Bronchial Flow Research Articles

Evaluation of the dual vascular supply patterns in ground-glass nodules with a dynamic volume computed tomography.

BACKGROUNDIn recent years, the detection rate of ground-glass nodules (GGNs) has been improved dramatically due to the popularization of low-dose computed tomography (CT) screening with high-resolution CT technique. This presents challenges for the characterization and management of the GGNs, which depends on a thorough investigation and sufficient diagnostic knowledge of the GGNs. In most diagnostic studies of the GGNs, morphological manifestations are used to differentiate benignancy and malignancy. In contrast, few studies are dedicated to the assessment of the hemodynamics, i.e., perfusion parameters of the GGNs. AIMTo assess the dual vascular supply patterns of GGNs on different histopathology and opacities.METHODSForty-seven GGNs from 47 patients were prospectively included and underwent the dynamic volume CT. Histopathologic diagnoses were obtained within two weeks after the CT examination. Blood flow from the bronchial artery [bronchial flow (BF)] and pulmonary artery [pulmonary flow (PF)] as well as the perfusion index (PI) = [PF/(PF + BF)] were obtained using first-pass dual-input CT perfusion analysis and compared respectively between different histopathology and lesion types (pure or mixed GGNs) and correlated with the attenuation values of the lesions using one-way ANOVA, student’s t test and Pearson correlation analysis.RESULTSOf the 47 GGNs (mean diameter, 8.17 mm; range, 5.3-12.7 mm), 30 (64%) were carcinoma, 6 (13%) were atypical adenomatous hyperplasia and 11 (23%) were organizing pneumonia. All perfusion parameters (BF, PF and PI) demonstrated no significant difference among the three conditions (all P > 0.05). The PFs were higher than the BFs in all the three conditions (all P < 0.001). Of the 30 GGN carcinomas, 14 showed mixed GGNs and 16 pure GGNs with a higher PI in the latter (P < 0.01). Of the 17 benign GGNs, 4 showed mixed GGNs and 13 pure GGNs with no significant difference of the PI between the GGN types (P = 0.21). A negative correlation (r = -0.76, P < 0.001) was demonstrated between the CT attenuation values and the PIs in the 30 GGN carcinomas. CONCLUSIONThe GGNs are perfused dominantly by the PF regardless of its histopathology while the weight of the BF in the GGN carcinomas increases gradually during the progress of its opacification.

A case of Mounier-Kuhn syndrome in a geriatric patient

Mounier-Kuhn syndrome, or tracheobronchomegaly, is a rare clinical and radiologic condition characterized by marked tracheobronchial dilation and recurrent lower respiratory tract infections. The syndrome was first described by Mounier-Kuhn in 1932, and few cases have been reported in the medical literature [1]. The clinical presentation varies widely, from asymptomatic disease with preserved lung functions to recurrent chest infections, exertional dyspnoea to even respiratory failure in severe cases. Diagnosis is often made by using CT, through which abnormally large air passages are detected. In adults, the diagnostic criteria are diameters of the trachea &gt;30 mm, right main bronchus &gt;20 mm and of the left main bronchus &gt;18 mm [2-4]. Upon pulmonary function testing, decreased bronchial flow speed, increased tidal volume, and dead spaces may be observed. Bronchoscopy can detect the pathologic processes that affect the tracheobronchial structures. Connective-tissue diseases, ataxia-telangiectasia, ankylosing spondylitis, EhlersDanlos syndrome, Marfan syndrome, Kenny-Caffey syndrome, Brachmann-de Lange syndrome, and cutis laxa (elastolysis) are also associated with secondary tracheobronchial enlargement [2-5]. All these conditions should be considered in the differential diagnosis.

CT perfusion imaging can detect residual lung tumor early after radiofrequency ablation: a preliminary animal study on both tumoral and peri-tumoral region assessment.

