Mechanical ventilation with positive end-expiratory pressure preserves arterial oxygenation during prolonged pneumoperitoneum

Abstract Background: Lung derecruitment is common during general anesthesia. Mechanical ventilation with physiological tidal volumes could magnify derecruitment, and produce lung dysfunction and inflammation. The authors used positron emission tomography to study the process of derecruitment in normal lungs ventilated for 16 h and the corresponding changes in regional lung perfusion and inflammation. Methods: Six anesthetized supine sheep were ventilated with VT = 8 ml/kg and positive end-expiratory pressure = 0. Transmission scans were performed at 2-h intervals to assess regional aeration. Emission scans were acquired at baseline and after 16 h for the following tracers: (1) 18F-fluorodeoxyglucose to evaluate lung inflammation and (2) 13NN to calculate regional perfusion and shunt fraction. Results: Gas fraction decreased from baseline to 16 h in dorsal (0.31 ± 0.13 to 0.14 ± 0.12, P < 0.01), but not in ventral regions (0.61 ± 0.03 to 0.63 ± 0.07, P = nonsignificant), with time constants of 1.5–44.6 h. Although the vertical distribution of relative perfusion did not change from baseline to 16 h, shunt increased in dorsal regions (0.34 ± 0.23 to 0.63 ± 0.35, P < 0.01). The average pulmonary net 18F-fluorodeoxyglucose uptake rate in six regions of interest along the ventral–dorsal direction increased from 3.4 ± 1.4 at baseline to 4.1 ± 1.5⋅10−3/min after 16 h (P < 0.01), and the corresponding average regions of interest 18F-fluorodeoxyglucose phosphorylation rate increased from 2.0 ± 0.2 to 2.5 ± 0.2⋅10−2/min (P < 0.01). Conclusions: When normal lungs are mechanically ventilated without positive end-expiratory pressure, loss of aeration occurs continuously for several hours and is preferentially localized to dorsal regions. Progressive lung derecruitment was associated with increased regional shunt, implying an insufficient hypoxic pulmonary vasoconstriction. The increased pulmonary net uptake and phosphorylation rates of 18F-fluorodeoxyglucose suggest an incipient inflammation in these initially normal lungs.

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Management of Intraoperative Mechanical Ventilation to Prevent Postoperative Complications after General Anesthesia: A Narrative Review

Journal of Clinical Medicine ◽

10.3390/jcm10122656 ◽

2021 ◽

Vol 10 (12) ◽

pp. 2656

Author(s):

Alberto Fogagnolo ◽

Federica Montanaro ◽

Lou’i Al-Husinat ◽

Cecilia Turrini ◽

Michela Rauseo ◽

...

Keyword(s):

Mechanical Ventilation ◽

Tidal Volume ◽

Pulmonary Complications ◽

Point Of View ◽

Whole Body ◽

Positive End Expiratory Pressure ◽

Ventilation Strategies ◽

Harmful Effects ◽

Ventilation Induced Lung Injury ◽

Different Levels

Mechanical ventilation (MV) is still necessary in many surgical procedures; nonetheless, intraoperative MV is not free from harmful effects. Protective ventilation strategies, which include the combination of low tidal volume and adequate positive end expiratory pressure (PEEP) levels, are usually adopted to minimize the ventilation-induced lung injury and to avoid post-operative pulmonary complications (PPCs). Even so, volutrauma and atelectrauma may co-exist at different levels of tidal volume and PEEP, and therefore, the physiological response to the MV settings should be monitored in each patient. A personalized perioperative approach is gaining relevance in the field of intraoperative MV; in particular, many efforts have been made to individualize PEEP, giving more emphasis on physiological and functional status to the whole body. In this review, we summarized the latest findings about the optimization of PEEP and intraoperative MV in different surgical settings. Starting from a physiological point of view, we described how to approach the individualized MV and monitor the effects of MV on lung function.

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Effects of Positive End-expiratory Pressure Titration and Recruitment Maneuver on Lung Inflammation and Hyperinflation in Experimental Acid Aspiration–induced Lung Injury

Anesthesiology ◽

10.1097/aln.0b013e31827542aa ◽

2012 ◽

Vol 117 (6) ◽

pp. 1322-1334 ◽

Cited By ~ 17

Author(s):

Aline M. Ambrosio ◽

Rubin Luo ◽

Denise T. Fantoni ◽

Claudia Gutierres ◽

Qin Lu ◽

...

Keyword(s):

Acute Lung Injury ◽

Lung Injury ◽

Lung Inflammation ◽

Recruitment Maneuver ◽

Alveolar Wall ◽

Arterial Oxygenation ◽

Positive End Expiratory Pressure ◽

Acid Aspiration ◽

Recruitment Maneuvers ◽

Alveolar Area

Background In acute lung injury positive end-expiratory pressure (PEEP) and recruitment maneuver are proposed to optimize arterial oxygenation. The aim of the study was to evaluate the impact of such a strategy on lung histological inflammation and hyperinflation in pigs with acid aspiration-induced lung injury. Methods Forty-seven pigs were randomly allocated in seven groups: (1) controls spontaneously breathing; (2) without lung injury, PEEP 5 cm H2O; (3) without lung injury, PEEP titration; (4) without lung injury, PEEP titration + recruitment maneuver; (5) with lung injury, PEEP 5 cm H2O; (6) with lung injury, PEEP titration; and (7) with lung injury, PEEP titration + recruitment maneuver. Acute lung injury was induced by intratracheal instillation of hydrochloric acid. PEEP titration was performed by incremental and decremental PEEP from 5 to 20 cm H2O for optimizing arterial oxygenation. Three recruitment maneuvers (pressure of 40 cm H2O maintained for 20 s) were applied to the assigned groups at each PEEP level. Proportion of lung inflammation, hemorrhage, edema, and alveolar wall disruption were recorded on each histological field. Mean alveolar area was measured in the aerated lung regions. Results Acid aspiration increased mean alveolar area and produced alveolar wall disruption, lung edema, alveolar hemorrhage, and lung inflammation. PEEP titration significantly improved arterial oxygenation but simultaneously increased lung inflammation in juxta-diaphragmatic lung regions. Recruitment maneuver during PEEP titration did not induce additional increase in lung inflammation and alveolar hyperinflation. Conclusion In a porcine model of acid aspiration-induced lung injury, PEEP titration aimed at optimizing arterial oxygenation, substantially increased lung inflammation. Recruitment maneuvers further improved arterial oxygenation without additional effects on inflammation and hyperinflation.

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