Temperature alters bronchial blood flow response to pulmonary arterial obstruction

Abstract

Lobar bronchial blood flow has been reported to increase and decrease acutely after pulmonary arterial obstruction (PAO). Because bronchial blood flow (Qbr) to the trachea and bronchi is influenced by inspired air temperature, we investigated whether temperature differences could explain these disparate results. In 10 open-chested dogs the left lower lobe (LLL) was isolated and perfused in situ with autologous blood at a controlled temperature with an independent vascular circuit. The abdomen and the chest of the dog were enclosed in a Plexiglas box in which air was fully humidified and temperature could be regulated. Qbr, determined by the reference flow technique using 16 micron microspheres, was measured before and 30 min after onset of PAO with the air in the box being either at 27 or 39 degrees C and with warmed LLL blood (37 degrees C) in the latter condition. Anastomotic bronchial blood flow [Qbr(s-p), determined as overflow from the closed LLL vascular circuit and measured in ml X min-1 X 100 g dry lung wt-1 X 100 Torr mean systemic pressure-1] was measured continuously at both temperatures. Both before and after PAO, Qbr and Qbr(s-p) were closely correlated: Qbr (ml/min) = 1.12 + 0.978Qbr(s-p); R = 0.912. This was true regardless of the presence or the absence of pulmonary flow, showing that the distribution of bronchial blood flow between the anastomotic and the nonanastomotic portion does not change acutely during PAO. When the air in the box was 27 degrees C, Qbr(s-p) was 19.5 +/- 5.2 (SE) and increased to 38.6 +/- 8.1 with PAO (P less than 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Vagal Cooling and Positive End-Expiratory Pressure Reduce Systemic to Pulmonary Bronchial Blood Flow in Dogs

“…However, these investigations utilized a preparation in which measurement of bronchial blood flow necessitated either unilateral pulmonary artery occlusion [8] or the absence of pul monary blood flow [7,15], both of which could by themselves affect bronchial blood How [4,14]. In the current study we confirmed that Qbr(s-p) is reduced by PEEP and that this effect was observed when pul monary blood flow was intact.…”

“…Qbr(s-p) to the LLL was measured according to a technique pre viously described [4,6]. The only flow of blood into the closed vas cular circuit of the LLL is from the bronchial vessels which anasto mose with the pulmonary circulation.…”

“…In another group of 7 dogs Qbr(s-p) was 46.5 ± 6.9 with PEEP = 5 cm H:0; it decreased to 28.3 ±6.8 with bilateral cervical vagal cooling (0-l.5°C) and did not de crease further after increasing PEEP to 15 cm H20. We conclude that the effect of resting vagal tone is to in crease Qbr(s-p) and that the effect of PEEP on Qbr(s-p) may be mediated at least partially by vagal influences.It has been suggested that bronchial blood How is important for the metabolic needs of the lung paren chyma particularly in lung injury [1] and pulmonary vascular occlusion [2] when pulmonary blood flow is compromised, (t has also been shown that systemic to pulmonary bronchial blood flow [Qbr(s-p)], which is the total bronchial blood flow to the intraparenchymal regions of the lung [3][4][5], increases in lung injury [I, 6], Ventilation with positive end-expiratory pres sure (PEEP) is often used in patients with respiratory failure. However, the application of PEEP has been shown to reduce bronchial blood How to the lung [7][8][9][10][11].…”

“…PEEP may reduce bronchial blood flow to the lung by different mechanisms: (a) by increasing bronchial vascular resistance due to direct mechanical compres sion of bronchial microvessels similar to the effect of PEEP on alveolar vessels [7,11]; (b) by increasing the downstream pressure for Qbr(s-p) due to an increase in pulmonary vascular pressures since all the intraparenchymal bronchial blood flow is drained into the pulmonary circulation [3][4][5]7], and (c) by increasing bronchial vascular resistance due to vasoconstriction secondary to stimulation of the slowly adapting pul monary stretch receptors and a vagally mediated re-…”

Systemic to Pulmonary Bronchial Blood Flow in Heart Failure

“…8 The partitioning between right and left drainage of bronchial blood flow is not influenced by the presence or absence (as it happens during total cardiopulmonary bypass) of pulmonary circulation . 21 Our technique for measuring Qbr(s-p) was derived from a technique utilized in studies of dogs. 12 • 21 In animal studies, the possible accumulation or loss of blood into the lungs is evaluated when calculating Qbr(s-p) by adding to the measured blood flow the lung weight changes.…”