Regional Distribution Of Pulmonary Blood Flow Research Articles

Reduced pulmonary blood flow in regions of injury 2 hours after acid aspiration in rats.

BackgroundAspiration-induced lung injury can decrease gas exchange and increase mortality. Acute lung injury following acid aspiration is characterized by elevated pulmonary blood flow (PBF) in damaged lung areas in the early inflammation stage. Knowledge of PBF patterns after acid aspiration is important for targeting intravenous treatments. We examined PBF in an experimental model at a later stage (2 hours after injury).MethodsAnesthetized Wistar-Unilever rats (n = 5) underwent unilateral endobronchial instillation of hydrochloric acid. The PBF distribution was compared between injured and uninjured sides and with that of untreated control animals (n = 6). Changes in lung density after injury were measured using computed tomography (CT). Regional PBF distribution was determined quantitatively in vivo 2 hours after acid instillation by measuring the concentration of [68Ga]-radiolabeled microspheres using positron emission tomography.ResultsCT scans revealed increased lung density in areas of acid aspiration. Lung injury was accompanied by impaired gas exchange. Acid aspiration decreased the arterial pressure of oxygen from 157 mmHg [139;165] to 74 mmHg [67;86] at 20 minutes and tended toward restoration to 109 mmHg [69;114] at 110 minutes (P < 0.001). The PBF ratio of the middle region of the injured versus uninjured lungs of the aspiration group (0.86 [0.7;0.9], median [25%;75%]) was significantly lower than the PBF ratio in the left versus right lung of the control group (1.02 [1.0;1.05]; P = 0.016).ConclusionsThe PBF pattern 2 hours after aspiration-induced lung injury showed a redistribution of PBF away from injured regions that was likely responsible for the partial recovery from hypoxemia over time. Treatments given intravenously 2 hours after acid-induced lung injury may not preferentially reach the injured lung regions, contrary to what occurs during the first hour of inflammation.Please see related article: http://dx.doi.org/10.1186/s12871-015-0014-z.

Regional hypoxic pulmonary vasoconstriction in prone pigs

Hypoxic pulmonary vasoconstriction (HPV) is known to affect regional pulmonary blood flow distribution. It is unknown whether lungs with well-matched ventilation (V)/perfusion (Q) have regional differences in the HPV response. Five prone pigs were anesthetized and mechanically ventilated (positive end-expiratory pressure = 2 cmH2O). Two hypoxic preconditions [inspired oxygen fraction (FI(O2)) = 0.13] were completed to stabilize the animal's hypoxic response. Regional pulmonary blood Q and V distribution was determined at various FI(O2) (0.21, 0.15, 0.13, 0.11, 0.09) using the fluorescent microsphere technique. Q and V in the lungs were quantified within 2-cm3 lung pieces. Pieces were grouped, or clustered, based on the changes in blood flow when subjected to increasing hypoxia. Unique patterns of Q response to hypoxia were seen within and across animals. The three main patterns (clusters) showed little initial difference in V/Q matching at room air where the mean V/Q range was 0.92-1.06. The clusters were spatially located in cranial, central, and caudal portions of the lung. With decreasing FI(O2), blood flow shifted from the cranial to caudal regions. We determined that pulmonary blood flow changes, caused by HPV, produced distinct response patterns that were seen in similar regions across our prone porcine model.

Effects of inertial load and countermeasures on the distribution of pulmonary blood flow.

