Impairment of respiratory muscle function in pulmonary hypertension

Abstract

It has been suggested that impaired respiratory muscle function occurs in patients with PH (pulmonary hypertension); however, comprehensive investigations of respiratory muscle function, including the application of non-volitional tests, needed to verify impairment of respiratory muscle strength in patients with PH have not yet been performed. In the present study, respiratory muscle function was assessed in 31 patients with PH (20 females and 11 males; mean pulmonary artery pressure, 51+/-20 mmHg; median World Health Organization class 3.0+/-0.5; 25 patients with pulmonary arterial hypertension and six patients with chronic thromboembolic PH) and in 31 control subjects (20 females and 11 males) well-matched for gender, age and BMI (body mass index). A 6-min walking test was performed to determine exercise capacity. Volitionally assessed maximal inspiratory (7.5+/-2.1 compared with 6.2+/-2.8 kPa; P=0.04) and expiratory (13.3+/-4.2 compared with 9.9+/-3.4 kPa; P<0.001) mouth pressures, sniff nasal (8.3+/-1.9 compared with 6.6+/-2.2 kPa; P=0.002) and transdiaphragmatic (11.3+/-2.5 compared with 8.7+/-2.5 kPa; P<0.001) pressures, non-volitionally assessed twitch mouth (1.46+/-0.43 compared with 0.97+/-0.41 kPa; P<0.001) and transdiaphragmatic (2.08+/-0.55 compared with 1.47+/-0.72 kPa; P=0.001) pressures during bilateral anterior magnetic phrenic nerve stimulation were markedly lower in patients with PH compared with control subjects. Maximal inspiratory mouth (r=0.58, P<0.001) and sniff transdiaphragmatic (r=0.43, P=0.02) pressures were correlated with the 6-min walking distance in patients with PH. In conclusion, the present study provides strong evidence that respiratory muscle strength is reduced in patients with PH compared with well-matched control subjects. Furthermore, the 6-min walking distance is significantly linked to parameters assessing inspiratory muscle strength.

Inspiratory muscle function, dynamic hyperinflation and exertional dyspnoea in pulmonary arterial hypertension

“…1) and the identical Poes,sniff values pre-and post-exercise in both PAH-H and PAH-NH patients. Differences in technique and disease stage/severity between our PAH population and those of other studies [14][15][16] may explain the differences between our results and those of other studies.…”

“…Although inspiratory muscle dysfunction has been suspected in PAH patients at rest [14,15], mostly in severely compromised PAH attending for pulmonary transplantation [16], the contribution of inspiratory muscle weakness/fatigue to the decreased IC can reasonably be ruled out in our PAH-H patients: inspiratory muscle strength was preserved, as highlighted by the preserved Poes,IC during CPET ( fig. 1) and the identical Poes,sniff values pre-and post-exercise in both PAH-H and PAH-NH patients.…”

Effects of exercise training in patients with idiopathic pulmonary arterial hypertension

“…More recently, several reports suggested muscle dysfunction in patients with pulmonary arterial hypertension [14][15][16]. Mechanisms are still unclear, but it can be speculated that inactivity of the skeletal muscles, together with a decreased cardiac output leading to a reduced oxygen transport to the skeletal muscles, trigger morphological changes, such as muscle atrophy, fibre type switching and reduced aerobic capacity [18].…”

“…Respiratory muscle dysfunction was found in two studies, both by voluntary and nonvoluntary techniques [14,15]. More recently, forearm muscle dysfunction has been reported in these patients [16].…”

Evaluating respiratory musculature, quality of life, anxiety, and depression among patients with indeterminate chronic Chagas disease and symptoms of pulmonary hypertension

“…Another experimental study evaluated changes in contractile performance, diaphragm morphology, and inspiratory muscle weakness in rats with PH, and revealed that these rats had a significant reduction in the diaphragm's maximal contraction and generation forces. As this weakness appears to be specific to the diaphragm muscle, rather than generalized weakness, it is possible that chronic activity of the diaphragm can be triggered in cases of PH 11,12 .…”