Table 1

Blood gas and ECG parameters at baseline and while breathing the 15% hypoxic mixture

Parameter	Mean	N	SD	SE mean	95% CI lower	95% CI upper	Significance
H⁺ (0.21%)	36.58 nmol/l	65	2.35	0.29
H⁺ (0.15%)	36.06 nmol/l	65	2.41	0.30
∆H⁺ (21–15%)	0.52 nmol/l	65	2.60	0.32	−0.1282	1.1590	0.12

Paco₂ (0.21%)	5.11 kPa	65	0.45	0.06
Paco₂ (0.15%)	4.87 kPa	65	0.47	0.06
∆Paco₂ (21–15%)	0.25 kPa	65	0.40	0.05	0.14904	0.34942	<0.001

Pao₂ (0.21%)	10.56 kPa	65	1.17	0.14
Pao₂ (0.15%)	6.82 kPa	65	0.77	0.09
∆Pao₂ (21–15%)	3.75 kPa	65	1.06	0.13	3.48188	4.00920	<0.001

HCO₃ (0.21%)	25.62 mmol/l	65	4.88	0.61
HCO₃ (0.15%)	24.46 mmol/l	65	2.33	0.29
∆HCO₃ (21–15%)	1.16 mmol/l	65	4.15	0.51	0.1310	2.1860	0.03

BE (0.21%)	1.09 mmol	65	2.04	0.25
BE (0.15%)	0.74 mmol	65	2.18	0.27
∆BE (21–15%)	0.35 mmol	65	1.7378	0.22	−0.0814	0.7798	0.11

Sao₂ (0.21%)	95.82%	65	1.19	0.15
Sao₂ (0.15%)	87.15%	65	3.61	0.45
∆Sao₂ (21–15%)	8.67%	65	3.38	0.42	7.8326	9.5090	<0.001

Ptcco₂ (0.21%)	5.12 kPa	39	0.69	0.11
Ptcco₂ (0.15%)	4.84 kPa	39	0.74	0.12
∆Ptcco₂ (21–15%)	0.28 kPa	39	0.28	0.05	0.1874	0.3715	<0.001

HR (21%)	83.22 bpm	101	14.97			1.49
HR (15%)	86.89 bpm	101	15.09			1.50
∆HR (21–15%)	3.67 bpm	101	0.58	−4.809	−2.537	0.57	<0.001

PR (21%)	161.23 ms	96	16.09			1.64
PR (15%)	158.01 ms	96	20.31			2.07
∆PR (21–15%)	3.22 ms	96	12.63	0.660	5.778	1.29	0.01

QRSD (21%)	91.93 ms	101	15.97			1.59
QRSD (15%)	90.27 ms	101	15.92			1.58
∆QRSD (21–15%)	1.66 ms	101	9.13	−0.138	3.465	0.91	0.07

QT (21%)	357.75 ms	101	40.97			4.08
QT (15%)	348.83 ms	101	35.03			3.49
∆QT (21–15%)	8.92 ms	101	24.05	4.173	13.669	2.39	<0.001

QTc (21%)	415.16 ms	101	25.86			2.57
QTc (15%)	416.95 ms	101	24.02			2.39
∆QTc (21–15%)	1.79 ms	101	26.70	−7.062	3.478	2.66	0.50

21%, baseline measurement while breathing room air; 15%, test measurement after breathing 15% O₂ hypoxic mixture for 15 min; BE, base excess; ∆BE, change in base excess between 21% and 15% O₂; H⁺, hydrogen ion concentration; ∆H⁺, change in hydrogen ion concentration between 21% and 15% O₂; HCO₃, bicarbonate ion concentration; ∆HCO₃⁺, change in bicarbonate ion concentration between 21% and 15% O₂; HR, electrocardiographic heart rate; ∆HR, change in heart rate between 21% and 15% O₂; Paco₂, partial pressure of CO₂; ∆Paco₂, change in partial pressure of CO₂ between 21% and 15% O₂; Pao₂, partial pressure of O₂; ∆Pao₂, change in partial pressure of O₂ between 21% and 15% O₂; PR, electrocardiographic PR interval; ∆PR, change in PR interval between 21% and 15% O₂; Ptcco₂, transcutaneous CO₂; ∆Ptcco₂, change in transcutaneous CO₂ between 21% and 15% O₂; QRSD, electrocardiographic QRSD interval; ∆QRSD, change in QRSD interval between 21% and 15% O₂; QT, electrocardiographic QT interval; ∆QT, change in QT interval between 21% and 15% O₂; QT_c, electrocardiographic QT_c interval; ∆QT_c, change in QT_c interval between 21% and 15% O₂; Sao₂, oxygen saturation; ∆SaO₂, change in oxygen saturations between 21% and 15% O₂.