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.
Hall LW, Trim CM.Horses breathing spontaneously under halothane anaesthesia were subjected to expiratory resistance by the introduction of a water-trap into the expiratory limb of a circle absorber. Resistances of 10 and 20 cm H2O produced no significant increase in PaO2 (P greater than 0.05) during halothane/air and halothane/oxygen anaesthesia. The imposition of resistance was associated with an increase in PaCO2 and a significant increase in mixed venous PCO2. In three animals subjected to 20 cm H2O resistance under halothane/air anaesthesia, the cardiac output was reduced (P less than 0.01). It was conclud...
Hillidge CJ, Lees P.Respiratory function and acid-base variables were studied in Welsh Mountain ponies before and at predetermined times after the intravenous injection of Immobilon and Revivon.A marked depression of respiratory rate was accompanied by large reductions in arterial blood oxygen tension and saturation and the development of a mild respiratory acidosis following the injection of Immobilon. It was concluded that at least three factors contributed to the hypoxic hypoxia produced by Immobilon; the posture of lateral recumbency, the decrease in respiratory rate and the laboured character of the respirat...
Cabler P, Geddes LA, Rosborough J.Ultrasonic energy, provided by a commercially available water vaporizer, was used to vaporize methoxyflurane, halothane, and chloroform. The vaporizer was placed directly in the respiratory line, and the anaesthetic liquid was vaporized one drop at a time. Anaesthesia was maintained for periods up to 6 hr in horses, ponies, calves, sheep, dogs, and one pig. This method of vaporizing liquids is applicable to a wide variety of anaesthetics. It is easily controlled, and the same vaporizer can be used with a wide range of sizes of subjects. The vaporizer can be placed directly in the respiratory c...
Brown DG.Physiologic responses of irradiated and nonirradiated Shetland Ponies to controlled exercise were measured over a period of 5 years. The 5-year test began when the ponies were 3 years old and 5 months after they were exposed to 650 R of 60-Co gamma radiation. Significant differences in heart rates, respiratory rates, and rectal temperatures were demonstrated between irradiated and nonirradiated ponies when subjected to exercise and high ambient temperatures. Inthe irradiated group, heart rates were usually slower, especially during recovery immediately after exercise, and respiratory rates and...
Rawlings CA, Birnbaum ML, Bisgard GE.Static pulmonary and total compliance during expiration was measured in fifteen healthy anesthetized ponies. Mean body weight of the ponies was 140.6 kg and ranged from 83.6 to 211.4 kg. For the fifteen ponies, mean values and SD were: total compliance (Ct), 168.7 plus or minus 47.2 ml/CMH2O, and mean pulmonary compliance (Cl), 368.4 plus or minus 90.3 ml/cmH2O. Both Ct and Cl were significantly dependent on body weight, calculated surface area, height at the withers, and circumference about the chest. Repeatability of compliance measurement from day to day was confirmed by measuring complianc...
Jones RS.Surgical repair of a cleft palate was carried out in three horses. Mandibular symphisotomy allowed adequate exposure of the defect. The first subject, a young foal died from inhalation pneumonia but the other two made satisfactory recoveries. The problems of closure of the lip and symphysis are discussed.
Lewis IM, McLan JG.The levels of 2,3-diphosphoglycerate (2,3-DPG), which affects the transport of oxygen by haemoglobin, were examined in horse blood. Resting levels of erythrocyte 2,3-DPG were established in thoroughbred horses, and levels of 2,3-DPG together with haemoglobin levels, were examined in a variety of conditions. A negative correlation was observed between erythrocyte 2,3-DPG and haemoglobin levels. Mares had higher erythrocyte 2,3-DPG levels was observed during training, and this variation may have a significant effect on haemoglobin oxygen transport. Erythrocyte 2,3-DPG levels were not affected by...