BackgroundRadiofrequency ablation (RFA) is a minimally invasive procedure to treat lung cancer. Timely evaluation on residual lung tumor after RFA is crucial to the prognosis, hence, our objective is to assess CT perfusion (CTP) on detection of residual lung tumor early after RFA.MethodsCTP imaging was performed in 24 lung VX2 tumor models 1 day before and within 1 hour after RFA. CTP maps with dual-input (n=24) and single-input [n=13, with predominant ground glass opacity (GGO) after RFA] models were generated using the maximal slope method. Regions of interest were independently placed on the maximal cross-sectional tumor before and after RFA and on GGO after RFA by two thoracic radiologists. The bronchial flow (BF), pulmonary flow (PF) and perfusion index (PI) were compared between pre-RFA and post-RFA images. The parameters (BF, PF and PI of tumor; PF of GGO) of the complete and incomplete RFA groups were compared based on nicotinamide adenine dinucleotide hydrogen (NADH) and TdT-mediated dUTP nick-end labeling (TUNEL) staining and were correlated with the microvascular density (MVD).ResultsThe BF and PF decreased after RFA (all P values <0.03). The decrease in BF and PF (ΔBF and ΔPF) in the complete RFA group was higher (P=0.01; 0.02). The areas under the curve (AUC) of ΔBF and ΔPF at 14.85 and 17.25 mL/min/100 mL in determination of tumor with complete ablation were 0.80 and 0.78, respectively. ΔBF was positively correlated with MVD (P=0.046, r=0.468). PF of GGO with incomplete RFA was higher (P=0.001). The AUC of PF ≤29.4 mL/min/100 mL in determination of tumor with complete ablation was 0.99.ConclusionsCTP could detect residual lung tumor early after RFA in a rabbit model, which might provide a clinical solution to early treatment assessment after RFA.

Pulmonary Thrombo-Endarterectomy for Chronic Thromboembolic Pulmonary Artery Hypertension: 17 Years Single Center Experience. Impact of Multidisciplinary Team Approach

Purpose Chronic thromboembolic pulmonary hypertension (CTEPH) is the only type of pulmonary hypertension (PH) with a surgical resolution which is the Pulmonary Thrombo-Endarterectomy (PTE) operation. Fibrotic thrombus extraction allows pulmonary vascular resistances (PVR) reduction until normalisation in most of cases. However, this sentence might be controversial since results are conditioned by the center experience on patients's selection, operation's timing, skills and management of such complex pathology. Seventeen years performing PTE and our multidisciplinary approach allowed us to obtain very good results. In here we report our data progress and results of PTE for CTEPH. Methods A total of 177 patients underwent PTE from 2003 until 2020. From 2003 to 2012 (Group 1) 96 patients were operated avoiding Deep Hypothermic Circulatory Arrest (DHCA) being applied only when blood bronchial flow ruled out a complete endarterectomy. Group 2, included 81 patients operated rom 2012 until the present, when DHCA was routinely adopted. Furthermore, the event of the Balloon Pulmonary Angioplasty (BPA) in 2015, conceded us a therapeutic alternative in high risk or unsuitable PTE patients. The impact of these and other variables in patients population profile and results of both groups have been retrospectively compare and analysed. Results Most relevant preoperative differences were related to worst clinical status and associated pathologies in Group 1 and wider use of specific pulmonary vasodilator in Group 2. Cross clamp time as well as time of cardiopulmonary bypass were significantly shorter in Group 2 in spite of a mean DHCA time of 33 minutes. In-hospital mortality and need of postoperative ECMO was respectively 15.6% vs 3.7% and 15.6% vs 8.6% in group 1 and 2 (p 0.001). Pulmonary hemodynamic as well as long term outcome equally and significantly improved in both groups. Conclusion Our reported results demonstrate that, DHCA is the best approach to perform PTE for CTEPH. Certainly experience, protocols and a multidisciplinary approach contribute to obtain the best hemodynamics, surgical and clinical outcomes.

Flow Field Analysis of Tracheal Bronchial Airway Passage Flow Field for Effective Drug Delivery

Flow Field Analysis of Tracheal Bronchial Airway Passage Flow Field for Effective Drug Delivery

Intra-observer and inter-observer agreements for the measurement of dual-input whole tumor computed tomography perfusion in patients with lung cancer: Influences of the size and inner-air density of tumors.

