Function of respiratory muscles during partial curarization in humans

Area of Science:

• Physiology
• Respiratory Medicine
• Neuromuscular Pharmacology

Background:

• Submaximal neuromuscular blockade (SMNB) can alter respiratory muscle function.
• Understanding the differential effects of neuromuscular blocking agents on various respiratory muscles is crucial for clinical applications.

Purpose of the Study:

• To investigate the effects of SMNB on respiratory muscle recruitment during different respiratory maneuvers.
• To elucidate the impact of SMNB on lung mechanics and respiratory muscle electrical activity.

Main Methods:

• Four healthy males received slow infusions of pancuronium to induce SMNB.
• Lung mechanics were assessed using pressure-volume curves.
• Electrical activity of respiratory muscles (diaphragm, abdominal, intercostal) was measured using concentric needle electrodes.

Main Results:

• SMNB shifted the chest wall pressure-volume curve to the right.
• Increased diaphragmatic contribution to pressure swings was observed, with higher gastric and transdiaphragmatic pressures.
• Marked decrease in electrical activity of abdominal and intercostal muscles, with a slight increase in diaphragmatic activity.

Conclusions:

• The human diaphragm exhibits greater resistance to curare compared to other respiratory muscles.
• The observed shift in the chest wall pressure-volume curve is linked to reduced tonic activity in intercostal muscles.
• Differential neuromuscular synapse safety margins likely explain the varying sensitivity of respiratory muscles to curare.