Table 3.
Ventilatory responses to hypoxia and hypercapnia.
| 33°C | 26°C | G × T | |||||
|---|---|---|---|---|---|---|---|
| Phox2b+/+ | Phox2b+/− | p | Phox2b+/+ | Phox2b+/− | p | p | |
| PEAK-VE RESPONSE TO HYPOXIA | |||||||
| n | 41 | 43 | 84 | 85 | |||
| ΔVE (%) | 95 (22) | 80 (17) | 0.0011 | 29 (19)**** | 51 (33)**** | <0.0001 | <0.0001 |
| ΔVT (%) | 32 (14) | 27 (12) | NS | 13 (13)**** | 23 (21) | 0.0004 | <0.0009 |
| ΔTTOT (%) | −32 (7) | −29 (8) | NS | −12 (8)**** | −18 (10)**** | 0.0001 | <0.0003 |
| Peak-VE latency (s) | 143 (29) | 148 (30) | NS | 99 (41)**** | 110 (44)**** | NS | NS |
| HYPOXIC VENTILATORY DECLINE | |||||||
| n | 41 | 43 | 84 | 85 | |||
| ΔVE (%) | −11 (7) | −7 (9) | 0.0173 | −33 (12)**** | −25 (18)**** | 0.0007 | NS |
| ΔVT (%) | −12 (10) | −8 (9) | NS | −23 (10)**** | −17 (13)*** | 0.0021 | NS |
| ΔTTOT (%) | 0 (14) | −1 (14) | NS | 18 (20) | 13 (17) | NS | NS |
| PEAK-VE RESPONSE TO HYPERCAPNIA | |||||||
| n | 34 | 36 | 51 | 45 | |||
| ΔVE (%) | 150 (62) | 118 (70) | 0.0489 | 96 (47)**** | 121 (71) | 0.0436 | <0.0044 |
| ΔVT (%) | 98 (23) | 83 (30) | 0.0300 | 81 (30)** | 89 (44) | NS | <0.0314 |
| ΔTTOT (%) | −19 (12) | −13 (13) | 0.0346 | −4 (14)**** | −11 (18) | 0.0440 | 0.0050 |
| Peak-VE latency (s) | 294 (65) | 292 (59) | NS | 194 (71)**** | 250 (90)* | 0.0010 | 0.0129 |
Values are percentage changes from pre-stimulus values. The peak-VE response to hypoxia and hypoxic ventilatory decline were calculated individually over the entire 3 min of hypoxia and the 3-min post-hypoxic period, respectively. The peak-VE response to hypercapnia was calculated over the entire 6 min of hypercapnia. Values indicate mean (SD) for each group. The p-value refers to the comparison between Phox2b+/+ and Phox2b+/ groups. Comparison of 33 versus 26°C for each genotype group; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. G × T: p-value for Genotype by Temperature interaction. Note that the G × T interaction was marginally significant for VT.