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Non-toxic alveolar oxygen concentration without hypoxemia during apnoeic oxygenation: an experimental 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 Medical Sciences.
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2011 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 55, no 9, 1078-1084 p.Article in journal (Refereed) Published
Abstract [en]

Background: Oxygenation without tidal breathing, i.e. apnoeic oxygenation in combination with extracorporeal carbon dioxide removal, might be an option in the treatment of acute respiratory failure. However, ventilation with 100% O(2), which is potentially toxic, is considered a prerequisite to ensure acceptable oxygenation. We hypothesized that trapping nitrogen (N(2)) in the lungs before the start of apnoeic oxygenation would keep the alveolar O(2) at a non-toxic level and still maintain normoxaemia. The aim was to test whether a predicted N(2) concentration would agree with a measured concentration at the end of an apnoeic period. Methods: Seven anaesthetized, muscle relaxed, endotracheally intubated pigs (22-27 kg) were ventilated in a randomized order with an inspired fraction of O(2) 0.6 and 0.8 at two positive end-expiratory pressure levels (5 cm and 10 cm H(2)O) before being connected to continuous positive airway pressure using 100% O(2) for apnoeic oxygenation. N(2) was measured before the start of and at the end of the 10-min apnoeic period. The predicted N(2) concentration was calculated from the initial N(2) concentration, the end-expiratory lung volume, and the anatomical dead space. Results: The mean difference and standard deviation between measured and predicted N(2) concentration was -0.5 +/- 2%, P = 0.587. No significant difference in the agreement between measured and predicted N(2) concentrations was seen in the four settings. Conclusions: This study indicates that it is possible to predict and keep alveolar N(2) concentration at a desired level and, thus, alveolar O(2) concentration at a non-toxic level during apnoeic oxygenation.

Place, publisher, year, edition, pages
2011. Vol. 55, no 9, 1078-1084 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-160124DOI: 10.1111/j.1399-6576.2011.02499.xISI: 000295102500006OAI: oai:DiVA.org:uu-160124DiVA: diva2:448635
Available from: 2011-10-17 Created: 2011-10-17 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Minimal volume ventilation in lung injury: With special reference to apnea and buffer treatment
Open this publication in new window or tab >>Minimal volume ventilation in lung injury: With special reference to apnea and buffer treatment
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A fairly large portion of patients receiving surgical or intensive care will need mechanical ventilation at some point. The potential ventilator-induced lung injury (VILI) is thus of interest. One of the main causal factors in VILI is the cyclic energy shifts, i.e. tidal volumes, in the lung during mechanical ventilation. The problem can be approached in two ways. Firstly, one can utilize apneic oxygenation and thus not cause any tidal injuries at all. Secondly, and more traditionally, one can simply lower the tidal volumes and respiratory rates used. The following describes a series of animal experiments exploring these options.

In the first two papers, I explored and improved upon the methodology of apneic oxygenation. There is a generally held belief that it is only possible to perform apneic oxygenation by prior denitrogenation and by using 100% oxygen during the apnea. As 100% oxygen is toxic, this has prevented apneic oxygenation from more widespread use. The first paper proves that it is indeed possible to perform apneic oxygenation with less than 100% oxygen. I also calculated the alveolar nitrogen concentration which would conversely give the alveolar oxygen concentration. The second paper addresses the second large limitation of apneic oxygenation, i.e. hypercapnia. Using a high dose infusion of tris(hydroxymethyl)aminomethane (THAM) buffer, a pH > 7.2 could be maintained during apneic oxygenation for more than 4.5 hours.

In the last two papers, THAM’s properties as a proton acceptor are explored during respiratory acidosis caused by very low volume ventilation. In paper III, I found that THAM does not, in the long term, affect pH in respiratory acidosis after stopping the THAM infusion. It does, however, lower PVR, even though the PaCO2 of THAM-treated animals had rebounded to levels higher than that of the controls. In the last experiment, I used volumetric capnography to confirm our hypothesis that carbon dioxide elimination through the lungs was lower during the THAM infusion. Again, the PaCO2 rebounded after the THAM infusion had stopped and I concluded that renal elimination of protonated THAM was not sufficient.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1267
Keyword
VILI, THAM, buffers, apneic oxygenation, respiratory acidosis, hypercapnia, low volume ventilation, mechanical ventilation, ultra-protective ventilation
National Category
Anesthesiology and Intensive Care
Research subject
Anaesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-305369 (URN)978-91-554-9727-9 (ISBN)
Public defence
2016-12-02, Grönwallsalen, Ing 70, Akademiska Sjukhuset, Uppsala, 09:00 (Swedish)
Opponent
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Available from: 2016-11-10 Created: 2016-10-16 Last updated: 2016-11-16

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Höstman, StaffanEngström, JoakimLarsson, Anders

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