The effects of lung volume recruitment therapy on respiratory function and quality of life in people with neuromuscular disease

Abstract

Respiratory muscle weakness results in substantial discomfort, disability and ultimately death in many neuromuscular diseases (NMDs). Respiratory compromise manifests as some or all of, shallow breathing, poor cough and associated difficulty clearing mucus, respiratory tract infections, hypoventilation, sleep-disordered breathing and chronic ventilatory failure. As survival outcomes improve for many NMDs, there is a shift towards more proactive and preventative chronic disease multi-disciplinary care models that manage symptoms, improve morbidity and reduce mortality. Unfortunately, clinical care guidelines for chronic NMD care are based largely on clinical rationale and consensus opinion rather than level A evidence. These guidelines typically recommend therapies to enhance lung inflation and cough effectiveness, however there is minimal evidence that performing techniques regularly is beneficial. Lung volume recruitment (LVR) is one such therapy. Simple, inexpensive and widely-accessible, it delivers air via a manual resuscitation bag to augment lung inflation above a person’s own deepest breath. Given the absence of prospective controlled research, this thesis aimed to investigate the effect of regular LVR in people with NMD.

Firstly, a cross-sectional cohort study of 80 community-dwelling adults with NMD and respiratory system impairment identified that participants with slowly-progressive forms of NMD have smaller lung volumes and respiratory system compliance (Crs) than participants with rapidly-progressive motor neurone disease, despite having a similar degree of respiratory muscle weakness. Stiffness was associated with smaller lung volume in long-standing NMD, supporting the hypothesis that maintaining lung volume and Crs may ameliorate respiratory decline.

The second component of this thesis confirmed the feasibility of LVR; 95% of participants naïve to the therapy could successfully augment their lung insufflation capacity (LIC, the maximum inflation capacity obtained by assisting inflation). Moreover, LIC and Crs increased following a single-session of LVR therapy. These immediate effects were only evident when naïve; when assessed three-months later there was no change in respiratory function following a single-session of LVR.

The third and primary component of this work, a randomised controlled trial of twice-daily LVR or an active control treatment for three-months, found a statistically significant difference in LIC between groups favouring LVR. No demonstrable change in lung volumes, respiratory muscle strength, symptoms or quality of life was found, suggesting a learning effect or acclimatisation to higher inflation pressures may be responsible for the increase. However, an improvement in Crs predominantly in the LVR group means a beneficial effect on underlying respiratory mechanics cannot be excluded, especially if conducted for a longer duration. Notwithstanding the need for further longitudinal studies, the observed improvement in the primary outcome of LIC in the absence of apparent harm or burden, provides robust preliminary data supporting clinical recommendations and practice that regular LVR be performed by people living with NMD. The clinical significance of a higher LIC is still to be fully realised, but this thesis has demonstrated an effect that is compatible with the clinical and biologically-plausible rationale for this therapy.