Table 2.
Cardiorespiratory responses during the last 10 s of an incremental exercise to exhaustion in severe hypoxia (PIO2 = 73 mmHg) and during the first 10 s of oxygenation with different gas mixtures.
| Exhaustion PIO2 = 73 mmHg | Start of PIO2 = 99 mmHg | Exhaustion PIO2 = 73 mmHg | Start of PIO2 = 92 mmHg | Exhaustion PIO2 = 73 mmHg | Start of PIO2 = 82 mmHg | Exhaustion PIO2 = 73 mmHg | Start of PIO2 = 73 mmHg | |
|---|---|---|---|---|---|---|---|---|
| FIO2 (%) | 10.78 ± 0.10 | 13.92 ± 0.23c | 10.82 ± 0.12 | 12.45 ± 0.75c | 10.78 ± 0.06 | 12.01 ± 0.25c | 10.79 ± 0.08 | 10.79 ± 0.20¶§‡ |
| SpO2 (%) | 62.4 ± 5.2 | 63.1 ± 5.5 | 64.3 ± 5.5 | 65.1 ± 5.7 | 63.5 ± 5.8 | 63.6 ± 5.9 | 64.7 ± 4.9 | 64.4 ± 5.7‡ |
| Wmax (W) | 172.0 ± 23.5 | 172.0 ± 23.5 | 170.0 ± 21.6 | 170.0 ± 21.6 | 168.0 ± 16.9 | 168.0 ± 16.9 | 172.0 ± 21.5 | 172.0 ± 21.5 |
| VO2peak (L.min−1) | 2.32 ± 0.17 | 2.81 ± 0.46b | 2.23 ± 0.25 | 2.53 ± 0.34a | 2.33 ± 0.15 | 2.45 ± 0.27T | 2.27 ± 0.29 | 2.29 ± 0.32¶§‡ |
| VE (L.min−1) | 118.2 ± 23.7 | 111.8 ± 20.8 | 114.8 ± 26.3 | 116.8 ± 22.6 | 117.5 ± 16.4 | 116.4 ± 15.1 | 114.8 ± 14.7 | 116.8 ± 15.6 |
| RR (breaths.min−1) | 51.7 ± 9.2 | 48.1 ± 7.2 | 51.3 ± 8.5 | 50.7 ± 8.2 | 51.5 ± 8.4 | 51.1 ± 7.6 | 51.3 ± 7.0 | 52.3 ± 7.7 |
| HR (beats.min−1) | 179.0 ± 10.2 | 179.3 ± 10.1 | 180.5 ± 8.2 | 181.0 ± 7.4 | 177.3 ± 7.4 | 177.5 ± 7.2 | 180.6 ± 7.9 | 180.8 ± 8.3¶ |
| PETO2 (mmHg) | 51.4 ± 3.0 | 62.9 ± 5.1c | 51.7 ± 3.1 | 58.1 ± 6.3c | 51.4 ± 2.9 | 56.1 ± 3.9c | 51.6 ± 2.0 | 51.9 ± 2.0¶§‡ |
| PETCO2 (mmHg) | 27.3 ± 2.9 | 27.3 ± 4.3 | 28.3 ± 2.9 | 28.4 ± 2.7 | 27.4 ± 3.7 | 27.6 ± 3.0 | 28.5 ± 2.3 | 28.2 ± 2.4 |
| RER | 1.32 ± 0.17 | 1.16 ± 0.15T | 1.36 ± 0.15 | 1.28 ± 0.13 | 1.32 ± 0.15 | 1.28 ± 0.15 | 1.36 ± 0.14 | 1.37 ± 0.17§ |
| VCO2 (L.min−1) | 3.06 ± 0.42 | 3.01 ± 0.44 | 3.03 ± 0.48 | 3.12 ± 0.41 | 3.07 ± 0.29 | 3.06 ± 0.28 | 3.08 ± 0.41 | 3.11 ± 0.39 |
