Table 3.
Comparison between responders and non-responders
| Responders (n=23) | Non-responders (n=23) | Difference (95% CI) | p value | ||
|---|---|---|---|---|---|
| Age, years | 58·5 (7·5) | 55·9 (7·0) | 2·7 (−7·0 to 1·7) | 0·22 | |
| Sex | .. | .. | .. | 1·0 | |
| Female | 6 (26%) | 6 (26%) | .. | .. | |
| Male | 17 (74%) | 17 (74%) | .. | .. | |
| BMI, kg/m2 | 27·3 (3·5) | 27·4 (3·7) | −0·12 (−2·3 to 2·1) | 0·92 | |
| Time between symptom onset and admission to hospital, days | 8·1 (4·8) | 7·4 (4·3) | −0·7 (−3·4 to 1·9) | 0·58 | |
| Time between admission to hospital and prone positioning, days | 2·7 (2·1) | 4·6 (3·7) | −1·9 (−3·7 to 0·1) | 0·04 | |
| Time between symptom onset and prone positioning, days | 10·8 (4·9) | 12·0 (4·3) | −1·1 (−3·9 to 1·6) | 0·41 | |
| Comorbidities | |||||
| Previous myocardial infarction | 1 (4%) | 1 (4%) | .. | .. | |
| Congestive heart failure | 0 | 0 | .. | .. | |
| Hypertension | 9 (39%) | 9 (39%) | .. | .. | |
| Vascular disease | 0 | 3 (13%) | .. | .. | |
| Chronic bronchopulmonary disease | 1 (4%) | 0 | .. | .. | |
| Gastric or liver disease | 1 (4%) | 1 (4%) | .. | .. | |
| Diabetes | 4 (17%) | 2 (9%) | .. | .. | |
| Moderate-to-severe chronic kidney disease (eGFR <59 mL/min) | 0 | 0 | .. | .. | |
| Solid malignancy | 1 (4%) | 2 (9%) | .. | .. | |
| Smoking history | |||||
| Active smoker | 0 | 1 (4%) | .. | .. | |
| Former smoker (<1 year) | 0 | 1 (4%) | .. | .. | |
| Former smoker (≥1 year) | 9 (39%) | 7 (30%) | .. | .. | |
| Never smoked | 12 (52%) | 13 (57%) | .. | .. | |
| Not declared | 2 (9%) | 1 (4%) | .. | .. | |
| Baseline blood values | |||||
| Sodium, mmol/L | 137·7 (2·6) | 138·78 (3·9) | −1·1 (− 3·1 to 0·9) | 0·27 | |
| Potassium, mmol/L | 3·9 (0·5) | 4·1 (0·6) | −0·2 (−0·5 to 0·1) | 0·21 | |
| Chlorine, mmol/L | 101·8 (3·3) | 100·2 (3·6) | 1·6 (−3·7 to 0·5) | 0·13 | |
| Creatinine, mg/dL | 0·9 (0·2) | 0·8 (0·2) | 0·0 (0·0 to 0·0) | 0·21 | |
| Urea, mg/dL | 31·0 (8·2) | 30·3 (8·0) | 0·7 (−5·8 to 4·4) | 0·78 | |
| White blood cells, 103/μL | 7·7 (3·6) | 7·3 (3·0) | 0·3 (−2·3 to 1·6) | 0·75 | |
| Platelets, 103/μL | 241·1 (101·9) | 319·8 (120·6) | −78·7 (−145·0 to 12·3) | 0·02 | |
| Haemoglobin, g/dL | 12·8 (2·0) | 12·4 (1·3) | 0·4 (−1·4 to 0·6) | 0·40 | |
| Haematocrit, % | 37·5 (5·5) | 36·5 (4·1) | 1·0 (−3·9 to 1·9) | 0·50 | |
| Bilirubin, mg/dL | 0·6 (0·5) | 0·5 (0·3) | 0·0 (−0·3 to 0·1) | 0·50 | |
| C-reactive protein, mg/L | 12·7 (6·9) | 8·4 (6·2) | 4·3 (8·3 to 0·3) | 0·03 | |
| Procalcitonin, ng/mL | 0·6 (1·1) | 0·4 (0·4) | 0·3 (−0·9 to 0·4) | 0·44 | |
| Lactate dehydrogenase, U/L | 449·7 (199·0) | 337·9 (94·1) | 111·8 (15·0 to 208·5) | 0·02 | |