BackgroundThis study was conducted to assess intra‐observer and inter‐observer agreements for the measurement of dual‐input whole tumor computed tomography perfusion (DCTP) in patients with lung cancer.MethodsA total of 88 patients who had undergone DCTP, which had proved a diagnosis of primary lung cancer, were divided into two groups: (i) nodules (diameter ≤3 cm) and masses (diameter >3 cm) by size, and (ii) tumors with and without air density. Pulmonary flow, bronchial flow, and pulmonary index were measured in each group. Intra‐observer and inter‐observer agreements for measurement were assessed using intraclass correlation coefficient, within‐subject coefficient of variation, and Bland–Altman analysis.ResultsIn all lung cancers, the reproducibility coefficient for intra‐observer agreement (range 26.1–38.3%) was superior to inter‐observer agreement (range 38.1–81.2%). Further analysis revealed lower agreements for nodules compared to masses. Additionally, inner‐air density reduced both agreements for lung cancer.ConclusionThe intra‐observer agreement for measuring lung cancer DCTP was satisfied, while the inter‐observer agreement was limited. The effects of tumoral size and inner‐air density to agreements, especially between two observers, should be emphasized. In future, an automatic computer‐aided segment of perfusion value of the tumor should be developed.

Modeling the Nonlinear Motion of the Rat Central Airways.

Advances in volumetric medical imaging techniques allowed the subject-specific modeling of the bronchial flow through the first few generations of the central airways using computational fluid dynamics (CFD). However, a reliable CFD prediction of the bronchial flow requires modeling of the inhomogeneous deformation of the central airways during breathing. This paper addresses this issue by introducing two models of the central airways motion. The first model utilizes a node-to-node mapping between the discretized geometries of the central airways generated from a number of successive computed tomography (CT) images acquired dynamically (without breath hold) over the breathing cycle of two Sprague-Dawley rats. The second model uses a node-to-node mapping between only two discretized airway geometries generated from the CT images acquired at end-exhale and at end-inhale along with the ventilator measurement of the lung volume change. The advantage of this second model is that it uses just one pair of CT images, which more readily complies with the radiation dosage restrictions for humans. Three-dimensional computer aided design geometries of the central airways generated from the dynamic-CT images were used as benchmarks to validate the output from the two models at sampled time-points over the breathing cycle. The central airway geometries deformed by the first model showed good agreement to the benchmark geometries within a tolerance of 4%. The central airway geometry deformed by the second model better approximated the benchmark geometries than previous approaches that used a linear or harmonic motion model.

Differentiation of malignant and benign pulmonary nodules with first-pass dual-input perfusion CT

To assess diagnostic performance of dual-input CT perfusion for distinguishing malignant from benign solitary pulmonary nodules (SPNs). Fifty-six consecutive subjects with SPNs underwent contrast-enhanced 320-row multidetector dynamic volume CT. The dual-input maximum slope CT perfusion analysis was employed to calculate the pulmonary flow (PF), bronchial flow (BF), and perfusion index [Formula: see text]. Differences in perfusion parameters between malignant and benign tumours were assessed with histopathological diagnosis as the gold standard. Diagnostic value of the perfusion parameters was calculated using the receiver-operating characteristic (ROC) curve analysis. Amongst 56 SPNs, statistically significant differences in all three perfusion parameters were revealed between malignant and benign tumours. The PI demonstrated the biggest difference between malignancy and benignancy: 0.30 ± 0.07 vs. 0.51 ± 0.13 , P < 0.001. The area under the PI ROC curve was 0.92, the largest of the three perfusion parameters, producing a sensitivity of 0.95, specificity of 0.83, positive likelihood ratio (+LR) of 5.59, and negative likelihood ratio (-LR) of 0.06 in identifying malignancy. The PI derived from the dual-input maximum slope CT perfusion analysis is a valuable biomarker for identifying malignancy in SPNs. PI may be potentially useful for lung cancer treatment planning and forecasting the therapeutic effect of radiotherapy treatment. • Modern CT equipment offers assessment of vascular parameters of solitary pulmonary nodules (SPNs) • Dual vascular supply was investigated to differentiate malignant from benign SPNs. • Different dual vascular supply patterns were found in malignant and benign SPNs. • The perfusion index is a useful biomarker for differentiate malignancy from benignancy.

