Evaluation of pressure-controlled vs volume-controlled ventilation in obese patients undergoing upper abdominal laparoscopic surgeries

an observational study

Abstract

BACKGROUND: Obesity is a global pandemic and is usually associated with other co-morbidities, its implications on pulmonary physiology are well documented. Hence, obesity carries additional risks during laparoscopic surgery under general anaesthesia due to special respiratory mechanics associated with obesity and difficulty in maintenance of oxygenation in these patients. Currently, there is no gold standard method for intraoperative ventilation in obese patients and in practice, the appropriate strategy of ventilation is based on the anesthesiologist’s preferences. Keeping in view these facts, we observed and evaluated volume-controlled and pressure-controlled modes of ventilation in obese patients undergoing laparoscopic upper abdominal surgery under general anaesthesia.

OBJECTIVE(S):         Primary: - To evaluate the effects of PCV and VCV in obese patients undergoing laparoscopic upper abdominal surgeries on lung mechanics, oxygenation parameters and airway pressures.

Secondary: - To evaluate the hemodynamic parameters and postoperative respiratory complications between the two groups.

STUDY DESIGN:     An observational study.

PARTICIPANTS:      60 obese patients (BMI ≥30 kg/m²) of either gender, age 18 to 60 years, with ASA II and III were subsequently divided each into PCV group and VCV group.

METHODS:        The patients were divided equally into VCV group and PCV group of 30 patients each and were put on the volume-controlled and pressure-controlled mode of ventilation respectively during the intra-operative period, the vitals of the patients were monitored and oxygenation and ventilatory parameters were recorded. After completion of the surgery, patients were extubated after fulfilling all extubation criteria. Postoperatively, vitals were monitored and blood gas analysis were done at 1 hour and 2 hours intervals in the recovery ward.

RESULTS:          The baseline characteristics of the patients were similar between the two groups. Mean spo₂, pH, pao₂ were higher in the PCV group and mean pco₂, tidal volume and peak airway pressures were lower in the PCV group with statically significant difference (p <0.05). Respiratory rate, etco₂, peak inspiratory pressure, plateau pressure and dynamic total compliance were similar between the two groups (p >0.05).

CONCLUSIONS:      PCV is a better mode of ventilation than VCV in obese patients undergoing laparoscopic upper abdominal surgeries as it provides better oxygenation and gas exchanges by improving ventilation-perfusion ratio at lower peak airway pressures.

IMPLICATIONS:      PCV mode is a common mode of ventilation routinely employed in anaesthetized patients and it can be used in obese patients with the benefits of improved oxygenation at lower airway pressures.