Dyspnea and long COVID patients.

Patients with prior COVID-19 infections often develop chronic post-COVID symptoms, such as fatigue and dyspnea. Some patients have residual pulmonary disorders with abnormal pulmonary function tests and/or chest radiographs to explain their dyspnea. However, other patients appear to have dyspnea that is out of proportion to any measurable change in lung function. Some of these patients have abnormal cardiopulmonary exercise testing with definite cardiac or respiratory limits. However, others have normal cardiopulmonary exercise testing based on VO2 measurement but pronounced dyspnea during this testing. These patients often have abnormal respiratory patterns, referred to as dysfunctional breathing, with irregular and variable respiratory rates and/or tidal volumes. Consequently, their control of breathing is impaired, and this may represent residual effects from prior COVID-19 infection involving the central nervous system. Alternatively, patients may have acquired "a memory" of respiratory symptoms during their infection which persists post-infection. These patients should participate in pulmonary rehabilitation and breathing retraining.