Table 2.
Control values for subjects who were responsive and nonresponsive to isocapnic, hypercapnic, and hyperoxic treatments
| To Isocapnia |
To Hypercapnia |
To Hyperoxia |
||||
|---|---|---|---|---|---|---|
| Responsive | Nonresponsive | Responsive | Nonresponsive | Responsive | Nonresponsive | |
| N | 14 (3F + l1M) | 12 (3F + 9M) | 17 (5F + 12M) | 4 (0F + 4M) | 7 (3F + 4M) | 12 (0F + 12M) |
| Age, yr | 59 ± 2 | 58 ± 3 | 58 ± 2 | 56 ± 2 | 62 ± 2 | 55 ± 3 |
| BMI, kg/m2 | 33 ± 2 | 34 ± 2 | 33 ± 2 | 36 ± 1 | 31 ± 2 | 34 ± 2 |
| AHI, no./h | 38 ± 6 | 48 ± 8 | 34 ± 4 | 68 ± 9 | 36 ± 7 | 52 ± 8 |
| CA/total apnea, % | 10.9 ± 3.7 | 3.9 ± 2.8 | 9.5 ± 3.2 | 0.2 ± 0.2 | 4.6 ± 3.3 | 5.2 ± 3.0 |
| AHI range, min–max | 12–92 | 12–93 | 12–57 | 49–93 | 12–60 | 10–85 |
| Mean SaO2 | 93 ± 1 | 91 ± 1 | 93 ± 1 | 87 ± 3* | 92 ± 2 | 93 ± 1 |
| Controller gain, l• min−1•mmHg−1 | 6.5 ± 1.7 | 2.1 ± 0.2** | 4.5 ± 1.2 | 2.6 ± 0.5 | 6.0 ± 2.3 | 3.6 ± 1.1 |
| Plant gain, mmHg•l−1•min | 0.33 ± 0.06 | 0.29 ± 0.04 | 0.31 ± 0.05 | 0.29 ± 0.06 | 0.38 ± 0.13 | 0.37 ± 0.04 |
| CO2 reserve, mmHg | 1.9 ± 0.3 | 4.3 ± 0.4** | 2.6 ± 0.3 | 4.5 ± 1.0 | 2.7 ± 0.8 | 3.2 ± 0.4 |
| Pcrit, cmH2O | −0.1 ± 1.2 (3 to −8) | 0.2 ± 0.9 (5 to −5) | −0.6 ± 1.0 (4 to −8) | 1.3 ± 0.5 (2 to 0.1) | −0.9 ± 1.8 (5 to −3.5) | 1.1 ± 0.7 (4 to −8) |
Values are means ± SE. Responsive group, apnea-hypopnea index (AHI) reduced by 30% of baseline value or more in response to isocapnic rebreathing (31 ± 6% of control) or hypercapnia (15 ± 4% of control) or hyperoxia (36 ± 11% of control); Nonresponsive group, the reduction in AHI was <30% of baseline during isocapnic rebreathing (112 ± 10% of control) or hypercapnia (98 ± 8% of control) or hyperoxia (149 ± 21% of control). BMI, body mass index; CA, central apnea; CO2 reserve, the proximity between eupneic PetCO2 and apneic threshold PetCO2. Pcrit, critical closing pressure.