Background: Respiratory muscle weakness in Duchenne (DMD) patients leads to respiratory failure, for which non-invasive positive pressure ventilation (NIPPV) is an effective treatment. This is used at night initially (n-NIPPV), but as the disease progresses, diurnal use (d-NIPPV) is often necessary. The connection between NIPPV and relief of respiratory muscle fatigue remains unclear.
Objectives: To study the extent to which nocturnal and diurnal NIPPV unload the respiratory muscles and improve respiratory endurance in DMD patients.
Methods: Fifty patients with DMD assessed at 8pm and 8am. More severely affected patients, with nocturnal hypoventilation, received n-NIPPV; those with daytime dyspnoea also received d-NIPPV via a mouthpiece (2-4 pm). Lung function, modified Borg dyspnoea score, spontaneous breathing pattern, tension-time index (TT0.1=P0.1/MIPxTi/Ttot) and respiratory muscle endurance time (Tlim) against a threshold load of 35% maximum inspiratory pressure were measured. Results: More severe respiratory muscle weakness was associated with a higher TT0.1 and lower Tlim. In contrast to non-dyspnoeic patients, dyspnoeic patients (Borg score>2.5/10) showed an increase in Tlim and decrease in TT0.1 after n-NIPPV. At 4pm, immediately after d-NIPPV, dyspnoeic patients had lower TT0.1 and Borg scores with unchanged Tlim. Compared to the control day without d-NIPPV, TT0.1, Borg scores and Tlim were all improved at 8pm.
Conclusions: In dyspnoeic DMD patients, the load on respiratory muscles increases and endurance capacity decreases with increasing breathlessness during the day, and this is reversed by nocturnal NIPPV. An additional two hours of d-NIPPV unloads respiratory muscles and reverses breathlessness more effectively than n-NIPPV alone.
- musculoskeletal diseases
- neuromuscular diseases
- non-invasive ventilation
- respiratory muscle fatigue