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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.
Observations on the muscle relaxant rocuronium bromide in the horse–a dose-response study. To investigate the onset and duration of neuromuscular blockade of rocuronium bromide and its associated haemodynamic effects at three doses in healthy horses. Methods: Prospective, randomized experimental study. Methods: Seven adult horses aged 3-20 (mean 10.3) years and weighing 466 +/- 44 (mean +/- SD) kg. Methods: Horses were anaesthetized three times with at least 2 weeks between. They were pre-medicated with 0.6 mg kg(-1) xylazine and 0.01 mg kg(-1) butorphanol i.v.. Anaesthesia was induced with 2.2 mg kg(-1) ketamine and 0.1 mg kg(-1) diazepam i.v.. Following orotracheal intubation anae...
Muc5b and Muc5ac are the major oligomeric mucins in equine airway mucus. Horses frequently suffer from respiratory diseases, which, irrespective of etiology, are often associated with airway mucus accumulation. Studies on human airways have shown that the key structural components of the mucus layer are oligomeric mucins, which can undergo changes of expression and properties in disease. However, there is little information on these gel-forming glycoproteins in horse airways mucus. Therefore, the aims of this study were to isolate equine airways oligomeric mucins, characterize their macromolecular properties, and identify their gene products. To this end, pooled tr...
Anesthetic and cardiopulmonary effects of total intravenous anesthesia using a midazolam, ketamine and medetomidine drug combination in horses. The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 microg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKM-drug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia wa...
Influx of neutrophils and persistence of cytokine expression in airways of horses after performing exercise while breathing cold air. To determine effects of exercise performed while breathing cold air on expression of cytokines and influx of neutrophils in airways of horses. Methods: 9 adult horses. Methods: In a crossover study, bronchoalveolar lavage fluid (BALF) was obtained 24 and 48 hours after each of 2 submaximal exercise sessions performed by horses while breathing warm (25 degrees C) or cold (-5 degrees C) air. Total and differential nucleated cell counts were determined for each BALF sample. Relative mRNA expression of cytokines in BALF cells was quantified by use of a reverse transcription-PCR assay. Results: Hor...
Stereoselective pharmacokinetics of ketamine and norketamine after racemic ketamine or S-ketamine administration during isoflurane anaesthesia in Shetland ponies. The arterial pharmacokinetics of ketamine and norketamine enantiomers after racemic ketamine or S-ketamine i.v. administration were evaluated in seven gelding ponies in a crossover study (2-month interval). Methods: Anaesthesia was induced with isoflurane in oxygen via a face-mask and then maintained at each pony's individual MAC. Racemic ketamine (2.2 mg kg(-1)) or S-ketamine (1.1 mg kg(-1)) was injected in the right jugular vein. Blood samples were collected from the right carotid artery before and at 1, 2, 4, 8, 16, 32, 64, and 128 min after ketamine administration. Ketamine and norketamine...
Lung surfactant function and composition in neonatal foals and adult horses. Lung surfactant function and composition are varied and adapted to the specific respiratory physiology of all mammalian species. Objective: Lung surfactant function and composition are different in neonatal foals as compared to adult horses. Methods: Six adult horses, 7 term foals (<24 hours old), and 4 premature foals were used. Animals were part of the Auburn University teaching herd except for 3 client-owned premature foals. Methods: Bronchoalveolar lavage fluid (BALF) was obtained from all animals. Ultracentrifugation of cell-free BALF separated surfactant into crude surfactant pellets ...
Segment-dependent expression of muscarinic acetylcholine receptors and G-protein coupling in the equine respiratory tract. Muscarinic receptors are considered to be of comparable clinical importance in chronic obstructive pulmonary disease (COPD) in equines and in humans. At present, data are scarce on the expression and distribution of probable subtypes of these receptors and their signalling pathways in airway segments, including lung parenchyma and bronchial and tracheal epithelium with the underlying smooth muscle in horses. Specific [N-methyl-3H]scopolamine chloride ([3H]NMS) binding to all three tissues was saturable and of high affinity, with KD values ranging between 1.6+/-0.7 and 1.9+/-0.3 nmol/L. [3H]NMS...