Boles C.Adequate post-operative management of equine abdominal patients is as necessary to patient survival as the most heroic corrective surgery. Post-operative management must begin during the anaesthesia recovery phase to insure adequate oxygen supply, ventilation, and minimize any abdominal discomfort. The animal's physiological status must be constantly monitored to detect and determine the degree of abnormalities concerning serum electrolytes, fluid balance, and acid-base abnormalities. The most commonly observed serum electrolyte imbalance is hypokalaemia. Replacement potassium is usually suppl...
Muir WW, Moore CA, Hamlin RL.The influence of various concentrations of CO2 and O2 in the inspired gases on minute volume (V), tidal volume (VT), and respiratory rate (breaths per min; BPM) was examined in nonanesthetized, nonsedated normal horses. The VT and BPM increased linearly in response to increases in inspired CO2 concentration and curvilinearly in response to decreases in inspired Os concentration. The V increased curvilinearly in response to both increases in inspired CO2 concentration and decreases in inspired O2 concentration.
Platt H.A series of 10 haemorrhagic polyps of the equine nasal cavity is described. The lesions show haematoma formation, abundant haemosiderin in macrophages and giant cells, and organising fibrous tissue. In one case, angiomatoid lesions were observed in the mucous membrane of the paranasal sinuses and it is suggested that some haemorrhagic nasal polyps may originate from pre-existing haemangiomatous areas in the respiratory mucosa.
Bisgard GE, Orr JA, Will JA.Hemodynamic measurements were made in 6 ponies at low altitude (Madison, WI, altitude, 250 m) and after 1, 2, 4, and 6 weeks at high altitude (Climax, CO, altitude, 3,400 m). The salient findings were that ponies maintain an increased heart rate and cardiac output and develop significant pulmonary hypertension at high altitude. The average control resting mean pulmonary artery pressure (BPpul) was 25.1 mm of Hg at 250 m; this value increased to 56.3 mm of Hg after 6 weeks at 3,400 m. An additional finding was that the pulmonary vascular response to acute hypoxia seemed to increase with time at...
Courtot D, Roux L, Mouthon G, Jeanin E.Doping with tranquilizers has appeared recently in horse-back riding sports. In this paper we study the effects of acepromazine, one of the main tranquilizers used, on various physiological and biochemical aspects of muscular activity (cardiac and respiratory rhythms, seric rates of glucose, urea, protein, creatine phosphokinase, glutamate oxalacetate transaminase, alkaline phosphatase). A low dose (0.02 mg/kg) of acepromazine is injected; the evolution of the variables is studied before and after a standardized effort. After the effort and during recuperation, acepromazine administration caus...
Weaver BM, Walley RV.Eleven out of 12 horses were underventilating while breathing spontaneously during halothane anaesthesia with high arterial carbon dioxide tensions. In addition, large alveolar to arterial oxygen tension gradients were found to be present. Mechanically, controlled ventilation with an intermittent positive pressure of 20-30 cm H2O reduced arterial carbon dioxide levels to normal. The alveolar to arterial oxygen gradients did not increase and in some cases decreased. These (A - a) Po2 gradients were due mainly to true shunt of the order of 30 per cent and not to ventilation perfusion inequality....
Ingvast-Larsson C, Kallings P, Persson S, Appelgren LE, Wiese B.The pharmacokinetics of theophylline at rest and the effects on cardio-respiratory and blood lactate responses to exercise were investigated after repeated oral administrations in six healthy Standardbred horses. A dose of 5 mg/kg body weight was administered every 12 h. The binding of theophylline to plasma protein was also determined. There was good agreement between predicted and observed plasma concentrations of theophylline at steady state. The mean half-life of elimination was shown to be 17.0 +/- 2.5 h, the mean half life of absorption was 1.6 +/- 1.8 h, the apparent volume of distribut...
Bennett RC, Steffey EP, Kollias-Baker C, Sams R.To quantitate the dose and time-related effects of morphine sulfate on the anesthetic sparing effect of xylazine hydrochloride in halothane-anesthetized horses and determine the associated plasma xylazine and morphine concentration-time profiles. Methods: 6 healthy adult horses. Methods: Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of halothane in O2 and characterize the anesthetic sparing effect (ie, decrease in MAC of halothane) by xylazine (0.5 mg/kg, i.v.) administration followed immediately by i.v. administration of saline (0.9% NaCI) solution, lo...
