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Topic:Bronchi
The bronchi are part of the lower respiratory tract in horses, serving as air passages that conduct inhaled air from the trachea into the lungs. These tubular structures branch into smaller bronchioles, leading to the alveoli where gas exchange occurs. The health and function of the bronchi are critical for maintaining respiratory efficiency and overall equine health. Conditions affecting the bronchi, such as bronchitis or bronchoconstriction, can impact a horse's respiratory performance and are often a focus in equine veterinary medicine. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of the bronchi in horses, as well as diagnostic and therapeutic approaches for bronchial conditions.
Spontaneous equine pulmonary granular cell tumors: morphologic, histochemical, and immunohistochemical characterization. Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negati...
Acetylcholine release from airway cholinergic nerves in horses with heaves, an airway obstructive disease. The present study was conducted to determine if acetylcholine (ACh) release from airway cholinergic nerves is increased and if modulation of ACh release by prejunctional receptors is altered in horses with heaves, an obstructive airway disease characterized by airway inflammation and bronchospasm. Trachealis strips and bronchial segments of normal horses and horses affected with heaves were suspended in 2-ml tissue baths. ACh release was induced by electrical field stimulation and the bath ACh content was measured by high performance liquid chromatography (HPLC) with electrochemical detection....
The effects of three models of airway disease on tidal breathing flow-volume loops of thoroughbred horses. The effects of histamine and methacholine aerosols and of a fixed inspiratory resistance on tidal breathing flow-volume loops (TBFVL) were investigated using 18 unsedated, standing, healthy thoroughbred horses. The data were first analysed using traditional flow-volume loop indices and then reduced using standardized factor scoring coefficients obtained in a previous study in this laboratory using similar experimental techniques. On the basis of resting TBFVL analysis, the degree of pulmonary dysfunction caused by inhalation of histamine and methacholine aerosols with concentrations of 10 and ...
Autologous blood instillation alters respiratory mechanics in horses. To investigate physiological consequences of autologous blood instillation in the lungs of healthy horses, respiratory mechanics and bronchial response to histamine were studied in 8 Thoroughbreds before and after introducing autologous blood (n = 5) and sterile saline solution (n = 3) into their lungs. Blood instillation resulted in a decrease in dynamic compliance (Cdyn) and increased respiratory resistance (R). Bronchial sensitivity and reactivity were unchanged after blood introduction. There were no significant changes in pulmonary mechanics or bronchial response after saline instillation...
Modulation of bronchial smooth muscle function in horses with heaves. Four mechanisms that modulate airway smooth muscle function in normal horses were studied in the bronchi of horses affected by the airway obstructive disease heaves. Results were compared with data from historical controls studied by the same personnel in the same laboratory. Rings from the left cranial lobar bronchus (LB1) and small bronchi (5 mm OD) were suspended in muscle baths, and the isometric tension were measured. The inhibitory nonadrenergic noncholinergic (iNANC) function was studied in LB1. After the LB1 segments were pretreated with atropine and contracted with histamine, electric...
Distribution of SP- and CGRP-like immunoreactive nerve fibers in the lower respiratory tract of neonatal foals: evidence for loss during development. The lungs of neonatal foals contain many nerves immunoreactive for substance P and calcitonin gene-related peptide. These nerves are closely associated with the epithelium, bronchial and pulmonary vessels and the airway smooth muscle of all intrathoracic airways, including non-cartilaginous bronchioles. Activation of sensory nerves in the respiratory epithelium could thus potentially affect, via local axon reflexes, vascular and respiratory smooth muscle in neonatal equine airways. Nerves immunoreactive for these peptides are much more widely distributed within the lung than in adult horses; t...
PGE2 inhibits acetylcholine release from cholinergic nerves in canine but not equine airways. The effects of exogenous prostaglandin E2 (PGE2) and endogenous prostanoids on cholinergic neurotransmission were determined by measurement of acetylcholine (ACh) release from canine and equine airway tissues. Trachealis strips and bronchial segments were suspended in 2 ml tissue baths. ACh release was induced by electrical field stimulation (EFS), and its content in tissue bath liquid was measured by high pressure liquid chromatography (HPLC) with electrochemical detection. In canine airways, exogenous PGE2 (10(-9) to 10(-7) M) inhibited ACh release concentration-dependently, whereas inhibiti...
Endoscopic anatomy and map of the equine bronchial tree. To develop a bronchoscopic map of the equine respiratory tree, the major airways of the lungs of 6 healthy Thoroughbred horses were systematically explored with a flexible fibreoptic endoscope through a tracheostomy while the horses were sedated in stocks. With the carina as the reference point, measurements were made of distances to the branches of the major airways using markers on the shaft of the endoscope. All branches were explored until the narrowing of their diameters prevented further advancement of the endoscope. Positions of origins of branches from the parent bronchus were recorded...