Management of bilateral choanal atresia in a foal. A 1-day-old Standardbred foal with a history of extreme respiratory distress after birth consistent with upper airway obstruction was evaluated. A temporary tracheostomy tube was placed by the referring veterinarian. Results: On initial examination, there was evidence of hypoxic-ischemic syndrome, secondary to perinatal asphyxia. Endoscopy revealed obstruction of both nares at the level of the choanae; a diagnosis of bilateral choanal atresia was made. Results: The foal was anesthetized and underwent transendoscopic laser fenestration of the buccopharyngeal membranes. Three weeks after surgery...
Factors influencing pre-race serum concentration of total carbon dioxide in Thoroughbred horses racing in California. Many racing jurisdictions monitor pre-race serum concentration of total carbon dioxide (TCO2) among racing horses. To our knowledge, factors influencing concentration of TCO2 among horses participating in racing have not been systematically evaluated and reported. Objective: To determine if characteristics of horses and racing conditions routinely recorded were significantly associated with pre-race concentration of TCO2, while accounting for and estimating effects of trainer and horse. Methods: Pre-race serum TCO2 concentrations from 5028 starts made by 2,349 horses trained by 287 trainers at...
Effects of unilateral laser-assisted ventriculocordectomy in horses with laryngeal hemiplegia. Recent studies have evaluated surgical techniques aimed at reducing noise and improving airway function in horses with recurrent laryngeal neuropathy (RLN). These techniques require general anaesthesia and are invasive. A minimally invasive transnasal surgical technique for treatment of RLN that may be employed in the standing, sedated horse would be advantageous. Objective: To determine whether unilateral laser-assisted ventriculocordectomy (LVC) improves upper airway function and reduces noise during inhalation in exercising horses with laryngeal hemiplegia (LH). Methods: Six Standardbred ho...
A comparison of total, respirable, and real-time airborne particulate sampling in horse barns. Measurements of total, respirable, and real-time airborne particulate were obtained in 12 horse barns in summer and winter. Respirable and total particulate concentrations were measured gravimetrically; real-time particulate was measured with an aerosol photometer. Total particulate (TP) ranged from nondetectable (ND) to 2.1 mg/m3 and from ND to 1.2 mg/m3 for winter and summer sampling, respectively. Respirable particulate (RP) ranged from ND to 0.2 mg/m3 and from ND to 0.7 mg/m3 for winter and summer measurements, respectively. The mean respirable fraction of particulate for summer and winter...
Pulmonary disposition of tilmicosin in foals and in vitro activity against Rhodococcus equi and other common equine bacterial pathogens. The objectives of this study were to determine the serum and pulmonary disposition of tilmicosin in foals and to investigate the in vitro activity of the drug against Rhodococcus equi and other common bacterial pathogens of horses. A single dose of a new fatty acid salt formulation of tilmicosin (10 mg/kg of body weight) was administered to seven healthy 5- to 8-week-old foals by the intramuscular route. Concentrations of tilmicosin were measured in serum, lung tissue, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and blood neutrophils. Mean peak tilmicosin conc...
Pharmacodynamic effects and pharmacokinetic profile of a long-term continuous rate infusion of racemic ketamine in healthy conscious horses. Ketamine (KET) possesses analgesic and anti-inflammatory activity at sub-anesthetic doses, suggesting a benefit of long-term KET treatment in horses suffering from pain, inflammatory tissue injury and/or endotoxemia. However, data describing the pharmacodynamic effects and safety of constant rate infusion (CRI) of KET and its pharmacokinetic profile in nonpremedicated horses are missing. Therefore, we administered to six healthy horses a CRI of 1.5 mg/kg/h KET over 320 min following initial drug loading. Cardiopulmonary parameters, arterial blood gases, glucose, lactate, cortisol, insulin, non...
Effects of the bronchoalveolar lavage procedure on lung function in horses with clinical exacerbation of recurrent airway obstruction. To evaluate whether bronchoalveolar lavage (BAL) alters respiratory mechanics of horses with recurrent airway obstruction (ie, heaves) over a 48-hour period. Methods: 6 horses affected with heaves. Methods: Horses were subjected to a complete BAL procedure, which included sedation with xylazine and butorphanol, intratracheal administration of lidocaine, and instillation and aspiration of two 250-mL boluses of saline (0.9% NaCl) solution through an endoscope (study 1). To evaluate the effects of saline solution, horses were subjected to the same procedure without saline solution instillation an...
