Table 2

Relationship between daytime EtCO₂, daytime SpO₂ and sleep variables at baseline (130 m) and altitude (3500 m)

	130 m				3500 m
	EtCO₂=38–47 mm Hg				Daytime EtCO₂=31–40 mm Hg
	R²	p Value	β	Range	R²	p Value	β	Range
Daytime SpO₂ (%)	0.32	0.1	−0.561	97–100	0.65	0.009	−0.806	85–92
Mean overnight SpO₂ (%)	0.12	0.4	0.353	96–98	0.40	0.066	−0.635	80–89
Minimum overnight SpO₂ (%)	0.46	0.046	0.675	84–94	0.38	0.078	−0.615	60–82
Number of desaturations/hour overnight	0.75	0.003	−0.865	0–1.7	0.16	0.3	0.398	0.7–49.3
Number of central apnoeas/hour overnight	0.78	0.002	−0.882	0–1.7	0.45	0.047	−0.673	0.3–9.5
% total sleep time spent in periodic breathing	0.76	0.017	−0.763	0–0.4	0.27	0.15	−0.159	0–17.5

EtCO₂, end-tidal partial pressure of carbon dioxide; SpO₂, haemoglobin oxygen saturation from pulse oximeter.