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.
Bayly WM, Slocombe RF, Schott HC, Hines MT, Sides RH, Hakala JE.The possibility that pre-exercise inhalation of a bronchodilator by healthy horses could improve their mechanics of breathing and enhance performance was investigated. Ipratropium bromide (0.35 microg/kg bwt; n = 7) was administered by nebulisation 30 min before exercise and frusemide (1 mg/kg bwt; n = 6) was given in the same manner 2 h before exercise. Albuterol sulphate (360 and 720 microg; n = 7) were administered with a metered dose inhaler 2 h before exercise. Each drug was investigated independently of the others using cross-over protocols. Horses completed incremental exercise tests an...
Peroni JF, Horner NT, Robinson NE, Stick JA.Six normal, healthy horses age 3-10 years underwent left and right thoracoscopic examination using a rigid telescope. A minimum of 30 days was allowed between procedures. Horses were restrained in stocks and sedated with a continuous detomidine infusion. After surgical preparation of the hemithorax elected for surgery, and administration of local or regional anaesthesia of the surgery sites, thoracoscopy was completed during two 15 min pneumothorax periods. During the procedures, the thoracic structures were viewed using a 57 cm, 10 mm diameter, 30 degrees rigid telescope connected to a digita...
Takahashi T, Hiraga A, Ohmura H, Kai M, Jones JH.To determine the frequency of epistaxis during or after racing among racehorses and identify factors associated with development of epistaxis. Methods: Retrospective study. Methods: 247,564 Thoroughbred and 4,045 Anglo-Arab race starts. Methods: Race start information (breed, age, sex, racing distance, and race type) was obtained for Thoroughbred and Anglo-Arab horses racing in Japan Racing Association-sanctioned races between 1992 and 1997. All horses that raced were examined by a veterinarian within 30 minutes of the conclusion of the race; any horse that had blood at the nostrils was examin...
Derksen FJ, Holcombe SJ, Hartmann W, Robinson NE, Stick JA.To record respiratory sounds in exercising horses and determine whether spectrum analysis could be use to identify sounds specific for laryngeal hemiplegia (LH) and dorsal displacement of the soft palate (DDSP). Methods: 5 Standardbred horses. Methods: Respiratory sounds were recorded and pharyngeal pressure and stride frequency were measured while horses exercised at speeds corresponding to maximum heart rate, before and after induction of LH and DDSP. Results: When airway function was normal, expiratory sounds predominated and lasted throughout exhalation. After induction of LH, expiratory s...
Cornelisse CJ, Holcombe SJ, Derksen FJ, Berney C, Jackson CA.To determine the effect of a tongue-tie on upper airway mechanics in exercising horses. Methods: 5 Standardbreds. Methods: Peak inspiratory and expiratory tracheal and pharyngeal pressures and airflow were measured while horses exercised on a treadmill with and without a tongue-tie. Respiratory rate was also measured. Horses ran at speeds that corresponded to 50 (HR50), 75, 90 (HR90), and 100% of maximal heart rate. The tongue-tie was applied by pulling the tongue forward out of the mouth as far as possible and tying it at the level of the base of the frenulum to the mandible with an elastic g...
Beard WL, Holcombe SJ, Hinchcliff KW.To determine the effect of a tongue-tie on upper airway mechanics in clinically normal horses exercising on a treadmill following sternothyrohyoid myectomy. Methods: 6 Standardbreds. Methods: Upper airway mechanics were measured with horses exercising on a treadmill at 5, 8, and 10 m/s 4 weeks after a sternothyrohyoid myectomy was performed. Pharyngeal and tracheal inspiratory and expiratory pressures were measured by use of transnasal pharyngeal and tracheal catheters connected to differential pressure transducers. Horses were fitted with a facemask and airflow was measured by use of a pneumo...
Bettschart-Wolfensberger R, Freeman SL, Jäggin-Schmucker N, Clarke KW.To determine the minimal infusion rate of propofol in combination with medetomidine for long-term anesthesia in ponies and the effects of atipamezole on recovery. Methods: 12 ponies. Methods: Ponies were sedated with medetomidine (7 microg/kg of body weight, IV). Ten minutes later, anesthesia was induced with propofol (2 mg/kg, IV). Anesthesia was maintained for 4 hours, using an infusion of medetomidine (3.5 microg/kg per hour, IV) and propofol at a rate sufficient to prevent ponies from moving after electrical stimulation. Arterial blood pressures and blood gas analysis, heart rates, and res...