| RPM | 63.6 ± 9.4 | 66.3 ± 10.3 | 68.5 ± 7.0 | 71.3 ± 11.4 | 67.1 ± 9.5 | 68.2 ± 12.0 | 71.2 ± 7.8 | 70.0 ± 9.3 |
| VM RMSraw (μV) | 105.9 ± 37.2 | 119.3 ± 43.5c | 106.3 ± 42.6 | 112.2 ± 38.1a | 113.5 ± 42.7 | 120.6 ± 50.2T | 97.2 ± 43.0 | 99.7 ± 42.6¶‡ |
| VL RMSraw (μV) | 108.8 ± 38.4 | 119.1 ± 39.9c | 97.3 ± 48.9 | 102.0 ± 49.2a | 115.8 ± 49.9 | 114.1 ± 45.1 | 85.9 ± 35.5 | 87.4 ± 40.6¶ |
| Average RMSraw (μV) | 107.4 ± 29.1 | 119.2 ± 33.4c | 101.8 ± 41.5 | 107.1 ± 39.1b | 114.7 ± 39.2 | 117.3 ± 40.6 | 91.5 ± 34.9 | 93.6 ± 38.0¶‡ |
| VM RMSNz (A.U.) | 176.2 ± 48.1 | 195.8 ± 56.9c | 178.0 ± 58.4 | 191.2 ± 57.2a | 180.9 ± 50.4 | 187.6 ± 41.7 | 164.8 ± 67.2 | 168.6 ± 64.2¶ |
| VL RMSNz (A.U.) | 182.5 ± 55.5 | 199.6 ± 52.2c | 160.2 ± 38.8 | 171.1 ± 35.5a | 189.6 ± 67.0 | 185.6 ± 45.4 | 151.7 ± 49.2 | 152.3 ± 51.7¶‡ |
| Average RMSNz (A.U.) | 179.4 ± 49.8 | 197.7 ± 52.5c | 169.1 ± 47.0 | 181.2 ± 45.0a | 185.2 ± 56.4 | 186.6 ± 40.2 | 158.2 ± 56.8 | 160.5 ± 56.9¶‡ |
| VM TAINz (A.U.) | 39.6 ± 17.6 | 44.5 ± 19.5b | 35.6 ± 14.8 | 38.0 ± 12.5 | 37.1 ± 14.1 | 37.6 ± 11.1 | 33.5 ± 13.3 | 35.5 ± 14.1¶ |
| VL TAINz (A.U.) | 36.8 ± 13.5 | 41.2 ± 14.4c | 30.2 ± 9.7 | 32.8 ± 7.1 | 37.1 ± 12.6 | 35.8 ± 8.7 | 29.3 ± 8.8 | 31.6 ± 14.0¶ |
| Average TAINz (A.U.) | 38.2 ± 15.4 | 42.8 ± 16.9c | 32.9 ± 11.8 | 35.4 ± 9.5 | 37.1 ± 13.2 | 36.7 ± 9.6 | 31.4 ± 10.6 | 33.6 ± 13.3¶ |
| VM MPF (Hz) | 96.0 ± 24.8 | 95.1 ± 24.2 | 89.2 ± 22.8 | 91.5 ± 23.9 | 91.2 ± 17.3 | 89.8 ± 15.0 | 84.9 ± 15.5 | 83.6 ± 13.8 |
| VL MPF (Hz) | 97.0 ± 27.0 | 96.0 ± 27.5 | 88.9 ± 22.6 | 90.2 ± 23.2 | 91.2 ± 17.3 | 89.5 ± 15.5 | 84.9 ± 15.9 | 83.5 ± 14.4 |
| Average MPF (Hz) | 96.5 ± 25.9 | 95.5 ± 25.7 | 89.1 ± 22.7 | 90.9 ± 23.5 | 91.2 ± 17.3 | 89.6 ± 15.3 | 84.9 ± 15.7 | 83.5 ± 14.1 |
| VM MdPF (Hz) | 76.3 ± 17.1 | 76.9 ± 17.1 | 70.3 ± 15.7 | 72.7 ± 14.7 | 70.8 ± 13.2 | 71.8 ± 11.6 | 66.9 ± 10.3 | 66.2 ± 10.5 |
| VL MdPF (Hz) | 77.8 ± 19.7 | 77.6 ± 20.0 | 69.8 ± 15.9 | 70.9 ± 15.0 | 70.7 ± 13.2 | 71.4 ± 12.0 | 66.4 ± 10.8 | 65.6 ± 10.2 |
