Effect of abdominal compression on maximum transdiaphragmatic pressure

Area of Science:

• Physiology
• Respiratory Mechanics

Background:

• Transdiaphragmatic pressure (Pdi) is crucial for assessing diaphragm function.
• Previous studies suggest increased Pdi during combined expiratory and inspiratory efforts may be due to neural activation or diaphragm stretching.

Purpose of the Study:

• To investigate the contribution of diaphragm stretching to Pdi measurements during maximal efforts.
• To determine if Pdi measurements during combined efforts overestimate diaphragm's inspiratory force capacity.

Main Methods:

• Three healthy subjects performed diaphragmatic Mueller maneuvers at functional residual capacity.
• Maneuvers were sustained during abdominal compression via voluntary expulsive effort or external pressure.
• Measurements included transdiaphragmatic pressure (Pdi), abdominal (Pab) and pleural (Ppl) pressures, and respiratory electromyograms.

Main Results:

• Maximal Pdi (Pdimax) increased significantly when expulsive effort was added to inspiratory effort (86±12 to 148±14 cmH2O).
• External compression also increased Pdimax (87±16 to 171±19 cmH2O).
• These increases suggest a significant contribution from diaphragm stretching.

Conclusions:

• Diaphragm stretching significantly contributes to increased Pdi during maximal combined efforts.
• Pdi measurements during combined efforts may overestimate the diaphragm's intrinsic inspiratory force generation capacity.