Herholz C, Straub R, Moens Y, Busato A.The shape of the volumetric capnogram is modified by airway obstruction, and the evaluation of this deformation could allow an indirect measurement of bronchial patency. The study included 35 horses; five horses without evidence of pulmonary disease (group I) and 30 horses suffering from different degrees of chronic obstructive pulmonary disease (COPD) (groups II-IV). Data of recorded CO2 and volume curves were off-line plotted and statistically analysed using regression analysis. Analyses were performed separately for fractions 25-95% (VTE25-95), 25-50% (VTE25-50) and 50-95% (VTE50-95) of exp...
Christley RM, Hodgson DR, Rose RJ, Hodgson JL, Wood JL, Reid SW.A matched case-control study was made of 100 thoroughbred horses which were coughing and 148 control horses which were free of clinical signs of respiratory tract disease. The variables identified by multivariable conditional logistic regression as being significantly associated with coughing included age (the risk decreased with age), the stage of training (horses in early training were at greatest risk), the time since the last race (horses that had never raced were at greatest risk) and the time since they were last transported (horses transported more than 14 days previously were more like...
King DS, Tulleners E, Martin BB, Parente EJ, Boston R.To describe the clinical findings in 52 racehorses with axial deviation of the aryepiglottic folds (ADAF) and to report outcome in 33 of these horses after either rest or transendoscopic laser excision of aryepiglottic fold tissue. Methods: Retrospective study. Methods: Racehorses admitted for high-speed treadmill (HST) evaluation of poor performance. Methods: Medical records and videotapes of resting and exercising videoendoscopic examinations were reviewed. Racing performance records and owner or trainer interviews, at least 1 year after HST examination, were used to compare results after ei...
MacKay RJ, Daniels CA, Bleyaert HF, Bailey JE, Gillis KD, Merritt AM, Katz TL, Johnson JC, Thompson KC.Ten horses were used in a crossover study to evaluate the effectiveness of eltenac against endotoxaemia. Eltenac (0.5 mg/kg bwt) or saline control was given i.v. then 15 min later, intravenous infusion of endotoxin was begun and continued for 120 min (total dose 100 ng/kg bwt). Horses were monitored for heart and respiratory rates, pulmonary and carotid arterial pressure and core body temperature. Blood was sampled at intervals for measurement of haematological variables and plasma concentrations of lactate, prostanoid metabolites, tumour necrosis factor (TNF) and stress hormones. In compariso...
Venugopal CS, Moore RM, Holmes EP, Koch CE, Seahorn TL, Beadle RE.To compare responses of bronchial rings obtained from healthy horses and horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) to selected mediators of airway hyperreactivity in vitro. Methods: Bronchial rings from 6 healthy horses and 6 horses affected with SPAOPD. Methods: Bronchial rings obtained from each group of horses were mounted in organ baths and attached to force transducers interfaced with a polygraph. After applying 2g of tension, each ring was allowed to equilibrate for 45 minutes in Tyrode's solution at 37 C. Cumulative concentration-response rela...
Hubbell JA, Hinchcliff KW, Schmall LM, Muir WW, Robertson JT, Sams RA.To determine the anesthetic, cardiorespiratory, and metabolic effects of 4 IV anesthetic regimens in Thoroughbred horses recuperating from a brief period of maximal exercise. Methods: 6 adult Thoroughbreds. Methods: Horses were preconditioned by exercising them on a treadmill. Each horse ran 4 simulated races, with a minimum of 14 days between races. Races were run at a treadmill speed that caused horses to exercise at 120% of their maximal oxygen consumption. Horses ran until fatigued or for a maximum of 2 minutes. Two minutes after exercise, horses received a combination of xylazine hydrochl...
Strand E, Martin GS, Haynes PF, McClure JR, Vice JD.To compare racing performance before and after prosthetic laryngoplasty for treatment of laryngeal neuropathy in inexperienced and experienced Thoroughbred racehorses. Methods: Retrospective study. Methods: 52 Thoroughbred racehorses treated with prosthetic laryngoplasty for laryngeal neuropathy. Methods: Lifetime race records were analyzed by use of a verified regression model. Individual race records and hospital records were also reviewed. Results: Experienced horses had a decline in performance, as measured by performance index, earnings percentage, and mean prediction error, during the 6-...
