Table 2.
Comparison of absolute and relative bias of estimate of PCO2 at baseline and during step changes in PCO2
| Pa,CO2 | PET,CO2 | ePa,CO2 | |
| Baseline | |||
| Mean ±s.d. (mmHg) | 40 ± 4 | 42 ± 3* | 42 ± 3* |
| B ± lA (mmHg) | — | 2 ± 4 | 2 ± 4 |
| RB ±s.d. (%) | — | 5 ± 2 | 5 ± 3 |
| 4% CO2 | |||
| Mean ±s.d. (mmHg) | 43 ± 4 | 47 ± 3* | 46 ± 3 |
| B ± lA (mmHg) | — | 4 ± 7 | 2 ± 6 |
| RB ±s.d. (%) | — | 8 ± 4 | 5 ± 3 |
| 8% CO2 | |||
| Mean ±s.d. (mmHg) | 55 ± 4 | 60 ± 3*† | 56 ± 3 |
| B ± lA (mmHg) | — | 5 ± 6 | 0.2 ± 6 |
| RB ±s.d. (%) | — | 9 ± 3 | 0.4 ± 3 |
| Hypo 1 | |||
| Mean ±s.d. (mmHg) | 35 ± 3 | 36 ± 4 | 34 ± 3 |
| B ± lA (mmHg) | — | 2 ± 9 | 2 ± 12 |
| RB ±s.d. (%) | — | 5 ± 5 | 5 ± 6 |
| Hypo 2 | |||
| Mean ±s.d. (mmHg) | 23 ± 4 | 23 ± 4 | 24 ± 4 |
| B ± lA (mmHg) | — | 0.3 ± 3 | 0.9 ± 3 |
| RB ±s.d. (%) | — | 1 ± 1 | 4 ± 1 |
Values are mean ±s.d.PET,CO2, end-tidal CO2; ePa,CO2, regression equation using both end-tidal PCO2 and tidal volume to estimat ePa,CO2; Pa,CO2, arterial PCO2; s.d., standard deviation; RB, relative bias; B, bias; LA, 95% limits of agreement (±1.96 ×s.d. of the bias).
*
Different from Pa,CO2 (P < 0.05);
†
different from ePa,CO2 (P < 0.05).