Time to Steady State after Changes in FIO₂ in Patients with COPD

Figures & data

Figure 1.  Measured values, from arterial blood gases, from patients 1 to 6, for wash out (circles) and wash in (stars) of PO2 (1a to 6a) and SO2 (1b to 6b), plus single exponential curves fitted to measured values.

Figure 2.  Measured values from arterial blood gases from patients 7 to 12, for wash out (circles) and wash in (stars) of PO2 (7a to 12a) and SO2 (7b to 12b), plus single exponential curves fitted to measured values.

Table 1a.  Oxygen administered, acid-base and oxygenation status in the 12 patients at the start and the end of oxygen wash out

	Wash out
	Start					End
	O2, l/min	pH	PCO2 (kPa)	SO2 (%)	PO2 (kPa)	pH	PCO2 (kPa)	SO2 (%)	PO2 (kPa)
1	0	7.46	5.7	95	9.8	7.44	5.8	90	7.6
2	0	7.46	5.0	93	7.9	7.47	5.0	88	6.8
3	1	7.40	9.0	93	9.4	7.42	8.6	88	6.6
4	1	7.36	8.3	91	7.9	7.38	7.9	86	6.9
5	0	7.43	5.5	98	12.5	7.45	5.4	90	7.2
6	0	7.43	7.5	96	10.4	7.44	7.4	87	6.5
7	0	7.44	5.3	98	10.5	7.45	5.3	95	8.7
8	0	7.42	5.4	98	14.4	7.43	5.5	94	9.8
9	0	7.36	8.7	94	8.1	7.39	8.1	90	7.1
10	0	7.40	6.5	94	8.1	7.41	6.3	91	7.6
11	2	7.46	4.9	95	9.2	7.46	4.8	94	8.5
12	0	7.46	5.3	97	12.8	7.46	5.1	93	8.6

Table 1b.  Oxygen administered, acid-base and oxygenation status in the 12 patients at the start and the end of oxygen wash in and 30 minutes following the end of wash in.

	Wash in
	Start					End				30 min
	O2, l/min	pH	PCO2 (kPa)	SO2 (%)	PO2 (kPa)	pH	PCO2 (kPa)	SO2 (%)	PO2 (kPa)	pH	PCO2 (kPa)	SO2 (%)	PO2 (kPa)
1	1.0	7.44	6.1	92	8.4	7.45	5.9	96	10.2	7.44	5.7	94	8.7
2	1.5	7.47	4.7	90	7.1	7.44	5.1	95	9.1	7.46	4.8	93	7.9
3	3.0	7.43	8.3	89	6.7	7.40	8.8	96	10.2	7.40	9.0	96	9.7
4	3.0	7.38	7.9	87	6.8	7.38	7.8	92	8.1	7.38	7.8	92	8.1
5	2.0	7.45	5.4	90	7.2	7.43	5.6	99	14.2	7.43	5.8	98	14.0
6	1.5	7.43	7.4	86	6.7	7.41	7.7	95	11.2	7.43	7.3	95	9.1
7	1.0	7.45	5.3	94	8.3	7.42	5.6	98	11.1	7.42	5.4	97	10.1
8	1.0	*	*	*	*	*	*	*	*	7.41	5.7	98	10.6
9	2.0	7.38	8.5	89	6.9	7.36	8.8	93	8.2	7.37	8.4	93	8.4
10	1.5	*	*	*	*	*	*	*	*	7.40	6.4	93	8.8
11	4.0	7.46	4.9	94	8.4	7.46	5.2	96	9.9	7.45	5.1	95	9.7
12	2.0	7.45	5.2	93	8.6	7.45	5.3	97	12.9	7.47	5.0	95	9.3

*Data missing, see text for details.

Table 2.  Lung function, time constants (τ) and time to clinical steady state (Tp, Ts) for oxygen wash out and wash in, in each of the 12 patients

			Wash out				Wash in
	Lung function		PO2		SO2		PO2		SO2
	FEV1%	FEV1/FVC	τ (min)	Tp (min)	τ (min)	Ts (min)	τ (min)	Tp (min)	τ (min)	Ts (min)
1	33	0.45	3.0	4.0	3.6	5.4	1.7	2.4	1.5	1.9
2	44	0.52	0.03	0.1	0.03	0.1	2.6	3.2	3.0	4.5
3	17	0.27	4.7	8.1	4.6	8.1	7.2	13.7	4.1	8.3
4	15	0.41	0.9	0.9	0.8	1.4	2.8	2.6	2.6	4.3
5	23	0.40	2.4	6.3	7.3	15.6	3.6	9.5	1.6	3.5
6	16	0.27	3.1	6.3	6.0	13.4	5.0	8.4	3.1	6.8
7	63	0.64	0.9	2.2	1.7	2.4	1.2	2.6	0.03	0.1
8	18	0.38	5.9	13.8	8.4	9.8	*	*	*	*
9	23	0.44	4.6	4.9	4.6	7.5	1.9	1.5	1.3	1.5
10	45	0.48	7.9	10.5	8.5	12.4	*	*	*	*
11	29	0.45	2.4	1.9	1.5	1.3	0.03	0.1	0.3	0.3
12	21	0.30	2.6	5.9	4.2	5.9	2.6	5.6	1.2	1.8

*Data missing, see text for details.

Figure 3.  The oxygen dissociation curve (ODC). A and B are used in the text to describe changes in oxygenation from these points.