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Table 5 Subgroup analysis - the effect on secondary 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

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

  1. 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