Lung cancer perfusion: can we measure pulmonary and bronchial circulation simultaneously?

To describe a new CT perfusion technique for assessing the dual blood supply in lung cancer and present the initial results. This study was approved by the institutional review board. A CT protocol was developed, and a dual-input CT perfusion (DI-CTP) analysis model was applied and evaluated regarding the blood flow fractions in lung tumours. The pulmonary trunk and the descending aorta were selected as the input arteries for the pulmonary circulation and the bronchial circulation respectively. Pulmonary flow (PF), bronchial flow (BF), and a perfusion index (PI, = PF/ (PF + BF)) were calculated using the maximum slope method. After written informed consent was obtained, 13 consecutive subjects with primary lung cancer underwent DI-CTP. Perfusion results are as follows: PF, 13.45 ± 10.97 ml/min/100 ml; BF, 48.67 ± 28.87 ml/min/100 ml; PI, 21 % ± 11 %. BF is significantly larger than PF, P < 0.001. There is a negative correlation between the tumour volume and perfusion index (r = 0.671, P = 0.012). The dual-input CT perfusion analysis method can be applied successfully to lung tumours. Initial results demonstrate a dual blood supply in primary lung cancer, in which the systemic circulation is dominant, and that the proportion of the two circulation systems is moderately dependent on tumour size. A new CT perfusion technique can assess lung cancer's dual blood supply. A dual blood supply was confirmed with dominant bronchial circulation in lung cancer. The proportion of the two circulations is moderately dependent on tumour size. This new technique may benefit the management of lung cancer.

Integration of baroreflex and autoregulation control of bronchial blood flow in awake dogs

Baroreflex control of the bronchial circulation is unresolved. Early studies suggested that baroreflexes dilate or have no effect, but recent studies in awake dogs suggested baroreflexes did not normally engage tonic vasoconstrictor efferents but during excitement systemic pressure rises may also trigger local sensory-motor dilator reflexes. We examined the postulate that bronchial flow is normally regulated at rest during controlled changes in pressure gradient (Pg) by integration of tonic autonomic activity with autoregulation. Twelve greyhounds were instrumented under general anaesthesia by surgical implantation of pulsed Doppler flow transducers on the right bronchial artery (BA). After recovery baroreflex effects were evoked by raising and lowering aortic pressure using a lower thoracic aortic balloon in 11 animals, and in six of these after cholinoceptor plus adrenoceptor blockade. The right BA bed showed pressure-passive responses and the time-dependent bronchial bed effects in the autonomically intact state (INT) were largely similar to those in the blocked state (TAB). When results were replotted as pressure-flow relationships and analysed using covariance, the regression line over the pressure range 70-135 mmHg for TAB demonstrated a significant slope (P < 0.05), a linear regression elevated 120% (P = 0.006) above and parallel to INT (Y(Q) = 0.034 + 0.00033(X(Pg) - 104.6). The regression fell on the line of equal proportional change. Baroreflexes do not functionally engage the autonomic outflow to the bronchial circulation. Under controlled conditions of systemic Pg change, the bronchial circulation is normally controlled by the integration of resting autonomic tone, myogenic autoregulation and pressure-passive effects.

The influence of methysergide on 5-hydroxytryptamine-induced changes in regional distribution of blood flow.

Systemic and regional haemodynamic variables were measured at the baseline and after saline or 5-HT infusions (5 microgram kg-1 min-1, i.v.) or methysergide injections (0.5 mg kg-1, i.v.). Cardiac output and its complete distribution were measured by the radioactive microsphere (15 micrometer diam) technique. Although 5-HT did not change the systemic variables, methysergide caused a moderate increase in systolic and mean blood pressure and heart rate. 5-HT caused a substantial increase in gastric and a moderate increase in cerebral and myocardial blood flow at the expense of that to the lungs (arteriovenous shunt + bronchial flows), kidneys and skin. While methysergide was able to reduce the vascular responses to 5-HT in stomach, skin, kidneys, heart, lungs and brain, the drug itself, like 5-HT, decreased the number of microspheres reaching the lungs. Since a large number of 15 micron microspheres can escape through the arteriovenous anastomoses to lodge in the lungs it seems likely that both 5-HT and methysergide can reduce the 'non-nutrient' flow through these anastomoses.

