Efficacy of long-term noninvasive positive pressure ventilation in stable hypercapnic COPD patients with respiratory failure: a meta-analysis of randomized controlled trials

Figures & data

Figure 1 Flowchart of the study selection process.

Abbreviation: NPPV, noninvasive positive pressure ventilation.

Table 1 Main characteristics of included studies

Study	Location	Study Design	Trial type	Main characteristics of the subjects	Population (n)	Intervention		IPAP/EPAP	Duration	Main outcomesa
					Randomized (treatment/control)	Treatment	Control
Gay et al (1996)^Citation27	America	RCT	S	FEV1 <40% predicted PaCO2 >45 mmHg	7/6	NPPV + LTOT	shamNPPV + LTOT	10/2	3 months	1, 2, 3, 4
Casanova et al (2000)^Citation25	Spain	RCT	M	FEV1 <45% predicted FEV1/FVC <70%	26/26	NPPV + LTOT	LTOT	12/4	1 year	1, 4, 5, 6, 7
Clini et al (2002)^Citation24	Italy, France	RCT	M	FEV1 <1.5 L FEV1/FVC <60% PaCO2 >50 mmHg PaO2 <60 mmHg	43/47	NPPV + LTOT	LTOT	14/2	2 years	1, 2, 3, 4, 5, 6, 7
McEvoy et al (2009)^Citation5	Australia	RCT	M	FEV1 <1.5 L or <50% predicted FEV1/FVC <60% PaCO2 >46 mmHg	72/72	NPPV + LTOT	LTOT	12.9/5.1	2.21 years	1, 2, 4, 5
Struik et al (2014)^Citation11	The Netherlands	RCT	M	FEV1 <50% predicted FEV1/FVC <70% PaCO2 >45 mmHg	101/100	NPPV + LTOT	LTOT	19.2/4.8	1 year	1, 2, 4, 5, 6
Köhnlein et al (2014)^Citation12	Germany, Austria	RCT	M	FEV1 <30% predicted FEV1/FVC <70% PaCO2 >51.9 mmHg	102/93	NPPV + LTOT	LTOT	21.6/4.8	1 year	1, 2, 3, 4, 5, 6
Zhou et al (2017)^Citation26	People’s Republic of China	RCT	M	FEV1 <50% predicted PaCO2 >50 mmHg	57/58	NPPV + LTOT	LTOT	17.8/4.2	3 months	1, 2, 3, 4, 5

Notes:

a Main outcomes: 1, gas exchange; 2, HRQL; 3, 6MWD; 4, lung function; 5, mortality; 6, hospitalization; 7, PI_max/PE_max.

Abbreviations: HRQL, health-related quality of life; IPAP, intermittent positive airway pressure; EPAP, expiratory positive airway pressure; RCT, randomized controlled trial; NPPV, noninvasive positive pressure ventilation; LTOT, long-term oxygen therapy; 6MWD, 6-minute walk distance; S, single center; M, multicenter; Treatment, treatment group; control, control group; PaCO₂, partial pressure of arterial carbon dioxide; PaO₂, partial pressure of arterial oxygen; PI_max, maximal inspiratory pressure; PE_max, maximal expiratory pressure.

Figure 2 Risk of bia summary.

Notes: The reviewers made judgments about the risk of bias for each item in each included study. +, low summary risk; ?, unclear risk.

Figure 3 Mortality forest plot.

Notes: Experimental, treatment group; control, control group.
Abbreviations: M–H, Mantel–Haenszel method; CI, confidence interval.

Figure 4 Partial pressure of carbon dioxide in arterial blood forest plot.

Notes: Experimental, treatment group; control, control group.

Abbreviation: CI, confidence interval.

Figure 5 Partial pressure of oxygen in arterial blood forest plot.

Notes: Experimental, treatment group; control, control group.
Abbreviation: CI, confidence interval.

Table 2 Meta-analysis of lung function and respiratory muscle strength

Outcomes	Reference numbers for contributing trials	Number of patients (treatment/control)	Treatment effect (WMD 95% CI)a	Homogeneity of treatment effect (P-value)
FEV1 (L)	11, 26, 27	109/110	−0.02 (−0.11 to 0.07)	0.51
FEV1%pred	5, 24, 25, 27	119/123	−0.64 (−3.80 to 2.51)	0.05
FVC (%)	24, 25	59/69	−4.91 (−10.66 to 0.84)	0.82
PImax	24, 25	58/70	−1.87 (−10.01 to 6.26)	0.25

Notes:

a Data presented as WMD (95% CI) unless otherwise stated. Treatment, treatment group; control, control group.

Abbreviations: FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity ratio; PI_max, maximal inspiratory pressure; WMD, weighted mean difference; CI, confidence interval.

Table 3 Subgroup analysis

Therapeutic aim (none vs reducing PaCO2)	Reference numbers	Number of patients (treatment/control)	Treatment effect (WMD 95% CI)	Study heterogeneity
				I^2	P-value
Mortality	5, 11, 24, 25/12, 26	401/396	0.78 (0.54 to 1.13)	0.19	0.003
PaCO2	5, 11, 24, 25, 27/12, 26	300/296	−3.73 (−5.83 to −1.64)	0.0005	93.3%, 0.0001
PaO2	5, 11, 24, 25, 27/12, 26	193/192	0.54 (−0.26 to 3.14)	0.69	0.0%, 0.91

Notes: Treatment, treatment group; control, control group.

Abbreviations: PaCO₂, partial pressure of carbon dioxide; PaO₂, partial pressure of oxygen; WMD, weighted mean difference; CI, confidence interval.

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