Freeman SL, Bowen IM, Bettschart-Wolfensberger R, England GC.The cardiopulmonary effects of romifidine at 80 microg/kg (R80) or 120 pg/kg (R120), and detomidine at 20 pg/kg (D20) when used as premedicants for ketamine/halothane anaesthesia were investigated in six ponies. Using a blinded crossover design, acepromazine (0-04 mg/kg) was administered followed by the alpha-2 agonist. Anaesthesia was induced with ketamine at 2.2 mg/kg and maintained with halothane (expired concentration 1.0 per cent) in oxygen for three hours. During anaesthesia, arterial blood pressure, cardiac index, PaO2 and PmvO2 decreased, and systemic vascular resistance and PaCO2 incr...
Hashikura S, Higuchi T, Taharaguchi S, Orita Y, Nanao Y, Takai S.The reliability of preparing bacteriological cultures from nasotracheal aspirates of foals routinely in order to diagnose R. equi pneumonia in foals was studied by isolating Rhodococcus equi from specimens obtained from 96 foals by nasotracheal aspiration with a silicon catheter. Results were compared with specimens obtained from 21 foals by transtracheal aspiration (percutaneous tracheal puncture). These 117 foals showed clinical signs of respiratory tract infection at sampling. R. equi was isolated from 14 of 21 (66.7%) specimens by transtracheal aspiration and from 59 of 96 (61.4%) specimen...
Booth TM, Hainisch EK, Knottenbelt DC, Edwards GB, Clegg PD, Kelly DF.An 11-year-old, eight-months pregnant mare suddenly developed severe respiratory distress. Endoscopic examination identified intralaryngeal granulation tissue obstructing the airway. In order to avoid general anaesthesia and the problems associated with a permanent tracheostomy, the mass was resected electrosurgically while the mare was standing. Patency was restored to the airway and the mare foaled without complication.
Bureau F, Delhalle S, Bonizzi G, Fiévez L, Dogné S, Kirschvink N, Vanderplasschen A, Merville MP, Bours V, Lekeux P.In most cells trans-activating NF-kappaB induces many inflammatory proteins as well as its own inhibitor, IkappaB-alpha, thus assuring a transient response upon stimulation. However, NF-kappaB-dependent inflammatory gene expression is persistent in asthmatic bronchi, even after allergen eviction. In the present report we used bronchial brushing samples (BBSs) from heaves-affected horses (a spontaneous model of asthma) to elucidate the mechanisms by which NF-kappaB activity is maintained in asthmatic airways. NF-kappaB activity was high in granulocytic and nongranulocytic BBS cells. However, NF...
McKenzie HC, Murray MJ.To compare concentrations of gentamicin in serum and bronchial lavage fluid after IV and aerosol administration of gentamicin to horses. Methods: 9 healthy adult horses. Methods: Gentamicin was administered by aerosolization (20 ml of gentamicin solution [50 mg/ml]) and IV injection (6.6 mg of gentamicin/kg of body weight) to each horse, with a minimum of 2 weeks between treatments. Samples of pulmonary epithelial lining fluid were collected by small volume (30 ml) bronchial lavage 0.5, 4, 8, and 24 hours after gentamicin administration. Serum samples were obtained at the same times. All sampl...
Steffey EP, Pascoe PJ, Woliner MJ, Berryman ER.To quantitate dose- and time-related anesthetic-sparing effects of xylazine hydrochloride (XYL) during isoflurane-induced anesthesia in horses and to characterize selected physiologic responses of anesthetized horses to administration of XYL. Methods: 6 healthy adult horses. Methods: Horses were anesthetized 2 times to determine the minimum alveolar concentration (MAC) of isoflurane in O2 and to characterize the anesthetic-sparing effect (MAC reduction) after IV administration of XYL (0.5 and 1 mg/kg of body weight, random order). Selected measures of cardiopulmonary function, blood glucose co...
Fenger CK, McKeever KH, Hinchcliff KW, Kohn CW.To determine components of the increase in oxygen consumption (VO2) and evaluate determinants of hemoglobin saturation (SO2) during incremental treadmill exercise in unfit horses. Methods: 7 unfit adult mares. Methods: Horses performed 1 preliminary exercise test (EXT) and 2 experimental EXT. Arterial and mixed venous blood samples and hemodynamic measurements were taken during the last 30 seconds of each step of the GXT to measure PO2, hemoglobin concentration ([Hb]), SO2, and determinants of acid-base state (protein, electrolytes, and PCO2). Results: Increased VO2 during exercise was facilit...
