Ventilation for horses involves the process of moving air in and out of the lungs to facilitate gas exchange, which is essential for maintaining respiratory health and overall well-being. Proper ventilation is influenced by various factors, including stable design, airflow patterns, and environmental conditions. It helps in regulating temperature, humidity, and the removal of airborne contaminants such as dust, ammonia, and pathogens. Effective ventilation systems aim to provide a consistent supply of fresh air while minimizing drafts and temperature fluctuations. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, design considerations, and impacts of ventilation on equine respiratory health and performance.
Lloyd KC, Kelly AB, Dunlop CI.A foal born 3 weeks prematurely was treated for respiratory distress, using a combination of oxygen therapy and mechanical ventilatory assistance. Clinical response and arterial blood gas tensions were monitored regularly. Continuous positive-airway pressure and intermittent positive-pressure ventilation administered via a nasotracheal tube were effective in improving arterial oxygenation and ventilatory function.
Gleed RD, Dobson A.Observations were made on horses spontaneously breathing oxygen, with halothane at a constant end tidal concentration. The horses were positioned in dorsal recumbency for the first 45 minutes of each anaesthetic episode during which the arterial oxygen tension (PaO2) was found to peak and then decline. The remaining 60 minutes of each anaesthesia was used to test the effect of various manoeuvres on PaO2. The PaO2 of horses decreased further both when remaining in dorsal recumbency and when repositioned in right or left recumbency. In contrast, placing the horses in sternal recumbency for these...
Hedenstierna G, Nyman G, Kvart C, Funkquist B.The multiple inert gas elimination technique was adapted for use in the conscious standing horse. The modifications included increased infusion rate of the inert gases (30 ml/min), extended infusion time (60 mins) in order to reach steady state, and construction of a nose mask mixing box system for collection of expired gas. Eight adult horses with a mean weight of 454 kg and a mean age of 6.1 years were studied while standing under resting conditions. Ventilation was 65.2 liters/min and cardiac output measured by thermodilution 40.2 liters/min. Systemic and pulmonary artery mean pressures wer...
Webster AJ, Clarke AF, Madelin TM, Wathes CM.The concentration of fungal spores, the main constituents of respirable dust in stables, is determined by rates of release from fodder and bedding and rate of clearance, principally by ventilation. This paper outlines the principles that govern the application of natural ventilation to the control of air hygiene in barns and individual boxes for horses. When release rates are low, ventilation rates over four air changes per hour are satisfactory. Ventilation was satisfactory in individual boxes but usually unsatisfactory in barns and specific recommendations are made for improvement. Prelimina...
Dunlop CI, Steffey EP, Miller MF, Woliner MJ.Cardiopulmonary function was monitored in 6 non-medicated, healthy male horses, anesthetized with halothane or isoflurane in O2 at a constant dose (1.2 times the minimum alveolar concentration). Horses were exposed once to each anesthetic agent, and a minimum of 2 weeks separated anesthetic exposures. All horses were studied in left lateral recumbency, and ventilation was mechanically controlled to induce a PaCO2 of 35 to 45 mm of Hg and an inspiratory peak airway pressure of 18 to 22 cm of H2O. After 1 hour of horse preparation, constant conditions were begun. With duration of anesthesia, car...
Stewart JH, Young IH, Rose RJ, Costas L, Barko AM.The distributions of ventilation-perfusion ratios, and the effects of 100% oxygen administration on the distributions, were studied in 3 foals from 4h to 9 days of age, using the multiple inert gas elimination technique. The distributions were calculated from the pulmonary clearance of 6 inert gases following infusion into a peripheral vein of a solution containing the inert gases. The results from a total of 8 studies showed several consistent features. The major findings were (i) the absence of low ventilation-perfusion ratios, i.e. regions where blood flow was greatly in excess of ventilati...
