Baseline characteristics of Ambulance CPAP: Use, Treatment effect and Economics trial participants by arm
| Baseline variable | Descriptive statistic | CPAP N=42 | Standard oxygen therapy N=35 | Total N=77 |
| Age | Median (IQR) | 70.0 (60.5 to 76.8) | 73.0 (65.0 to 77.0) | 71.0 (62.0 to 77.0) |
| Sex | Male | 27 (64.3%) | 21 (60.0%) | 48 (62.3%) |
| Hospital ARF diagnosis* | n= | 36 | 30 | 66 |
| Asthma | 1 (2.8%) | 1 (2.9%) | 2 (3.0%) | |
| COPD | 10 (27.8%) | 11 (36.7%) | 21 (31.8%) | |
| Heart Failure | 4 (11.1%) | 2 (6.7%) | 6 (9.1%) | |
| LRTI | 17 (47.2%) | 11 (36.7%) | 28 (42.4%) | |
| Pulmonary embolism | 1 (2.8%) | 0 (0.0%) | 1 (1.5%) | |
| Other | 3 (8.3%) | 4 (13.3%) | 7 (10.8%) | |
| Breathlessness at enrolment (VAS 0–10) | n= | 41 | 35 | 76 |
| Median (IQR) | 9.0 (8.0 to 10.0) | 9.0 (8.0 to 9.5) | 9.0 (8.0 to 10.0) | |
| First systolic blood pressure (mm Hg) | n= | 40 | 30 | 70 |
| Median (IQR) | 136.0 (115.2 to 150.5) | 126.5 (112.0 to 152.0) | 134.5 (112.2 to 152.0) | |
| First Glasgow Coma Score | n= | 42 | 35 | 77 |
| Median (IQR) | 15.0 (14.0 to 15.0) | 15 (14.5 to 15.0) | 15 (14.0 to 15.0) | |
| First oxygen saturations (%) | n= | 41 | 35 | 76 |
| Median (IQR) | 78 (74.0 to 85.0) | 82 (75.5 to 86.0) | 78.5 (74.8 to 86.0) | |
| First pulse rate (beats/min) | n= | 42 | 33 | 75 |
| Median (IQR) | 117.0 (105.0 to 125.8) | 111 (92.0 to 121.0) | 115 (100.0 to 124.0) | |
| First respiratory rate (breaths/min) | n= | 42 | 35 | 77 |
| Median (IQR) | 36.0 (30.5 to 40.0) | 32 (24.0 to 40.0) | 34 (28.0 to 40.0) | |
| Duration between arrival at scene and departure to hospital (min) | Median (IQR) | 43.0 (34.0 to 49.8) | 36.0 (32.5 to 46.5) | 40.00 (34.0 to 49.0) |
| Duration between leaving the scene and arriving at hospital (min) | Median (IQR) | 13.0 (9.00 to 18.75) | 15.0 (10.0 to 20.5) | 13.0 (10.0 to 20.0) |
'N' refers to the total sample. 'n' refers to the subgroup numbers.
*Consent was declined for data collection in nine cases, clinical records were unavailable in two cases, and in one case there was no clear underlying diagnosis apparent in the notes.
ARF, acute respiratory failure; COPD, chronic obstructive pulmonary disease; LRTI, lower respiratory tract infection; VAS, Visual Analogue Scale.