Robinson NE, Olszewski MA, Boehler D, Berney C, Hakala J, Matson C, Derksen FJ.During a trial to determine the dose response to the beta2-adrenergic agonist pirbuterol, we judged the severity of airway obstruction by use of a clinical scoring system and compared this to objective data obtained by quantitative measures of lung function. Six horses affected by recurrent airway obstruction were used in this trial. Four hundred and sixty-eight measurements of lung function and clinical scores were obtained from 13 measurement periods when horses received each of 6 doses of pirbuterol. Scores of 1-4 were assigned to degree of nasal flaring and abdominal effort and summed for ...
Langsetmo I, Meyer MR, Erickson HH.Exercise-induced pulmonary haemorrhage (EIPH) is characterised by blood in the airways after strenuous exercise and results from stress failure of the pulmonary capillaries. The purpose of this experiment was to establish a threshold value of transmural pulmonary arterial pressure at which haemorrhage occurs in the exercising horse. Five geldings, age 4-14 years, were run in random order once every 2 weeks at 1 of 4 speeds (9, 11, 13, 15 m/s); one day with no run was used as a control. Heart rate, pulmonary arterial pressure and oesophageal pressure were recorded for the duration of the run. T...
Raulo SM, Sorsa TA, Maisi PS.To determine whether samples of tracheal epithelial lining fluid (TELF) obtained from horses have elastinolytic activity characteristic of metalloproteinases, to compare elastinolytic activity in TELF obtained from healthy horses and horses with chronic obstructive pulmonary disease (COPD), and to determine whether chemically modified tetracycline-3 (CMT-3) inhibits elastinolytic activity in TELF ANIMALS: 10 horses with COPD and 10 healthy control horses. Methods: Zymography and fluorometry were used to measure elastinolytic activity, and EDTA was used to inhibit elastinolytic activity and ver...
Rush BR, Raub ES, Thomsen MM, Davis EG, Matson CJ, Hakala JE.To evaluate clinical response, pulmonary function, and adrenal gland response to incremental doses of beclomethasone dipropionate in horses with recurrent airway obstruction. Methods: Crossover trial. Methods: 8 horses with recurrent airway obstruction. Methods: Horses randomly assigned to 4 groups were treated twice daily via aerosol administration of placebo or 500, 1,000, or 1,500 micrograms of beclomethasone dipropionate in a crossover design with a 10-day minimum washout period. Subjective assessment of airway obstruction, serum cortisol concentration, and maximum change in pleural pressu...
Kumar P, Timoney JF, Southgate HH, Sheoran AS.The nasal turbinates of 5 young horses were studied by light and scanning electron-microscopy. Stratified cuboidal epithelium lined the rostral part of the dorsal and ventral nasal turbinates of the vestibular region. The polyangular microvillus cells of this region were separated by linear depressions. The mid and caudal parts of the dorsal and ventral nasal turbinates and the rostral part of the ethmoturbinates were lined by pseudostratified columnar ciliated respiratory epithelium. Numerous cilia with dilated blebs on the ciliated cells concealed adjacent non-ciliated supporting cells and g...
Jansson N, Ducharme NG, Hackett RP, Mohammed HO.To examine the effect of cordopexy, laryngoplasty, and cordopexy combined with a modified laryngoplasty on airway mechanics. Methods: Experimental airway mechanics were determined by subjecting equine cadaveric larynges to airflows similar to inspiratory airflow of exercising horses. Methods: Twenty equine larynges. Methods: Using cadaveric larynges, we developed and tested a new technique of arytenoid cartilage abduction. All larynges had the right arytenoid cartilage abducted to mimic the degree of arytenoid abduction that occurs at maximal exertion in live horses. Three surgical techniques ...
Christley RM, Rose RJ, Hodgson DR, Reid SW, Evans S, Bailey C, Hodgson JL.This study evaluated a questionnaire investigating the attitudes and behaviours of veterinarians regarding the cause, diagnosis and treatment of lower respiratory-tract disease in racehorses. The questionnaire was sent to all non-student members (648) of the Australian Equine Veterinary Association: two mailings and a single telephone contact (each separated by four weeks). Subsequent phases were only administered to those who had not responded to earlier phases. In total, 467 (72.1%) of the 648 mailed questionnaires were returned. Of these, 354 were usable. The remaining 113 respondents gave ...
