To the Editor:
We wish to thank Dr Ospan A. Mynbaev for commenting on our publication regarding the ventilation modes in obese patients undergoing gynecological laparoscopy.
Every 100 mL increase in the tidal volume reduces partial arterial pressure of CO2(PaCO2) on an average by 5.3 mmHg in normal-weight patients and by 3.6 mmHg in morbidly obese patients.1 This indicated that tidal volumes were associated with the capacity of CO2 elimination. Although CO2-pneumoperitoneum would resulted in increase of end-tidal carbon dioxide pressure (PetCO2) or PaCO2.
A clinical study could not monitor all their parameters and harmed the patient's benefit because of minimal invasive surgery in this study. PetCO2 could be continuously monitored. If PaCO2 was continuously monitored, arterial blood was collected usually and analyzed. On the whole, arterial-to-end tidal CO2 gradient considered about 5–10 mmHg.
CO2 accumulation is mainly related to the absorption of CO2 in the patients’ blood. Usually this parameter is adjusted at a higher level of 40–50 mmHg in most studies during CO2-pneumoperitoneum, taking into account laparsopic surgery. The large tidal volumes can decrease CO2 concentration.
In conclusion, Volume-controlled IRV with I:E ratio of 2:1 can be an effective mode of ventilation in obese gynecologic patients undergoing laparoscopic surgery. It is an unconventional ventilation mode and can be used when conventional methods seem inadequate to achieve enough tidal volumes at a certain high peak airway pressure. It delivers better tidal volume than the conventional ventilation with I:E ratio of 1:2.2 It is associated with the rise in oxygenation, the mean airway pressure, and dynamic lung compliance, which is superior to conventional ratio ventilation.
Conflicts of interest
There are no conflicts of interest in connection with this article.