Orr JA, Erichsen DF, Shirer HW, Allen PL, Payne PA.The aim of this study was to determine whether increases in ventilation would occur during intravenous acid infusion even if systemic arterial pH was held constant. In six awake ponies, HCl (500 ml, approximately 0.312 M) was infused into the right atrium at a total dose of 1.0 meq/kg over 18 min while an equivalent dose of NaOH was infused into the left heart to restore systemic arterial pH to normal. Total ventilation increased at the onset of the infusion and remained elevated although systemic arterial pH was normal to slightly alkaline. The increase in ventilation during the initial 2 min...
Robinson NE.The primary function of the equine respiratory system is the exchange of oxygen and carbon dioxide at a rate that is matched to metabolism. Gas exchange requires ventilation, distribution of gas within the lung, perfusion of blood through pulmonary capillaries, matching of ventilation and blood flow, diffusion of gases between air and blood, and transport of gases to and from the muscles. In this article, the author reviews what is known about each of these processes in the resting and exercising horse.
Orr JA, Fraser DB, Shirer HW, Wagerle LC, DeSoignie RC.Carbon dioxide concentrations were increased during expiration in the upper one-half of the trachea, pharynx, and nasal sinuses to determine if elevation of upper airway CO2 would alter breathing or arterial blood gases in the awake pony. Carbon dioxide (100%) was injected into the midcervical trachea via a chronically implanted transcutaneous cannula during the first part of the animal's expiration. This maneuver elevated upper airway expiratory CO2 concentrations but prevented any exogenous CO2 from entering the lung and being absorbed into the arterial blood. Twelve experiments were perform...
Schatzmann U, Koehli M, Dudan F, Rohr W, Jones RS.Certain circulatory and respiratory values were measured in horses in the standing, lateral, and supine positions. Twelve adult horses were kept in the standing position under the influence of glycerol guiacolate. Alterations in position to lateral and dorsal recumbencies were achieved without any further drug administration. The changes from the standing to the lateral position decreased the arterial oxygen tension, but left the arterial carbon dioxide tension unchanged. There was no statistically significant effect of body position on respiratory flow rates or volumes. The shift from the lat...
Sainsbury DW.The physiological requirements of the horse appear to be reasonably well established and should be adequately provided by ventilation based on straightforward principles, relying largely on natural air flow. On the other hand, there are few objective values for ventilation required to promote good health or alleviate equine respiratory disease. In the absence of such knowledge it is only possible to rely on a logical application of sound principles and experience. Both indicate the satisfactory nature of ventilation by stack effect, aspiration and perflation. Buildings should be well insulated...
Riebold TW, Evans AT, Robinson NE.Arterial blood gas values, rate of pulmonary nitrogen washout, respiratory rate, arterial blood pressure, heart rate, and cardiac output were determined during ventilation of six anesthetized horses, with a demand valve. The horses were allowed to ventilate spontaneously, or intermittent positive pressure ventilation was utilized. When compared with spontaneous ventilation, intermittent positive pressure ventilation caused a significant increase in the rate of pulmonary nitrogen washout and a significant decrease of arterial carbon dioxide. It was concluded that intermittent positive pressure ...
Orr JA, Busija DW.Unanesthetized ponies were given 4% CO2 (inspired CO2 pressure = 28 Torr) to breathe at two levels of arterial O2 pressure (PaO2): 1) near 75 Torr and 2) near 200 Torr. During 4% CO2 breathing, at either level of PaO2, the mean arterial CO2 pressure (PaCO2) was unchanged from control measurements (control measurements were made at the same PaO2, but with no CO2 in inspired air), suggesting that awake ponies can "clear" 4% CO2. The ability of individual ponies to clear 4% CO2 was quite variable: some ponies did not clear 4% CO2 and others cleared 4% CO2 on one day but not on the following day. ...
