Human bronchial artery blood flow after lung Tx with direct bronchial artery revascularization

Tissue hypoxaemia causes oedema, inflammation and fibrosis in porcine bronchial transsection

OBJECTIVES

Bronchial artery revascularization in lung transplantation is disputed. This study examined the physiological consequences of porcine bronchial transsection and reanastomosis with and without bronchial artery blood supply with relation to lung transplantation.

DESIGN

Translational, controlled animal study. Twelve pigs were operated through a left lateral thoracotomy. The left bronchus was transsected and reanastomosed. In the control group (n = 6), the bronchial arteries were preserved and in the study group (n = 6) they were severed. Bronchial mucosa blood flow (BMBF) was measured with laser-Doppler velocimetry and bronchial mucosa haemoglobin saturation and concentration with diffuse reflectance spectrophotometry. Measurements were made preoperatively, postoperatively and after 1 week.

RESULTS

In the study group, left postoperative BMBF was significantly lower than preoperatively (115 vs. 210 PU/s, p = 0.0001) and lower than in the control group (115 vs. 205 PU/s, p = 0.002). Repeated measurement ANOVA showed a significant treatment effect depending on time (p = 0.0034). The left mucosal haemoglobin saturation in the study group was significantly reduced postoperatively, 92% versus 61%, with a treatment effect depending on time (p = 0.0080). The reduction in left/right ratio of the mucosal haemoglobin concentration 1 week postoperatively in the study group was insignificant.

CONCLUSION

Bronchial transsection and reanastomosis without bronchial artery blood supply was followed by significant decrease in mucosal blood flow and saturation postoperatively, and also in tissue haemoglobin concentration at section, and provides a physiologic explanation of histological changes.

Airway endothelial dysfunction in asthma and chronic obstructive pulmonary disease: a challenge for future research

Endothelial dysfunction in the extrapulmonary circulation has been linked to cardiovascular disease. Recent investigations have revealed that in the airway circulation, cigarette smoking, chronic obstructive pulmonary disease (COPD), and asthma are also accompanied by endothelial dysfunction. Inhaled glucocorticosteroids can partially or fully restore normal endothelium-dependent vasodilation in these conditions, thereby identifying the airway endothelium as a novel therapeutic target in the treatment of airway disease. The role of the defective endothelium-dependent vasodilation in the pathophysiology in asthma and COPD is still subject to speculation. However, there appears to be an association between COPD and extrapulmonary vascular dysfunction, and the possibility exists that the use of inhaled glucocorticosteroids has a beneficial effect on cardiovascular disease in COPD as suggested by database studies showing that inhaled glucocorticosteroids reduce the incidence of nonfatal and fatal cardiovascular events in COPD.

Diffuse reflectance spectrophotometry with visible light: comparison of four different methods in a tissue phantom

The purpose of the study was to compare algorithms of four methods (plus two modifications) for spectrophotometric haemoglobin saturation measurements. Comparison was made in tissue phantoms basically consisting of a phosphate buffer, Intralipid and blood, allowing samples to be taken for reference measurements. Three experimental series were made. In experiment A (eight phantoms) we used the Knoefel method and measured specific extinction coefficients with a reflection spectrophotometer. In experiment B (six phantoms) the fully oxygenated phantoms were gradually deoxygenated with baker's yeast, and simultaneous measurements were made with our spectrophotometer and with a reference oxymeter (ABL-605) in 3 min intervals. For each spectrophotometric measurement haemoglobin saturation was calculated with all algorithms and modifications, and compared with reference. In experiment C (11 phantoms) we evaluated the ability of a modification of the Knoefel method to measure haemoglobin concentration in absolute quantities using extinction coefficients from experiment A.Results. Experiment A: with the Knoefel method extinction coefficients (+/-SD) for oxyhaemoglobin at 553.04 and 573.75 nm were 1.117 (+/-0.0396) ODmM(-1) and 1.680 (+/- 0.0815) ODmM(-1), respectively, and for deoxyhaemoglobin 1.205 (+/- 0.0514) ODmM(-1) and 0.953 (+/-0.0487) ODmM(-1), respectively. Experiment B: high correlation with the reference was found in all methods (r = 0.94-0.97). However, agreement varied from evidently wrong in method 3 and the original method 4 (e.g. saturation above 160%) to high agreement in method 2 as well as the modifications of methods 1 and 4, where oxygen dissociation curves were close to the reference method. Experiment C: with the modified Knoefel method the mean haemoglobin concentration difference from reference was 8.3% and the correlation was high (r = 0.91). We conclude that method 2 and the modifications of 1 and 4 were superior to the others, but depended on known values in the same or similar phantoms. The original method 1 was independent of results from the tissue phantoms, but agreement was slightly poorer. Method 3 and the original method 4 could not be recommended. The ability of the modified method 1 to measure haemoglobin concentration is promising, but needs further development.

Bronchial artery revascularization restores peribronchial tissue oxygenation after lung transplantation

With the interruption of the bronchial arteries after lung transplantation, nutritive support is dependent on collateral flow by the pulmonary arteries with desaturated venous blood. Consequently, oxygen deficiency of the peribronchial and dependent lung tissue may occur. Using a canine model for left lung transplantation, we investigated hypoxic peribronchial tissue after conventional lung transplantation and demonstrated restitution of tissue oxygenation after transplantation with bronchial artery revascularization (BAR) (BAR group: Po2 120.4 +/- 28.7 mm Hg; control group Po2 6.8 +/- 2.8; p < 0.001). BAR in lung transplantation protects peribronchial tissue of the transplanted graft from hypoxia in the early phase after reperfusion.