Evaluation of a technique for detection of pulmonary hemorrhage in horses, using carbon monoxide uptake. The diffusing capacity for carbon monoxide (DLCO) and the functional residual capacity (FRC) of the lung were measured in 5 healthy Thoroughbreds before and after instillation of autologous blood into their lungs, in an attempt to develop a method to quantitate extravascular blood in the lungs of horses with exercise-induced pulmonary hemorrhage. Mean (+/- SD) baseline values of DLCO and FRC were 333.8 +/- 61.9 ml/min/mm of Hg and 21.464 +/- 4.156 L, respectively. Blood instillation resulted in decreases in DLCO and FRC. The paradoxic decrease in DLCO (we were expecting to find an increase owi...
Inhibitory nerve distribution and mediation of NANC relaxation by nitric oxide in horse airways. The distribution of inhibitory nerves and the mediator of the inhibitory nonadrenergic noncholinergic (iN-ANC) nervous system were investigated in smooth muscle preparations from seven regions of equine airways. In tissues incubated with atropine and precontracted with histamine, electrical field stimulation produced frequency-dependent relaxation, and the magnitude of the relaxation decreased from trachea to central bronchi and was absent in peripheral airways. The degree of relaxation in bronchi was not simply a function of bronchial size or generation. Propranolol inhibited part of the rela...
Prejunctional alpha 2-adrenoceptors inhibit acetylcholine release from cholinergic nerves in equine airways. To determine the presence and function of alpha 2-adrenoceptors on cholinergic nerves innervating horse airway smooth muscle, the effects of some alpha 2-adrenoceptor agents on contractions of and acetylcholine (ACh) release from equine airway smooth muscle preparations were studied. Muscle contractions were elicited by either electrical field stimulation (EFS) or exogenous ACh. ACh release was induced by EFS and measured by high-pressure liquid chromatography and electrochemical detection. The alpha 2-adrenoceptor agonists clonidine (10(-7) to 10(-5) M) and UK-14,304 (10(-8) to 10(-6) M) conc...
Modulation of bronchial responsiveness in horses by phenylbutazone and furosemide. Effects of phenylbutazone (PBZ) and furosemide (FUR) on the respiratory tract of horses were evaluated, focusing on bronchial responsiveness. Four healthy Thoroughbreds were used and data were analyzed by use of a Latin square design. Histamine provocation tests (0.5, 1, 2, and 4 micrograms/min, i.v.) were done: (1) without prior treatment with PBZ or FUR, (2) 30 minutes after administration of PBZ (8 mg/kg, i.v.), (3) 1 hour after administration of FUR (1 mg/kg, i.v.), and (4) after administration of PBZ plus FUR. Pulmonary function tests (dynamic compliance, resistance, respiratory frequency...
Independent modulation of horse airway smooth muscle by epithelium and prostanoids. The effects of epithelial removal and cyclooxygenase inhibition on contractions induced by exogenous acetylcholine (ACh) and electrical field stimulation (EFS) were evaluated in horse tracheal strips and bronchial rings. Epithelial removal potentiated the response to ACh but had no influence on the response to EFS. The effect of epithelial removal was not altered by pretreating the tissues with meclofenamate, a cyclooxygenase inhibitor. In trachealis strips, meclofenamate augmented contractions induced by EFS but not by ACh. In bronchial rings, meclofenamate augmented EFS-induced contraction t...
Bronchointerstitial pneumonia and respiratory distress in young horses: clinical, clinicopathologic, radiographic, and pathological findings in 23 cases (1984-1989). Twenty-three foals, between 1 and 7 months old, with signs of acute respiratory distress, were examined at the Veterinary Medical Teaching Hospital (VMTH), University of California, Davis, between 1984 and 1989. Characteristic features included sudden onset of severe respiratory distress and tachypnea, cyanosis unresponsive to nasal oxygen, pyrexia, hypoxemia, hypercapneic respiratory acidosis, poor response to treatment, and histopathologic lesions of bronchiolitis and bronchointerstitial pneumonia. Seven of the 23 foals were normal before the onset of respiratory distress, 3 foals were found...
