Submaximal 2-day cardiopulmonary exercise testing to assess exercise capacity and post-exertional symptom exacerbation in people with long COVID

Area of Science:

• Cardiopulmonary exercise testing
• Long COVID physiology
• Post-exertional symptom exacerbation (PESE)

Background:

• Long COVID presents complex pathology and diverse symptoms affecting quality of life.
• Post-exertional symptom exacerbation (PESE) impacts one-third of long COVID patients.
• The physiological underpinnings of impaired physical function in PESE remain unclear.

Purpose of the Study:

• To investigate the physiological basis of impaired physical function in individuals with long COVID experiencing PESE.
• To assess changes in cardiopulmonary exercise parameters 24 hours after submaximal exercise in long COVID patients.

Main Methods:

• Sixty-eight long COVID patients with PESE underwent two submaximal cardiopulmonary exercise tests (CPET) 24 hours apart.
• Work rate was stratified (10, 20, or 30 W) and increased by 5 W/min for up to 12 minutes.
• Key parameters measured included oxygen uptake (V̇O2), oxygen pulse, and end-tidal carbon dioxide (PETCO2) at the first ventilatory threshold (VT1).

Main Results:

• Oxygen uptake (V̇O2) at VT1 decreased significantly from Day 1 (0.73 L/min) to Day 2 (0.68 L/min) (P=0.003).
• Work rate at VT1 was lower on Day 2 (24 W) compared to Day 1 (28 W) (P=0.004).
• Oxygen pulse at VT1 was reduced on Day 2 (7.5 mL/beat) versus Day 1 (8.2 mL/beat) (P=0.002), and PETCO2 also decreased on Day 2 (37 mmHg vs 38 mmHg, P=0.010).

Conclusions:

• Impaired V̇O2 at VT1 on Day 2 indicates worsened physiological function 24 hours after exercise in long COVID patients with PESE.
• Reduced oxygen pulse and PETCO2 suggest potential issues with oxygen transport and utilization.
• Findings suggest multiple physiological mechanisms contribute to impaired physical function, warranting further investigation.