Dynamic Ventilatory Reserve During Incremental Exercise: Reference Values and Clinical Validation in Chronic...

Area of Science:

• Pulmonary Physiology
• Cardiopulmonary Exercise Testing
• Respiratory Medicine

Background:

• Current assessment of ventilatory demand-capacity imbalance relies on peak cardiopulmonary exercise testing (CPET) ventilatory reserve.
• Peak ventilatory reserve is insufficient for detecting submaximal, dynamic mechanical ventilatory abnormalities contributing to dyspnea and exercise intolerance.
• There is a need for improved methods to assess ventilatory limitations during exercise in chronic obstructive pulmonary disease (COPD).

Purpose of the Study:

• Establish sex- and age-corrected norms for dynamic ventilatory reserve across different work rates.
• Compare the efficacy of peak versus dynamic ventilatory reserve in identifying exertional dyspnea and exercise intolerance in COPD patients.
• Investigate the relationship between dynamic ventilatory reserve, ventilatory requirements, and dyspnea scores at submaximal exercise.

Main Methods:

• Analyzed resting and incremental CPET data from 275 controls and 359 COPD patients (Global Initiative for Chronic Obstructive Lung Disease stages 1-4).
• Measured peak and dynamic ventilatory reserve, operating lung volumes, and dyspnea scores (Borg scale).
• Calculated centile distribution for dynamic ventilatory reserve to establish lower limits of normal, considering sex and age.

Main Results:

• Dynamic ventilatory reserve norms were established, with lower limits of normal varying by sex and age.
• Significant disagreement was observed between peak and dynamic ventilatory reserve in identifying abnormalities in COPD patients (50% with normal peak VR had reduced dynamic VR).
• Reduced dynamic ventilatory reserve at submaximal workloads (40 W) correlated with higher ventilatory requirements, earlier inspiratory reserve limitation, increased dyspnea, and poorer exercise tolerance.

Conclusions:

• Reduced submaximal dynamic ventilatory reserve is a potent predictor of exertional dyspnea and exercise intolerance in COPD, even with preserved peak ventilatory reserve.
• Dynamic ventilatory reserve offers a more sensitive measure of ventilatory demand-capacity mismatch than peak ventilatory reserve.
• This novel parameter can enhance the clinical utility of CPET for diagnosing activity-related breathlessness in COPD and other cardiopulmonary diseases.