Breathing by double-lung recipients during exercise: response to expiratory threshold loading

Area of Science:

• Pulmonary Physiology
• Exercise Physiology
• Transplant Medicine

Background:

• Ventilation in double-lung transplant recipients is generally near-normal during exercise despite denervation.
• The impact of lung denervation on respiratory control during loaded breathing is not fully understood.

Purpose of the Study:

• To investigate if lung denervation effects in double-lung transplant recipients are revealed under expiratory loading during exercise.
• To compare respiratory responses to expiratory loading between transplant recipients and healthy controls.

Main Methods:

• Eight double-lung transplant recipients and nine healthy control subjects underwent graded ergometer exercise.
• Expiratory threshold loading (4 cm H2O) was applied intermittently during exercise.
• Ventilation, oxygen consumption, breathing frequency, tidal volume, and flow rates were measured.

Main Results:

• Transplant recipients achieved lower maximal work and oxygen consumption compared to controls.
• Expiratory loading reduced expiratory flow, breathing frequency, and minute ventilation in both groups.
• Unlike controls, transplant recipients exhibited slowed inspiratory flow and prolonged inspiration during loading, exaggerating ventilation reduction.

Conclusions:

• Afferent signals from pulmonary receptors normally modulate inspiration during expiratory loading.
• Bilateral lung denervation in transplant recipients disrupts these neural pathways.
• This disruption leads to abnormal inspiratory adjustments and slower breathing in double-lung recipients under expiratory load.