Ebert R.A retrospective study was performed on 271 horses with colic referred to the I. Medizinische Tierklinik within a period of 2 years, to examine the prognostic value of different clinical and diagnostic laboratory parameters by Student's t-test and the Chi-quadratic test. The following quantitative parameters presented a highly significant prognostic value (P < 0.0001): capillary refill time, pulse rate, heart rate, respiratory rate, hematocrit, hemoglobin concentration, blood lactate, base excess and anion gap. The intensity of colic signs, the degree of disturbance of the patient's gen...
Vail KJ, Stranahan LW, Richardson LM, Yanchik AE, Arnold CE, Porter BF, Wiener DJ.Mycobacterial infections in horses are uncommon, but are caused most frequently by Mycobacterium bovis of the Mycobacterium tuberculosis complex or Mycobacterium avium of the M. avium complex. Disease caused by Mycobacterium intracellulare, the second most common species within the M. avium complex, has not been reported in horses to date. Mycobacteriosis in horses most often presents as enteric, pulmonary or, rarely, systemic disease. Here we report a case of M. intracellulare infection in a horse presenting as a granulomatous nasal mass.
Crandall A, Hopster K, Grove A, Levine D.In horses undergoing castration, direct comparison of intratesticular lidocaine vs mepivacaine as analgesic adjuncts has not yet been analysed. Objective: To compare the effects of intratesticular lidocaine and mepivacaine during equine castration using the Henderson drill under total intravenous anesthesia. Methods: Randomised, double-blinded clinical study. Methods: Thirty-four stallions were anaesthetised using xylazine-ketamine and randomly selected to receive 10 mL either lidocaine or mepivacaine injected into each testicle. Both surgeon and anaesthetist were blinded to the selected trea...
Ainsworth DM, Smith CA, Eicker SW, Ducharme NG, Henderson KS, Snedden K, Dempsey JA.In exercising quadrupeds, limb movement is often coupled with breathing frequency. This finding has lead some investigators to conclude that locomotory forces, associated with foot plant, abdominal visceral displacements or lumbo-sacral flexion, are the primary determinants of airflow generation. Analysis of respiratory muscle electrical activation (EMG) and contraction profiles in chronically instrumented dogs and horses, along with measurements of esophageal pressure (Pes) changes and limb movements, provide evidence that each breath during the exercise hyperpnea is determined by respiratory...
Pre-clinical studies on human isolated bronchi have relevant translational value in human in vivo, conversely no investigation has been performed to assess whether data resulting from equine isolated airways can have any translational application in asthmatic horses. Thus, a meta-regression analysis via random-effect method was carried out to correlate the pharmacological characteristics of bronchodilators resulting from experiments performed in equine isolated bronchi with their impact on the lung function outcomes in asthmatic horses. Data on the potency of different bronchodilators were ext...
Soma LR, Beech J, Gerber NH.The effect of disodium cromoglycate (cromolyn) in preventing the pulmonary dysfunction caused by the inhalation of barn and hay dust was studied in 5 horses with confirmed chronic obstructive pulmonary disease (COPD). The horses were studied before (Con) and after exposure to hay and dust allergens (Expos) and after pretreatment with cromolyn followed by exposure (Cr-Expos). There was a significant reduction in PaO2 from 86.8 +/- 8.3 to 73.1 +/- 8.8 when the horses were exposed to hay and dust allergens. The PaO2 after pretreatment with cromolyn and exposures was 78.1 +/- 5.5. There were no si...
Kirschvink N, Art T, Smith N, Lekeux P.To test whether isoprostanes could be used as markers of oxidative stress in horses, their concentration was determined in plasma and in pulmonary epithelial lining fluid (PELF) in 3 models of oxidative stress: (1) strenuous exercise, (2) acute COPD crisis and (3) exercise combined with COPD crisis. Four horses were investigated twice, once in crisis and once in remission. The animals underwent a standardised treadmill exercise test. Isoprostane assessment was performed in plasma and bronchoalveolar lavage fluid 24 h before and 1 h after exercise and in plasma also immediately after exercise. ...
Watney GC, Jordan C, Hall LW.The effects of halothane, enflurane and isoflurane on bronchial calibre were investigated in five anaesthetized ponies using a computer-aided forced airflow oscillation technique to derive specific lower airways conductance (s.Glaw) and expiratory reserve volume (ERV). All the agents tended to increase s.Glaw (indicating bronchodilatation), but ERV was reduced by halothane and enflurane, and increased by isoflurane. It was concluded that the effects of these agents on bronchomotor tone were similar to those which occur in man. However, the reasons for the differences in their effects on ERV co...
