Table 1.
Clinical studies on muscle dysfunction in ILD.a
| Author, year | Study design | Cases/controls | Disease [n]. Restrictive defect | Muscle strength | Findings in ILD | Limitations |
|---|---|---|---|---|---|---|
| De Troyer et al.,34 1980 | Prospective case control | 12/135 | Sarcoidosis-assoc. ILD [1], asbestosis [2], CTD [3] and HP [1]. TLC 75% pred. | Ppl min. | Ppl min. normal relative to lung volume over much of the inspiratory capacity suggesting preservation of the inspiratory muscle strength. | Volitional tests. Heterogeneity of the study population. |
| Gorini et al.,41 1989 | Prospective case control | 12/18 | IPF [8] and CTD [1]. TLC 67% pred. | PImax | Reduced PImax %pred. (69%). | Volitional tests. Results might have been confounded by chronic steroid treatment (received by 10 patients). |
| Nishimura et al.,36 1989 | Prospective cross section | 15/0 | IPF. TLC 71% pred. | PImax and PEmax | Preserved PImax. Reduced PEmax %pred. (57%). Significant negative correlation between lung volumes %pred. and PImax %pred. but not with PEmax %pred. Respiratory muscle strength had no correlation with PaO2 or PaCO2. | Volitional tests. PImax and PEmax were overestimated (not corrected for lung volume). The method of diagnosis of IPF is unclear. |
| O’Donnell et al.,8 1998 | Prospective case control | 12/12 | IPF [3], Sarcoidosis [2], CTD [1] and other [3].TLC 70% pred. | PImax and PEmax | Preserved PImax and PEmax. | Volitional tests. Heterogeneity of the study population. |
| Baydur et al.,50 2001 | Prospective case control | 36/25 | Sarcoidosis. TLC 84% pred. | PImax and PEmax | Reduced PImax (37% less) and PEmax (39% less). Strong inverse relationships between PEmax and PImax with dyspnoea/activity. | Volitional tests. Only 24 patients had ILD. No restrictive defect. |
| Garcia-Rio et al.,37 2003 | Prospective case control | 14/11 | UIP. TLC 68% pred. | PImax, PI mean, Pdi and Pes | Increased PI mean. Preserved PImax, Pdi and Pes. | Volitional tests. The method of estimation may have led to an overestimation of PI mean. |
| Nishiyama et al.,2 2005 | Retrospective cross section | 41/0 | IPF. TLC 77% pred. | PImax, PEmax, QF and HF | Preserved PImax and HF. Reduced PEmax (68% pred.) and QF (65% pred.). QF was independent predictor of V▪O2max in patients who discontinued exercise because of dyspnoea and/or leg fatigue. | Retrospective. Volitional tests. |
| Walterspacher et al.,40 2013 | Prospective case control | 25/24 | UIP [16], NSIP [3], HP [1], AIP [1] and unspecified [4]. TLC 55% pred. | PImax, PEmax, SNiP, TwPmo and TwPdi | Reduced TwPmo (35% less) and TwPdi (29% less). Preserved PImax, SNiP and PEmax. | Heterogeneity of the study population. Results might have been confounded by chronic steroid treatment (received by 19 patients). |
| Elia et al.,44 2013 | Prospective cross section | 16/0 | IPF [1], HP [3] and CTD [9]. TLC 74% pred. | PImax, PEmax, TwPdi, TwT10Pga, SNiP, SnPdi and cough Pga | During maximal exercise, TwPdi did not change but TwT10Pga fell by 12%. The fall in TwT10Pga correlated with V▪O2max and the decrease in EELV. Fatiguers (defined as having a ≥10% fall in TwT10Pga) had a fall in EELV and lower pre-exercise TwPdi. | Results might have been confounded by chronic steroid treatment (received by all patients). |
| Watanabe et al.,39 2013 | Retrospective cross section | 30/0 | f-NSIP. VC 75% pred. | PImax, PEmax, QF and HF | Preserved PImax and HF. Decreased PEmax (75% pred.) and QF (82% pred.). Adjusted for sex, QF was an independent predictor of 6MWD. | Retrospective. Volitional tests. Mild disease. PImax, PEmax and HF were related to predicted values derived from populations different from the study population. |
| Mendoza et al.,38 2014 | Prospective case control | 25/33 | IPF and f-NSIP. TLC 68% pred. | PImax, PEmax, SNiP, QMVC, TwQ and QE | Reduced TwQ (20% less) and QE. Preserved PImax, PEmax, and SNiP. PImax correlated with 6MWD. | Use of 6MWT instead of formal CPET for the assessment of exercise capacity. |
ILD: interstitial lung disease; SNiP: sniff nasal inspiratory pressure; Pes: oesophageal pressure; HF: handgrip peak voluntary force; QF: quadriceps peak voluntary force; QMVC: quadriceps maximum voluntary contraction; TwQ: quadriceps twitch force in response to magnetic femoral nerve stimulation; QE: quadriceps endurance using the decay in force in response to repetitive magnetic stimulation of the quadriceps over 5 min; EELV: end-expiratory lung volume; VC: vital capacity; SVC: slow vital capacity; FVC: forced vital capacity; TLC: total lung capacity; PaO2/PaCO2: partial pressure of oxygen/carbon dioxide in the arterial blood; V▪O2max: maximum oxygen uptake; 6MWD: 6-minute walk distance; CPET: cardiopulmonary exercise test; f-NSIP: fibrotic non-specific interstitial pneumonia, HP: hypersensitivity pneumonitis; AIP: acute interstitial pneumonia; CTD: connective tissue disease; PImax/PEmax: maximum inspiratory/expiratory mouth pressure; Ppl min.: minimum (greatest negative) pleural pressure; Pdi: maximum transdiaphragmatic pressure during volitional manoeuvers; SnPdi: sniff transdiaphragmatic pressure; TwPmo/TwPdi: twitch mouth/transdiaphragmatic pressure during bilateral magnetic phrenic nerve stimulation; TwT10Pga: gastric pressure at twitch T10 nerve roots; IPF: idiopathic pulmonary fibrosis; UIP: usual interstitial pneumonia; assoc.: associated; pred.: predicted.
aAll studies are single centred. Data are presented as n or mean unless otherwise stated.