Evaluation of local endobronchial antigen challenges in the investigation of equine chronic obstructive pulmonary disease. Local transendoscopic endobronchial antigen challenge, which has proved to be a valuable clinical and research technique in the study of human pulmonary hypersensitivity, was evaluated in control and asymptomatic COPD--affected horses. Transendoscopic endobronchial challenges with phosphate-buffered saline (PBS), Micropolyspora faeni extract at 60 and 600 micrograms/ml and mouldy hay extract elicited neutrophilic airway inflammatory responses in control (N = 5-7) and asymptomatic COPD-affected (N = 5-7) horses, as determined by cytological examinations of bronchoalveolar lavage fluid (BALF) ha...
The bronchial tree and lobular division of the horse lung. The lungs of five horses were examined. At present, in veterinary anatomy, the horse lung is divided into the cranial and caudal lobes by the cardiac notch on either side. In addition to these lobes, in the right lung, the accessory lobe is present. However, from the viewpoint of the bronchial ramifications, the horse lung can be divided into the cranial, middle, caudal and accessory lobes bilaterally. The horse lung has four bronchiole systems on either side, dorsal, lateral, ventral and medial. The cranial lobe is formed by the first bronchiole of the dorsal bronchiole system. The middle lob...
In vitro effects of alpha 2-adrenergic receptor stimulation on cholinergic contractions of equine distal airways. In horses with noninduced, reversible airway obstruction (heaves), pulmonary function is improved after sedation with the alpha 2-adrenergic agonist xylazine. The mechanism of this effect is undetermined. Because the predominant excitatory innervation of equine airways is cholinergic, the influence of alpha 2-adrenergic receptor stimulation on the response of isolated distal airways to cholinergic stimulation was determined. Distal bronchial segments from 22 healthy horses were suspended in isolated organ baths where their mechanical responses to various stimuli could be studied. Each tissue w...
Distribution of dopamine beta-hydroxylase and neuropeptide Y-immunoreactive nerves in healthy equine lungs. Immunohistochemical methods were used to determine the distribution of pulmonary nerves containing either an enzymatic marker of adrenergic nerves, dopamine beta hydroxylase, or the putative neurotransmitter neuropeptide Y in 7 equids with healthy lungs. Nerves immunoreactive for these substances were found on airway smooth muscle in nearly all the samples of healthy equine lung examined. These nerves were generally more numerous in the larger airways but could be detected even in noncartilaginous bronchioles. Pulmonary and bronchial vessels also contained numerous immunoreactive nerves. On th...
Primary pulmonary neoplasm in a horse. A 16-year-old Thoroughbred gelding was evaluated for respiratory disease and found to have a primary lung tumor on postmortem examination. A tentative antemortem diagnosis was made on the basis of results of radiography and cytologic examination of a needle aspirate guided by ultrasonography. A histologic diagnosis of bronchioalveolar adenocarcinoma was made. Thoracic neoplasia is rare in horses. The most frequently reported primary pulmonary tumor is the granular cell tumor.
Bronchoscopy of the horse. The endobronchial anatomy of 12 lung specimens from horses and 12 healthy, standing, sedated horses was evaluated, using a 200-cm-long, 9.5-mm-diameter videoendoscope. On the basis of these findings, the nomenclature system of Amis and McKiernan was modified for identification of airways of horses during bronchoscopy. Lobar bronchi are identified on the basis of the side of the bronchial tree on which they were found and the order in which they originated from the primary bronchus. Thus, RB1, RB2, and RB3 referred to right cranial lobar bronchus, respectively. On the left side, the designation...
Respiratory mucociliary clearance in the horse in health and disease, and its pharmaceutical modification. The structure and possible functions of respiratory secretions are reviewed. In the equine, goblet (mucus producing) cells are the main source but little information is available on the volume or composition of equine respiratory secretions. Airway mucus has complex and incompletely understood physical characteristics which can be partially assessed by a wide range of in vitro and biological techniques. The complex relationship between mucus structure and its propulsion by the airway cilia are discussed, both in health and with pulmonary disease. Mucokinesis in the horse has been assessed visu...
Decreased airway mucosal prostaglandin E2 production during airway obstruction in an animal model of asthma. Heaves is a respiratory disorder of horses and ponies characterized by bouts of acute airway obstruction and airway hyperresponsiveness. We measured prostaglandin E2 (PGE2) and 15-hydroxyeicosatetraenoic acid (15-HETE) production in vitro in tracheal epithelium obtained from six affected horses at the time of acute airway obstruction as compared with six matched control horses. Strips of epithelium and subepithelial tissue were prepared and stimulated with A23187, histamine, and bradykinin. The PGE2 and 15-HETE in media from strips was quantitated by radioimmunoassay. 15-HETE above the limits ...