Chesnel MA, Aprea F, Clutton RE.A traumatic pneumothorax and severe hemorrhage were present in a mare with a large thoracic wall defect, lung perforation, and multiple rib fractures. General anesthesia was induced to allow surgical exploration. We describe the anesthetic technique, and discuss the management of the ventilatory, hemodynamic, and metabolic disturbances encountered. Gestion de l’anesthésie générale d’un cheval avec un pneumothorax d’origine traumatique. Nous décrivons le cas d’une jument présentée avec un important déficit de la paroi thoracique d’origine traumatique, une perforation pulmonaire...
Dodman NH, Lehr JL, Spaulding GL, Gavriely N.Three sheep, a foal, a pony, and a calf were anesthetized and ventilated for short periods, using a high-frequency oscillatory ventilator. The efficiency of CO2 elimination was characterized at various oscillatory frequencies (50 to 30 Hz) and various tidal volumes, although the tidal volume used was always less than the measured dead space of the animal. In general, increasing either the oscillatory frequency or tidal volume increased CO2 elimination, but increasing the tidal volume had more effect. The relationship between these 3 variables was best described by a power law equation. Ventila...
Still J, Serteyn D, van der Merwe CA.Anaesthesia was induced in horses (n = 6) with a mixture of thiopentone and guaiphenesin and maintained by mechanical ventilation with a mixture of oxygen, air and isoflurane. Inspiratory and end-expiratory concentrations of oxygen, carbon dioxide and isoflurane were measured. Electrocardiography was used to evaluate heart rate and rhythm. Mean systemic arterial pressure (SAPm), pulmonary artery pressure (PAPm), right atrial pressure (RAPm) and pulmonary capillary wedge pressure (PCWP) were measured directly. Cardiac output was determined using the thermodilution method. Microcirculation in th...
Muir WW, Sams RA, Ashcraft S.The hemodynamic, respiratory, and behavioral effects, as well as the pharmacokinetic properties of methocarbamol, were determined in horses. Heart rate, cardiac output, arterial and venous blood pressures, respiratory rate, and arterial blood gases did not change after IV methocarbamol (4.4, 8.8, 17.6 mg/kg) administration. There were no signs of behavior modification or ataxia observed. Analysis of plasma concentration time data indicated that the disposition of methocarbamol may be dose-dependent. Clearance and steady-state volume of distribution decreased as the dose increased. Plasma conce...
Bakos Z, Vörös K.The application of equine thoracic percussion has been ignored because of the availability of modern imaging techniques. Ultrasonography is a reliable tool in determining the caudal lung border of horses. The aim of the study was to compare percussion with ultrasonography to determine lung borders in horses. Objective: That thoracic percussion can detect the caudal lung border and that its accuracy is comparable with thoracic ultrasonography. Methods: Fifteen randomly chosen, healthy, Warmblood horses. Methods: The caudal lung border was detected by percussion and ultrasonography at the end of...
Ross MW, Stephens PR, Reimer JM.A 9-year-old pregnant Standardbred broodmare was evaluated for signs of mild abdominal pain, failure to defecate, and mild abdominal distention. Rectal examination revealed the leading edge of a small colon intussusception, and peritoneal fluid analysis indicated suppurative peritonitis. Surgical management, including reduction of the intussusception and small colon resection with end-to-end anastomosis, resulted in successful outcome (1-year follow-up evaluation). Postoperative complications including dehiscence of the ventral midline surgical incision and simple obstruction at the anastomosi...
Harmegnies NF, Duvivier DH, Vandenput SN, Art T, Lekeux PM, Votion DM.This study aimed to compare exercise-induced pulmonary perfusion redistribution in healthy vs. 'heavey' horses using scintigraphy, a minimally invasive technique. Six healthy (A) and 5 'heavey' horses in remission (B(I)) and during clinical signs of disease (B(II)) were investigated. Dimensions of the exercising pulmonary perfusion (QE) images were expressed in percent of the resting perfusion (QR) images. Computed QE to QR ratios (QE/QR) images enabled the definition of the region more perfused at exercise than at rest (R1). In all groups, exercise induced a major enlargement of the Q image b...
