Impact of inspiratory muscle training in patients with COPD: what is the evidence?

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Figure 1–
Effect of inspiratory muscle strength and endurance training on maximal inspiratory strength (P_I,max). ^#: excluded from the analyses.
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Figure 2–
Effect of general exercise reconditioning (GER) plus inspiratory muscle training versus GER alone on inspiratory muscle strength. P_I,max: maximal inspiratory pressure.
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Figure 3–
Effect of inspiratory strength and endurance training on functional exercise capacity (6-min walk distance).
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Figure 4–
Effect of general exercise reconditioning (GER) plus inspiratory muscle training versus GER alone on functional exercise performance. P_I,max: maximal inspiratory pressure. ^#: result from random effects model.

Table 1– Overall results of the meta-analysis

Outcome measures	Subjects n	Q-statistic	I²	SES	95% CI	p-value (z-statistic)	Natural units
P_I,max	32	57.8	46	0.73	0.53–0.93	0.001	+13 cmH₂O
RMET	14	47.3	73	1.05	0.62–1.49	0.001	+261 s
ITL	11	16.8	3	0.98	0.72–1.25	0.001	+13 cmH₂O
MVV	4	1.2	0	0.23	-0.27–0.72	0.373	+3 L·min⁻¹
Functional exercise capacity	22	14.3	0	0.28	0.12–0.44	0.001	6MWD: +32 m 12MWD: +85 m
Endurance exercise capacity	3	4.6	57	0.72	-0.12–1.55	0.087	+198 s
V′_O₂,max L·min⁻¹	9	6.0	0	-0.13	-0.38–0.11	0.293	-0.04 L·min⁻¹
V′_O₂,max mL·min⁻¹·kg⁻¹	5	5.0	20	0.3	-0.02–0.63	0.067	+1.3 mL·min⁻¹·kg⁻¹
V′_E,max	9	5.5	0	-0.04	-0.3–0.2	0.696	-0.7 L·min⁻¹
W_max	10	5.1	0	0.07	-0.16–0.3	0.562	+1.7 W
Dyspnoea Borg score	14	15.6	17	-0.45	-0.66– -0.24	0.001	-0.9
Dyspnoea TDI	4	6.3	52	1.58	0.86–2.3	0.001	+2.8
Dyspnoea CRQ-Dyspnoea	9	16.6	52	0.34	-0.03–0.71	0.068	+1.1
Quality of life CRQ	9	10.4	20	0.34	0.09–0.60	0.007	+3.8
CRQ fatigue	10	8.2	0	0.27	0.03–0.50	0.024	+0.9
CRQ emotion	10	7.6	0	0.19	-0.04–0.42	0.107	+0.5
CRQ mastery	10	8.5	0	0.09	-0.14–0.33	0.432	-0.005

n = 32. SES: summary effect size; P_I,max: maximal inspiratory pressure; RMET: respiratory muscle endurance test: ITL: incremental threshold loading; MVV: maximal voluntary ventilation; V′_O₂,max: maximal oxygen uptake; V′_E,max: maximal minute ventilation; W_max: maximal power output; TDI: transition dyspnoea index; CRQ: chronic respiratory questionnaire.