Table 1.
Studies of inspiratory muscle training in patients with heart disease and heart failure.
| Study (year) | n | Mode of IMT | Study measurements | Study outcomes | Ref. |
|---|---|---|---|---|---|
| Mancini et al. (1995) | Exp = 8 Con = 6 |
Threshold at 30% of MIP + a variety of BE for 12 weeks (90 min, 3×/week) | MIP, MEP, IME, 6-MWT, exercise duration, peak VO2, HR, BP, RR, VT, VE, dyspnea | Improved MIP, MEP, IME, 6-MWT, exercise duration, peak VO2, VE and dyspnea | [4] |
| Cahalin et al. (1997) | 8 | Threshold at 20% of MIP for 8 weeks (5–15 min, 3×/day, 7×/week) | MIP, MEP, dyspnea | Improved MIP, MEP and dyspnea | [5] |
| Johnson et al. (1998) | Exp = 8 Con = 8 |
Threshold at 30% of MIP for 8 weeks (15 min, 2×/day, 7×/week) | MIP, MEP, exercise duration, 100-m walk test and QoL | Improved MIP and MEP, but no significant change in other measures | [6] |
| Darnley et al. (1999)† | 9 | Hans-Rudolph valve attached to tubing with a progressive increase in the length of tubing each week of a 4-week study (four, 5-min BE/60-min session, 3×/week) | Exercise duration, PFTs, HR and diaphragmatic excursion and velocity | Improved exercise duration and diaphragmatic velocity | [7] |
| Weiner et al. (1999) | Exp = 10 Con = 10 |
Threshold at 60% of MIP for 12 weeks (30 min, 6×/week) | MIP, MEP, IME, PFTs, peak VO2, 12-MWT and dyspnea | Improved MIP, MEP, IME, PFTs, 12-MWT and dyspnea | [8] |
| Martinez et al. (2001)‡ | Exp = 11 Con = 9 |
Threshold at 30% of MIP for 6 weeks (15 min, 2×/day, 6×/week) | MIP, IME, peak VO2, 6-MWT and dyspnea | Improved MIP, IME, peak VO2, 6-MWT and dyspnea | [9] |
| Cahalin et al. (2001) | Exp = 6 Con = 6 Cross-over |
Threshold IMT at 40% of MIP and Threshold EMT at 5–15% of MEP for 12 weeks (30–40 min, 5×/week) | MIP, MEP, IME, PFTs, peak VO2, 6-MWT, cycling endurance, dyspnea and QoL | Improved MIP, MEP, IME, PFTs, peak VO2, 6-MWT, dyspnea and QoL | [10] |
| Laoutaris et al. (2004) | Exp = 20 Con = 15 |
TIRE at 60% of MIP/SMIP for 10 weeks (3×/week for an uncertain duration) | MIP, SMIP, peak VO2, VE, HR, 6-MWT, dyspnea and QoL | Improved MIP, SMIP, peak VO2, HR, 6-MWT, dyspnea and QoL | [11] |
| Hulzebos et al. (2006)§ | Exp = 139 Con = 137 |
Threshold at 30% of MIP for 14–90 days (mean = 30) prior to CABG surgery (20 min, 7×/week) | MIP, MEP, IME, and postoperative pulmonary complications | Improved MIP, IME and postoperative pulmonary complications | [12] |
| Dall’Ago et al. (2006) | Exp = 16 Con = 16 |
Threshold at 30% of MIP for 12 weeks (30 min, 7×/week) | MIP, MEP, IME, peak VO2, VE, VE/VCO2 slope, recovery O2, 6-MWT and dyspnea | Improved MIP, MEP, IME, peak VO2, VE, VE/VECO2 slope, recovery O2, 6-MWT and dyspnea |
[13] |
| Laoutaris et al. (2007) | Exp = 15 Con = 23 |
TIRE at 60% of MIP/SMIP for 10 weeks (3×/week for an uncertain duration) | MIP, SMIP, PFTs, peak VO2, VE, 6-MWT, dyspnea, TNF-α, TNF receptor I, IL-6, CRP, Fas and Fas ligand | Improved MIP, SMIP, PFTs, peak VO2, 6-MWT, dyspnea and TNF receptor I change | [14] |
| Laoutaris et al. (2008) | Exp = 14 Con = 9 |
TIRE at 60% of MIP/SMIP for 10 weeks (3×/week for an uncertain duration) | MIP, SMIP, peak VO2, dyspnea, VE, VE/VCO2 slope, HRV, NT-proBNP and endothelial vasodilation |
Improved MIP, SMIP, peak VO2 and dyspnea | [15] |
| Chiappa et al. (2008) | 18 | Threshold at 30% of MIP for 4 weeks (30 min, 7×/week) | MIP, MEP, diaphragm thickness and resting and exercise calf and forearm blood flow | Improved MIP, MEP, diaphragm thickness and resting and exercise calf and forearm blood flow | [16] |
