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Ventilation-perfusion distributions and gas exchange during carbon dioxide-pneumoperitoneum in a porcine model
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
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 Oncology, Radiology and Clinical Immunology, Avdelningen för sjukhusfysik.
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2010 (English)In: British Journal of Anaesthesia, ISSN 0007-0912, E-ISSN 1471-6771, Vol. 105, no 5, 691-697 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: /st> Carbon dioxide (CO(2))-pneumoperitoneum (PP) of 12 mm Hg increases arterial oxygenation, but it also promotes collapse of dependent lung regions. This seeming paradox prompted the present animal study on the effects of PP on ventilation-perfusion distribution (V/Q) and gas exchange. METHODS: /st> Fourteen anaesthetized pigs were studied. In seven pigs, single photon emission computed tomography (SPECT) was used for spatial analysis of ventilation and perfusion distributions, and in another seven pigs, multiple inert gas elimination technique (MIGET) was used for detailed analysis of V/Q matching. SPECT/MIGET and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia before and 60 min after induction of PP. RESULTS: /st> SPECT during PP showed no or only poorly ventilated regions in the dependent lung compared with the ventilation distribution during anaesthesia before PP. PP was accompanied by redistribution of blood flow away from the non- or poorly ventilated regions. V/Q analysis by MIGET showed decreased shunt from 9 (sd 2) to 7 (2)% after induction of PP (P<0.05). No regions of low V/Q were seen either before or during PP. Almost no regions of high V/Q developed during PP (1% of total ventilation). Pa(o(2)) increased from 33 (1.2) to 35.7 (3.2) kPa (P<0.01) and arterial to end-tidal Pco(2) gradient (Pae'(co(2))) increased from 0.3 (0.1) to 0.6 (0.2) kPa (P<0.05). CONCLUSIONS: /st> Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction.

Place, publisher, year, edition, pages
2010. Vol. 105, no 5, 691-697 p.
Keyword [en]
blood flow, gas exchange, laparoscopy, lung, measurement techniques, model, pig, respiratory, surgery
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-132501DOI: 10.1093/bja/aeq211ISI: 000283119200020PubMedID: 20693177OAI: oai:DiVA.org:uu-132501DiVA: diva2:358171
Available from: 2010-10-21 Created: 2010-10-21 Last updated: 2017-12-12Bibliographically approved
In thesis
1. The Effect of CO2-Pneumoperitoneum on Ventilation Perfusion Distribution of the Lung
Open this publication in new window or tab >>The Effect of CO2-Pneumoperitoneum on Ventilation Perfusion Distribution of the Lung
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laparoscopic operations are a common and popular way for abdominal procedures. They are usually performed by insufflation of carbon dioxide (CO2) into the abdominal cavity. However, insufflation of CO2 may interfere with cardiac and circulatory as well as respiratory functions. The CO2-pneumoperitoneum (PP) may cause hypercarbia and acidosis. The direct effects of CO2 and acidosis lead to decreased cardiac contractility, sensitization of the myocardium to arrhythmogenic effects of catecholamines and systemic vasodilatation. There may even be long-lasting post-operative effects on breathing control.

The pneumoperitoneum may also cause several respiratory changes, e.g. decreased functional residual capacity (FRC) and vital capacity (VC), formation of atelectasis, reduced respiratory compliance and increased airway pressure. Still, arterial oxygenation is mostly maintained or even improved during PP.

In view of the apparently contradictory results in respiratory mechanics and gas exchange, the present studies were performed to evaluate respiratory changes on gas exchange and ventilation-perfusion distributions during PP in a porcine model. It was demonstrated that atelectasis during anaesthesia and PP may be estimated by an increased arterial to endtidal PCO2-gradient (study I). Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better ventilation-perfusion match (study II). Increasing abdominal pressure shifted blood flow more and more away from collapsed lung tissue, decreased pulmonary shunt and improved oxygenation from 8 to 16 mmHg PP, despite an increase of atelectasis formation (study III). CO2-PP enhanced the shift of blood flow towards better ventilated parts of the lung compared to Air-PP. Moreover, sodium natriumprusside worsened the ventilation-perfusion match even more and blunted the effects previously seen with carbon dioxide. CO2 should therefore be the mediator of enhancing HPV during PP.

In conclusion, pneumoperitoneum with CO2 causes atelectasis with elimination of ventilation in the dependent lung regions. However, an efficient shift of blood flow away from collapsed, non-ventilated regions results in a better ventilation-perfusion matching and better oxygenation of blood than without PP. A prerequisite for the beneficial effect is the use of carbon dioxide for the abdominal inflation, since it enhances HPV.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 58 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 662
Keyword
lung, atelectasis; computed tomography; multiple inert gas elimination technique; model, pig; Pa–ECO2 ratio; surgery, laparoscopy; lung, blood flow; single photon emission computed tomography; ventilation/perfusion distribution; gas exchange; hypoxic pulmonary vasoconstriction
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-149746 (URN)978-91-554-8045-5 (ISBN)
Public defence
2011-05-11, Enghoff Salen, Akademiska Hospital, Entrance 30, Uppsala, 13:15 (English)
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Supervisors
Available from: 2011-04-20 Created: 2011-03-22 Last updated: 2011-05-05Bibliographically approved

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