Table 3

Time interval from admission to receiving NIV for patients

	ACIDOTIC on admission, this being the lowest pH (group 1)		ACIDOTIC on admission, later lowest pH ALSO ACIDOTIC (group 2)		NON-ACIDOTIC on admission, later lowest pH ACIDOTIC (group 3)
	%	N=433	%	N=317	%	N=219
<30 min	17	75	7	23	2	5
30–60 min	20	86	14	44	4	8
1–3 h	32	140	31	98	9	20
3–24 h	25	109	38	119	38	84
Beyond 24 h	5	23	10	33	47	102