Doherty TJ, Geiser DR, Rohrbach BW.This study determined the effects of epidurally administered morphine, ketamine and butorphanol on halothane minimum alveolar concentration (MAC) in ponies. Seven ponies were anaesthetised with thiopentone and succinylcholine, intubated and anaesthesia maintained with halothane. Ventilation was controlled and blood pressure was maintained within normal limits. Following the determination of baseline halothane MAC for the pelvic and thoracic limbs the ponies were given morphine (0.1 mg/kg bwt), ketamine (0.8 or 1.2 mg/kg bwt), butorphanol (0.05 mg/kg bwt) or saline, epidurally, to a final volum...
Hanka J, van den Hoven R, Schwarz B.Cor pulmonale is considered an uncommon complication in horses with recurrent airway obstruction (RAO). This case report describes the history, clinical and further examination findings, treatment, progression and outcome of a horse diagnosed with cor pulmonale and paroxysmal atrial fibrillation of 2 days duration due to a severe exacerbation of RAO. To our best knowledge, this is the first report of RAO induced pulmonary hypertension in a horse causing atrial fibrillation. However, even severe cardiac changes due to respiratory dysfunction seem to be largely reversible in horses.
Lindegaard C, Husted L, Ullum H, Fjeldborg J.Endoscopy of the upper airways of horses is used as a diagnostic tool and at purchase examinations. On some occasions it is necessary to use sedation during the procedure and it is often speculated that the result of the examination might be influenced due to the muscle-relaxing properties of the most commonly used sedatives. Objective: To evaluate the effect of detomidine (0.01 mg/kg bwt) and acepromazine (0.05 mg/kg bwt) on the appearance of symmetry of rima glottidis, ability to abduct maximally the arytenoid cartilages and the effect on recurrent laryngeal neuropathy (RLN) grade. Methods: ...
Perkins JD, Hughes TK, Brain B.To describe and evaluate the use of a transoral, endoscope-guided technique for transection of an entrapping epiglottic fold in sedated standing horses. Methods: Retrospective study. Methods: Horses (n=16) with epiglottic fold entrapment (EFE). Methods: Medical records (2005-2006) of 16 horses with EFE were reviewed to determine history, physical and endoscopic examination findings, postoperative complications, and outcome after axial division of EFE using a hooked bistoury, under an endoscopic-guided, transoral approach. Results: EFE was confirmed by endoscopy. Axial division was successfully...
Olszewski MA, Robinson NE, Derksen FJ.In vitro responses of equine small peripheral airways (SA) and lung parenchyma (LP) were studied. We examined their contractile and relaxant responses and investigated effects of histamine, and endogenous prostanoids as these mediators may play a role in development or recurrent airway obstruction in horses (heaves). SA and LP electrical field stimulation (EFS) induced nearly maximal and partial frequency-dependent contractions, respectively. These contractions were virtually abolished in SA but only partially inhibited in LP by atropine (ATR) and tetrodotoxin (TTX). Methacholine (MCh) contrac...
Hornof WJ, Dunlop CI, Prestage R, Amis TC.Six horses were anesthetized and placed in lateral recumbency for 1 hour and then were turned to the opposite side for an additional hour. A short-lived radioactive gas, 81mKr, was used to determine the relative spatial distribution of ventilation (V) and perfusion (Q) in these horses. Effects of time, side down, and turning on the distribution were evaluated. A consistent gradient of V/Q was found at all times, with the highest V/Q values at the top (non-dependent) portion of the lung field and the lowest at the bottom (dependent). This gradient was also present within each lung, as well as b...
Greene HM, Wickler SJ, Anderson TP, Cogger EA, Lewis CC, Wyle A.Arterial and venous blood were analysed at rest and post exercise for pH, PCO2, and PO2, and bicarbonate ([HCO3-]), base excess (BE), and strong ion difference (SID) were calculated in response to a 10 day sojourn to 3800 m. Pulmonary artery pressures (PAP) were measured at rest. Post exercise samples were restricted to venous blood. The equids (n = 6) experienced a profound hypoxia-hypocapnia and a respiratory alkalosis. PaO2 decreased 42% and PaCO2 41%. PaCO2 increased to 80% of initial values after 8 days at altitude. Arterial [HCO3-] decreased by 34%; however, it returned to normal by Day ...
