Use of Cardiopulmonary Stress Testing for Patients With Unexplained Dyspnea Post–Coronavirus Disease

OBJECTIVES: The authors used cardiopulmonary exercise testing (CPET) to define unexplained dyspnea in patients with post-acute sequelae of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection (PASC). We assessed participants for criteria to diagnose myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). BACKGROUND: Approximately 20% of patients who recover from coronavirus disease (COVID) remain symptomatic. This syndrome is named PASC. Its etiology is unclear. Dyspnea is a frequent symptom. METHODS: The authors performed CPET and symptom assessment for ME/CFS in 41 patients with PASC 8.9 ± 3.3 months after COVID. All patients had normal pulmonary function tests, chest X-ray, and chest computed tomography scans. Peak oxygen consumption (peak VO(2)), slope of minute ventilation to CO(2) production (VE/VCO(2) slope), and end tidal pressure of CO(2) (PetCO(2)) were measured. Ventilatory patterns were reviewed with dysfunctional breathing defined as rapid erratic breathing. RESULTS: Eighteen men and 23 women (average age: 45 ± 13 years) were studied. Left ventricular ejection fraction was 59% ± 9%. Peak VO(2) averaged 20.3 ± 7 mL/kg/min (77% ± 21% predicted VO(2)). VE/VCO(2) slope was 30 ± 7. PetCO(2) at rest was 33.5 ± 4.5 mm Hg. Twenty-four patients (58.5%) had a peak VO(2) <80% predicted. All patients with peak VO(2) <80% had a circulatory limitation to exercise. Fifteen of 17 patients with normal peak VO(2) had ventilatory abnormalities including peak respiratory rate >55 (n = 3) or dysfunctional breathing (n = 12). For the whole cohort, 88% of patients (n = 36) had ventilatory abnormalities with dysfunctional breathing (n = 26), increased VE/VCO(2) (n = 17), and/or hypocapnia PetCO(2) <35 (n = 25). Nineteen patients (46%) met criteria for ME/CFS. CONCLUSIONS: Circulatory impairment, abnormal ventilatory pattern, and ME/CFS are common in patients with PASC. The dysfunctional breathing, resting hypocapnia, and ME/CFS may contribute to symptoms. CPET is a valuable tool to assess these patients.