A comparison of laryngoplasty and modified partial arytenoidectomy as treatments for laryngeal hemiplegia in exercising horses. To compare upper airway mechanics, arterial blood gases, and tracheal contamination in horses with induced left laryngeal hemiplegia (recurrent laryngeal neuropathy [RLN]) treated by laryngoplasty/vocal cordectomy (LPVC) or modified partial arytenoidectomy (MPA). Methods: Repeated measures under the following conditions: Control, RLN, LPVC, and MPA. Methods: Six horses. Methods: Two trials were conducted under all conditions at 80% and 100% of maximal heart rate (HR(max)). In Trial 1, arterial blood gases, tracheal and pharyngeal pressures, and laryngeal videoendoscopy were recorded. In Trial ...
cDNA cloning and substrate specificity of equine tryptase, a possible mediator in equine heaves. Mast cell mediators are believed to play a central role in inflammatory lung disorders such as human allergic and occupational asthma. Equine heaves is characterized by reversible neutrophilic airway inflammation and airway obstruction, primarily due to bronchospasm and mucus hypersecretion, following exposure of susceptible horses to organic stable dusts. As such, heaves shares many similarities with human occupational dust-induced asthma and therefore it is proposed that mast cells may also be implicated in the pathogenesis of heaves. Tryptase, a mast cell-specific proteinase, can be used as...
Ultrasonography of the equine larynx. Nasopharyngeal and laryngeal evaluation is important when examining horses with upper airway signs for poor performance. Currently endoscopy is the most common method to evaluate the equine upper airway. Ultrasonography of the equine larynx has not previously been described. Using six cadaveric specimens and four standing horses, the ultrasonographic appearance of the equine larynx was established. A scanning technique, including useful acoustic windows and the normal ultrasonographic appearance at each site, is described. Ultrasound allowed visualization of portions of the hyoid apparatus, la...
Occupational respiratory health of New Zealand horse trainers. To confirm that working with horses is an occupational respiratory hazard and observed associations are not attributable to confounding. Methods: A postal survey of the respiratory health of 659 horse trainers and a comparison group of 506 vegetable growers was conducted. Data were analysed using logistic regression. Results: Relative to vegetable growers, horse trainers reported higher rates of chronic bronchitis [odds ratio (OR) = 6.8, 95% confidence interval (CI): 2.2-21.4] and organic dust toxic syndrome/farmers' lung (ODTS/FL) (OR = 3.5, 95% CI: 1.8-6.8). Grinding oats, spreading hay, and...
Dynamic obstructions of the equine upper respiratory tract. Part 2: comparison of endoscopic findings at rest and during high-speed treadmill exercise of 600 Thoroughbred racehorses. The reliability of diagnoses of obstructive conditions of the upper respiratory tract (URT) based on examinations performed at rest vs. at exercise is controversial. Objective: To compare diagnosis of URT by endoscopy at rest with that achieved during high-speed treadmill exercise (HSTE). Objective: Endoscopy of URT at rest, when performed in isolation from other simpler techniques is unreliable in the prediction of dynamic respiratory obstructions. Methods: Endoscopic findings of 600 Thoroughbred racehorses during quiet breathing were compared with findings during high-speed treadmill exercis...
Dynamic obstructions of the equine upper respiratory tract. Part 1: observations during high-speed treadmill endoscopy of 600 Thoroughbred racehorses. To review the prevalence of single and complex forms of dynamic airway obstructions within a large group of Thoroughbred horses in training referred for investigation of poor performance. Methods: Video-endoscopic recordings of the upper respiratory tract made during a standardised treadmill exercise test of 600 Thoroughbred racehorses were reviewed and analysed in real time and slow motion to identify dynamic collapse by the tissues bordering onto the pharyngeal and laryngeal airways. Results: Dynamic collapse within the nasopharynx or larynx was confirmed in 471 of the 600 horses. Dorsal dis...