Kruger K, Stegmann GF, Becker PJ.To characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine. Methods: Prospective four-period, four-treatment, blinded, randomized, crossover trial. Methods: Five, healthy, mixed breed horses. Methods: Prior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg(-1) ) romifidin...
Schlocker N, Gerber-Bretscher R, von Fellenberg R.In a search of viral agents in pulmonary macrophages of horses with chronic pulmonary disease, equine herpesvirus 2 was found to be unique. In 8 of 9 horses with chronic pulmonary disease, antigens of equine herpesvirus 2 were detected by indirect immunofluorescence staining of scattered foamy macrophages immediately after harvesting by bronchoalveolar lavage and fractionation on metrizamide gradients. In a healthy horse, antigens were not found. After 1 week of cultivation of bronchoalveolar lavage cells from a second group of 9 horses with chronic pulmonary disease, viral antigens were detec...
Cascardo B, Bernardes C, de Souza GN, Silva KM, Pires NR, de Alencar NX, Lessa DAB.Lower airway cytology has been proposed as a complementary diagnostic method to confirm the presence and quantifying the severity of exercise-induced pulmonary hemorrhage (EIPH). Bronchoalveolar lavage is usually preferred over tracheal wash (TW), yet the need for sedation imposes as a limitation for active sport horses in addition to be a highly invasive technique. This study aims to evaluate the diagnostic value of TW with Total Hemosiderin Score (THS) for monitoring EIPH in active Thoroughbred racehorses. A sampling of 47 randomly selected Thoroughbreds were endoscopically examined for EIPH...
Heinonen E, Nyman G, Meriläinen P, Högman M.Dependent atelectatic lung areas open towards the end of inspiration when the lung opening pressure increases, and recollapse during expiration. We hypothesized that inhaled nitric oxide (NO) counteracts hypoxic vasoconstriction in these collapsing lung areas, resulting in increased pulmonary shunt perfusion. Methods: We administered NO as a pulse and varied the pulse timing during inspiration in equine anaesthesia, where atelectasis develops regularly. Six spontaneously breathing standard breed trotters were studied under isoflurane anaesthesia in lateral recumbency. NO pulsed into the first ...
McDonough P, Kindig CA, Erickson HH, Poole DC.The exercising Thoroughbred horse (TB) is capable of exceptional cardiopulmonary performance. However, because the ventilatory equivalent for O2 (VE/VO2) does not increase above the gas exchange threshold (Tge), hypercapnia and hypoxemia accompany intense exercise in the TB compared with humans, in whom VE/VO2 increases during supra-Tge work, which both removes the CO2 produced by the HCO buffering of lactic acid and prevents arterial partial pressure of CO2 (PaCO2) from rising. We used breath-by-breath techniques to analyze the relationship between CO2 output (VCO2) and VO2 [V-slope lactate t...
Gerber V, De Feijter-Rupp H, Wagner J, Venta P, Harkema JR, Robinson NE.Airway mucus accumulation is associated with indoor irritant and allergen exposure in horses with recurrent airway obstruction (RAO). Epidermal growth factor receptor (EGFR) and a chloride channel (calcium activated, family member 1; CLCA1) are key signalling molecules involved in mucin gene expression. Objective: We hypothesised that exposure to irritants and aeroallergens would lead to increased expression of the mucin gene eqMUC5AC and increased stored mucosubstance in the airways of RAO-affected horses, associated with increased neutrophils and CLCA1 and EGFR mRNA levels. Methods: We perfo...
Willoughby RA, Ecker GL, McKee SL, Riddolls LJ.Mucociliary clearance rates from the trachea were determined in normal, sedated, diseased and exercised horses from scintigraphs obtained after an injection of technetium-99m sulphide colloid into the tracheal lumen. The group mean tracheal clearance rate of eight clinically normal horses during 42 trials was 2.06 +/- 0.38 cm/min. Significant between horse differences were found (p less than 0.05). When six and seven of these horses were given xylazine and detomidine hydrochloride, respectively, mean group tracheal clearance rates dropped significantly (p less than 0.05). The decreases from ea...
