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Table 4 Subgroup analysis - the effect on primary outcomes

From: Noninvasive ventilation with helmet versus control strategy in patients with acute respiratory failure: a systematic review and meta-analysis of controlled studies

  No. of studies Helmet NIV event/total Control event/total I2 (%) P value for heterogeneity OR 95 % CI Overall effect Z/P value
Hospital mortality
 Type of ARF
  Hypercapnic 2 8/58 11/56 0 0.8 0.65 [0.28, 2.06] 0.81/0.42
  Hypoxemic 5 29/153 62/182 0 0.97 0.38 [0.22, 0.65] 3.49/0.0005
 Ventilation mode in the experimental group
  CPAP 2 6/57 15/58 0 0.79 0.30 [0.10, 0.89] 2.17/0.03
  PSV 5 31/154 58/180 0 0.77 0.46 [0.27, 0.79] 2.8/0.005
 Interfaces used in the control group
  Facial mask 6 35/171 66/197 0 0.97 0.45 [0.27, 0.74] 3.12/0.002
  Venturi mask 1 2/40 7/41 NA NA 0.26 [0.05, 1.32] 1.63/0.1
Intubation rate
 Type of ARF
  Hypercapnic 5 15/132 29/132 0 0.42 0.42 [0.20, 0.85] 2.41/0.02
  Hypoxemic 5 33/153 88/143 61 0.03 0.28 [0.17, 0.45] 5.16/<0.0001
 Ventilation mode in the experimental group
  CPAP 2 10/57 34/58 42 0.19 0.16 [0.07, 0.36] 4.28/<0.0001
  PSV 8 38/228 83/256 30 0.19 0.39 [0.25, 0.62] 4.05/<0.0001
 Interfaces used in the control group
  Facial mask 8 42/206 89/232 29 0.2 0.39 [0.25, 0.61] 4.16/<0.0001
  Oronasal mask 1 0/39 2/41 NA NA 0.20 [0.01, 4.30] 1.03/0.3
  Venturi mask 1 6/40 26/41 NA NA 0.32 [0.21, 0.47] 5.56/<0.0001
Complications
 Type of ARF
  Hypercapnic 3 20/97 35/97 77 0.01 0.45 [0.23, 0.86] 2.42/0.02
  Hypoxemic 6 28/164 48/193 17 0.30 0.76 [0.43, 1.32] 0.98/0.33
 Ventilation mode in the experimental group
  CPAP 3 7/68 7/69 57 0.10 1.01 [0.36, 2.89] 0.03/0.98
  PSV 6 41/193 76/221 46 0.10 0.55 [0.34, 0.87] 2.35/0.06
 Interfaces used in the control group
  Facial mask 7 31/182 72/208 25 0.24 0.40 [0.24, 0.67] 3.49/0.0005
  Oronasal mask 1 11/39 9/41 NA NA 1.40 [0.51, 3.86] 0.64/0. 52
  Venturi mask 1 6/40 2/41 NA NA 3.44 [0.65, 18.2] 1.45/0.15
  1. NIV noninvasive ventilation, OR odds ratio, CI confidence interval, ARF acute respiratory failure, CPAP continuous positive airway pressure, PSV pressure support ventilation, NA not applicable