Table 2

Baseline characteristics of Ambulance CPAP: Use, Treatment effect and Economics trial participants by arm

Baseline variableDescriptive statisticCPAP
N=42
Standard oxygen therapy
N=35
Total
N=77
AgeMedian (IQR)70.0 (60.5 to 76.8)73.0 (65.0 to 77.0)71.0 (62.0 to 77.0)
SexMale27 (64.3%)21 (60.0%)48 (62.3%)
Hospital ARF diagnosis*n=363066
Asthma1 (2.8%)1 (2.9%)2 (3.0%)
COPD10 (27.8%)11 (36.7%)21 (31.8%)
Heart Failure4 (11.1%)2 (6.7%)6 (9.1%)
LRTI17 (47.2%)11 (36.7%)28 (42.4%)
Pulmonary embolism1 (2.8%)0 (0.0%)1 (1.5%)
Other3 (8.3%)4 (13.3%)7 (10.8%)
Breathlessness at enrolment
(VAS 0–10)
n=413576
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=403070
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 Scoren=423577
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=413576
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=423375
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=423577
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.