Efeitos da PEEP na ventilação controlada a volume sobre parâmetros hemodinâmicos em suínos submetidos ao pneumoperitônio associado ao cefalodeclive / Effects of PEEP on hemodynamic variables in pigs submitted to volume-controlled ventilation under pneumoperitoneum associated to cephalodeclive

Videolaparoscopic procedures have gained prominence due to their low invasiveness, causing less surgical trauma and better post-surgical recovery. However, the increase in intra-abdominal pressure due to the institution of pneumoperitoneum can alter the patient's homeostasis. Therefore, volume-controlled ventilation, associated with positive end-expiratory pressure (PEEP), improves arterial oxygenation and prevents pulmonary collapse, but it can lead to important hemodynamic changes. The aim of this study was to evaluate, comparatively, the effects of positive end expiratorypressure (PEEP) on hemodynamic variables of pigs submitted to volume-controlled ventilation, during pneumoperitoneum and maintained in head-down tilt and determine which PEEP value promotes greater stability on hemodynamic variables. Twenty-four pigs were used, between 55 and 65-day-old, weighing between 15 and 25 kg, randomly divided into 3 distinct groups differentiated by positive end-expiratory pressure: PEEP 0 (volume-controlled ventilation and PEEP of 0 cmH2O), PEEP 5 (volume-controlled ventilation and PEEP of 5 cmH2O) and PEEP 10 (volume-controlled ventilation and PEEP of 10 cmH2O). Volume-controlled ventilation was adjusted to 8 mL/kg of tidal volume and a respiratory rate of 25 movements per min. Anesthesia was maintained with continuous infusion of propofol (0.2 mg/kg/min) and midazolam (1 mg/kg/h). Pneumoperitoneum was performed with carbon dioxide (CO2), keeping the intraabdominal pressure at 15 mmHg and the animals were positioned on a 30° head-down tilt. The evaluations of hemodynamic variables started 30 min after induction of anesthesia (M0), followed by measurements at 15-min intervals (from M15 to M90), completing a total of 7 evaluations. The variables of interest were collected over 90 min and submitted to analysis of variance followed by Tukey's post-hoc test, with P < 0.05. The PEEP 10 group had higher values of CVP and mCPP, while the PEEP 5 group, mPAP and PVR were higher. The PEEP 0 group, on the other hand, had higher means of CI. Regarding the moments, there were differences in HR, SAP, DAP, MAP, CO, IC and TPR. According to the literature, important hemodynamic effects due to pneumoperitoneum are reported, which can be caused by the pressure used in abdominal insufflation, CO2 accumulation, duration of the surgical procedure, hydration status and patient positioning. Mechanical ventilation associated with PEEP can also cause an increase in intrathoracic pressure and, therefore, reduce cardiac output. Cardiovascular changes are proportional to the PEEP used. Central venous pressure (PVC) measure the patient's preload, and intrathoracic pressure can interfere with this parameter. The peak pressure values in the PEEP 10 group were higher than the other groups, demonstrating that the increase in intrathoracic pressure results in higher PVC values. Regarding PAPm and PCPm, these variables can be influenced according to the PEEP values and the patient's position. In relation to CI, the increase in PEEP may reflect on intrathoracic pressure, resulting in greater compression of the heart, with a consequent reduction in cardiac output and cardiac index. Therefore, it is concluded that the PEEP effects of 0 cmH2O and 5 cmH2O on hemodynamics are discrete, under the proposed conditions.(AU)

Comparative Study of Volume Controlled Ventilation Mode (VCV) and Pressure Controlled Ventilation Mode (PCV) Intra Operatively in Patient Undergoing Coronary Artery Bypass Graft Surgery

Introduction: Despite numerous advances in anaesthesia,surgical techniques, and postoperative care for coronaryartery bypass graft (CABG) surgery, postoperative pulmonarycomplications still account for postoperative morbidity.Primary aim of the study was to compare two modes ofventilation on gas exchange in form of PaO2/FiO2 ratio inintraoperative period at time of expected significant respiratoryalterations during CABG surgery. We compared VCV andPCV mode intra operatively as both ventilation modes arestandard of care. It was also intended to compare effectsof these modes on lungs to diagnose significant respiratorychanges with Chest X ray findings, and postoperative lengthof ICU stay.Material and methods: 60 patients posted for electivecoronary artery bypass graft surgery (CABG) were dividedinto two groups. Group 1 (VCV group) and group 2(PCV)group divided by sequentially numbered opaque sealedenvelope method. Baseline PaO2/FiO2 was observed beforeinduction, half hour after induction, post cardiopulmonarybypass (CPB) and at the end of surgery noted. Postoperativechest x ray findings, length of postoperative ICU stay alsocompared within two groups.Results: In terms of demographic data both modes werecomparable. After comparing both the modes it was observedthat PaO2/FiO2 ratio was better in PCV group half hour afterinduction and after CPB the end of surgery while no significantdifference between two modes on postoperative ray changesand length of ICU stay.Conclusion: Both the modes of ventilation can be used forCABG surgery with CPB which are standard of care wherePCV mode offers better oxygenation in terms of PaO2/FiO2at the end of the surgery after CPB.

A Comparison of Adaptive Support Ventilation (ASV) and Conventional Volume-Controlled Ventilation on Respiratory Mechanics in Acute Lung Injury/ARDS / 대한구급학회지

BACKGROUND: ASV is a closed-loop ventilation system that guarantees a user-set minimum per-minute volume in intubated patients, whether paralyzed or with spontaneous breathing. Here, we tested the effects of ASV onrespiratory mechanics and compared them with volume-controlled ventilation (VCV). METHODS: Thirteen patients meeting the criteria for acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) were enrolled. All patients were paralyzed to eliminate spontaneous breathing. We started with VCV (VCV1), then used ASV followed by VCV modes (VCV2), maintaining minute volume as much as that of VCV1. RESULTS: During ASV, compared with VCV1, the inspiratory and expiratory tidal volumes and expiratory resistance increased. Conversely, the total respiratory rate and maximum pressure decreased. No changes in the arterial blood gases, heart rate, or mean systemic pressure were noted during the trial. CONCLUSIONS: In ALI/ARDS patients, although no differences were observed in the arterial blood gas analysis between the two modes, ASV provided better respiratory mechanics in terms of peak airway pressure and tidal volume than VCV.