Lung insufflation capacity in neuromuscular disease

Area of Science:

• Pulmonary Medicine
• Neurology
• Rehabilitation Therapy

Background:

• Neuromuscular diseases (NMD) often impair respiratory muscle function, leading to reduced lung volumes and vital capacity (VC).
• Effective lung inflation techniques are crucial for managing respiratory complications in NMD patients.
• Assessing glottic function and cough peak flows (CPF) is important for evaluating disease severity and progression.

Purpose of the Study:

• To compare maximal passive lung insufflation capacity (LIC) with air stacking (maximum insufflation capacity [MIC]) and vital capacity (VC) in NMD patients.
• To investigate the correlation between lung inflation variables, glottic function, and CPF.
• To evaluate the impact of routine lung inflation therapy on LIC and MIC and its relation to disease severity.

Main Methods:

• A case series of 282 NMD patients (age ≥7 years, VC <70% predicted) was conducted.
• Patients received prescribed thrice-daily air stacking and/or maximal passive lung insufflation (40-80 cm H2O).
• Measurements included VC, MIC, LIC, and unassisted/assisted CPF during clinic visits.

Main Results:

• Mean values: VC (1131±744 ml), MIC (1712±926 ml), LIC (2069±867 ml), unassisted CPF (2.5±2.0 L/sec), assisted CPF (4.3±2.2 L/sec) (all P < 0.001).
• MIC-VC correlated inversely with LIC-MIC (P=0.01), indicating a link to glottic function.
• Both MIC and LIC improved with practice (P < 0.001); LIC gains over VC were greatest in patients with the lowest VC (P < 0.05).

Conclusions:

• Maximal passive lung insufflation achieves greater lung distension than air stacking in NMD patients, particularly those with severe glottic/bulbar dysfunction.
• LIC, MIC, and VC measurements provide a quantifiable assessment of glottic integrity and bulbar muscle function in NMD.
• Patients with the lowest vital capacity demonstrate the most significant benefit from lung insufflation therapy.