Table 1.
Ventilatory responses to hypoxia: parameter values (mean ±s.e.m) for the model of the ventilatory response to acute hypoxia for the trimetaphan and control protocols before and after an 8 h period of sustained hypoxic exposure
| Protocol/factor | G100 (l min−1%−1) | V̇c(l min−1) | Tp (s) | Dp (s) | Gh (l min−1%−2) | Th (s) | Kp (%) |
|---|---|---|---|---|---|---|---|
| AM measurements – before sustained hypoxia | |||||||
| Control 1 | 0.85 ± 0.20 | 7.58 ± 1.51 | 11.77 ± 4.40 | 5.83 ± 147 | 0.028 ± 0.011 | 537 ± 135 | 3.48 ± 1.41 |
| Trimetaphan | 0.78 ± 0.23 | 4.17 ± 1.28 | 9.09 ± 5.40 | 5.69 ± 1.17 | 0.022 ± 0.008 | 820 ± 136 | 10.64 ± 7.49 |
| Control 2 | 1.01 ± 0.20 | 7.45 ± 1.39 | 11.88 ± 4.21 | 6.12 ± 1.71 | 0.030 ± 0.010 | 643 ± 162 | 1.99 ± 1.62 |
| PM measurements – after sustained hypoxia | |||||||
| Control 1 | 1.82 ± 0.29 | 15.58 ± 1.28 | 20.97 ± 3.47 | 6.10 ± 2.19 | 0.054 ± 0.023 | 471 ± 115 | 1.54 ± 0.89 |
| Trimetaphan | 1.40 ± 0.23 | 12.03 ± 2.95 | 12.17 ± 3.60 | 4.63 ± 0.91 | 0.045 ± 0.021 | 880 ± 114 | 2.77 ± 1.57 |
| Control 2 | 1.75 ± 0.15 | 16.61 ± 0.99 | 12.83 ± 3.96 | 2.74 ± 0.63 | 0.030 ± 0.020 | 594 ± 134 | 0.83 ± 0.77 |
| Statistical analysis – ANOVA | |||||||
| Time (before/after sustained hypoxia) | < 0.001 | < 0.001 | — | — | — | — | — |
| Protocol (C1, C2 versus T) | — | — | — | — | — | — | — |
| Interactive term | — | — | — | — | — | — | — |
G100, steady-state chemoreflex sensitivity to hypoxia in absence of any hypoxic ventilatory depression (arterial oxygen saturation is 100%); V̇E, hypoxia independent (central chemoreflex) contribution to V̇c; Tp, time constant for the peripheral chemoreflex responses to hypoxia; Dp, time delay for the peripheral chemoreflex; Gh, sensitivity to hypoxic ventilatory decline, expressed as the ratio of the decrease in the sensitivity of the peripheral chemoreflex to the decrease in conditioning arterial oxygen saturation; Th, time constant associated with the development of hypoxic ventilatory decline; Kp, bias term, representing peripheral drive in absence of hypoxia; AM, morning; PM, afternoon. ANOVA conducted on the parameter values with fixed factors Time (before/after sustained hypoxia) and Protocol (control protocols (Protocols C1, C2) versus Protocol T). Statistical significance was accepted at P < 0.05.