Condensed by Claudio López Bruzual, MD.
Hospital survival in case of severe COVID-19 involvement is often associated with residual fibrotic lung abnormalities, evidenced by pulmonary CT at the time of discharge, and lung function tests. Given the severe multisystemic damage typically suffered by these patients, several forms of pulmonary vascular impact (macro and micro embolism or inflammatory endothelitis with neo angiogenesis) have been reported; additionally, the severe inflammatory response can lead to anemia with a reduction in oxygen carrying capacity.
On the other hand, prolonged hospitalization often promotes profound deconditioning and muscle atrophy; there is also some concern that direct muscle damage may occur from the virus itself.
Thus, in Milan, Italy, took place a study to evaluate if hospital discharged COVID-19 patients could perform exercise. The study enrolled 18 clinically healed COVID-19 patients that matched 18 control subjects for age, sex, and BMI.
Enrolled participants underwent spirometry, echocardiography at rest, cardiopulmonary stress test, and exercise stress echocardiography. Recovered COVID-19 patients were also taken samples for arterial gases at rest and during exertion.
Cardiorespiratory function at rest. Relatively lower lung volumes were observed in post-COVID-19 patients to that in control subjects, with an average decrease of FVC of 22% and of FEV1 of 26%. In addition, recovered COVID-19 patients showed:
- Their respiratory dynamics were characterized by higher respiratory rate (24 vs. 18.5), with higher end‐inspiratory lung volume (1.97 vs. 1.06).
- A slightly lower O2 saturation, albeit within the normal range.
- The Arterial Blood Oxygen Content (CAO2) was lower, associated with lower levels of Hb.
- Arteriovenous O2 difference was significantly lower in post-COVID-19 patients, but peripheral O2 extraction at rest was not different between COVID‐19, and controls.
Cardiorespiratory function during exercise. At peak exercise effort, consumption of VO2 was significantly lower in post-COVID-19 patients than that of controls. 95% of postCOVID-19 subjects had a reduced capacity of exercise with a peak VO2 less than 70% of predicted in 61% of patients. The VO2/work slope was also significantly lower than that of controls.
This paper is a first depiction of cardiorespiratory adaptation to exercise in the COVID-19 pneumonia recovery phase. So far, this is the outcome:
- Patients recovering from COVID-19 pneumonia have a significant reduction of exercise capacity.
- Functional capacity impairment is primarily related to peripheral factors (anemia and O2 extraction) rather than cardiac or respiratory limitation.
- Despite severe lung damage, pulmonary vascular function is not severely impaired.
- Exercise hyperventilation after COVID-19 is mainly due to an enhanced chemoreflex sensitivity, rather than increased VD/VT.
Careful patient follow-up
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