PURPOSE: Cigarette smoke-induced alterations of pulmonary vascular responses may be a precursor to smoking-related emphysema. There is little data on effect of acute cigarette smoke exposure on regional pulmonary blood flow. We hypothesized that smoking causes acute changes in microvascular function.
METHODS: Smokers with normal spirometry were recruited. Regional blood flow and mean transit time of blood in pulmonary vasculature were measured with dynamic 4D EKG gated multi-detector row CT scans at total lung capacity, before and 3 minutes after smoking a cigarette. Co-efficient of variation was calculated to assess heterogeneity. Changes in air and tissue densities were measured to assess inflammation and fluid extravasation. Plasma interleukin-6 before and after smoking was measured by ELISA. Data are expressed as mean [SD].
RESULTS: Heart rate increased significantly with smoking. Bioimpedence cardiac output increased after smoking in one patient in whom this was measured, with increase in heart rate but without change in stroke volume. Smoking increased whole lung blood flow (pre-smoke 173.5 [63.8] vs post-smoke 228.7 [40.6] ml/100ml/min) and decreased mean transit time (pre-smoke 5.8 [1.9] vs post-smoke 4.4 [0.9] sec). Smoke induced similar blood flow changes in both dependent (posterior) lung regions (pre-smoke 174.2 [64.1] vs post-smoke 229.0 [41.6]), and non-dependent (anterior) lung regions (pre-smoke 173.9 [64.5] vs post-smoke 229.7 [41.6]). There was a trend toward decrease in heterogeneity of blood flow in both dependent (co-efficient of variation pre-smoke 0.36 [0.04] vs post-smoke 0.34 [0.04]) and non-dependent (co-efficient of variation pre-smoke 0.38 [0.03] vs post-smoke 0.35 [0.03]) lung zones. Smoking increased plasma inteleukin-6 levels. Smoking also decreased air density slightly and increased tissue density in the two patients in whom these were measured.
CONCLUSIONS: Acute exposure to cigarette smoke causes an increase in pulmonary blood flow with decreased heterogeneity in all lung zones, suggesting recruitment of regions that previously had lower blood flow. Cigarette smoke also acutely induces inflammation.
CLINICAL IMPLICATIONS: Cigarette smoking causes acute changes in pulmonary blood flow and inflammation, with possible implications for smoking related lung disease.
DISCLOSURE: The following authors have nothing to disclose: Surya Bhatt, Olga Kravchuk, Bryon Johnson, Angela Delsing, Eric Hoffman, Kevin Doerschug
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