McPherson EA, Lawson GH, Murphy JR, Nicholson JM, Breeze RG, Pirie HM.Breed, age, weight, type of work performed, seasonal onset, poor ventilation and exposure to moulds in the habitat were investigated in relation to the occurrence of chronic obstructive pulmonary disease (COPD). COPD was most commonly detected in showjumping and hacking horses. The older a horse, the more likely it was to become affected although most were 6 to 10 years of age. Of the horses in this sample of the population, which was not a random one, thoroughbred horses were affected least and ponies most often. The high incidence in ponies was related to their more frequent exposure to poor...
Bisgard GE, Forster HV, Byrnes B, Stanek K, Klein J, Manohar M.Ventilation, metabolism, arterial blood gases, and blood and cerebrospinal fluid (CSF) acid-base status were measured in exercise studies on seven ponies during mild, moderate, and near-maximal treadmill exercise. CSF and arterial blood were sampled via indwelling catheters. Generally measurements were made during the 3rd, 6th, and 9th minute of steady-state exercise, with CSF sampled only during the 9th minute. Alveolar ventilation (VA) and metabolic rate (VO2) increased proportionately during exercise below the anaerobic threshold, but above this threshold, VA increased at a faster rate than...
Steffey EP, Howland D.The minimal alveolar concentration (MAC) of halothane which just prevented purposeful movement in response to electrical stimulation was determined in 11 young, healthy, unpremedicated horses breathing oxygen (O2) or nitrous oxide (N2O) and O2. Ventilation was controlled during these MAC studies. The arterial PO2 was always greater than 90 mm of Hg and the average PaCO2. range was 36 to 40 mm of Hg. The MAC for halothane in O2 was 0.93 vol %. Alveolar N2O concentrations of 25% and 50% reduced the halothane MAC about 12% and 25%, respectively. In 8 of these horses, the cardiovascular effects of...
Forster HV, Bisgard GE, Dempsey JA, Orr JA.Numerous studies have demonstrated the existence of an intracranial [H+] chemoreceptor mechanism capable of stimulating ventilation. 1 Supposedly, this chemoreceptor is located 0.2 mm below the surface of the ventrolateral side of the medulla and is responsive to [H+] in the surrounding cerebral extracellular fluid (ECF). During chronic conditions, ECF [H+] is supposedly in equilibrium with CSF [H+]; hence, stimulus level can be established through sampling and analysis of CSF. In this presentation, we summarize data from studies on spontaneously breathing, unanesthetized ponies which suggests...
Steffey EP, Wheat JD, Meagher DM, Norrie RD, McKee J, Brown M, Arnold J.Effects of body position and type of ventilation were determined on arterial blood gases (PaO2, PaCO2) and pH during and immediately following clinical halothane anesthesia in 36 young, physically conditioned horses. Horses in dorsal recumbency had a lower PaO2 than did similarly breathing horses in a lateral position. Predictably controlled positive-pressure ventilation inproved arterial oxygenation and permitted maintenance of a normal PaCO2. Most horses, regardless of type of ventilation and operative body positioning, were hypoxemic in the immediate postanesthetic period.
Hall SA.A brief historical review is given of the incidence and types of respiratory disease that occurred in Britain in the 18th and 19th centuries. The significance of poor stabling and overcrowding in the causation and spread of coughing is emphasised and its dramatic reduction by simple methods of hygiene and ventilation.
Forster HV, Bisgard GE, Rasmussen B, Orr JA, Buss DD, Manohar M.The present study was designed to provide further insight into the role of the carotid and aortic chemoreceptors in ventilatory (VE) acclimatization during sojourn at altitude. Measurements were made: 1) on 10 ponies near sea level (SL, 740 Torr) under normal conditions, 2) on 6 of these at SL following chemoreceptor denervation (CD), and 3) subsequently on all 10 during 4 days of hypobaric hypoxia (PaO2 = 40-47 Torr). CD resulteo in hypoventilation at SL (deltaPaCO2 = d8 Torr, P less than 0.05), and it prevented hyperventilation normally observed with injection of NaCN and acute exposure to h...