Funktionelle 3He-MRT der Lunge

Pulmonary diseases have a high health-related and economic significance. (3)He-MRI is an alternative imaging method which can detect ventilatory disturbances with a high sensitivity. The application of different pulse sequences allows static and dynamic assessment of ventilation and bronchial gas flow, non-invasive measurement of intrapulmonary oxygen partial pressure and quantification of pulmonary parenchyma destruction and overinflation. Generally, the method is applicable for obstructive and restrictive ventilatory disturbances but initial approaches also exist for vascular pulmonary diseases. Specific clinical applications remain to be determined but (3)He-MRI is an excellent instrument for the assessment of physiologic and pathophysiologic interrelations in the distribution of ventilation.

Pulmonary endarterectomy: is there an alternative to profound hypothermia with cardiocirculatory arrest?

The current surgical strategy for pulmonary endarterectomy (PEA) involves the use of extracorporeal circulation and hypothermic circulatory arrest (HCA). The aim of the present study was to test the feasibility of a different strategy of extracorporeal circulation, which could prevent bronchial back bleeding and allow a bloodless operating field, avoiding the risks associated with HCA in patients undergoing pulmonary endarterectomy. Between June 2004 and September 2005, eight patients underwent PEA without HCA. We introduced a double venting of the left heart sections, utilizing two cannulas placed in the left ventricle and atrium. Both vent cannulas are connected with vacuum device to prevent back-bleeding and left heart distension from the large amount of bronchial flow. We were able to perform pulmonary endarterectomy avoiding circulatory arrest and deep hypothermia without sacrificing the effectiveness of the procedure. The initial encouraging results have convinced us to apply systematically this technique in the cases operated in our center, even though further investigations are necessary to fully examine this technique.

Role of Bronchial Artery Systemic Lymph Flow After Smoke Burn Injury

Role of Bronchial Artery Systemic Lymph Flow After Smoke Burn Injury

Analysis of Bronchovascular Downstream Blood Pressure Changes in Exercising Sheep

The relative roles of neural and pressure gradient factors, causing a fall or maintenance of bronchial blood flow in exercising sheep, are unknown. These were examined in sheep prepared under thiopentone/isoflurane general anaesthesia with a pulsed Doppler probe mounted on the bronchial artery, and aortic pressure (Pa) catheter in superficial cervical artery. After recovery, Swan-Ganz catheters were inserted under local anaesthesia into the pulmonary artery. Bronchial flow and conductance (Qbr, Cbr), and pressure gradients (Pg; i.e. aortic minus right atrial, Pg_RAP; pulmonary artery, Pg_Ppa; and, left atrial (wedge) Pg_LAP) were derived from continuous records, after switching between downstream sites during and after moderately severe treadmill exercise (3.8 km.h−1, for 1.7 min, 6 min recovery). The protocol was repeated after combined α1,α2–adrenoceptor/cholinoceptor blockade using phentolamine methanesulfonate and methscopolamine bromide. Bronchial flow fell in both receptor intact (INT) and (BL) blocked state. Pa rose in INT, but downstream pressures rose only 3.7 (RAP), 2.8 (Ppa) and 2.0 (LAP) mmHg (P for each <0.05) in both INT and BL. Pg_RAP and Pg_Ppa did not rise, but Pg_LAP rose 4.0 mmHg (P < 0.05). In BL, Pa fell, as did Pg_RAP (7.0 mmHg, P < 0.05), Pg_Ppa (8.9 mmHg, P < 0.001), but Pg_LAP did not change. Thus, downstream pressures change by small amounts, and pressure gradients to RAP and Ppa sites do not change during moderately severe exercise in normal sheep. The fall in Qbr in INT is due to neural factors, but in BL is due to a fall in Pg. The relative rise in Pg_LAP in both INT and BL favours redistribution within total Qbr to the pulmonary capillary/vein/left atrium site.