| Average MdPF (Hz) | 77.0 ± 18.3 | 77.3 ± 18.4 | 70.0 ± 15.8 | 71.8 ± 14.7 | 70.8 ± 13.2 | 71.6 ± 11.7 | 66.7 ± 10.5 | 65.9 ± 10.3§ |
| VM Burst (ms) | 361.5 ± 110.1 | 349.9 ± 85.9 | 310.7 ± 88.3 | 305.1 ± 81.2 | 310.3 ± 62.5 | 304.9 ± 94.7 | 309.3 ± 80.7 | 318.2 ± 74.7 |
| VL Burst (ms) | 343.2 ± 91.7 | 324.8 ± 81.7 | 297.8 ± 55.6 | 300.1 ± 70.7 | 310.2 ± 59.7 | 303.9 ± 91.5 | 300.0 ± 63.7 | 316.5 ± 86.6 |
| Average Burst (ms) | 352.4 ± 95.3 | 337.3 ± 79.0 | 304.3 ± 71.3 | 302.6 ± 75.4 | 310.2 ± 60.8 | 304.4 ± 93.0 | 304.7 ± 71.0 | 317.4 ± 76.5 |
| VM Timing (%) | 48.8 ± 3.8 | 47.6 ± 4.2a | 49.4 ± 2.5 | 49.1 ± 3.2 | 49.4 ± 2.3 | 49.3 ± 2.9 | 47.9 ± 3.9 | 48.3 ± 4.2‡ |
| VL Timing (%) | 50.7 ± 2.1 | 50.0 ± 2.3 | 50.2 ± 2.3 | 49.9 ± 2.5 | 50.3 ± 2.1 | 50.3 ± 2.4 | 49.5 ± 2.9 | 49.6 ± 3.0 |
| Average Timing (%) | 49.7 ± 2.6 | 48.8 ± 2.7 | 49.8 ± 2.3 | 49.5 ± 2.7 | 49.8 ± 2.2 | 49.8 ± 2.6 | 48.7 ± 3.4 | 49.0 ± 3.5 |
FIO2, inspiratory oxygen fraction; SpO2, hemoglobin saturation in capillary blood measured by pulse oximetry; Wmax, power output at exhaustion; VO2, oxygen consumption; VE, pulmonary ventilation; RR, respiratory rate; HR, heart rate; PETO2, end-tidal O2 pressure; PETCO2, end-tidal CO2 pressure; RER, respiratory exchange ratio; VCO2, CO2 production; RPM, revolutions per minute; VL, vastus lateralis; VM, vastus medialis; RMSraw, raw root mean square; RMSNz, normalized root mean square; TAINz: normalized total activation index (arbitrary units, A.U.); MPF, mean power frequency; MdPF, median power frequency; Burst, contraction burst duration; Timing: start of activation expressed as percentage of total revolution duration.
P < 0.05;
P < 0.01;
P < 0.001; and
P < 0.1 (FIO2 = 73 mmHg vs. new gas mixture).
P < 0.05 ANOVA breathing gas switch main effect;
P < 0.05 ANOVA oxygenation level main effect;
P < 0.05 ANOVA breathing gas switch x oxygenation level interaction; n = 10.