Bisgard GE, Forster HV, Orr JA, Buss DD, Rawlings CA, Rasmussen B.Seven ponies were subjected to carotid body denervation (CD) and two ponies were sham operated (S). Measurement of arterial blood gases and arterial blood and cerebrospinal fluid (CSF) acid-base balance were made prior to and 1,2,4,9, and 17 wks after surgery in unanesthetized animals. Resting ventilation and ventilatory responsiveness to hypoxia and NaCN infusion were assessed prior to and 2,9, and 17 wks after surgery. Alveolar hypoventilation in the CD ponies was marked 1-2 wk after surgery when VE and VA were reduced 40% and 10%, respectively, from control and PaCO2 was 12-15 mmHg above co...
Orr JA, Erichsen DF, Shirer HW, Allen PL, Payne PA.The aim of this study was to determine whether increases in ventilation would occur during intravenous acid infusion even if systemic arterial pH was held constant. In six awake ponies, HCl (500 ml, approximately 0.312 M) was infused into the right atrium at a total dose of 1.0 meq/kg over 18 min while an equivalent dose of NaOH was infused into the left heart to restore systemic arterial pH to normal. Total ventilation increased at the onset of the infusion and remained elevated although systemic arterial pH was normal to slightly alkaline. The increase in ventilation during the initial 2 min...
Kerr CL, Keating SCJ, Arroyo LG, Viel L.Neonatal foals may require prolonged sedation to permit ventilatory support in the first few days of life. The objective of this study was to evaluate and compare the cardiopulmonary effects and clinical recovery characteristics of 2 sedative/analgesia protocols in healthy foals receiving assisted ventilation. Foals were randomized to receive dexmedetomidine, butorphanol, and propofol (DBP) or midazolam, butorphanol, and propofol (MBP) during a 24-hour period. Infusion rates of dexmedetomidine, midazolam, and propofol were adjusted and propofol boluses administered according to set protocols t...
Riebold TW, Evans AT, Robinson NE.Arterial blood gas values, rate of pulmonary nitrogen washout, respiratory rate, arterial blood pressure, heart rate, and cardiac output were determined during ventilation of six anesthetized horses, with a demand valve. The horses were allowed to ventilate spontaneously, or intermittent positive pressure ventilation was utilized. When compared with spontaneous ventilation, intermittent positive pressure ventilation caused a significant increase in the rate of pulmonary nitrogen washout and a significant decrease of arterial carbon dioxide. It was concluded that intermittent positive pressure ...
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...
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...
Orr JA, Fraser DB, Shirer HW, Wagerle LC, DeSoignie RC.Carbon dioxide concentrations were increased during expiration in the upper one-half of the trachea, pharynx, and nasal sinuses to determine if elevation of upper airway CO2 would alter breathing or arterial blood gases in the awake pony. Carbon dioxide (100%) was injected into the midcervical trachea via a chronically implanted transcutaneous cannula during the first part of the animal's expiration. This maneuver elevated upper airway expiratory CO2 concentrations but prevented any exogenous CO2 from entering the lung and being absorbed into the arterial blood. Twelve experiments were perform...
Bukoski A, Hodgson D, Downs J, LeBert C, Thombs L, Bailey J.To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. Methods: Randomized, crossover design. Methods: A total of 10 healthy adult horses from a university-owned herd. Methods: Following xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (FiO) = 0.3 initially, with subsequent titration to maintain PaO ≥ 85 mmHg (11.3 kPa)]. Horses ...
Kähn W, Palmer J, Vaala W.Various techniques for support and control of respiration in neonatal foals are described. It is crucial to evaluate respiration through frequent arterial blood gas analysis. Details for blood sampling from the metatarsal arteries and interpretation of results are provided. Typical diseases in newborn foals, which cause hypoxemia and/or hypercapnia and can be indications for respiratory support are apnea, hypopnea, pulmonary atelectasis, surfactant deficiency, meconium-, fetal fluid- and milk aspiration, maladjustment syndrome, cardiovascular abnormalities, anemia, airway obstruction, compromi...
