Purpose： This prospective observational study aims to evaluate the accuracy of dead-space fraction derived from the ventilator volumetric capnography （volumetric CO2） or a prediction equation to predict the surviva...Purpose： This prospective observational study aims to evaluate the accuracy of dead-space fraction derived from the ventilator volumetric capnography （volumetric CO2） or a prediction equation to predict the survival of mechanically ventilated patients with acute respiratory distress syndrome （ARDS）. Methods： Consecutive VDJVT measurements were obtained based upon a prediction equation validated by Frankenfield et al for dead-space ventilation fraction： VD/VT = 0.320 ＋ 0.0106 （PaCO2-ETCO2） 4- 0.003 （RR） ＋ 0.0015 （age） in adult patients who had infection-related severe pneumonia and were confirmed as having ARDS. Here PaCO2 is the arterial partial pressure of carbon dioxide in mmHg; ETC02, the end- tidal carbon dioxide measurement in mmHg; RR, respiratory rate per minute; and age in years. Once the patient had intubation, positive end expiratory pressure was adjusted and after Phigh reached a steady state, VD/VT was measured and recorded as the data for the first day. VD/VT measurement was repeated on days 2, 3, 4, 5 and 6. Meanwhile we collected dead-space fraction directly from the ventilator volu- metric CO2 and recorded it as Vd/Vt. We analyzed the changes in VD/VT and Vd/Vt over the f-day period to determine their accuracy in predicting the survival of ARDS patients. Results： Overall, 46 patients with ARD5 met the inclusion criteria and 24 of them died, During the first 6 days of intubation, VD/VT was significantly higher in nonsurvivors on day 4 （0.70 ± 0,01 vs 0.57 ± 0.01 ）, day 5 （0.73 ± 0.01 vs, 0.54 ± 0.01 ）, and day 6 （0.73 ±0,02 vs. 0.54 ± 0.01 ） （all p - 0.000）. Vd/Vt showed no significant difference on days 1-4 but it was much higher in nonsurvivors on day 5 （0.45 ± 0.04 vs. 0.41 ±0.06） and day 6 （0.47 ± 0,05 vs. 0.40 ± 0.03） （both p - 0.008）. VD/VT on the fourth day was more accurate to predict survival than Vd/Vt. The area under the receiver-operating characteristic curve for VD/VT and Vd/Vt in evaluating ARDS patients survival was day 4 （0,974 ± 0.093 vs. 0.701 ± 0.023, p = 0.0024） with the 95% confidence interval being 0.857-0.999 vs, 0.525-0.84L Conclusion： Compared with Vd/Vt derived from ventilator volumetric CO2, VD/VT on day 4 calculated by Frankenfield et al＇s equation can more accurately predict the survival of ARDS patients.展开更多
文摘Purpose： This prospective observational study aims to evaluate the accuracy of dead-space fraction derived from the ventilator volumetric capnography （volumetric CO2） or a prediction equation to predict the survival of mechanically ventilated patients with acute respiratory distress syndrome （ARDS）. Methods： Consecutive VDJVT measurements were obtained based upon a prediction equation validated by Frankenfield et al for dead-space ventilation fraction： VD/VT = 0.320 ＋ 0.0106 （PaCO2-ETCO2） 4- 0.003 （RR） ＋ 0.0015 （age） in adult patients who had infection-related severe pneumonia and were confirmed as having ARDS. Here PaCO2 is the arterial partial pressure of carbon dioxide in mmHg; ETC02, the end- tidal carbon dioxide measurement in mmHg; RR, respiratory rate per minute; and age in years. Once the patient had intubation, positive end expiratory pressure was adjusted and after Phigh reached a steady state, VD/VT was measured and recorded as the data for the first day. VD/VT measurement was repeated on days 2, 3, 4, 5 and 6. Meanwhile we collected dead-space fraction directly from the ventilator volu- metric CO2 and recorded it as Vd/Vt. We analyzed the changes in VD/VT and Vd/Vt over the f-day period to determine their accuracy in predicting the survival of ARDS patients. Results： Overall, 46 patients with ARD5 met the inclusion criteria and 24 of them died, During the first 6 days of intubation, VD/VT was significantly higher in nonsurvivors on day 4 （0.70 ± 0,01 vs 0.57 ± 0.01 ）, day 5 （0.73 ± 0.01 vs, 0.54 ± 0.01 ）, and day 6 （0.73 ±0,02 vs. 0.54 ± 0.01 ） （all p - 0.000）. Vd/Vt showed no significant difference on days 1-4 but it was much higher in nonsurvivors on day 5 （0.45 ± 0.04 vs. 0.41 ±0.06） and day 6 （0.47 ± 0,05 vs. 0.40 ± 0.03） （both p - 0.008）. VD/VT on the fourth day was more accurate to predict survival than Vd/Vt. The area under the receiver-operating characteristic curve for VD/VT and Vd/Vt in evaluating ARDS patients survival was day 4 （0,974 ± 0.093 vs. 0.701 ± 0.023, p = 0.0024） with the 95% confidence interval being 0.857-0.999 vs, 0.525-0.84L Conclusion： Compared with Vd/Vt derived from ventilator volumetric CO2, VD/VT on day 4 calculated by Frankenfield et al＇s equation can more accurately predict the survival of ARDS patients.
