Table 2.
Physiological measures during the cardiopulmonary exercise testing protocol of all patients who attended the Defence Medical Services COVID-19 Recovery Service and differences between patients classified with and those without dysautonomia
| Variable | All patients (n = 205) | Without dysautonomia (n = 154) | With dysautonomia (n = 51) | t | P value | Effect size |
|---|---|---|---|---|---|---|
| CPET | ||||||
| V̇o2 at rest (mL/kg/min) | 5.1 ± 1.04 | 5.1 ± 1.1 | 5.2 ± 0.8 | –0.454 | .650 | 0.073 |
| V̇o2 at VT1 (mL/kg/min) | 13.7 ± 3.0 | 14.1 ± 3.2 | 12.6 ± 2.1 | 3.273 | .001† | 0.529 |
| V̇o2 at peak (mL/kg/min) | 34.5 ± 7.4 | 35.8 ± 7.6 | 30.6 ± 5.5 | 4.544 | <.001‡ | 0.734 |
| Work rate at VT1 (W) | 78 ± 23 | 80 ± 24 | 71 ± 16 | 2.345 | .020∗ | 0.379 |
| Work rate at peak (W) | 245 ± 51 | 253 ± 52 | 219 ± 37 | 4.329 | <.001‡ | 0.699 |
| ΔV̇o2 (L/min)/ΔWork (W) | 10.7 ± 1.4 | 10.7 ± 1.4 | 10.7 ± 1.2 | –0.008 | .994 | 0.001 |
| Lactate at rest (mmol/L) | 1.3 ± 0.5 | 1.3 ± 0.5 | 1.5 ± 0.5 | –3.254 | .001† | 0.545 |
| Lactate at peak (mmol/L) | 12.7 ± 2.6 | 12.9 ± 2.6 | 12.2 ± 2.6 | 1.582 | .115 | 0.280 |
| O2 pulse | 17.7 ± 4.4 | 17.9 ± 4.5 | 17.0 ± 3.9 | 1.264 | .208 | 0.204 |
| HR profile | ||||||
| HR at rest (bpm) | 84 ± 13 | 81 ± 12 | 95 ± 12 | –7.343 | <.001‡ | 1.186 |
| HR at VT1 (bpm) | 109 ± 16 | 107 ± 17 | 114 ± 15 | –2.408 | .017∗ | 0.389 |
| HR at peak (bpm) | 175 ± 15 | 177 ± 15 | 170 ± 13 | 2.956 | .003† | 0.478 |
| Percent of predicted max HR | 109 ± 8 | 109 ± 8 | 109 ± 8 | –0.030 | .976 | 0.005 |
| HR recovery after 1 min (bpm) | 27 ± 16 | 31 ± 17 | 17 ± 4 | 5.730 | <.001‡ | 0.926 |
| HR increase from rest to peak (bpm) | 91 ± 17 | 96 ± 13 | 75 ± 12 | 10.304 | <.001‡ | 1.665 |
| HRV | ||||||
| RMSSD at rest (m∙s-1) | 26 ± 14 | 29 ± 13 | 15 ± 9 | 6.243 | <.001‡ | 1.057 |
| RMSSD (30–60 s recovery, m∙s-1) | 8 ± 10 | 8 ± 10 | 9 ± 10 | –0.527 | .599 | 0.089 |
| RMSSD (90–120 s recovery, m∙s-1) | 9 ± 9 | 10 ± 10 | 7 ± 7 | 1.578 | .116 | 0.267 |
| RMSSD (150–180 s recovery, m∙s-1) | 9 ± 10 | 9 ± 9 | 10 ± 12 | –1.013 | .312 | 0.172 |
| BP (mm Hg) | ||||||
| Resting systolic BP (mm Hg) | 121 ± 11 | 120 ± 10 | 121 ± 12 | –0.735 | .463 | 0.119 |
| Resting diastolic BP (mm Hg) | 81 ± 9 | 81 ± 9 | 82 ± 10 | –0.682 | .496 | 0.110 |
| VT1 systolic BP (mm Hg) | 140 ± 17 | 139 ± 17 | 141 ± 16 | –0.464 | .643 | 0.076 |
| VT1 diastolic BP (mm Hg) | 83 ± 12 | 82 ± 13 | 86 ± 9 | –1.811 | .072 | 0.295 |
| Peak systolic BP (mmHg) | 169 ± 21 | 169 ± 21 | 166 ± 22 | 1.056 | .292 | 0.171 |
| Peak diastolic BP (mmHg) | 75 ± 22 | 73 ± 23 | 83 ± 16 | –2.819 | .005† | 0.455 |
| Ventilation | ||||||
| BF at rest (breaths/min) | 16 ± 5 | 16 ± 4 | 18 ± 5 | –2.756 | .006† | 0.449 |
| BF at VT1 (breaths/min) | 20 ± 6 | 19 ± 5 | 23 ± 6 | –3.609 | <.001‡ | 0.588 |
| BF at peak (breaths/min) | 47 ± 9 | 46 ± 9 | 48 ± 9 | –1.234 | .219 | 0.201 |
| V̇E/V̇co2 at rest | 30.2 ± 4.3 | 29.8 ± 4.3 | 31.3 ± 4.2 | –2.107 | .036∗ | 0.340 |
| V̇E/V̇co2 at VT1 | 26.6 ± 3.4 | 26.1 ± 3.2 | 28.0 ± 3.7 | –3.462 | .001† | 0.559 |
| V̇E/V̇co2 at peak | 33.7 ± 7.7 | 32.7 ± 4.7 | 36.4 ± 12.9 | –2.973 | .003† | 0.480 |
| V̇E/V̇co2 slope | 28.3 ± 4.8 | 27.7 ± 4.7 | 29.9 ± 4.9 | –2.839 | .005† | 0.490 |
| pco2 rest | 5.0 ± 0.6 | 5.0 ± 0.5 | 5.0 ± 0.8 | 0.037 | .970 | 0.006 |
| pco2 peak | 4.4 ± 0.8 | 4.4 ± 0.8 | 4.2 ± 0.6 | 1.191 | .235 | 0.209 |
Values are given as mean ± SD unless otherwise indicated.
Effect size calculated using Cohen’s d (small 0.2–0.5; medium 0.5–0.8; large >0.8).
Significant P values
BF = breathing frequency; BP = blood pressure; COVID-19 = coronavirus disease 2019; CPET = cardiopulmonary exercise testing; HR = heart rate; HRV = heart rate variability; RMSSD = root mean square of successive differences of R-R intervals; V̇co2 = expired carbon dioxide; V̇e = ventilation; V̇o2 = oxygen consumption; VT1 = first ventilatory threshold.
P <.05
P <.01
P <.001 and medium/large effect sizes are shown in bold.