Steffey EP, Howland D.The minimal alveolar concentration (MAC) of halothane which just prevented purposeful movement in response to electrical stimulation was determined in 11 young, healthy, unpremedicated horses breathing oxygen (O2) or nitrous oxide (N2O) and O2. Ventilation was controlled during these MAC studies. The arterial PO2 was always greater than 90 mm of Hg and the average PaCO2. range was 36 to 40 mm of Hg. The MAC for halothane in O2 was 0.93 vol %. Alveolar N2O concentrations of 25% and 50% reduced the halothane MAC about 12% and 25%, respectively. In 8 of these horses, the cardiovascular effects of...
Hopkins SR, Bayly WM, Slocombe RF, Wagner H, Wagner PD.During short-term maximal exercise, horses have impaired pulmonary gas exchange, manifested by diffusion limitation and arterial hypoxemia, without marked ventilation-perfusion (VA/Q) inequality. Whether gas exchange deteriorates progressively during prolonged submaximal exercise has not been investigated. Six thoroughbred horses performed treadmill exercise at approximately 60% of maximal oxygen uptake until exhaustion (28-39 min). Multiple inert gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained at rest and 5-min intervals during exercise. Oxygen uptake, cardiac ...
Crumley MN, Hodgson DS, Kreider SE.To measure the effects of tidal volume, ventilatory frequency, and oxygen insufflation flow on the fraction of inspired oxygen in cadaveric horse heads attached to a lung model. Methods: 8 heads of equine cadavers. Methods: Each cadaveric horse head was intubated with a nasotracheal tube that extended into the proximal portion of the trachea. Oxygen was delivered through an oxygen catheter contained within and extending to the tip of the nasotracheal tube. The trachea was connected to the lung model by use of a spiral-wound hose with a sampling adaptor. Eight treatment combinations involving 2...
Heinonen E, Hedenstierna G, Meriläinen P, Högman M, Nyman G.To study the effect of the pulsed delivery of nitric oxide (NO) on pulmonary gas exchange in the anaesthetized horses. Design Prospective, controlled randomized. Methods: Five healthy Standardbred trotters, three geldings and two mares. Methods: The horses were anaesthetized with thiopentone and isoflurane and positioned in dorsal recumbency. Nitric oxide was added as a pulse to the inspired gas during the first half of each inspiration. In three horses the effect of NO on the ventilation-perfusion distribution was also investigated using the multiple inert gas elimination technique. Data w...
Frampton A, Floriano D, Simpson K, Hopster K.To evaluate the agreement between the Tafonius large animal ventilator-integrated volumetric capnography (vCap) software and the Respironics NICO noninvasive cardiac output monitor reference system. Methods: Data were collected from 56 healthy adult horses undergoing general anesthesia. Methods: Animals were placed under general anesthesia and connected to the Tafonius large animal ventilator circle system. A flow partitioning device with CO2 and flow sensors was utilized to couple the endotracheal tube to the NICO monitor. Tafonius CO2 and flow sensors are incorporated into the Y-piece of the...
Araos J, Driessen B, Brandly J, Gorenberg E, Heerdt P, Bruhn A, Martin-Flores M, Adler A, Hopster K.To investigate the mechanisms underlying the improved arterial oxygenation described with flow-limited expiration (FLEX) ventilation in anesthetized horses. Methods: 5 healthy adult research horses. Methods: Horses underwent volume-controlled ventilation for 60 minutes (VCV1), followed by 60 minutes of FLEX, and 30 minutes of VCV (VCV2). Main outcomes included the arterial partial pressure of oxygen-to-Fio2 (PF) ratio and electrical impedance tomography (EIT)-derived functional indices at the end of each phase. The EIT data were used to create regional maps of relative lung ventilation and per...