| Aspartate aminotransferase, U/L | 49·7 (26·5) | 48·0 (24·4) | 1·7 (−18·7 to 15·2) | 0·83 | |
| Alanine aminotransferase, U/L | 49·4 (37·5) | 57·7 (37·0) | −8·2 (−31·2 to 14·7) | 0·47 | |
| International normalised ratio | 1·3 (0·6) | 1·1 (0·1) | 0·2 (−0·4 to 0·1) | 0·24 | |
| Activated partial thromboplastin time ratio | 1·1 (0·1) | 1·0 (0·1) | 0·0 (−0·1 to 0·0) | 0·43 | |
| D-dimer, ng/mL | 576·4 (432·2) | 632·9 (431·8) | −56·5 (−342·4 to 229·3) | 0·69 | |
| Arterial blood gas at SP1 | |||||
| pH | 7·46 (0·0) | 7·5 (0·0) | 0·0 (0·0 to 0·0) | 0·79 | |
| PaO2, mm Hg | 114·5 (49·1) | 119·7 (46·7) | −5·2 (−33·6 to 23·3) | 0·72 | |
| PaCO2, mm Hg | 35·1 (5·2) | 35·4 (4·6) | −0·3 (−3·2 to 2·6) | 0·85 | |
| SaO2, % | 97·1 (2·1) | 97·3 (1·9) | −0·2 (−1·4 to 1·0) | 0·73 | |
| Arterial blood gas at PP1 | |||||
| pH | 7·5 (0·0) | 7·5 (0·0) | 0·0 (0·0 to 0·0) | 0·44 | |
| PaO2, mm Hg | 225·3 (112·6) | 175·5 (105·8) | 49·8 (−15·2 to 114·7) | 0·13 | |
| PaCO2, mm Hg | 35·3 (5·4) | 36·0 (3·6) | −0·7 (−3·4 to 2·0) | 0·61 | |
| SaO2, % | 98·5 (1·4) | 98·4 (1·3) | 0·2 (−1·0 to 0·7) | 0·72 | |
| Arterial blood gas at SP2 | |||||
| pH | 7·5 (0·0) | 7·5 (0·0) | 0·0 (0·0 to 0·0) | 0·84 | |
| PaO2, mm Hg | 154·0 (84·9) | 88·7 (21·8) | 65·3 (28·4 to 102·1) | <0·0001 | |
| PaCO2, mm Hg | 35·1 (4·5) | 36·0 (4·3) | −1·0 (−3·6 to 1·7) | 0·47 | |
| SaO2, % | 97·8 (2·1) | 96·4 (1·8) | 1·4 (0·2 to 2·6) | 0·03 | |
| Secondary outcomes | |||||
| Tracheal intubation | 7 (30·4%) | 6 (26·1%) | 4·3 (−30·7 to 21·6) | 0·74 | |
| Time to intubation | 2 (2 to 4) | 2·5 (1·0 to 5·0) | .. | 0·45 | |
| Duration of prone positioning, h | 3·5 (3·0 to 4·0) | 3·5 (3·0 to 4·0) | .. | 0·99 | |
| Prone positioning for >3 h | 12 (52·2%) | 13 (56·5%) | −4·3% (−33·1 to 24·4) | 0·77 | |
| Number of prone positioning cycles | 2 (1 to 3) | 2 (1 to 3) | .. | 0·94 | |
| More than one prone positioning cycle | 12 (52·1%) | 11 (47·8%) | 4·3% (−34·0 to 24·9) | 0·76 | |
Data are mean (SD) or n (%), unless otherwise indicated. Differences are not calculated for data presented as median (range) or for small proportions. p values were calculated using Student's t test for continuous variables and the χ2 test for categorical variables. BMI=body-mass index. CPAP=continuous positive airway pressure. FiO2=fractional concentration of oxygen in inspired air. eGFR=estimated glomerular filtration rate. PaCO2=arterial partial pressure of carbon dioxide. PaO2=arterial partial pressure of oxygen. PEEP=positive end-expiratory pressure. SaO2=arterial oxygen saturation of haemoglobin. SP1=baseline supine position. PP1=10 min after prone positioning. SP2=1 h after resuming supine position. SpO2=peripheral oxygen saturation of haemoglobin.