States of low pulmonary blood flow can be detected non-invasively at the bedside measuring alveolar dead space
2012 (English)In: Journal of clinical monitoring and computing, ISSN 1387-1307, E-ISSN 1573-2614, Vol. 26, no 3, 183-190 p.Article in journal (Refereed) Published
We tested whether the ratio of alveolar dead space to alveolar tidal volume (VDalv/VTalv) can detect states of low pulmonary blood flow (PBF) in a non-invasive way. Fifteen patients undergoing cardiovascular surgeries with cardiopulmonary bypass (CPB) were studied. CPB is a technique that excludes the lungs from the general circulation. The weaning of CPB is a model that manipulates PBF in vivo because each time blood flow through the CPB decreases, expected PBF (ePBF) increases. Patients were liberated from CPB in steps of 20 % every 2' starting from 100 % CPB (very low ePBF) to 0 % CPB (100 % ePBF). During constant ventilation, volumetric capnograms were recorded and Bohr's dead space ratio (VDBohr/VT), VDalv/VTalv and the ratio of airway dead space to tidal volume (VDaw/VT) were calculated. Before CPB, VDBohr/VT was 0.36 +/- A 0.05, VDaw/VT 0.21 +/- A 0.04 and VDalv/VTalv 0.18 +/- A 0.06 (mean +/- A SD). During weaning from CPB, VDaw/VT remained unchanged while VDBohr/VT and VDalv/VTalv decreased with increasing ePBF. At CPB of 80, 60, 40 and 20 % VDBohr/VT was 0.64 +/- A 0.06, 0.55 +/- A 0.06, 0.47 +/- A 0.05 and 0.40 +/- A 0.04, respectively; < 0.001 and VDalv/VTalv 0.53 +/- A 0.07, 0.40 +/- A 0.07, 0.29 +/- A 0.06 and 0.25 +/- A 0.04, respectively; < 0.001). After CPB, VDBohr/VT and VDalv/VTalv reached values similar to baseline (0.37 +/- A 0.04 and 0.19 +/- A 0.06, respectively). At constant ventilation the alveolar component of VDBohr/VT increased in proportion to the deficit in lung perfusion.
Place, publisher, year, edition, pages
2012. Vol. 26, no 3, 183-190 p.
Alveolus, Dead space, Pulmonary blood flow, Volumetric capnography, CO2
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-175179DOI: 10.1007/s10877-012-9358-9ISI: 000303881700007OAI: oai:DiVA.org:uu-175179DiVA: diva2:531895