Schumacher J, Crossland LE.Primary paranasal sinusitis, complicated by inspissated purulent exudate in a ventral conchal sinus, was diagnosed in 3 horses. Partial nasal obstruction, caused by axial deviation of the ventral concha, was detected endoscopically in 2 of the horses. A mass, dorsal to the maxillary molars, was detected via a lateral radiographic view of the skull of 3 horses and on the dorsoventral view of 1 of the horses. Inspissated purulent exudate was removed from the ventral conchal sinus of the horses via trephination of the conchofrontal sinus and penetration of the caudal wall of the ventral conchal s...
Hinchcliff KW, McKeever KH, Muir WW.The systemic haemodynamic and acid-base effects of the administration of phenylbutazone (4.4 mg kg-1 intravenously) to standing and running horses were investigated. Phenylbutazone, or a placebo, was administered to each of six mares either 15 minutes before, or after 30 minutes of a 60-minute submaximal exercise test which elicited heart rates approximately 55 per cent of maximal, and to the same horses at rest. The variables examined included the cardiac output, heart rate, systemic and pulmonary arterial pressures, right atrial and right ventricular pressures, and arterial and mixed venous ...
Dunlop CI, Hodgson DS, Watson JW, Gillespie JR, Steffey EP, Jackson AC.High frequency jet ventilation (HFJV) is a recently developed mode of ventilation that delivers small tidal volumes at frequencies greater than 60 cycles per min via an injection catheter to the animal's airway. The construction of a high frequency jet ventilator suitable for use in adult horses is described. The effectiveness of this ventilator in maintaining normal arterial blood-gas tension was evaluated in five healthy adult horses. The horses were anaesthetised with intravenous acetylpromazine, guaifenesin, and thiamylal, positioned in lateral recumbency and baseline measurements were mad...
Geisel O, von Sandersleben J.The chronic obstructive pulmonary disease (COPD) in horses is primarily based on a chronic bronchitis/bronchiolitis with constriction of the tubes in the lower respiratory tract. The outward appearance of the lung is characterized by a diffuse or marginal alveolar emphysema. The big bronchial tubes are usually not altered. Small bronchi and bronchioli can often be seen through the pulmonal pleura. On the sectional area they are visible as opaque grey-red nodules with a central lumen detectable under a magnifying glass. The histopathological picture of alterations in the bronchial tree can vary...
Camargo FC, Robinson NE, Dirikolu L, Berney C, Eberhart S, Derksen FJ, Lehner AF, May J, Hughes C, Tobin T.Trimetoquinol (TMQ) is a very potent and fast acting bronchodilator in horses with heaves. This study assessed the plasma and urinary concentrations of TMQ in horses with heaves following administration via the intravenous (IV, 0.2 microg/kg) and intra-tracheal (IT, 2 microg/kg) routes. TMQ was administered to six horses affected with heaves (RAO - Recurrent Airway Obstruction, used interchangeably) by the above routes and plasma and urine samples collected and stored at -20 degrees C until analyzed. Solid Phase Extraction (SPE) of TMQ was followed by highly sensitive ESI(+)-LC-MS-MS (ElectroS...
Koterba AM, Kosch PC.Breathing pattern, respiratory muscle activation pattern, lung volumes and volume-pressure characteristics of the respiratory system of normal, term, neonatal foals on Days 2 and 7 of age were determined to test the hypothesis that the foal actively maintains end-expiratory lung volume (EEV) greater than the relaxation volume of the respiratory system (Vrx) because of a highly compliant chest wall. Breathing pattern was measured in the awake, unsedated foal during quiet breathing in lateral and standing positions. The typical neonatal foal breathing pattern was characterized by a monophasic in...
