Introduction and method
Titrating PEEP above the Pflex can improve oxygenation and survival when compared to the conventional ventilation in ARDS patients. In order to study the dynamics of CO2 in ARDS patients as well as the effects of setting PEEP above the Pflex on the CO2 dynamics we studied seven patients with ARDS criteria (less than 5 days of installation), with mean age of 63 ± 0.11 years and mean APACHE score of 21.4. After performing the PxV curve (random volumes) we ventilated the patients with 8 ml/kg TV and RR of 15 and PEEP of 5 cmH2O. Then we kept the same MV and set PEEP 2 cmH2O above Pflex for 30 min. Then we decreased PEEP to 5 for more 30 min. All the patients have a Swan-Ganz catheter and a continuous tonometer.
Results
See Table.
Table.
| 30 min PEEP=5 | 30 min PEEP >Pflex | 30 min PEEP of 5 | |
|---|---|---|---|
| PaO2/FiO2 | 81 ± 24 | 128 ± 42* | 101 ± 47 |
| PvO2 | 42.7 ± 5.8 | 47.2 ± 7* | 42 ± 3 |
| PaCO2 | 40.6 ± 12 | 37.5 ± 12 | 35 ± 12 |
| PvCO2/v-a (CO2) | 43 ± 13/4.3 ± 1.5 | 42 ± 12/4.5 ± 0.3 | 40 ± 10/4.7 ± 2. |
| ETCO2/a-ET(CO2) | 23.7 ± 8/16.6 ± 3.4 | 24 ± 7/13.5 ± 4.3* | 23 ± 6/12.2 ± 6.5 |
| PgCO2/g-v (CO2) | 47 ± 13/3.6 ± 1.2 | 46 ± 13/4.5 ± 0.3 | 45 ± 13/5.3 ± 3 |
| CI (l/min/m2) | 4.6 ± 1 | 4.05 ± 0.9* | 4.5 ± 1.4 |
Conclusion
PEEP above the Pflex decreased the cardiac index and the arterial-expired CO2 gradient while increased the oxygenation and the PvO2.