Use of twitch mouth pressure to assess diaphragm strength in patients with chronic obstructive pulmonary disease

Inspiratory muscle training for children and adolescents with neuromuscular diseases: A systematic review

Patients with neuromuscular diseases are at risk of morbidity and mortality due to respiratory compromise caused by respiratory muscle weakness. A systematic review was performed using pre-specified search strategies to determine the safety of inspiratory muscle training (IMT) and whether it has an impact on inspiratory muscle strength and endurance, exercise capacity, pulmonary function, dyspnoea and health-related quality of life. Randomised, quasi-randomised, cross-over and clinical controlled trials were included if they assessed the use of an external IMT device compared to no, sham/placebo, or alternative IMT treatment in children aged 5-18 years with neuromuscular diseases. Seven full-text articles and two on-going trials (n = 168) were included. Most studies used threshold IMT devices over a medium to long-term period, and none reported any adverse events. Studies differed regarding intensity, repetitions, frequency, rest intervals and duration of IMT. Six studies reported no significant improvement in pulmonary function tests following IMT. Two comparable studies reported significant improvement in inspiratory muscle endurance and four studies reported significantly greater improvement in inspiratory muscle strength in experimental groups. The latter was confirmed in a meta-analysis of two comparable studies (overall effect p < 0.00001). Other outcome measures could not be pooled. There is currently insufficient evidence to guide clinical IMT practice, owing to the limited number of included studies; small sample sizes; data heterogeneity; and risk of bias amongst included studies. Large sample randomised controlled trials are needed to determine safety and efficacy of IMT in paediatric and adolescent patients with neuromuscular diseases.

Use of a two-way non-rebreathing valve to simplify the measurement of twitch mouth pressure using an inspiratory pressure trigger and the establishment of an optimal trigger threshold for healthy subjects and COPD patients

OBJECTIVE

Controlled twitch mouth pressure (Tw Pmo) via the use of a two-way non-rebreathing valve is a new method to assess diaphragm contractility. The optimal trigger threshold was confirmed.

DESIGN

We sought to determine the optimal trigger threshold for 17 healthy subjects (29±4 years) and 17 COPD patients (64±10 years). The Tw Pmo, twitch oesophageal pressure (Tw Pes) and twitch transdiaphragmatic pressure (Tw Pdi) in response to phrenic nerve stimulation were measured using an inspiratory pressure trigger at -1, -2, -3, -4, -5 and -6 cmH2O.

RESULTS

The lung volume did not change during triggering at different trigger thresholds using a two-way non-rebreathing valve. The highest correlation between Tw Pmo and Tw Pes in healthy subjects and COPD patients occurred for a -2 cmH2O trigger threshold (r=0.939 and r=0.869, P<0.0001). The narrowest limits of agreement for Tw Pmo and Tw Pes both occurred at -2 cmH2O in healthy subjects, with a bias (range) of -0.4 cmH2O (-1.85 to 1.41), and in COPD patients, with a bias (range) of 0.1 6cmH2O (-1.36-1.67).

CONCLUSIONS

We conclude that the measurement of Tw Pmo using a two-way non-rebreathing valve is of clinical value to investigate the suspected diaphragm contractility. The highest trigger threshold for clinical applications was -2 cmH2O.