Table 2

Parameter estimates for changes in ln(Hbmass) from baseline (prealtitude) values during altitude exposure, derived via linear mixed modelling, and their interpretation in terms of percentage changes (increases) in Hbmass

Model/parameterChange in ln(Hbmass) from prevaluesPercentage of increase in Hbmass
Estimate95% CIp ValueTime at altitude (h)Estimate95% CI
Linear*
slope1.07×10−4(0.94×10−4 to 1.20×10−4)<0.0011001.08(0.94 to 1.21)
Linear1.39×10−4(1.10×10−4 to 1.69×10−4)<0.0011001.33(1.10 to 1.56)
3003.56(3.13 to 4.00)
Time as a factor (h)
18–240.22×10−4(−0.80×10−4 to 1.23×10−4)0.66418–240.22(−0.80 to 1.24)
96–1121.29×10−4(0.66×10−4 to 1.93×10−4)<0.00196–1121.30(0.66 to 1.95)
144–2242.41×10−4(1.82×10−4 to 3.01×10−4)<0.001144–2242.44(1.84 to 3.06)
266–2943.25×10−4(2.50×10−4 to 4.00×10−4)<0.001266–2943.30(2.53 to 4.08)
312–3643.89×10−4(3.09×10−4 to 4.70×10−4)<0.001312–3643.97(3.14 to 4.81)
408–4564.00×10−4(2.91×10−4 to 5.09×10−4)<0.001408–4564.08(2.95 to 5.22)
504–6726.28×10−4(4.96×10−4 to 7.59×10−4)<0.001504–6726.48(5.09 to 7.89)
• *For the linear and quadratic models, the time at altitude is measured in hours so that, for example, the linear model implies an increase in ln(Hbmass) of 0.0107/100 h, which translates to an increase of 1.08% in Hbmass.

• p Values refer to testing whether the associated parameter is equal to zero.

• Hbmass, haemoglobin mass; ln(Hbmass); natural log of Hbmass.