Role of Bronchial Artery Systemic Lymph Flow After Smoke Burn Injury

Role of Bronchial Artery Systemic Lymph Flow After Smoke Burn Injury

Methods to track leukocyte and erythrocyte transit through the bronchial vasculature in sheep

Study of the underlying mechanisms of leukocyte recruitment in the airway circulation is a crucial aspect of understanding the pathology of inflammatory airways disease. However, few in vivo studies have focused on leukocyte kinetics through the systemic airway vasculature. Because the bronchial vasculature of the sheep shows anatomical similarity to that of the human as well as being easily accessible for perfusion, we developed methods to study leukocyte transit through the sheep bronchial circulation. Leukocytes were isolated from whole blood after hypotonic lysis of red cells and labeled with 5-(and 6) carboxyfluorescein succinimidylester (CFSE; 0.1 μM), a green fluorescent dye. Red blood cells were labeled using PKH26-GL Red Fluorescent Cell Linker and served as a marker for blood flow and volume. Labeled leukocytes were tested for activation during the labeling process by monitoring surface levels of leukocyte adhesion molecules CD11b and l-selectin. When activated with phorbol myristate acetate (10 ng/ml), sheep leukocytes showed a marked increase in CD11b expression and a decrease in l-selectin. However, sheep leukocytes labeled with CFSE showed no significant increase of CD11b or shedding of l-selectin, suggesting that the labeling process did not significantly activate the adhesion properties of the cells. Aliquots containing both labeled erythrocytes and leukocytes were infused into the bronchial vasculature of the sheep through the cannulated bronchial artery at normal bronchial flow (0.6 ml/kg). Serial blood samples were withdrawn from the outflow of the bronchial vasculature (the left atrium) and analyzed using conventional flow cytometry. Retention of leukocytes and transit relative to red cell transit could then be evaluated with this technique. In addition, since cells are stably labeled, airway tissue samples can be removed and analyzed histologically to determine sites of extravasation. These methods offer an approach for examining leukocyte kinetics in situ in the airways of a relevant animal model.

Effects of Inactivated Influenza Virus Vaccination on Bronchial Reactivity Symptom Scores and Peak Expiratory Flow Variability in Patients with Asthma

Even though annual influenza vaccinations are recommended by many authorities, some doctors may be reluctant to vaccinate asthmatic patients because of the risk of inducing bronchial reactivity and exacerbating the asthma. In this study we investigated the effect of inactivated trivalent influenza vaccine on airway reactivity symptom scores and peak expiratory flow (PEF) variability in 24 patients with mild stable asthma. Baseline spirometry and methacholine challenge tests were performed on all patients. Patients were then asked to record their peak expiratory flow every morning and evening, complete daily symptom score charts (morning tightness, daytime asthma, cough, and night asthma), and note bronchodilator usage for 1 week. After baseline measurements, the patients were allocated to inactivated vaccine and placebo in a random and single-blind manner. The lung function measurements and methacholine challenge tests were repeated 1 week after vaccination and placebo administration at the same time of day. PD20 (mg/mL) methacholine doses were 3.06 ± 3.0 mg/mL before vaccination, 2.96 ± 3.2 mg/mL after vaccination, and 2.76 ± 2.91 mg/mL after placebo administration. There were no significant changes in PD20 methacholine after influenza vaccination (p > 0.05). There were also no significant changes in symptom scores, bronchodilator usage, and PEFR after vaccination (p > 0.05). None of the patients experienced significant local or systemic side effects after vaccination. Immunization with inactivated influenza vaccine does not induce clinical exacerbations of asthma or airway hyperreactivity in patients with mild asthma.

Time course and pattern of pulmonary flow distribution following unilateral airway occlusion in sheep.