Peloso JG, Stick JA, Nickels FA, Lumsden JM, Derksen FJ.A 2-year-old 400-kg Standardbred colt with a history of exercise intolerance was determined to have dorsal displacement of the soft palate (DDSP). Standing endoscopy revealed a soft, flaccid, and hypoplastic epiglottis and arytenoid cartilages that moved symmetrically and abducted fully. Lateral laryngeal radiography was used to calculate a corrected thyroepiglottic length of 6.48 cm. Videoendoscopy during exercise on a high-speed treadmill at standardized treadmill speeds was performed weekly for 3 consecutive weeks. The soft palate dorsally displaced at each examination. A sternohyoideus/ste...
Lawn K.During training, a 6-year-old standardbred gelding collapsed, exhibiting severe epistaxis and agonal breathing and was euthanized. The horse had a recent history of poor performance, lethargy, and unilateral eyelid swelling with serous ocular discharge. Postmortem and histopathologic examination findings revealed thoracic lymphosarcoma and concurrent exercise-induced pulmonary hemorrhage. Résumé — Mort subite d’un cheval de course de race standardbred causée par un lymphome thoracique. En cours d’entraînement, un standardbred hongre âgé de 6 ans s’est effondré, présentant des s...
Crisman MV, Hodgson DR, Bayly WM, Liggitt HD.To determine whether road transport affected pulmonary phagocyte activity, 7 healthy Thoroughbred horses were shipped 1,160 kilometers over 36 hours. Fluid collected by bronchoalveolar lavage (BAL) 12 hours, and 7 and 14 days after transport was analyzed. Results were compared to those from the same horses pre-transport, and 7 non-transported control horses that had BAL performed at the same times as the transported horses. Of cells recovered with BAL the percentage of viable pulmonary alveolar macrophages (PAMs) declined from 90.0 +/- 0.9% pre-transport to 80.0 +/- 3.7% by 2 weeks post transp...
Art T, Tack S, Kirschvinck N, Busoni V, Votion D, Freeman K, Lekeux P.This study aimed at measuring the functional consequences and the pulmonary cytology changes following a simulation of pulmonary haemorrhage. Pulmonary function tests including lobeline-induced hyperventilation, cytology of tracheo-bronchial wash (TBW) and thoracic radiographs were performed before, as well as 1, 7, 14 and 28 days after, the instillation of 300 ml of blood into the lungs of 4 horses deemed free of exercise-induced pulmonary haemorrhage (Group 1). Control data (Group 2) were obtained by instilling the same volume of saline into the lungs of the same horses in a crossover design...
Staddon GE, Weaver BM.The regional perfusion to the lungs of 14 ponies was studied using radioactively labelled microspheres injected intravenously. It was found that within half an hour of induction of anaesthesia the perfusion to the dependent lung had decreased significantly from the values in the standing animal. When anaesthesia was maintained for more than two and a half hours, however, the lung perfusions were not significantly different from the standing values when the animals were lying in lateral or supine recumbency.
Barton AK, Gehlen H.The term remodeling describes the process resulting in a tissue that is structurally and architecturally altered compared to its healthy counterpart. At least in severe equine asthma, this occurs mainly, but not exclusively, as a consequence of neutrophilic airway inflammation and is characterized by hypertrophy of the smooth muscle layers in airway and arterial walls as well as fibrosis of the bronchial walls and pulmonary interstitial tissue. To date, much less is known for mild to moderate equine asthma. For a long time it was assumed that these processes are irreversible, and at least for ...
Steffey EP, Woliner MJ, Dunlop C.Circulatory and respiratory effects of five h of constant 1.06 per cent alveolar halothane in oxygen were identified in eight healthy horses, which breathed spontaneously, were otherwise unmedicated and positioned in sternal recumbency. Only a few important significant (P less than 0.05) changes occurred with time. Total peripheral resistance was about 15 per cent lower after two hours of constant dose halothane than after 30 mins of constant dose (P less than 0.05) and accounted for the significant 10 per cent reduction in mean carotid arterial blood pressure. By 5 h, the reduction in resista...