We assessed the influence of cranial-to-caudal inertial force (+G(z)) and the countermeasures of anti-G suit and positive pressure breathing during G (PBG), specifically during +G(z), on regional pulmonary blood flow distribution. Unanesthetized swine were exposed randomly to 0 G(z) (resting), +3 G(z), +6 G(z), and +9 G(z), with and without anti-G suit and PBG with the use of the Air Force Research Laboratory centrifuge at Brooks Air Force Base (the gravitational force of the Earth, that is, the dorsal-to-ventral inertial force, was present for all runs). Fluorescent microspheres were injected into the pulmonary vasculature as a marker of regional pulmonary blood flow. Lungs were excised, dried, and diced into approximately 2-cm(3) pieces, and the fluorescence of each piece was measured. As +G(z) was increased from 0 to +3 G(z), blood flow shifted from cranial and hilar regions toward caudal and peripheral regions of the lung. This redistribution shifted back toward cranial and hilar regions as anti-G suit inflation pressure increased at +6 and +9 G(z). Perfusion heterogeneity increased with +G(z) stress and decreased at the higher anti-G suit pressures. The distribution of pulmonary blood flow was not affected by PBG. ANOVA indicated anatomic structure as the major determinant of pulmonary blood flow.

Effects of partial liquid ventilation on regional pulmonary blood flow distribution of isolated rabbit lungs.

Partial liquid ventilation with perfluorocarbons may increase alveolar hydrostatic transmural pressure and may result in a redistribution of pulmonary blood flow from dependent to nondependent lung regions. To test this hypothesis under controlled study conditions, we determined intrapulmonary blood flow distributions during gas and perfluorocarbon ventilation in isolated rabbit lungs. Controlled animal study with an ex vivo isolated lung preparation. Research laboratory for Experimental Anesthesiology at the Heinrich-Heine-University of Düsseldorf. New Zealand White rabbits. The lungs were perfused with autologous blood at constant flow (150 mL/min) and ventilated with 5% C(O2) in air (positive end-expiratory pressure, 2 cm H2O; tidal volume, 10 mL/kg body weight; respiratory rate, 30 breaths/ min) without and with perfluorocarbon administered intratracheally (15 mL/kg). Regional lung perfusion was measured with colored microspheres in apical, central, peripheral, and basal samples before and after bronchial instillation of perfluorocarbons. Compared with gas ventilation, intrapulmonary blood flow during perfluorocarbon ventilation was higher in apical samples (49.4+/-8.6 mL/min/g vs. 38.3+/-6.8 mL/min/g dry weight; p = .03) and lower in basal samples (22.2+/-5.1 mL/min/g vs. 39.9+/-8.2 mL/min/g; p = .04). Our findings suggest that during partial liquid ventilation, intrapulmonary blood flow is redistributed toward less-dependent lung regions. (Crit Care Med 2000; 28:1522-1525)

Alteration of pulmonary blood flow distribution in patients with congenital left to right cardiac shunt--pre- and postoperative study with macroaggregates of 99mTc-labeled human serum albumin.

The pulmonary blood flow in 84 patients with left to right cardiac shunts was preoperatively and postoperatively examined by scintigram with macroaggregates of 99mTc-labeled human serum albumin. Lung biopsy was also performed in 28 patients. The regional pulmonary blood flow distribution curves obtained from perpendicular scintillation to the long axis of the right lung in the supine position were classified into 4 patterns (normal and types 1 to 3). The normal pattern displayed uniform distribution, however type 1 demonstrated a lack of upper corner in the curve. Type 2 showed 2 peaks (a lower peak in the upper and a higher peak in the lower part of the lung) with a dip between them. Finally only 1 peak in the lower part of the lung was manifest in type 3. The right Upper/Lower lung count ratio, R(U/L), expressed as the mean +/- standard deviation in each curve type was 0.82 +/- 0.12 (n = 23), 0.71 +/- 0.11 (n = 28), 0.6 +/- 0.08 (n = 17) and 0.58 +/- 0.18 (n = 16), respectively. The count ratios from the 3 abnormal types were statistically significant compared to the normal curve type (p < 0.01). In addition, the type 1 and 2 curves were significant compared to type 3 (p < 0.05-0.01). In patients under 3 years of age, lower R (U/L) count ratio expressed more severe pulmonary hypertension. Negative correlations were observed with the peak pulmonary/peak systemic pressure ratio, Pp/Ps, (r = -0.66, p < 0.01) and with the pulmonary vascular resistance index, PVRI, (r = -0.45, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)