Details

Autor(en) / Beteiligte

• Tsang, John Y. C
• Lamm, Wayne J. E
• Starr, Ian R
• Hlastala, Michael P

Titel

Spatial pattern of ventilation-perfusion mismatch following acute pulmonary thromboembolism in pigs

Ist Teil von

• Journal of applied physiology (1985), 2005-05, Vol.98 (5), p.1862-1868

Ort / Verlag

Bethesda, MD: Am Physiological Soc

Erscheinungsjahr

2005

Quelle

MEDLINE

Beschreibungen/Notizen

• 1 James Hogg iCAPTURE Research Laboratory, Vancouver, British Columbia, Canada; and Departments of 2 Physiology and Biophysics and 3 Medicine, University of Washington, Seattle, Washington Submitted 15 September 2004 ; accepted in final form 29 November 2004 We studied the spatial distribution of the abnormal ventilation-perfusion ( A / ) units in a porcine model of acute pulmonary thromboembolism (APTE), using the fluorescent microsphere (FMS) technique. Four piglets ( 22 kg) were anesthetized and ventilated with room air in the prone position. Each received 20 g of preformed blood clots at time t = 0 min via a large-bore central venous catheter, until the mean pulmonary arterial pressure reached 2.5 times baseline. The distributions of regional A and blood flow ( ) at five time points ( t = –30, –5, 30, 60, 120 min) were mapped by FMS of 10 distinct colors, i.e., aerosolization of 1-µm FMS for labeling A and intravenous injection of 15-µm FMS for labeling . Our results showed that, at t = 30 min following APTE, mean A / ( A / = 2.48 ± 1.12) and A / heterogeneity (log SD A / = 1.76 ± 0.23) were significantly increased. There were also significant increases in physiological dead space (11.2 ± 12.7% at 60 min), but the shunt fraction ( A / = 0) remained minimal. Cluster analyses showed that the low A / units were mainly seen in the least embolized regions, whereas the high A / units and dead space were found in the peripheral subpleural regions distal to the clots. At 60 and 120 min, there were modest recoveries in the hemodynamics and gas exchange toward baseline. Redistribution pattern was mostly seen in regional , whereas A remained relatively unchanged. We concluded that the hypoxemia seen after APTE could be explained by the mechanical diversion of to the less embolized regions because of the vascular obstruction by clots elsewhere. These low A / units created by high flow, rather than low A , accounted for most of the resultant hypoxemia. acute pulmonary embolism; cluster analyses; fluorescent microspheres; gas exchange; hypoxemia; regional blood flow; regional ventilation Address for reprint requests and other correspondence: J. Y. C. Tsang, James Hogg iCAPTURE Research Laboratory, 1081 Burrard St., Vancouver, BC, Canada V6Z 1Y6 (E-mail: jtsang{at}interchange.ubc.ca )