Table 5.
Subgroup analysis - the effect on secondary outcomes
| No. of studies | Patients (n) H/C | I2 (%) | P value for heterogeneity | MD 95 % CI | Overall effect Z/P value | |
|---|---|---|---|---|---|---|
| Length of ICU stay | ||||||
| Type of ARF | ||||||
| Hypercapnic | 2 | 48/48 | 0 | 0.69 | −1.22 [−3.47, 1.04] | 1.06/0.29 |
| Hypoxemic | 2 | 52/85 | 0 | 0.37 | −1.38 [−4.63, 1.88] | 0.83/0.41 |
| Ventilation mode in the experimental group | ||||||
| CPAP | 1 | 15/15 | NA | NA | −1.10 [−3.43, 1.23] | 0.93/0.35 |
| PSV | 3 | 85/118 | 0 | 0.63 | −1.56 [−4.63, 1.50] | 1/0.32 |
| Study design | ||||||
| Case-control trial | 3 | 85/118 | 0 | 0.63 | −1.56 [−4.63, 1.50] | 1/0.32 |
| RCT | 1 | 15/15 | NA | NA | −1.10 [−3.43, 1.23] | 0.93/0.35 |
| Oxygenation (PaO2/FiO2) | ||||||
| Type of ARF | ||||||
| Hypercapnic | 3 | 68/68 | 0 | 0.38 | 1.23 [−9.32, 11.78] | 0.23/0.38 |
| Hypoxemic | 4 | 80/113 | 59 | 0.06 | 2.37 [−23.34, 28.08] | 0.18/0.86 |
| Ventilation mode in the experimental group | ||||||
| CPAP | 2 | 28/28 | 53 | 0.15 | −66.01 [−130.73, −1.28] | 2/0.05 |
| PSV | 5 | 120/153 | 0 | 0.59 | 2.96 [−6.91, 12.83] | 0.59/0.56 |
| Study design | ||||||
| Case-control trial | 5 | 113/146 | 49 | 0.1 | 4.16 [−22.55, 14.22] | 0.44/0.66 |
| RCT | 2 | 35/35 | 0 | 0.33 | 3.57 [−7.95, 15.09] | 0.61/0.54 |
| pH | ||||||
| Type of ARF | ||||||
| Hypercapnic | 3 | 68/68 | 16 | 0.3 | −0.00 [−0.02, 0.02] | 0.01/1 |
| Hypoxemic | 3 | 63/96 | 28 | 0.25 | −0.02 [−0.04, 0.00] | 1.59/0.11 |
| Ventilation mode in the experimental group | ||||||
| CPAP | 1 | 11/11 | NA | NA | −0.04 [−0.11, 0.03] | 1.19/0.24 |
| PSV | 5 | 120/153 | 30 | 0.22 | −0.01 [−0.02, 0.01] | 0.74/0.46 |
| Study design | ||||||
| Case-control trial | 4 | 96/129 | 0 | 0.43 | −0.02 [−0.04, −0.00] | 2.02/0.04 |
| RCT | 2 | 35/35 | 0 | 0.73 | 0.01 [−0.01, 0.03] | 0.85/0.4 |
| PaCO2 | ||||||
| Type of ARF | ||||||
| Hypercapnic | 3 | 68/68 | 0 | 0.5 | 6.15 [4.17, 8.13] | 6.08/<0.00001 |
| Hypoxemic | 3 | 63/96 | 0 | 0.7 | −1.76 [−5.13, 1.60] | 1.03/0.30 |
| Ventilation mode in the experimental group | ||||||
| CPAP | 1 | 11/11 | NA | NA | −1.40 [−16.96, 14.16] | 0.18/0.86 |
| PSV | 5 | 120/153 | 77 | 0.002 | 4.18 [2.46, 5.90] | 4.76/<0.00001 |
| Study design | ||||||
| Case-control trial | 4 | 96/129 | 61 | 0.05 | 0.15 [−2.90, 3.20] | 0.1/<0.92 |
| RCT | 2 | 35/35 | 0 | 0.39 | 5.92 [3.85, 7.98] | 5.62/<0.00001 |
| Respiratory rate | ||||||
| Type of ARF | ||||||
| Hypercapnic | 3 | 87/89 | 23 | 0.27 | −0.56 [−1.85, 0.74] | 0.84/0.4 |
| Hypoxemic | 3 | 63/96 | 65 | 0.06 | 0.58 [−3.52, 4.69] | 0.28/0.78 |
| Ventilation mode in the experimental group | ||||||
| CPAP | 1 | 11/11 | NA | NA | 6.00 [−0.08, 12.08] | 1.93/0.05 |
| PSV | 5 | 139/174 | 0 | 0.44 | −0.81 [−1.92, 0.30] | 1.42/0.15 |
| Study design | ||||||
| Case-control trial | 4 | 96/129 | 57 | 0.07 | 0.07 [−1.45, 1.60] | 0.1/0.92 |
| RCT | 2 | 54/56 | 0 | 0.98 | −1.29 [−2.86, 0.28] | 1.61/0.11 |
| Interfaces used in the control group | ||||||
| Facial mask | 5 | 111/144 | 51 | 0.08 | −0.49 [−1.66, 0.69] | 0.81/0.42 |
| Oronasal mask | 1 | 39/41 | NA | NA | −1.26 [−4.28, 1.76] | 0.82/0.41 |
H/C helmet/control, MD mean difference, CI confidence interval, ICU intensive care unit, ARF acute respiratory failure, CPAP continuous positive airway pressure, PSV pressure support ventilation, high quality randomized controlled trial, PaO 2 /FiO 2 the ratio of the partial pressure of oxygen in arterial blood to the inspired oxygen fraction, pH potential of hydrogen, PaCO 2 partial pressure of carbon dioxide, NA not applicable