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Prevention of atelectasis in morbidly obese patients during general anesthesia and paralysis: a computerized tomography study
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Upper Abdominal Surgery.
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2009 (English)In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 111, no 5, 979-987 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Morbidly obese patients show impaired pulmonary function during anesthesia and paralysis, partly due to formation of atelectasis. This study analyzed the effect of general anesthesia and three different ventilatory strategies to reduce the amount of atelectasis and improve respiratory function. METHODS: Thirty patients (body mass index 45 +/- 4 kg/m) scheduled for gastric bypass surgery were prospectively randomized into three groups: (1) positive end-expiratory pressure of 10 cm H2O (PEEP), (2) a recruitment maneuver with 55 cm H2O for 10 s followed by zero end-expiratory pressure, (3) a recruitment maneuver followed by PEEP. Transverse lung computerized tomography scans and blood gas analysis were recorded: awake, 5 min after induction of anesthesia and paralysis at zero end-expiratory pressure, and 5 min and 20 min after intervention. In addition, spiral computerized tomography scans were performed at two occasions in 23 of the patients. RESULTS: After induction of anesthesia, atelectasis increased from 1 +/- 0.5% to 11 +/- 6% of total lung volume (P < 0.0001). End-expiratory lung volume decreased from 1,387 +/- 581 ml to 697 +/- 157 ml (P = 0.0014). A recruitment maneuver + PEEP reduced atelectasis to 3 +/- 4% (P = 0.0002), increased end-expiratory lung volume and increased Pao2/Fio2 from 266 +/- 70 mmHg to 412 +/- 99 mmHg (P < 0.0001). PEEP alone did not reduce the amount of atelectasis or improve oxygenation. A recruitment maneuver + zero end-expiratory pressure had a transient positive effect on respiratory function. All values are presented as mean +/- SD. CONCLUSIONS: A recruitment maneuver followed by PEEP reduced atelectasis and improved oxygenation in morbidly obese patients, whereas PEEP or a recruitment maneuver alone did not.

Place, publisher, year, edition, pages
2009. Vol. 111, no 5, 979-987 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-113069DOI: 10.1097/ALN.0b013e3181b87edbISI: 000271172500009PubMedID: 19809292OAI: oai:DiVA.org:uu-113069DiVA: diva2:289527
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Open lung concept in high risk anaesthesia: Optimizing mechanical ventilation in morbidly obese patients and during one lung ventilation with capnothorax
Open this publication in new window or tab >>Open lung concept in high risk anaesthesia: Optimizing mechanical ventilation in morbidly obese patients and during one lung ventilation with capnothorax
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Formation of atelectasis, defined as reversible collapse of aerated lung, often occurs after induction of anaesthesia with mechanical ventilation. As a consequence, there is a risk for hypoxemia, altered hemodynamics and impaired respiratory system mechanics. In certain situations, the risk for atelectasis formation is increased and its consequences may also be more difficult to manage. Anesthesia for bariatric surgery in morbidly obese patients and surgery requiring one-lung ventilation (OLV) with capnothorax are examples of such situations.

In Paper I (30 patients with BMI > 40 kg/m2 scheduled for bariatric surgery) a recruit­ment maneuver followed by positive end-expiratory pressure (PEEP) re­duced the amount of atelectasis and improved oxygenation for a prolonged period of time. PEEP or a recruitment maneuver alone did not reduce the amount of atelectasis.

In paper II we investigated whether it is possible to predict respiratory function impairment in morbidly obese patients without pulmonary disease from a preoperative lung function test. Patients with mild signs of airway obstruction (reduced end-expiratory flow) in the preoperative spirometry developed less atelectasis during anaesthesia.

In paper III we developed an experimental model of sequential OLV with capnothorax using electrical impedance tomography (EIT) that in real-time detected lung separation and dynamic changes in pulmonary ventilation and perfusion distributions. OLV to the left side caused a decrease in cardiac output, arterial oxygenation and mixed venous saturation.

In paper IV we used our model of OLV with capnothorax and applied a CO2-insufflation pressure of 16 cm H2O. We demonstrated that a PEEP level of 12-16 cm H2O is needed for optimal oxygenation and lowest possible driving pressure without compromising hemodynamic variables. Thus, the optimal PEEP was closely related to the level of the capnothorax insufflation pressure. With insufficient PEEP, ventilation/perfusion mismatch in the ventilated lung and redistribution of blood flow to the non-ventilated lung occurred.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1169
Keyword
Anaesthesia, mechanical ventilation, atelectasis, morbidly obese, one-lung ventilation, PEEP, recruitment maneuver, spirometry, EIT
National Category
Anesthesiology and Intensive Care
Research subject
Anaesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-268498 (URN)978-91-554-9440-7 (ISBN)
Public defence
2016-02-12, Grönwallssalen, Ing. 70, Akademiska sjukhuset, Uppsala, 13:00 (Swedish)
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Available from: 2016-01-22 Created: 2015-12-06 Last updated: 2016-02-12

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Reinius, HenrikJonsson, LennartGustafsson, SvenSundbom, MagnusDuvernoy, OlovFredén, Filip

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