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Topic:Respiratory Health
Respiratory health in horses encompasses the study of the equine respiratory system, its function, and the various conditions that can affect it. The respiratory system in horses includes the upper airways, lungs, and associated structures, which facilitate gas exchange and are vital for maintaining physiological homeostasis during rest and exercise. Common respiratory conditions in horses include equine asthma, infectious diseases like strangles, and exercise-induced pulmonary hemorrhage (EIPH). These conditions can impact a horse's performance and overall health. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathophysiology, and management of respiratory health in horses.
Preliminary studies on the measurement of conjunctival oxygen tension in the foal. The capability of a transconjunctival oxygen monitoring system to provide an accurate and reliable means of observing arterial oxygenation trends was evaluated in 12 horse and pony foals between 5 and 20 days of age. Ten of the foals were anesthetized with isoflurane in oxygen and nitrous oxide, and 2 foals were conscious. Inspired oxygen concentration was manipulated by differing proportions of oxygen and nitrous oxide in the fresh gas supplied to the breathing circuit. With arterial oxygen tension values ranging from less than 20 to greater than 400 mm of Hg, all foals had significant positi...
Effects of a demand valve on pulmonary ventilation in spontaneously breathing, anaesthetised horses. The pressure flow characteristics of a demand valve which has been suggested to be suitable for use in anaesthetised horses were determined at a range of flow rates commonly encountered in equine anaesthesia. The resistance of the valve was found to be very much greater than the resistance of normal large animal anaesthetic apparatus or the equine lower respiratory tract. The effects of the valve on pulmonary ventilation were investigated in seven anaesthetised, intubated horses. Respiratory rate and dynamic compliance were unaffected by connection of the valve but mean tidal and minute volume...
Changes in breathing when switching from nares to tracheostomy breathing in awake ponies. We assessed the consequences of respiratory unloading associated with tracheostomy breathing (TBr). Three normal and three carotid body-denervated (CBD) ponies were prepared with chronic tracheostomies that at rest reduced physiological dead space (VD) from 483 +/- 60 to 255 +/- 30 ml and lung resistance from 1.5 +/- 0.14 to 0.5 +/- 0.07 cmH2O . l-1 . s. At rest and during steady-state mild-to-heavy exercise arterial PCO2 (PaCO2) was approximately 1 Torr higher during nares breathing (NBr) than during TBr. Pulmonary ventilation and tidal volume (VT) were greater and alveolar ventilation was le...
In vitro phagocytosis and killing of Corynebacterium equi by alveolar macrophages of foals. Bronchoalveolar lavage was performed 5 times, sequentially, on 3 healthy foals while each foal was 6 to 63 days of age. Phagocytosis and bactericidal assays were performed on recovered alveolar macrophages. Corynebacterium equi and alveolar macrophages at a ratio of 10:1 were incubated for 1 hour in medium containing 1% heat-inactivated rabbit anti-C equi serum. After incubation, greater than 90% of the alveolar macrophages contained at least 1 ingested bacterium and each alveolar macrophage contained 9.4 +/- 1.0 bacteria (mean +/- SE). After alveolar macrophages and C equi were incubated for ...
Role of hilar nerve afferents in hyperpnea of exercise. The objective of this study was to determine the role of hilar nerve (lung vagal) afferents in the hyperpnea of exercise. Ten ponies were studied before and 2-4 wk and 3-12 mo after sectioning only the hilar branches of the vagus nerves (HND). After HND, lung volume feedback to the medullary centers was attenuated as indicated in the anesthetized state by 1) attenuation or absence of the Hering-Breuer inflation reflex (P less than 0.01) and 2) attenuation of the lengthened inspiratory time (TI) when the airway was occluded at end expiration (P less than 0.01). Moreover, after HND in the awake ...
Unusual response following use of succinylcholine in a horse anesthetized with halothane. A syndrome similar to malignant hyperthermia developed in a 545-kg Quarter Horse while anesthetized with halothane for cataract removal. Succinylcholine administration caused prolonged, severe muscle fasciculations followed by tachycardia, and an elevated blood pressure. Later, while the horse was still under anesthesia, its body temperature rose 2 degrees C, and respiratory acidosis developed. Myositis developed after surgery, but the horse recovered.
