Table 4.

Univariate analyses of individual patient factors in relation to receipt of mechanical ventilation in the first 24 hours after admission to the Case Mix Programme unit

	na	% Mechanically ventilatedb	% Not mechanically ventilatedb	OR (95% CI)
Age (years)
0–19	237	40.5	59.5	1.28 (1.22–1.34) per 10 year increase
20–29	365	43.3	56.7
30–39	367	47.1	52.9
40–49	354	62.1	37.9
50–59	340	65.6	34.4
60+	489	72.2	27.8
Steroid treatment in previous 6 months
No	1849	57.0	43.0	1.00
Yes	303	56.1	43.9	0.97 (0.76–1.23)
CPR within 24 hours before admission
No	1966	54.1	45.9	1.00
Yes	171	88.9	11.1	6.78 (4.18–11.02)
Neurological insult in first 24 hours
No	1,930	52.6	47.4	1.00
Yes	222	93.7	6.3	13.39 (7.74–23.18)
Highest heart rate (beats/min)
<124	697	55.2	44.8	1.04 (1.00–1.08) per 10 beats/min increase
124–141	739	58.1	41.9
≥141	672	59.4	40.6
Lowest PaO2 (kPa)
<9.8	615	66.0	34.0	0.83 (0.76–0.91) per 5 kPa increase
9.8–12.4	652	66.6	33.4
≥12.4	652	55.5	44.5
pH from ABG with lowest PaO2
<7.32	591	84.8	15.2	0.99 (0.99–1.00) per pH 0.1 increase
7.32–7.41	686	58.5	41.5
≥7.41	640	46.7	53.3
PaCO2 from ABG with lowest pH (kPa)
<5.7	607	34.8	65.2	6.61 (5.21–8.40) per 5 kPa increase
5.7–8.2	597	65.0	35.0
≥8.2	619	88.2	11.8
Acute Physiology Score
0–8	682	41.4	58.6	1.18 (1.16–1.21) per 1 point increase
9–12	620	60.3	39.7
13+	602	80.6	19.4
APACHE II score
0–10	621	39.8	60.2	1.15 (1.13–1.17) per 1 point increase
11–15	626	58.8	41.2
16+	657	80.1	19.9

^aExcluding admissions missing the specified factor. ^bIn first 24 hours after admission to the Case Mix Programme (CMP) unit. ABG, arterial blood gas; APACHE, Acute Physiology and Chronic Health Evaluation; CI, confidence interval; CPR, cardiopulmonary resuscitation; OR, odds ratio; Paco₂, arterial carbon dioxide tension; Pao₂, arterial oxygen tension.