A Comparison between Volume-Controlled Ventilation versus Pressure Controlled-Volume Guaranteed in Prone Position
Authors: Hegab Sakr Mohamed Mohamed , Fawaz Ahmed Ali , Kasem Amr Ahmed , Al-Ansary Amin Mohammed 
Published: November 2024

Abstract

Background
Prone positioning of a patient under anesthesia is a way of ensuring optimum surgical access for a number of procedures, providing that the risks are fully understood. The most important effect of turning a patient prone under anesthesia is a drop in cardiac output. As regard the respiratory system, prone positioning has a broadly positive effect on the respiratory system providing that abdominal compression is avoided. Functional residual capacity and arterial oxygen tension both increases. During anesthesia the use of volume-controlled ventilation (VCV) is common, as this has been the only available mode on ventilators for a long time. Pressure-controlled ventilation (PCV) was proposed as an alternative to VCV in ICU patients with ARDS, and in the last few years in anesthesia, to achieve adequate oxygenation and normocapnia in obese patients. The two main differences between VCV and PCV are the chosen target and the flow pattern.

Objective
To compare effects of volume-controlled ventilation with pressure controlled-Volume guaranteed ventilation (with the same tidal volume) on respiratory mechanics (peak airway pressure, dynamic compliance, dead space and shunt fraction) and hemodynamics (heart rate and mean arterial blood pressure) in patients undergoing elective spine surgeries in prone position.

Methods
This Prospective randomized study was conducted in Ain Shams University hospitals on 60 patients divided into two groups. Each group includes 30 patients, Group A patients who received VCV and Group B patients who received PCV-VG.

Results
There was no statistically significant difference between the studied groups as regard demographic data and surgery data. While Ppeak was significantly higher in group A compared to group B at all measurements (15 min after induction, 15 min after positioning, 30 min after positioning, and supine position at the end). There was no statistically significant difference between the studied groups as regard Pmean. Respiratory rate at supine position at the end was significantly higher in group A compared to group B with no statistically significant difference between both groups at the rest of measurements. Dynamic lung compliance (Cdyn) was significantly lower in group A compared to group B at all measurements. ETCO2 at 15 min after positioning was significantly lower in group A compared to group B with no statistically significant difference between both groups at the rest of measurements. There was no statistically significant difference between the studied groups as regard SaO2, mean arterial pressure, heart rate. Meanwhile PH was significantly higher in group A compared to group B. PaO2 and PaCO2 were insignificantly different between both groups at all measurements.

Conclusion
PCV-VG provided a lower Ppeak and improved Cdyn, compared VCV, with no significant difference in Pmean, oxygen saturation (SaO2), hemodynamics as (heart rate and mean arterial blood pressure), with reduction in PaO2 and increasing in PaCo2. PCV-VG was superior to VCV in its ability to provide mechanical ventilation for patients undergoing elective spine surgeries in prone position.