Laclaire AL, Manguin E, Tanquerel L.Effects of general anesthesia with controlled ventilation on the respiratory system have had limited evaluation in horses. A prospective observational study was performed with eleven client-owned horses undergoing elective surgery. Physical examination, auscultation with a rebreathing bag, complete blood cell count, lung ultrasound imaging, tracheal endoscopy imaging and transendoscopic tracheal wash were conducted before and 24 hours after anesthesia. Lung ultrasound imaging was also repeated just after recovery. A significant increase in blood neutrophil count between pre- and post-anesthesi...
Diez de Castro E, Fernandez-Molina JM.Environmental practices related to the inhalation of airborne dust have been identified as the main cause of equine asthma (EA) and reasonably, they are truly relevant in its treatment and control, especially for horses with its severe form. Vast research regarding environmental recommendations has been conducted in recent years. However, no recent exhaustive reviews exist that gather all this new evidence. The aim of this review is to report and compare the most pertinent information concerning the environmental management of EA. The main findings highlight the importance of the type of forag...
Byrne DP, Studer N, Secombe C, Cieslewicz A, Hosgood G, Raisis A, Adler A, Mosing M.Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were re...
Poochipakorn C, Joongpan W, Tongsangiam P, Phooseerit A, Leelahapongsathon K, Chanda M.The severe outbreak of African horse sickness (AHS) in Thailand has forced horses to reside full-time inside barns that are covered by a small mesh net to prevent minuscule AHS insect vectors from gaining access. However, housing in the net-covered barn induces stress in horses, which compromises their welfare. Implementing strategic airflow adjustment while retaining the vector-protection characteristics has been proposed to help alleviate this problem. The present study aimed to investigate the effect of strategic ventilation adjustment on blood cortisol levels, heart rate and behaviour in h...
Massie S, Bayly W, Ohmura H, Takahashi Y, Mukai K, Léguillette R.Comparatively little is known regarding the initial cardiorespiratory response of young racehorses to training. The objectives were to compare physiological parameters before and after introductory training and determine whether young Thoroughbreds show endoscopic signs of exercise-induced pulmonary hemorrhage (EIPH). Ten Thoroughbreds (20-23 months) underwent 12-weeks of introductory training, including weekly speed sessions. Two 600 m high-speed exercise tests (HSET) were performed following weeks 4 and 12 while wearing a validated ergospirometry facemask. Peak oxygen consumption (V̇Opk...
Leguillette R, McCrae P, Massie S, Filho SA, Bayly W, David F.Swimming has been used empirically for rehabilitation and conditioning of horses. However, due to challenges imposed by recording physiological parameters in water, the intensity of free swimming effort is unknown. Objective: Measure the physiological workload associated with untethered swimming in horses. Five fit Arabian endurance horses were assessed while swimming in a 100 m-long indoor pool. Horses were equipped with a modified ergospirometry facemask to measure oxygen consumption (V̇O) and ventilatory parameters (inspired/expired volumes, V, V; peak inspiratory/expiratory flows, PkV, P...
Dupont J, Roman Dura B, Salciccia A, Serteyn D, Sandersen C.To study the changes in dynamic compliance (C), ventilation/perfusion (V˙/ Q˙) mismatch and haemodynamic variables in hypoxaemic anaesthetized horses whose PaO increased following salbutamol inhalation. Methods: Retrospective, clinical, cohort study. Methods: A group of 73 client-owned horses treated with salbutamol when PaO <100 mmHg (13.3 kPa) during anaesthesia. Methods: Horses were divided into two groups: responders (R), where PaO after salbutamol ≥1.2 PaO before treatment (i.e. ≥20% increase), and non-responders (NR), where PaO after salbutamol <1.2 PaO before treatment. Demographi...