Preliminary observations on inhalation and intradermal challenges of horses with oil seed rape. Horses with asymptomatic or symptomatic chronic obstructive pulmonary disease (COPD) and control horses were challenged with oil seed rape either by exposure to a field of flowering Brassica campestris for six days, or by an inhalation challenge with freshly collected pollen from Brassica napus, or by inhalation challenge with a commercial extract of B napus pollen. Clinical and bronchoscopic examinations showed that the challenges did not induce detectable pulmonary disease in the control or asymptomatic COPD affected horses and did not significantly affect their pulmonary mechanics, arterial...
Mechanical properties of small airways in excised pony lungs. We evaluated the pressure-flow relationships in collaterally ventilating segments of excised pony lungs by infusing N2, He, Ne, or SF6 at known flows (V) through a catheter wedged in a peripheral airway. Measurements were made at segment- (Ps) to-airway opening (Pao) pressure differentials of 3-15 cmH2O when the lungs were held at transpulmonary pressures of 5, 10, and 15 cmH2O. The data were analyzed both by calculating collateral resistance (Ps-Pao/V) and by constructing Moody-type plots of normalized pressure drop [(Ps-Pao)/(1/2 rho U2, where rho is density and U is velocity)] against Reyno...
Bronchial circulation during prolonged exercise in ponies. Tracheal, bronchial, and renal flow were studied in 8 healthy ponies at rest and during exercise performed on a treadmill at a speed setting of 20.8 km/h and 7% grade (incline) for 30 minutes. Blood flow was determined with 15-microns-diameter radionuclide-labeled microspheres that were injected into the left ventricle when the ponies were at rest, and at 5, 15, and 26 minutes of exertion. Heart rate and mean aortic pressure increased from resting values (40 +/- 2 beats/min and 124 +/- 3 mm of Hg, respectively) to 152 +/- 8 beats/min and 133 +/- 4 mm of Hg at 5 minutes of exercise, to 169 +/- ...
A tracheal tube-in-tube technique for functional separation of the lungs in the horse. The tube-in-tube technique for the functional separation of the lungs in intact anaesthetised adult horses is based on fibre-optic-guided left-sided endobronchial intubation avoiding tracheostomy. It facilitates a valid separation of the two lungs despite variability in bronchial and carinal anatomy. No clinical complications that could be related to its use have been seen.
Paralaryngeal accessory bronchial cyst as a cause of laryngeal haemiplegia in a horse. LARYNGEAL haemiplegia is common in horses and most often
involves the left haemilarynx (Baker 1983; Haynes 1984).
Although specific processes have been incriminated in the
pathogenesis of laryngeal haemiplegia, most cases involve an
idiopathic distal axonopathy of the recurrent laryngeal nerve. The
purpose of this report is to describe a case of laryngeal
haemiplegia associated with an anomalous respiratory cyst. A
description of the lesion, method of surgical repair of the
laryngeal collapse and a proposed term to describe the
abnormality based on pathological and functional consider...
Modelling exercise-induced pulmonary hemorrhage in racing thoroughbreds. Exercise-induced pulmonary hemorrhage (EIPH) affects a large portion of racing thoroughbred horses. Sites of hemorrhage and causal mechanisms remain unestablished. Our mathematical model was constructed to test the hypothesis that EIPH could be caused by a combination of respiratory and circulatory mechanical factors occurring during exercise. Various physiological data for respiration, blood circulation and exercise were incorporated into the model. Results show that inhalation pressure drops across airway resistances become great enough during exercise to cause rupture of capillaries for bot...
Exercise-induced pulmonary hemorrhage in horses with experimentally induced allergic lung disease. The lungs of sensitized horses were exposed to aerosolized ovalbumin. Some horses (n = 4) were given ovalbumin in 1 lung only, whereas in others (n = 7), ovalbumin or vehicle were inoculated in the cranial, ventral, and caudal regions of the caudal lung lobe. Horses were exercised 5 hours after ovalbumin exposure. Immediately before exercise, endoscopy failed to reveal any abnormality. After exercise, endoscopic examination of horses subjected to unilateral ovalbumin exposure revealed extensive blood in airways leading to the exposed lung in all horses. Blood was not observed in the airways le...
The genetic basis of equine allergic diseases. 1. Chronic hypersensitivity bronchitis. The genetic influence on chronic hypersensitivity bronchitis (CB) was investigated in families at two studs and among half-siblings of three affected and three non-affected sires at several farms. The family members at the two studs were born and raised under the same conditions, whereas the half-siblings were kept individually under very different conditions and were exposed to various environmental factors. The diagnosis was based on long-term observations and multiple clinical examinations at each of the two studs. In the half-sibling group, the diagnosis was based on the individual history...