Total intravenous anaesthesia in the horse with propofol. The use of propofol, solubilised in a non-ionic emulsifying agent, for the induction and maintenance of anaesthesia in experimental ponies was assessed. Pilot studies revealed that premedication with xylazine (0.5 mg/kg bodyweight [bwt]) intravenously (iv) followed by propofol (2.0 mg/kg bwt) iv provided a satisfactory smooth induction. Two infusion rates (0.15 mg/kg bwt/min and 0.2 mg/kg bwt/min) were compared for maintenance of anaesthesia. An infusion rate of 0.2 mg/kg/min produced adequate anaesthesia in these ponies. Cardiovascular changes included a decrease in arterial pressure and card...
Cardiovascular and respiratory effects of acetylpromazine and xylazine on halothane-anesthetized horses. Circulatory and respiratory effects of intravenously administered acetylpromazine (0.033 and 0.067 mg/kg) and xylazine (0.5 and 1.0 mg/kg) were studied in drug cross-over fashion in eight laterally recumbent horses anesthetized only with halothane (1.06%, end-tidal) in O2. Both doses of acetylpromazine caused a significant and sustained elevation in cardiac output via a rise in stroke volume. Xylazine produced an initial significant fall in cardiac output followed by a return to control levels. Halothane anesthesia did not prevent xylazine-related atrioventricular conduction block. All treatme...
Transendoscopic electrosurgery for epiglottal entrapment in the horse. Monopolar electrosurgical cutting was used to correct epiglottal entrapment in 5 horses. The operations were carried out in the conscious animal, using topical anesthesia. The procedure required the use of a coagulation electrode designed specifically for electrosurgery, introduced through the instrument channel of a fiberoptic endoscope. The results were satisfactory and serious complications were not encountered. In 2 horses, excessive submucosal swelling developed at the site of the surgical wound, and the tumefaction took several weeks to subside in one of these horses. In both horses, the...
Efficacy of furosemide in the treatment of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses. The repeatability of endoscopic observations of exercise-induced pulmonary hemorrhage (EIPH) and the efficacy of furosemide as a prophylactic treatment of horses with EIPH were studied in Thoroughbred race horses after consecutive breezes (at or near maximum speed, approx 16 m/s). Of 56 horses examined greater than or equal to 2 times, 21 (38%) had identical EIPH scores, whereas 26 (46%) and 9 (16%) had scores that differed by greater than or equal to 1 grade. In 56 nontreated horses, there was good agreement between 2 consecutive observations (K = 0.59, Z = 4.54, P less than 0.001). Similar c...
Upper respiratory tract obstruction caused by a pharyngeal abscess in a filly. A 3-year-old Thoroughbred filly had a pharyngeal abscess causing obstruction of the upper respiratory tract. Diagnosis was made by a combination of endoscopy, biopsy, cytology, and radiography. Treatment with antimicrobials and analgesics resulted in successful resolution of the abscess.
Differential diagnosis of equine respiratory noises. EXAMINATION of a horses 'wind' has long been a requirement at the time of sale. More recently the respiratory system has been the subject of investigation in the assessment of poor performance, although an examination for these purposes must be pan of a full clinical examination with special attention paid to the respiratory and cardiovascular systems. The differential diagnosis of adventitious respiratory sounds heard at exercise is considered here.
Antagonism of xylazine-pentobarbital anesthesia by yohimbine in ponies. Effects of yohimbine on xylazine-pentobarbital anesthesia were evaluated in ponies. Five minutes after the IV injection of xylazine (1.1 mg/kg of body weight), pentobarbital sodium (12.7 mg/kg, IV) and additional xylazine (2.2 mg/kg, IM) were given and produced anesthesia in 12 ponies for 64.0 +/- 16.4 minutes (mean +/- SD) as well as immobilization for 89.8 +/- 34.2 minutes. Eleven ponies were given yohimbine (0.1 mg/kg, IV) 50 minutes after pentobarbital dosing. In these 11 ponies, durations of anesthesia and immobilization were shorter, 52.0 +/- 1.4 and 65.5 +/- 14.8 minutes, respectively. ...
