Intercostal electromyographic responses to multi-site chest wall vibration at an optimal frequency

Area of Science:

• Respiratory physiology
• Neuromuscular control
• Non-invasive ventilation techniques

Background:

• High-frequency mechanical vibration stimulates respiratory muscles via muscle spindle afferents.
• Synchronized multi-site chest wall vibration enhances ventilation, but its effects on intercostal electromyographic (EMG) responses and ventilatory changes are not fully understood.

Purpose of the Study:

• To investigate the impact of multi-site chest wall vibration on intercostal muscle activation and overall ventilation in healthy adults.

Main Methods:

• Twenty healthy adults received phase-synchronized chest wall vibration at four or eight intercostal sites.
• Surface EMG of intercostal muscles, tidal volume (VT), respiratory rate, and thoracoabdominal motion were recorded.
• EMG amplitudes were normalized to maximal voluntary contraction (%MVC).

Main Results:

• Multi-site chest wall vibration significantly increased intercostal EMG activity during both inspiration and expiration.
• Eight-site stimulation yielded greater EMG responses than four-site stimulation.
• Increased EMG activity correlated positively with tidal volume and minute ventilation, alongside enhanced rib cage displacement.

Conclusions:

• Synchronized multi-site chest wall vibration effectively enhances intercostal muscle activation and ventilation.
• This enhancement is likely mediated by spatial summation of proprioceptive input, leading to increased respiratory motor output.
• This technique shows promise as a non-invasive strategy for augmenting ventilation.