Altitude performance (4559 m) at rest, 45%, and maximum power (Pmax) for placebo and Az groups, and comparisons between matched pairs
| Test variable | Comparison of placebo versus Az for groups | Comparison of placebo versus Az for matched pairs | |||
| Placebo versus Az at rest* | Placebo versus Az at 45% Pmax* | Placebo versus Az at Pmax* | Change from rest to Pmax† | Difference in pairs at Pmax‡ | |
| Pmax (W) as % of sea-level values | – – | – – | §76.6 (7.4) versus 65 (14.1) P=0.03 | – − | P = 0.007 |
| Heart rate (b/min) | 92 (18.4) versus 93 (15.7) P=0.88 | 146 (17) versus 140 (17) P=0.43 | 167 (16) versus 154 (25) P=0.33 | 75 (21) versus 61 (20) P=0.1 | P=0.007 |
| RPE (Borg scale: 6–20) | 10(2) versus 9 (1) P=0.36 | 14(2) versus 14(1) P=0.56 | 17(2) versus 17 (2) P=0.81 | 7 (2) versus 8 (2) P=0.36 | NS |
| VE (L/min) | 34(9) versus 37(10) P=0.48 | 75(13) versus 88(22) P=0.11 | 150(22) versus 125(27) P=0.04 | 116 (21) versus 88 (28) P=0.05 | NS |
| SpO2 (%) | 79.0 (4.1) versus 84.6 (4.7) P=0.004 | 74.1 (5.2) versus 75.5 (5.1) P=0.55 | 77.0 (4.4) versus 77.2 (6.3) P=0.7 | −2.4 (5.7) versus −7.4 (6.3) P=0.13 | NS |
| PetO2 (mm Hg) | 54.9 (2.7) versus 58.4 (2.7) P=0.007 | 57.8 (2.7) versus 61.9 (3.8) P=0.01 | 64.2 (2.0) versus 65.0 (2.0) P=0.45 | 9.3 (1.8) versus 6.6 (2.3) P=0.009 | P=0.07 |
| PetCO2 (mm Hg) | 21.0 (1.5) versus 17.5 (1.5) P=0.0006 | 20.5 (2.1) versus 16.6 (2.7) P<0.01 | 16.8 (1.5) versus 15.2 (1.5) P=0.05 | −4.2 (1.37) versus −2.3 (0.95) P=0.005 | P=0.0003 |
| VO2 uptake: (mL/kg/min) | 10.8 (3.2) versus 10.9 (2.8) P=0.97 | 19.5 (5.5) versus 18.4 (2.8) P=0.56 | 24.6 (5.1) versus 20.7 (5.2) P=0.063 | 13.8 (4.9) versus 9.8 (6.2) P=0.04 | P=0.0003 |
| VCO2 production (mL/kg/min) | 8.7 (2.5) versus 8.7 (2.3) P=0.91 | 18.7 (4.8) versus 18.3 (2.3) P=0.82 | 29.5 (4.6) versus 23.4 (5.5) P=0.01 | 20.8 (5.0) versus 14.7 (6.0) P=0.009 | P=0.0003 |
| VE/VO2 produced | 44 (5.8) versus 50 (6.8) P=0.04 | 55.0 (8.0) versus 70.8 (18.2) P=0.03 | 86 (16.0) versus 88 (11.5) P=0.78 | 42 (13.0) versus 38 (7.1) P=0.68 | NS |
| VE/VCO2 produced | 55 (4.1) versus 64 (5.3) P=0.001 | 56.9 (6.7) versus 70.8 (14.2) P=0.02 | 70 (6.3) versus 79 (9.7) P=0.04 | 15 (5.2) versus 15 (4.8) P=0.80 | P=0.0003 |
| CO2 prodn/O2 uptake (RER) | 0.81 (0.07) versus 0.78 (0.06) P=0.44 | 0.96 (0.06) versus 0.99 (0.07) P=0.44 | 1.23 (0.16) versus 1.12 (0.1) P=0.14 | 0.42 (0.12) versus 0.34 (0.09) P=0.19 | P=0.007 |
Data are mean values (±SD) with P values in bold when P=0.05 or less. Symbols indicate type of statistical test used:
*Mann-Whitney U test for differences of means.
†Pearson’s correlation for changes in paired individuals.
‡Pearson’s χ2 test for observed differences between matched pairs.
§Percentage reduction of individuals mean values between baseline and altitude.
Az, acetazolamide; PetCO2, end tidal CO2; PetO2, end tidal O2; RER, respiratory exchange ratio; RPE, rate of perceived effort; SpO2, peripheral blood O2 saturation; VCO2, CO2 production; VE, ventilation; VO2, O2 uptake.