Surgical and medical management of rhinophycomycosis (conidiobolomycosis) in a horse. A horse had severe granulomatous lesions of the upper airways that were attributable to Conidiobolus coronatus. Therapeutic success was documented by clinical examination of the horse 4 years after treatment by surgical extirpation and intralesional and topical use of amphotericin B.
Effects of altered ambient temperature on metabolic rate during CO2 inhalation. The purpose of this study was to determine if the changes in O2 consumption (VO2) during CO2 inhalation could in part be due to stimulation of thermogenesis for homeothermy. Twelve ponies were exposed for 30-min periods to inspired CO2 (PIco2) levels of less than 0.7, 14, 28, and 42 Torr during the winter at 5 (neutral) and 23 degrees C ambient temperatures (TA) and during the summer at 21 (neutral TA), 30, and 12 degrees C. Elevating TA in both seasons resulted in an increased pulmonary ventilation (VE) and breathing frequency (f) (P less than 0.01) but no significant increase in VO2 (P great...
Roaring in Clydesdales. An endoscopic survey was performed to assess arytenoid cartilage movement during quiet respiration in 48 Clydesdale horses. Physical characteristics which could influence the length of the recurrent laryngeal nerves were also recorded from these horses and the relationship of these characteristics to the presence of abnormal left arytenoid cartilage movements was assessed statistically. Some degree of abnormal arytenoid movement was observed in 50% of the animals over one year of age. No significant correlation between sex, age, estimated weight, height, or neck length could be found although ...
Effect of altered ambient temperature on breathing in ponies. The objective was to determine the effect of moderate changes in ambient temperature (TA) on breathing and body temperature in ponies chronically exposed to a TA of 21 degrees C in the summer and 5 degrees C in the winter. Normal (n = 6) and chronic carotid body-denervated (n = 6, 1-2 yr) ponies were studied during 1) winter months over 3-4 days at 5 (control TA) and 23 degrees C and 2) summer months over 2-4 days at 21 (control TA), 30, and 12 degrees C. Neither rectal nor arterial temperature changed with any alteration of TA (P greater than 0.10). Skin temperature (Tsk) always changed by 2-...
Review of exercise induced pulmonary haemorrhage and its possible relationship with mechanical stress. Exercise induced pulmonary haemorrhage (EIPH) is a condition of uncertain aetiology. This article reviews the evidence relating to its incidence, clinical findings, radiological observations, histopathology and certain aspects of respiratory physiology. It is proposed that EIPH is primarily caused by mechanical stress in the dorsocaudal region of the lung.
Bilateral laryngeal paralysis in the horse. Four two-year-old Thoroughbreds suffered an acute gastrointestinal illness shortly after dosing with mineral oil which was thought to have been contaminated with an organophosphate compound. Three weeks later all four were noted to be dyspnoeic and endoscopic examination showed that they had developed bilateral laryngeal paralysis. Two of the horses died during severe bouts of dyspnoea six and eight months later and the third was killed shortly thereafter. Examination of the left and right recurrent laryngeal nerves from these horses showed a severe loss of myelinated fibres distally, especial...
The ‘Turner’ circle absorber: an anaesthetic breathing system for the horse. An inhalation anaesthetic apparatus for the horse is described and the physiological concepts pertaining to its design presented. The internal diameter of all breathing components is 6.2 cm with no change in cross sectional area throughout the circle system. The soda lime capacity is 25 litres (approximately 20 kg). In the horse, which is apparently predisposed to alveolar hypoventilation during inhalation anaesthesia, it is apparent that adequate anaesthetic apparatus design should be directed towards minimising resistance and dead space and providing maximal and efficient carbon dioxide elim...
Intensive care of the neonatal foal. The basic concepts of diagnosis and treatment in the abnormal neonatal foal are presented. Methods of restraint, sedation, and general nursing care are discussed, as well as more specific techniques of respiratory and circulatory system support.
