A prospective, randomized, comparative study between volume controlled, pressure controlled and pressure regulated volume controlled ventilation in improving respiratory dynamics during laparoscopic cholecystectomy

BACKGROUND: Volume controlledventilation (VCV) mode is the most commonly used conventional mode inanesthesia. VCV follows a constant flow pattern to deliver a preset tidal volumein the preset inspiratory time, thus ensuring constant minute ventilation. Thisflow pattern generates high inspiratory pressure that can lead to shear stressinjury, barotrauma and volutrauma to the alveoli[1] leading tomicroatelectasis and inflammatory mediator release characteristic of ventilator‑associated lung injury.

Pressure controlled ventilation(PCV) mode came as an alternative mode in laparoscopic surgeries. PCV deliverstidal volume at a preset pressure and inspiratory time. The flow, unlike VCV,is decelerating. This flow pattern has a high initial rise followed by adecrease and helps to attain the tidal volume at lower peak inspiratorypressures, and oxygenation is also better due to the initial high flow rates.However, with changing lung compliance, the tidal volume delivered varies, andthere is always a risk of hypoventilation or hyperventilation.

Pressure regulated volume controlled mode(PRVC) is a new mode introduced recently in anesthesia workstations. PRVCfeatures a user select tidal volume target that is autoregulated and pressurecontrolled.[2] The ventilator calculates the compliance of the lungand establishes the lowest possible pressure to deliver the target tidalvolume. It has the characteristic decelerating flow pattern, thus incorporatingthe benefits of both VCV and PCV.[3]

Recently, few studies comparing theefficacy of PRVC over other modes on selected surgical cohorts have beenpublished with varying results. Boules NS et al. has not observed anydifference in respiratory and ventilatory parameters. Oxygenation index wascomparable between both PCV and PRVC modes of ventilation when compared inpatients undergoing abdominal cancer surgery under general anaesthesia.[4]

Kothari A et al. had observed similarresult when the compared patients’ undergoing laparoscopic cholecystectomy. Intheir study it was found that PCV and PRVC modes are superior to VCV mode in providingadequate oxygenation at lower peak inspiratory pressures but no significantdifference has been observed between PCV and PRVC modes in context ofoxygenation, airway pressure and compliance.[5]Kocis KC et al. in infants undergoingsurgery for congenital heart disease has found PRVC mode superior to VCV.[6]

Due to varying results in differentprevious studies, in the present study we are going to compare conventional VCVmode with relatively newer PCV and PRVC modes of ventilation.

METHODOLOGY: 105patients undergoing laparoscopic cholecystectomy under general anaesthesia willbe randomly allocated to receive volume controlled (group V), pressurecontrolled (group P), or pressure regulated volume controlled (group PV) modesof ventilation. The randomization will be done after patients consented for thestudy. Randomization will be done by computer‑generated numbering system. A standardgeneral anesthesia technique will be followed in all cases. Standard monitorsincluding noninvasive blood pressure monitor, pulse oximeter,electrocardiogram, and capnogram will be done.

Ventilation will be carried out using Dameca Siesta i Whispaworkstation in all patients. . In VCV mode, patients will be ventilated with atidal volume of 8 mL/kg body weight In PCV mode, ventilation will be startedwith airway pressure which is needed to deliver tidal volume of 8 mL/kg bodyweight. In PRVC mode a target tidal volume of 8 mL/kg will be set with airwaypressure limit of 20 cm of H2O. Inspiratory to expiratory ratio (0.5), inspiredoxygen concentration (40%) and positive end‑expiratory pressure of 5 cm of H2Owill be same in all modes. During insufflation of the abdomen, theintra-abdominal pressure will be maintained between 12 to 15 mmHg in allpatients. Initial respiratory rate will be 12 breaths/ min in all patients, butafter pneumoperitoneum is developed, the respiratory rate will be adjusted toachieve an end‑tidal carbondioxide (EtCO2) between 33 and 37 mm of Hg.

Arterial blood gas analysis (ABG) will be done in all patients 10min after pneumoperitonium is developed and just before desufflation.

**EXPECTED OUTCOME:**Inthis study we will find out in which of these three ventilator modes volumecontrolled ventilation mode (VCV), pressure controlled ventilation mode (PCV)and pressure regulated volume controlled ventilation mode (PRVC), the airwaypressures, gas exchange, oxygenation, and lung compliance are bettermaintained.

References:

1. Maeda Y, Fujino Y,Uchiyama A, Matsuura N, Mashimo T, Nishimura M. Effects of peak inspiratoryflow on development of ventilator‑inducedlung injury in rabbits. Anesthesiology 2004;101:722‑8.

2. Keszler M. Volume‑targeted ventilation.Early Hum Dev 2006;82:811‑8.

3. Keszler M, AbubakarK. Volume guarantee: Stability of tidal volume and incidence of hypocarbia.Pediatr Pulmonol 2004; 38:240‑5.

4. Boules NS, El RamelyMA.Does pressure-controlled ventilation–volume guaranteed differ frompressure-controlled ventilation in anesthetized patients.Ain-Shams Journal of Anesthesiology2014; 07:96–100.

5. Kothari A, BaskaranD. Pressure‑controlled Volume Guaranteed Mode Improves RespiratoryDynamics during Laparoscopic Cholecystectomy: A Comparison with ConventionalModes. Anesthesia: Essays and Researches 2017;12(1): 206-11

6. Kocis KC, Dekeon MK, Rosen HK, Bandy KP, Crowley DC, Bove EL.Pressure-RegulatedVolume Control vs Volume Control Ventilation in Infants After Surgery forCongenital Heart Disease. Pediatr Cardiol 2001; 22:233–7.