| Training and internal validation cohort | External validation cohort | ||||
---|---|---|---|---|---|---|
COVID-19 patients (Zurich / Rotterdam/The Hague cohorts) n = 59 | Healthy volunteers (Hamburg cohort) n = 40 | P value | COVID-19 patients (Leiden cohort) n = 25 | Healthy volunteers (Zurich cohort) n = 33 | P value | |
Characteristics at study inclusion | ||||||
Age | 59.5 ± 10.6 | 24.1 ± 1.8 | < 0.0001 | 60.8 ± 10.7 | 45.8 ± 12.1 | < 0.0001 |
Sex [male] | 43/54 (80%) | 17/40 (42.5) | < 0.0001 | 18/25 (72%) | 15/33 (55%) | < 0.0001 |
Body mass index [kg m−2] | 29.0 ± 6.0 | 22.8 ± 2.9 | < 0.0001 | 30.0 ± 6.0 | 23.1 ± 4.5 | < 0.0001 |
Duration of COVID symptoms before inclusion [days] | 17 (12–27) | – | – | 10 (9–11) | – | – |
Days from ICU admission to inclusion [days] | 7 (4–12) | – | – | 2 (1–3) | – | – |
Physiological status at study inclusion | ||||||
O2 saturation [%] | 93 ± 3 | – | – | 92 ± 10 | 98 ± 1 | 0.0006 |
PaO2 [mmHg] | 77 ± 24 | – | – | 84 ± 21 | 95 ± 8 | < 0.0001 |
FiO2 [%] | 48 ± 17 | 21 ± 0 | < 0.0001 | 51 ± 18 | 21 ± 0 | < 0.0001 |
PaO2/FiO2 ratio | 178 ± 79 | – | – | 187 ± 67 | 454 ± 38 | < 0.0001 |
PEEP [cmH2O] | 15.7 ± 6.9 | – | – | 11.5 ± 4.1 | – | – |
pH | 7.39 ± 0.08 | – | – | 7.39 ± 0.07 | 7.44 ± 0.02 | < 0.0001 |
Lactate [mmol L−1] | 1.2 ± 0.4 | – | – | 2.1 ± 0.7 | 0.8 ± 0.2 | < 0.0001 |
Hemoglobin [g L−1] | 97 ± 18 | – | – | 127 ± 14 | 148 ± 9 | < 0.0001 |
Systemic hematocrit [%] | 31 ± 5 | – | – | 39 ± 4 | 43 ± 3 | < 0.0001 |
Heart rate [bpm] | 92 ± 19 | 69.3 ± 12.1 | < 0.0001 | 69 ± 17 | 59.2 ± 5.3 | 0.001 |
Mean arterial pressure [mmHg] | 85 ± 12 | 85.8 ± 8.19 | 0.32 | 80 ± 11 | 89.6 ± 9.6 | 0.0001 |
ICU course and outcome | ||||||
Full anticoagulation | 23/42 (55%) | 0/40 (0%) | < 0.0001 | 7/21 (33%) | 0/33 (0%) | < 0.0001 |
Prophylactic anticoagulation | 19/42 (45%) | 0/40 (0%) | < 0.0001 | 14/21 (67%) | 0/33 (0%) | < 0.0001 |
Pulmonary embolism or macro-thrombosis during ICU stay | 19/39 (49%) | – | – | 4/19 (21%) | – | – |
ICU mortality | 10/44 (23%) | – | – | 7/21 (33%) | – | – |
Microcirculatory hemodynamic variables | ||||||
Total vessel density, TVD [mm mm−2] | 21.8 ± 5.2 | 19.2 ± 4.1 | < 0.0001 | 22.6 ± 3.7 | 19.1 ± 4.3 | < 0.0001 |
Functional capillary density, FCD [mm mm−2] | 21.2 ± 4.9 | 18.2 ± 3.8 | < 0.0001 | 21.6 ± 3.6 | 18.3 ± 4.1 | < 0.0001 |
Red blood cell velocity, RBCv [μm s−1] | 349 ± 41 | 325 ± 49 | < 0.0001 | 336 ± 35 | 316 ± 52 | < 0.0001 |
Capillary hematocrit, cHct [%] | 5.17 ± 1.21 | 5.18 ± 0.87 | < 0.0001 | 5.21 ± 0.81 | 4.62 ± 0.83 | < 0.0001 |