Parasites in lungs of dead equids in Kentucky: emphasis on Dictyocaulus arnfieldi. Prevalence of natural infections of parasites from the lungs of 488 dead Thoroughbreds in Kentucky was investigated. The horses varied from 1 to 32 years of age; 419 horses were from 215 farms and 69 horses were from 68 individual sources for which a specific farm was not identified. Examinations of the lungs were made from Mar 1, 1983 through Feb 29, 1984. Dictyocaulus arnfieldi was recovered from 56 (11%) of the horses. Other parasites found were larvae of Parascaris equorum in 37 (8%) and of Habronema/Draschia in 67 (14%) of the horses. The possible effect of ivermectin treatment on the pre...
Effects of aerosolized histamine and carbachol in the conscious horse. Pulmonary function tests were performed in seven conscious, standing horses. Changes in pulmonary mechanics and ventilation volumes were measured after inhalation challenge with saline (baseline), histamine (1% w/v solution for 5 min) and carbachol (0.5% w/v solution for 3 min). Comparisons between baseline and posthistamine values revealed a significant (P less than 0.05) increase in nonelastic work of breathing (Wb), maximum change in transpulmonary pressure (max delta Ppl), and pulmonary resistance (RL), while dynamic compliance (Cdyn) decreased (P less than 0.05). Tripelennamine completely...
Respiratory problems in foals. Despite major advances in our knowledge and ability to treat respiratory diseases in neonatal foals, neonatal respiratory medicine is still in its infancy. It is hoped that this article may serve as a guideline for diagnosis and treatment. Specific antibiotic regimens and emergency procedures are covered in other articles in this symposium. Because management factors play a critical role in the pathogenesis of respiratory disease, education of clients as to their importance would help both prophylactically and therapeutically. The necessity of very careful monitoring of neonates, which is crit...
Effects of furosemide on the racing times of horses with exercise-induced pulmonary hemorrhage. In 3 groups of horses with exercise-induced pulmonary hemorrhage (EIPH), comparisons of racing times and finishing positions were made between the 5 races before the horses were given furosemide and 5 races after furosemide administration. The horses were grouped according to 3 methods used to diagnose EIPH: group 1, observation of hemorrhage at the nostrils within 1 hour after a workout or race; group 2, observation of pulmonary hemorrhage only by endoscopic examination after a race or workout; and group 3, observation of hemorrhage at the nostrils during a race or immediately after a race. G...
Changes in blood flow distribution in equine lungs induced by anaesthesia. The distribution of blood flow to the lungs was measured with labelled microspheres injected into horses before and during anaesthesia. Anaesthesia was induced with glycerol guaiacolate ether and ketamine, and maintained with the spontaneous breathing of halothane in oxygen. In a preliminary group of six horses, flow distribution was observed during anaesthesia in sternal, dorsal and right lateral recumbency. In two other groups, each of four horses, the flow distribution with time during either sternal or right lateral recumbency was observed. A small, constant proportion of the 15 micron dia...
Pharyngeal lymphoid hyperplasia in Thoroughbred racehorses in training. The prevalence of pharyngeal lymphoid hyperplasia in Thoroughbred racehorses in training was investigated using a fibre optic endoscope. Of the 70 horses examined, all but 8 showed evidence of pharyngeal lymphoid hyperplasia and the severity of the pharyngeal changes decreased with age. Two-year old horses had greater pharyngeal lymphoid hyperplasia (p less than 0.05) when compared to all other age groups. More horses (p less than 0.05) with Grade 3 or Grade 4 pharyngeal lymphoid hyperplasia experienced recent mild respiratory disease than did horses with Grade 2 or less pharyngeal lymphoid hy...
Endoscopic and virological observations on respiratory disease in a group of young Thoroughbred horses in training. A group of racehorses in training was examined on several occasions with a fibreoptic endoscope and monitored for viral infection. Only equine herpes virus-2 (EHV-2) infection was detected. Pharyngeal lymphoid hyperplasia (PLH) was present in all horses and decreased in severity with age. There was no association between PLH severity and antibody titres to EHV-1, or with the isolation of EHV-2. Finishing position in races was not affected by PLH severity. Exercise induced pulmonary haemorrhage (EIPH) was evident on 23 out of 49 (47 per cent) examinations after maximal speed training exercise. ...