Hopster K, D￮ LR, Hopster-Iversen CCS, Driessen B.OBJECTIVE To evaluate efficacy of an alveolar recruitment maneuver (ARM) with positive end-expiratory pressures (PEEPs) in anesthetized horses ventilated with oxygen or heliox (70% helium and 30% oxygen). ANIMALS 6 healthy adult horses. PROCEDURES In a randomized crossover study, horses were anesthetized and positioned in dorsal recumbency. Volume-controlled ventilation was performed with heliox or oxygen (fraction of inspired oxygen [Fio] > 90%). Sixty minutes after mechanical ventilation commenced, an ARM with PEEP (0 to 30 cm HO in steps of 5 cm HO every 5 minutes, followed by incremental s...
Klein JP, Forster HV, Bisgard GE, Kaminski RP, Pan LG, Hamilton LH.The purpose of these studies was to gain insight into mechanisms regulating pulmonary ventilation (VE), arterial CO2 partial pressure (PaCO2), and arterial pH (pHa) in ponies when inspired CO2 partial pressure (PICO2) is above normal. Ponies were studied four times daily each weekday for 2 wk in an environmental chamber. Each study consisted of a 15-min control period (PICO2 = 0.7 Torr) followed by a 15- to 30-min experimental period during which PICO2 in the chamber was 0.7, 7, 14, 21, 28, or 42 Torr (PIO2 = 147 Torr throughout). Between 11 and 15 min of each period, four 3-ml samples of arte...
Mosing M, Senior JM.In the first edition of this journal, Barbara Weaver wrote a review titled 'Equine Anaesthesia', stating that, at that time, it was quickly becoming accepted practice that many horses were being anaesthetised 'by essentially similar procedures, i.e. premedication, induction and then maintenance by controlled inhalation'. To celebrate the 50th anniversary of the first edition of this journal, this review covers the development of understanding and practice of inhalational anaesthesia and controlled ventilation in horses over the last 50 years. We review how the perceived benefits of halothane ...
Grandy JL, Steffey EP, Miller M.Arterial blood was collected from 25 clinically normal horses immediately before and serially throughout the first hour of halothane oxygen anaesthesia. Blood was analysed for oxygen and carbon dioxide partial pressure (PaO2, PaCO2). Measurements of inspired oxygen concentration during anaesthesia permitted direct correlation with blood gases. Horses were divided arbitrarily into two groups based on their age: two to seven years, n = 15; over seven years, n = 10. Average (+/- sd) PaO2 and PaCO2 was 14.1 +/- 1.5 kPa (106 +/- 11 mmHg) and 5.9 +/- 0.6 kPa (44.4 +/- 4.4 mmHg) respectively in consc...
Viljoen A, Saulez MN, Donnellan CM, Bester L, Gummow B.Medical records of equine after-hours admissions from 1998 to 2007 are reviewed. Data extracted from the medical records included signalment, reason for admission, pre-admission treatment, clinical presentation, procedures performed, final diagnoses, complications occurring in hospital, length of stay and outcome. Eight hundred and twenty after-hours admissions were available of which 75% were classified as emergencies. Most horses originated from Gauteng province (82%), with Thoroughbred, Arabian, and Warmbloods representing 46%, 10% and 7% of horses. Horses had a median age of 7 years and we...
Pozzoli C, Bertini S, Poli E, Placenza G, Menozzi A.β-adrenoceptor agonists are considered the most effective drugs to counteract bronchoconstriction in horses with asthma, but only clenbuterol is commonly employed in clinical practice. We evaluated the effects of different selective β agonists: clenbuterol, ritodrine, salbutamol, and fenoterol on the contractions of isolated bronchial muscle of horses induced by electrical field stimulation (EFS), carbachol, histamine, and KCl. All β agonists reduced the amplitude of contraction induced by the different stimuli but with variable efficacy and potency. Fenoterol and salbutamol were more effec...
Herholz C, Straub R, Busato A.Several indices of ventilatory heterogeneity can be identified from the volumetric capnogram and its graphic presentation, the single-breath diagram for CO2 (SBD-CO2). Physiologically based indices of pulmonary function (VTE, VCO2, FACO2, VDBohr% VDBohr%, VD/VTE, A1/A2) were calculated for healthy horses (group I, n = 5) and for horses with subclinical (group II, n = 7) or clinically manifest chronic obstructive pulmonary disease (COPD) (group III, n = 8) during tidal breathing and after medication with lobelin hydrochloride (Lobelin). We investigated the variability and repeatability of the l...
Yu MF, Wang ZW, Robinson NE, Derksen FJ.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...
