Calculating mechanical power for pressure-controlled ventilation

For perioperative mechanical ventilation under general anesthesia, modern respirators aim at combining the benefits of pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) in modes typically named “volume-guaranteed” or “volume-targeted” pressure-controlled ventilation (PCV-VG). This systematic review and meta-analysis tested the hypothesis that PCV-VG modes of ventilation could be beneficial in terms of improved airway pressures (Ppeak, Pplateau, Pmean), dynamic compliance (Cdyn), or arterial blood gases (PaO2, PaCO2) in adults undergoing elective surgery under general anesthesia. Three major medical electronic databases were searched with predefined search strategies and publications were systematically evaluated according to the Cochrane Review Methods. Continuous variables were tested for mean differences using the inverse variance method and 95% confidence intervals (CI) were calculated. Based on the assumption that intervention effects across studies were not identical, a random effects model was chosen. Assessment for heterogeneity was performed with the χ2 test and the I2 statistic. As primary endpoints, Ppeak, Pplateau, Pmean, Cdyn, PaO2, and PaCO2 were evaluated. Of the 725 publications identified, 17 finally met eligibility criteria, with a total of 929 patients recruited. Under supine two-lung ventilation, PCV-VG resulted in significantly reduced Ppeak (15 studies) and Pplateau (9 studies) as well as higher Cdyn (9 studies), compared with VCV [random effects models; Ppeak: CI −3.26 to −1.47; p < 0.001; I2 = 82%; Pplateau: −3.12 to −0.12; p = 0.03; I2 = 90%; Cdyn: CI 3.42 to 8.65; p < 0.001; I2 = 90%]. For one-lung ventilation (8 studies), PCV-VG allowed for significantly lower Ppeak and higher PaO2 compared with VCV. In Trendelenburg position (5 studies), this effect was significant for Ppeak only. This systematic review and meta-analysis demonstrates that volume-targeting, pressure-controlled ventilation modes may provide benefits with respect to the improved airway dynamics in two- and one-lung ventilation, and improved oxygenation in one-lung ventilation in adults undergoing elective surgery.

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0435. Pressure-support ventilation compared to pressure-controlled ventilation in experimental emphysema

Intensive Care Medicine Experimental ◽

10.1186/2197-425x-2-s1-p27 ◽

2014 ◽

Vol 2 (S1) ◽

Author(s):

GA Padilha ◽

I Henriques ◽

L Moraes ◽

MV Oliveira ◽

IP Ramos ◽

...

Keyword(s):

Pressure Support Ventilation ◽

Pressure Support ◽

Support Ventilation ◽

Controlled Ventilation ◽

Pressure Controlled Ventilation ◽

Experimental Emphysema ◽

Pressure Controlled

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Lung regional stress and strain as a function of posture and ventilatory mode

Journal of Applied Physiology ◽

10.1152/japplphysiol.00439.2010 ◽

2011 ◽

Vol 110 (5) ◽

pp. 1374-1383 ◽

Cited By ~ 35

Author(s):

Gaetano Perchiazzi ◽

Christian Rylander ◽

Antonio Vena ◽

Savino Derosa ◽

Debora Polieri ◽

...

Keyword(s):

Computed Tomography ◽

Volume Control ◽

Dynamic Strain ◽

Positive Pressure ◽

Stress And Strain ◽

Prone Positioning ◽

Ventilatory Mode ◽

Controlled Ventilation ◽

Pressure Controlled Ventilation ◽

Pressure Controlled

During positive-pressure ventilation parenchymal deformation can be assessed as strain (volume increase above functional residual capacity) in response to stress (transpulmonary pressure). The aim of this study was to explore the relationship between stress and strain on the regional level using computed tomography in anesthetized healthy pigs in two postures and two patterns of breathing. Airway opening and esophageal pressures were used to calculate stress; change of gas content as assessed from computed tomography was used to calculate strain. Static stress-strain curves and dynamic strain-time curves were constructed, the latter during the inspiratory phase of volume and pressure-controlled ventilation, both in supine and prone position. The lung was divided into nondependent, intermediate, dependent, and central regions: their curves were modeled by exponential regression and examined for statistically significant differences. In all the examined regions, there were strong but different exponential relations between stress and strain. During mechanical ventilation, the end-inspiratory strain was higher in the dependent than in the nondependent regions. No differences between volume- and pressure-controlled ventilation were found. However, during volume control ventilation, prone positioning decreased the end-inspiratory strain of dependent regions and increased it in nondependent regions, resulting in reduced strain gradient. Strain is inhomogeneously distributed within the healthy lung. Prone positioning attenuates differences between dependent and nondependent regions. The regional effects of ventilatory mode and body positioning should be further explored in patients with acute lung injury.

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Effect of mechanical pressure-controlled ventilation in patients with disturbed respiratory function during laparoscopic cholecystectomy

Vojnosanitetski pregled ◽

10.2298/vsp1301009s ◽

2013 ◽

Vol 70 (1) ◽

pp. 9-15

Author(s):

Maja Surbatovic ◽

Zoran Vesic ◽

Dragan Djordjevic ◽

Sonja Radakovic ◽

Snjezana Zeba ◽

...

Keyword(s):

Laparoscopic Cholecystectomy ◽

Respiratory Function ◽

Respiratory Diseases ◽

Positive Pressure ◽

Time Interval ◽

Time Intervals ◽

Controlled Ventilation ◽

Arterial Blood ◽

Pressure Controlled Ventilation ◽

Pressure Controlled

Background/Aim: Laparoscopic cholecystectomy is considered to be the gold standard for laparoscopic surgical procedures. In ASA III patients with concomitant respiratory diseases, however, creation of pneumoperitoneum and the position of patients during surgery exert additional negative effect on intraoperative respiratory function, thus making a higher challenge for the anesthesiologist than for the surgeon. The aim of this study was to compare the effect of intermittent positive pressure ventilation (IPPV) and pressure controlled ventilation (PCV) during general anesthesia on respiratory function in ASA III patients submitted to laparoscopic cholecystectomy. Methods. The study included 60 patients randomized into two groups depending on the mode of ventilation: IPPV or PCV. Respiratory volume (VT), peak inspiratory pressure (PIP), compliance (C), end-tidal CO2 pressure (PETCO2), oxygen saturation (SpO2), partial pressures of O2, CO2 (PaO2 and PaCO2) and pH of arterial blood were recorded within four time intervals. Results. There were no statistically significant differences in VT, SpO2, PaO2, PaCO2 and pH values neither within nor between the two groups. In time interval t1 there were no statistically significant differences in PIP, C, PETCO2 values between the IPPV and the PCV group. But, in the next three time intervals there was a difference in PIP, C, and PETCO2 values between the two groups which ranged from statistically significant to highly significant; PIP was lower, C and PETCO2 were higher in the PCV group. Conclusion. Pressure controlled ventilation better maintains stability regarding intraoperative ventilatory parameters in ASA III patients with concomitant respiratory diseases during laparoscopic cholecystectomy.

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