Functional Capacity Impairment in Long COVID After 17 Months of Severe Acute Disease

Long COVID represents a significant challenge in understanding the prolonged impact of the disease. Despite its increasing recognition, detailed insights into the long-term cardiopulmonary consequences remain sparse. This study aimed to evaluate the functional capacity of individuals with persistent symptoms after severe COVID-19 infection compared to control individuals without symptomatic COVID or mild COVID after 17 months. This is a case-control study assessing 34 individuals divided into two groups regarding functional capacity by distance in a 6-min walk test (D6MWT) associated with gas analysis, spirometry, respiratory muscle strength, and quality of life. During the 6 MWT, an important lower heart rate (HR) was observed for the COVID group (106 ± 10 bpm, difference mean: 21.3; <i>p</i> < 0.001), with greater exertional perception (Borg dyspnea: 4.5 [2.0-9.0], <i>p</i> < 0.001 and Borg fatigue: 4.0 [2.0-7.0], <i>p</i> = 0.01), a significant decrease in the distance covered (416 ± 94 m, difference mean: 107; <i>p</i> = 0.002), and a low value of O₂ uptake (V˙_O2) (11 ± 5.0 mL/(kg min), difference mean: 8.3; <i>p</i> = 0.005) and minute ventilation (22 ± 8 L/min, difference mean: 18.6; <i>p</i> = 0.002), in addition to very low quality of life scores. Regression analysis showed a significant association between D6MWT and Borg fatigue and Borg dyspnea at rest (<i>p</i> = 0.003; <i>p</i> = 0.009). V˙_O2 and HR were also significantly associated with the outcomes of the D6MWT (<i>p</i> = 0.04 and <i>p</i> = 0.004, respectively). In conclusion, individuals who have severe COVID-19 and persist with symptoms have low functional capacity, low V˙_O2, low HR behavior, and low quality of life.