryngoscopy to intubation for 11 patients (2.7%): 7 in the bag-mask ventilation group and 4 in the no-ventilation group; and from induction to intubation for 9 patients (2.2%): 6 in the bag-mask ventilation group and 3 in the no-ventilation group.