Schellenberg LM, Regenthal R, Abraham G.The present study addresses the effect of the Rho-kinase (ROCK) inhibitor Y-27632 on the β-adrenoceptor density and β-agonist-stimulated intracellular second messenger cAMP formation in primary equine bronchial epithelial cells (EBEC). Y-27632 significantly decreased the β-adrenoceptor number (B) without markedly affecting the receptor affinity (dissociation constant, K) to the radioligand [I]-iodocyanopindolol (ICYP). In contrast, Y-27632 augmented the β-agonist-stimulated intracellular cAMP production. Herein, Y-27632 markedly increased the maximal cAMP responses (E) (isoproterenol >...
Haynes PF.The intent and extent of the respiratory tract examination relevant to purchase are dictated by numerous factors, including historical information, signs suggestive of respiratory tract abnormalities, intended use of the horse, and economic considerations. Following a thorough and systematic examination of the horse at rest, evaluation during and following exercise may be warranted. The physical examination should include evaluation of regional symmetry of the head, neck, and thorax; evaluation of nasal airflow and patency; palpation of the nasal septum, larynx, and trachea; examination for su...
Luna SP, Taylor PM, Brearley JC.Glucose was infused intravenously into six ponies during halothane anaesthesia, to evaluate its effect on their endocrine response to anaesthesia. The ponies were premedicated with acepromazine, and anaesthesia was induced with thiopentone and maintained with halothane in oxygen for two hours. Glucose was infused to maintain the plasma glucose concentration above 20 mmol/litre. Anaesthesia was associated with hypothermia, a decrease in haematocrit, hypotension, hyperoxaemia, respiratory acidosis and an increase in the plasma concentrations of lactate and arginine vasopressin. The concentration...
Rush BR.Pharmacologic manipulation of pulmonary immunity plays an important role in primary and adjunct therapy for equine respiratory disease. Frequent exposure to respiratory viral pathogens, strenuous exercise, long distance transport, and inhalation of harmful substances destroy various aspects of the pulmonary defense system and predispose performance horses to development of infectious and noninfectious respiratory disease. Pulmonary immunity may be bolstered by nonspecific immunostimulants to combat primary or secondary immunodeficiency. State of the art technology improves active and passive-s...
Marqués FJ, Hehenberger E, Dickinson R, Wojnarowicz C, Lohmann K.A 9-year-old, 1494-lb (679-kg) Quarter horse gelding in good body condition was admitted to the Veterinary Teaching Hospital, Western College of Veterinary Medicine (WCVM), University of Saskatchewan, for evaluation and treatment of acute respiratory distress. On a trail ride 26 days before presentation, the gelding had been exposed to a horse with clinical signs of an upper respiratory tract infection. The gelding performed well on the trail ride but, 4 days later, developed a mild swelling in the retropharyngeal area and a slight bilateral mucoid nasal discharge. The gelding was examined at ...
Jann HW, Cook WR.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...
Conceição ML, Alonso JM, Alves ALG, Hussni CA, Rodrigues CA, Watanabe MJ.Dorsal displacement of the soft palate (DDSP) usually occurs in athletic adult horses. Congenital DDSP in foals secondary to the persistent frenulum of the epiglottis is rarely observed. The aim of this report was to describe a case of a seven-day-old female neonate Quarter Horse presenting dysphagia, milk reflux through the nostrils and mouth, and expiratory dyspnea since 4 days. Thoracic auscultation was indicative of aspiration pneumonia. Diagnosis of DDSP associated with local inflammation was made after endoscopic examination of upper respiratory tract. Radiographic examination was perfo...
Duvivier DH, Votion D, Vandenput S, Art T, Lekeux P.Development of dry powder inhalation (DPI) for horses requires the use of an adapted face mask. In experiment I, 4 masks (A, B, C and D) were tested and factors influencing the delivery of the dry powder were determined. Mask A was one which is commercially available for metered-dose inhalation. Mask B had the same shape as Mask A but an airtight rubber seal was added for the connection between the mask and horse's head. Mask C was a prototype adapted for DPI with connection for the DPI device between the nostrils, airtight expiratory valves in front of each nostril and airtight rubber seal to...
