Table 2. Between-group comparison of responses at peak and recovery from cardiopulmonary exercise testing.
| Variables | COVID-19 survivors (n=29) | Control group (n=18) | P |
|---|---|---|---|
| Peak | |||
| Work rate (W) | 121±39 | 168±68* | 0.005 |
| Metabolic responses | |||
| V̇O2 (mL/min) | 1508±418 | 1979±781* | 0.01 |
| V̇O2 (mL·kg−1·min−1) | 17.20±5 | 27.08±7* | <0.001 |
| V̇O2 pred (%) | 61±13 | 86±19* | <0.001 |
| V̇O2/WR (mL·min−1·W−1) | 12.72±2.2 | 12±1.4 | 0.20 |
| V̇CO2 (mL/min) | 1581±495 | 2223±826* | 0.002 |
| RER peak | 1.06±0.11 | 1.14±0.04* | 0.01 |
| Ventilatory responses | |||
| V̇ E (L/min) | 51±16 | 71±19* | 0.001 |
| BF (breaths/min) | 33±7 | 40±10* | 0.01 |
| V̇ E/V̇CO2 slope | 35±9 | 28±2* | 0.007 |
| P ETCO2 peak (mmHg) | 32.87±4.1 | 36.59±3.4* | 0.003 |
| Δ P ETCO2 (mmHg) | 1.96±2.8 | 3.97±1.6* | 0.009 |
| OUES | 2.64±1.1 | 3.07±1.4 | 0.26 |
| VP (mmHg) | 6.31±2.15 | 7.00±1.12 | 0.22 |
| SpO2peak (%) | 95±2 | 96±1* | 0.04 |
| Cardiovascular responses | |||
| HR peak (bpm) | 145±24 | 164±17* | 0.006 |
| Δ HR rest (bpm) | 20±14 | 24±8 | 0.30 |
| SBP peak (mmHg) | 205±24 | 199±22 | 0.41 |
| SBP rest (mmHg) | 151±20 | 135±12* | 0.004 |
| DBP peak (mmHg) | 94±11 | 93±9 | 0.65 |
| DBP rest (mmHg) | 86±8 | 80±3* | 0.01 |
| PD peak (mmHg/bpm) | 29698±514 | 32780±441* | 0.04 |
| Peak O2 pulse (mL/bpm) | 10±3 | 12±4 | 0.22 |
| CP (mmHg·mL−1·kg−1·min−1) | 3130±101 | 4046±189* | 0.03 |
| Perception of symptoms | |||
| Peak dyspnea score (0-10) | 5±2 | 5±2 | 0.85 |
| Peak leg effort score (0-10) | 6±3 | 7±1* | 0.05 |
| Test interruption criteria | |||
| Peak leg effort score | 13 (45) | 0 (0)* | 0.001 |
| Peak dyspnea score | 4 (14) | 0 (0) | 0.09 |
| Ventilation reserve | 4 (14) | 4 (22) | 0.45 |
| Heart rate reserve | 5 (17) | 3 (17) | 0.95 |
| Time | 5 (17) | 0 (0) | 0.06 |
| RER peak | 13 (45) | 15 (83)* | 0.009 |
| HR máx | 3 (10) | 0 (0) | 0.15 |
| SBP | 6 (21) | 0 (0)* | 0.03 |
| ECG | 0 (0) | 0 (0) | - |
Data are reported as means±SD. *P ≤0.05, unpaired Student's t-test was used for continuous variables and chi-squared test for categorical variables. W: watts; V̇O2: oxygen uptake; V̇CO2: carbon dioxide output; RER: respiratory exchange ratio; V̇ E: ventilation; BF: breathing frequency; V̇ E/V̇CO2 slope: linear relation between minute ventilation and carbon dioxide output; P ETCO2 peak: end-tidal pressure for carbon dioxide; OUES: linear relation between oxygen uptake and minute ventilation; PV: ventilatory power; SpO2: peripheral saturation of oxygen; HR: heart rate; SBP: systolic blood pressure; DBP: diastolic blood pressure; DP: double product; CP: circulatory power; ECG: electrocardiogram.