1. Unilateral bronchial occlusion causes ipsilateral hypoxic pulmonary vasoconstriction, which shifts blood flow towards the other lung. We studied the time course of flow diversion following acute bronchial occlusion, and the temporal effect of the latter on blood gases and vertical distribution of blood flow within the two lungs. 2. Serial infusion of radioactive or fluorescent microspheres were given to each of seven adult standing sheep before, during occlusion of the left mainstem bronchus for up to 6 min, and after release of occlusion. Pulmonary and systemic arterial pressures were recorded continuously and arterial and mixed venous blood gases were determined intermittently. Post-mortem, the lungs were inflated, dried and cut into slices. Relative blood flow at the time of infusion was expressed as the weight-normalized intensity of each tracer in each slice or lung divided by the weight-normalized intensity in the two lungs. 3. Within 30 s, 1 min and 2 min after onset of occlusion, flow in the occluded lung had decreased to 68-84% (range), 51-78% and 43-79% respectively, of the initial value. In the contralateral lung, flow increased by 10-24%, 14-37% and 23-39% respectively. The distribution of flow along the gravitational axis within each lung varied widely between animals, both before and during occlusion. The during-occlusion profiles in the occluded lung differed from those in the non-occluded lung. In either lung, during-occlusion profiles could not be predicted with certainty from the pre-occlusion profiles. Two minutes post-occlusion, inter- and intra-lung flow distribution were nearly the same as before occlusion. Arterial oxygen tension fell in the first minute of occlusion, but never below 7.5 kPa, and increased slowly thereafter. Arterial carbon dioxide tension increased slightly throughout the occlusion period. No appreciable changes in systemic or pulmonary artery pressure were observed. Post-occlusion, arterial oxygen tension was still sub-normal, while carbon dioxide tension continued to increase. 4. We conclude that acute unilateral bronchial occlusion diverts blood flow within 30 s towards the contralateral lung. This rapidly occurring flow diversion prevents the development of severe arterial hypoxaemia. The variable and largely unpredictable distribution of blood flow in the hyperfused non-occluded lung might explain some of the gas-exchange abnormalities observed in physiologically hyperfused lungs and in patients with one hyperfused lung.

Autonomic control of bronchial circulation in awake sheep during rest and behaviour.

1. We tested the hypothesis that the pattern and the intensity of autonomic mechanisms causing vasoconstriction in the resting bronchial circulation of awake dogs also exists in awake sheep. It was also postulated that sighing behaviour and the associated bronchovascular dilatation induced by non-adrenergic, non-cholinergic (NANC) mechanisms observed in the dog exist in sheep. 2. Bronchial arterial blood flow to lower airways of both lungs of awake sheep was measured continuously using pulsed Doppler flow probes mounted on the bronchial artery at prior thoracotomy. 3. Cumulative and factorial analysis of responses to randomized combinations of autonomic alpha 1-, alpha 2-, beta 1- and beta 2-adrenoceptors and cholinoceptor autonomic blockade suggests that resting vasoconstrictor activity is less in sheep than in dogs. At normal aortic pressure, the autonomic activity of these receptor groups in the sheep lowers bronchial blood flow and conductance by 30%, whereas in the awake dog, the corresponding autonomic effect is 50%. 4. Tonic autonomic control of bronchial conductance can be partitioned in sheep to show significant and separate alpha- and beta-adrenoceptor vasoconstrictor activity at a ratio of 1.8:1, an effect normally offset by a weaker vasodilator alpha-/beta-adrenoceptor interaction. In contrast to the situation in awake dogs, cholinoceptors do not play a role in awake sheep. 5. Nitric oxide (NO) synthase inhibition in sheep using NG-nitro-L-arginine following blockade of alpha- and beta-adrenoceptors and cholinoceptors causes hypertension, but minor changes, if any, in pulmonary pressures or heart rate. Bronchial flow and conductance, however, fall from a higher resting conductance by approximately 50%, suggesting that, normally, resting bronchial flow conductance is dominated by strong tonic NO vasodilator effects that interact with weaker tonic autonomic vasoconstrictor effects. 6. Superimposed (respiratory) behaviours of sighing, sneezing and coughing, which involve negative swings in intrathoracic pressure and the movement of inspired air, evoke large active bronchovascular dilator effects. These appear to be largely NANC in origin and appear to be dependent, in part, on mechanisms associated with NO release. It is postulated that the C-fibre axon reflex using substance P, calcitonin gene-related peptide and neurokinin A may be involved. Vocalization and eructation do not evoke bronchovascular effects.