[Pasteurella] caballi infection not limited to horses – a closer look at taxon 42 of Bisgaard. To investigate if taxon 42 of Bisgaard isolated from pigs represents genuine [Pasteurella] caballi, which was previously only isolated from horses. Results: A total of 15 field isolates from horses and pigs from five different countries representing three continents were subjected to extended phenotypical characterization. Although minor differences were observed between taxon 42 and [P.] caballi, these differences did not allow phenotypic separation. Ribotyping based on HindIII digestion showed five profiles based on nine band positions. One [P.] caballi strain and two taxon 42 strains shared...
Temporal clinical exacerbation of summer pasture-associated recurrent airway obstruction and relationship with climate and aeroallergens in horses. To describe the seasonal pattern of clinical exacerbation of summer pasture-associated recurrent airway obstruction (SPA-RAO) in relation to climate and aeroallergens in horses. Methods: 19 horses with SPA-RAO and 10 nonaffected horses. Methods: Daily examinations were performed on all horses while they were kept on pasture for 3 years. Onset and progression of clinical exacerbation based on a clinical score of respiratory effort were evaluated in relation to changes in maximum temperature, minimum temperature, mean temperature, maximum dew-point temperature, minimum dew-point temperature, and...
Placement of a long term tracheal cannula in a Thoroughbred racehorse with bilateral laryngeal dysfunction. A Thoroughbred horse with bilateral laryngeal dysfunction was treated by placement of a long term tracheal cannula in order to restore full athletic function. The horse initially presented with right-sided arytenoid dysfunction that was considered to be due to a congenital malformation of the laryngeal cartilage. This was corrected by a right-sided laryngoplasty and ventriculectomy. The horse re-presented 1 year later with idiopathic left laryngeal hemiplegia. The decision was made to place a long-term tracheal cannula due to the low success rate and high complication rate associated with othe...
Cricothyroid muscle function and vocal fold stability in exercising horses. To determine (1) if the cricothyroid muscle had respiratory-related electromyographic (EMG) activity that increased with respiratory effort and (2) if bilateral cricothyroid myotomy resulted in vocal fold instability and collapse in exercising horses. Methods: Experimental. Methods: Seven (3 EMG; 4 cricothyroid myotomy) Standardbred horses. Methods: Three horses exercised on a treadmill at speeds corresponding to the speed that produced maximum heart rate (HR(max)), 75% of maximum heart rate (HR(75%max)), and 50% of maximum heart rate (HR(50%max)) for 60 seconds at each speed while EMG activit...
Advanced techniques in the diagnosis and management of infectious pulmonary diseases in horses. Techniques for novel approaches to the diagnosis and management of equine pulmonary disease continue to be developed and used in clinical practice. Diagnostic techniques involving immunoassays and nucleic acid-based tests not only decrease the time in which results become available but increase the sensitivity and specificity of test results. These assays do not substitute for careful clinical evaluation but can shorten the time to a confirmed accurate diagnosis, and thus allow for early initiation of therapeutic strategies and prevention protocols. With further understanding of the molecular ...
Measurement of abnormal respiratory sounds during over-ground exercise. The presence of abnormal respiratory sounds is commonly associated with obstructions of the upper respiratory tract. In order to establish their clinical significance measurements are required of both normal and abnormal respiratory sounds produced by horses exercising over-ground. Objective: To determine whether high quality recordings of respiratory sound can be made during over-ground exercise, and to develop a convenient measurement system that can be used to obtain respiratory sounds from horses exercising in field conditions. Methods: A range of prototypes was evaluated against the requi...
An unusual mucinous osteoma with features of an ossifying fibroma in the nasal cavity of a horse. A 4-month-old Warm-blooded colt presented with facial distorsion and an abnormal respiratory noise of 2 weeks' duration. A proliferative mass was found endoscopically and by computer tomography. Clinical differential diagnosis included cyst formation of the concha, malformation and neoplasia. Euthanasia was followed by post-mortem examination, which revealed a well-circumscribed, semi-solid, jelly like structure, measuring 14.5 x 9.0 x 12.0 cm, in the left posterior nasal cavity extending into the left frontal and maxillary sinus. Histologically, the mass consisted of trabeculae of woven bone,...