| Padula et al. (2009)¶ | Exp = 15 Con = 17 |
Threshold at 30% of MIP for 12 weeks (10–20 min, 7×/week) | MIP, RR, dyspnea, self efficacy and QoL | Improved MIP, RR and dyspnea | [17] |
| Stein et al. (2009) | Exp = 16 Con = 16 |
Threshold at 30% of MIP for 12 weeks (30 min, 7×/week) | MIP, OUES | Improved MIP and OUES | [18] |
| Winkelmann et al. (2009) | Exp = 12 Con = 12 |
Threshold at 30% of MIP for 12 weeks (30 min, 7×/week) | MIP, MEP, IME, OUES, peak VO2, VE, VE/VCO2 slope, VE oscillation, recovery O2 kinetics, 6MWT and QoL | Improved MIP, MEP, IME, OUES, peak VO2, VE, VE/VCO2 slope, VE oscillation and recovery O2 kinetics | [19] |
| Bosnak-Guclu et al. (2011) | Exp = 16 Con = 14 |
Threshold at 40% of MIP for 6 weeks (30 min, 7×/week) | MIP, MEP, 6MWT, balance, quadriceps isometric strength, dyspnea, fatigue, PFTs, depression and QoL | Improved MIP, MEP, PFTs, 6MWT, balance, quadriceps isometric strength, dyspnea, depression and QoL | [20] |
| Mello et al. (2012) | Exp = 15 Con = 12 |
Threshold at 30% of MIP for 12 weeks (10 min, 3×/day, 7×/week); mostly home-based | MIP, peak VO2, VE/VCO2, VE/VCO2 slope, HRV, MSNA and QoL | Improved MIP, peak VO2, VE/VCO2, VE/VCO2 slope, HRV, MSNA and QoL | [21] |
| Laoutaris et al. (2012) | Exp = 13 Con = 14 |
TIRE at 60% of MIP/SMIP for 12 weeks (20 min, 3×/week) | MIP, SMIP, peak VO2, dyspnea, VE, VE/VCO2 slope, VT, CP, quadriceps isometric strength and endurance, LVEF, LVESD, LVEDD and QoL | Improved dyspnea, MIP, SMIP, peak VO2, VE/VCO2 slope, VT, CP, quadriceps isometric strength and endurance, LVEF, LVESD, LVEDD, QoL | [22] |
All but one of the nine subjects with ischemic heart disease had a LVEF <50%; the one other subject had a LVEF of 52% (mean LVEF: 46.6 ± 4%).
The control group performed IMT in the same manner as the experimental group except that the IMT workload was less (10% of MIP), which may have been responsible for the improvement in dyspnea, MIP, IME and peak VO2 in the control group. Only the experimental group had a significant improvement in the 6MWT distance ambulated.
Approximately, 40% of the subjects had a LVEF <50%; 63% of the IMT group and 76.5% of the usual care group experienced New York Heart Association class III symptoms and approximately 2% of the IMT group and usual care group experienced New York Heart Association class IV symptoms.
The control group consisted of patient education which included information on basic anatomy and physiology of the heart, diet, medication regimen, sleep, rest and activity patterns, and what and when to report to the doctor.
BE: Breathing exercises; BP: Blood pressure; CABG: Coronary artery bypass graft; Con: Control group; CP: Circulatory power (peak VO2 × peak systolic blood pressure); CRP: C-reactive protein; EMT: Expiratory muscle training; Exp: Experimental group; HR: Heart rate; HRV: Heart rate variability; IME: Inspiratory muscle endurance; IMT: Inspiratory muscle training; LVEDD: Left ventricular end-diastolic diameter; LVEF: Left ventricular ejection fraction; LVESD: Left ventricular end-systolic diameter; MEP: Maximal expiratory pressure; MIP: Maximal inspiratory pressure; MSNA: Muscle sympathetic nervous activity; MWT: Minute walk test; NT-proBNP: N-terminal fragment of basic natriuretic peptide; OUES: Oxygen uptake efficiency slope; PFTs: Pulmonary function tests; QoL: Quality of life; RR: Respiratory rate; SMIP: Sustained maximal inspiratory pressure; TIRE: Rest of incremental respiratory endurance; VE/VCO2: Ventilation to carbon dioxide ratio; VE: Ventilation; VO2: Oxygen consumption; VT: Ventilatory threshold.