Table 2

Incidence rate for hospital admission according to use of home oxygen therapy

Respiratory impairment rating*	Before matching				After matching (1:1)
	Yes	No	Yes	No	Yes	No	Yes	No
	N=1330	N=35 431	ID†	ID†	N=1239	N=1239	ID†	ID†
Grade 1
Total number of hospital admissions	416	748	0.60	1.01	244	319	0.62	0.79
Person-years	694.1	743.3	0.60	1.01	390.8	406.0	0.62	0.79
Grade 2
Total number of hospital admissions	358	601	0.61	0.63	291	128	0.59	0.37
Person-years	585.6	953.4	0.61	0.63	495.9	341.4	0.59	0.37
Grade 3
Total number of hospital admissions	245	672	0.47	0.46	245	81	0.47	0.23
Person-years	517.8	1455.4	0.47	0.46	517.8	348.3	0.47	0.23
No grade
Total number of hospital admissions	1409	9286	0.34	0.05	1409	322	0.34	0.07
Person-years	4123.0	184 555.3	0.34	0.05	4123.0	4837.3	0.34	0.07

*Grade 1 patients were defined as having chronic respiratory failure requiring oxygen therapy and an FEV₁ ≤25% predicted or resting PaO₂ ≤55 mm Hg (room air); grade 2 patients were defined as having dyspnoea when walking at home and an FEV₁ ≤30% predicted or PaO₂ 56–60 mm Hg (room air); grade 3 patients were defined as having dyspnoea when walking at their own pace on level ground and FEV₁ ≤40% predicted or PaO₂ 61–65 mm Hg (room air); ‘no grade’ was defined as predicted FEV₁ or PaO₂ unknown.
†Calculated total number of hospital admissions divided into sum of person-years.
ID, incidence rate.