Table 2

Changes in daytime arterial blood gases

	ITT baseline	n	Completers baseline	n	Completers 12 months	n	Change over 1 year*	n	Change over 1 year similar circumstances†	n
pH
NIV	7.38±0.04	93	7.38±0.04	46	7.40±0.04	46	0.026 (0.010 to 0.042)‡	46	0.022 (0.005 to 0.039)‡	37
Controls	7.39±0.04	99	7.39±0.04	48	7.39±0.03	48	−0.005 (−0.016 to 0.006)	48	−0.005 (−0.020 to 0.010)	37
Treatment effect							0.03 (0.012 to 0.050)§		0.030 (0.005 to 0.050)§
PaCO₂ (kPa)
NIV	7.9±1.2	100	7.7±1.1	50	6.4±1.0	50	−1.3 (−1.6 to −0.9)‡	50	−1.0 (−1.4 to −0.7)‡	38
Controls	7.7±1.3	99	7.4±0.9	48	6.6±1.0	48	−0.8 (−1.1 to −0.5)‡	48	−0.9 (−1.2 to −0.5)‡	37
Treatment effect							−0.5 (−0.9 to −0.04)§		−0.2 (−0.6 to 0.3)
PaO₂ (kPa)
NIV	7.9±2.1	93	8.3±1.6	45	8.3±1.6	45	0 (−0.6 to 0.6)	45	0.3 (−0.3 to 0.9)	35
Controls	7.5±1.6	99	7.9±1.9	48	8.4±1.4	48	0.6 (−0.1 to 1.2)	48	0.6 (−0.1 to 1.3)	37
Treatment effect							0.6 (−1.4 to 0.2)		−0.3 (−1.2 to 0.6)
HCO₃ (mmol/L)
NIV	33.7±4.6	94	33.0±4.5	47	29.3±3.5	47	−3.7 (−5.2 to −2.1)‡	47	−3.0 (−4.8 to −1.2)‡	36
Controls	33.6±4.8	98	32.6±4.1	48	28.8±4.2	48	−3.8 (−5.0 to −2.6)‡	48	−4.1 (−5.5 to −2.7)‡	37
Treatment effect							0.1 (−1.8 to 2.1)		1.0 (−1.2 to 3.3)
BE
NIV	7.8±4.8	90	7.0±3.2	38	4.5±2.5	38	−2.5 (−3.6 to −1.3)‡	38	−2.2 (−3.4 to −0.9)‡	31
Controls	7.7±3.8	93	6.9±3.2	44	3.9±3.2	44	−2.9 (−4.0 to −1.8)‡	44	−3.2 (−1.8 to −4.5)‡	35
Treatment effect							0.5 (−1.1 to 2.0)		1.0 (−0.8 to 2.8)
Sat (%)
NIV	87.4±6.4	95	90.0±4.4	43	91.0±5.1	43	1.1 (−0.9 to 3.0)	43	2.2 (0.2 to 4.2)‡	34
Controls	88.4±6.6	88	88.4±6.1	43	91.1±4.8	43	2.7 (0.5 to 5.0)‡	43	2.7 (−0.03 to 5.5)	33
Treatment effect							−1.6 (−4.6 to 1.3)		−0.5 (−3.9 to 2.8)

Data presented as means (±SD) and mean change (95% CIs); controls, standard treatment.
*Measurement performed regardless of oxygen use.
†Only comparing baseline and 12-month data when the measurements were both on room air or both on oxygen at the same flow rate. N=37 (out of 38 NIV) and n=35 (out of 37 controls) for which both measurements were performed on room air.
‡p<0.05 significant change after 12 months within the group.
§p<0.05 significant difference in change after 12 months between the groups (treatment effect).
BE, base excess; HCO₃, bicarbonate (mmol/L); ITT, intention-to-treat; n, numbers for analysis; NIV, non-invasive positive pressure ventilation; PaCO₂, arterial carbon dioxide pressure (kPa); PaO₂, arterial oxygen pressure (kPa); Sat, saturation (%).