Oxygen is a fundamental element involved in various physiological processes in horses, primarily through its role in cellular respiration and energy production. It is transported in the blood, bound to hemoglobin within red blood cells, and is essential for the metabolism of nutrients into usable energy. The efficiency of oxygen uptake, transport, and utilization can significantly impact equine performance and overall health. Research in this area often focuses on respiratory function, cardiovascular health, and the effects of exercise on oxygen dynamics in horses. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms of oxygen transport and utilization, as well as their implications for equine health and performance.
Floriano D, Watkins AR, Hopster K.To evaluate the efficacy of 2 different oxygen delivery strategies-intranasal and tracheal insufflation-on the inspired fraction of oxygen (FIO2) in standing horses and to determine the time needed for arterial oxygen partial pressure (PaO2) equilibration. Methods: 6 healthy adult horses. Methods: In this blinded, randomized crossover design study, horses were randomly assigned to receive oxygen via nasal cannula (group N) or transcutaneous tracheal catheter (group T). After placement of venous and arterial catheters, FIO2 was measured through a catheter placed into the distal portion of the t...
Tucker L, Almeida D, Wendt-Hornickle E, Baldo CF, Allweiler S, Guedes AGP.Lower than expected arterial oxygen tension (PaO) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO), PaO, inspired oxygen fraction (FiO), and end-tidal carbon dio...
Auckburally A, Wiklund MK, Lord PF, Hedenstierna G, Nyman G.To measure changes in pulmonary perfusion during pulsed inhaled nitric oxide (PiNO) delivery in anesthetized, spontaneously breathing and mechanically ventilated ponies positioned in dorsal recumbency. Methods: 6 adult ponies. Methods: Ponies were anesthetized, positioned in dorsal recumbency in a CT gantry, and allowed to breathe spontaneously. Pulmonary artery, right atrial, and facial artery catheters were placed. Analysis time points were baseline, after 30 minutes of PiNO, and 30 minutes after discontinuation of PiNO. At each time point, iodinated contrast medium was injected, and CT angi...
Dupont J, Gougnard A, Salciccia A, Detilleux J, Serteyn D, Sandersen C.To compare the efficacy of single-breath continuous positive airway pressure manoeuvre (CPAP-M) with inhaled salbutamol, and a combination of both. Methods: Randomized, clinical study. Methods: A total of 62 client-owned horses (American Society of Anesthesiologists status III-V) anaesthetized for laparotomy. Methods: Horses were premedicated with intravenous (IV) xylazine (0.4-0.6 mg kg), anaesthesia was induced with midazolam (0.06 mg kg IV) and ketamine (2.2 mg kg IV) and maintained with isoflurane in oxygen using volume-controlled ventilation without positive end-expiratory pressure. If Pa...
Floyd E, Danks S, Comyn I, Mackenzie C, Marr CM.Respiratory disease is common in critically ill neonatal foals. Traditional oxygen therapy (TOT) with nasal insufflation of oxygen is often used to provide first-line respiratory support. Mechanical ventilation is used in foals which require a greater level of support but requires specialist expertise and can be associated with significant complications. Non-invasive ventilation (NIV) enables a greater level of respiratory support without the need for intubation. High flow oxygen therapy (HFOT) is a mode of NIV commonly used in human intensive care. Objective: To describe the use of HFOT in ho...
Cowling N, Woldeyohannes S, Sole Guitart A, Goodwin W.Near infrared spectroscopy (NIRS) noninvasively measures peripheral tissue oxygen saturation (StO) and may be useful to detect early changes in StO in anaesthetized and critically ill horses. This study aimed to identify the muscle belly that provided the highest percentage of successful StO readings and the highest mean StO value. Fifty adult horses were enrolled in a prospective controlled study. StO was measured at six different muscles in each horse, for each intervention: hair overlying the muscle was clipped (post clipping: PC), clipped skin was cleaned with chlorhexidine (post-surgical ...
Scherrer NM, Hopster K.To study the surgical, anesthetic and recovery qualities of horses receiving either a neuromuscular blocking agent (atracurium) or intravenous lidocaine (treatment groups A and L, respectively). Methods: A total of thirty horses presented for ocular surgery were used in this study. Methods: Horses were randomly assigned to receive either atracurium (group A) or a lidocaine constant rate infusion (group L). Surgical quality was graded on a scale from 1 (excellent)-5 (poor). While anesthetized, the heart rate, oxygen saturation and mean arterial blood pressure, and end-expiratory carbon dioxide ...
Calero Rodriguez A, de Grauw JC, van Loon JPAM.To determine the effect of fraction of inspired oxygen (FiO) on intrapulmonary shunt fraction as measured by F-shunt in ponies during isoflurane anaesthesia. Methods: Prospective, randomized clinical study. Methods: A group of 23 adult Shetland ponies undergoing a total of 32 anaesthetic procedures. Methods: Ponies were premedicated intravenously (IV) with detomidine (0.01 mg kg) and either morphine (0.1 mg kg) or butorphanol (0.02 mg kg). Anaesthesia was induced with ketamine (2.2 mg kg) and midazolam (0.07 mg kg) administered IV. Ponies were randomly allocated to maintenance of anaesthesia w...
Roşu O, Melega I, Evans AL, Arnemo JM, Küker S.Feral horses are immobilized for a variety of reasons including population control via contraceptives. Although opioid combinations have been successfully used for immobilization of feral horses, there is a need for combinations using drugs that are more readily available and present less of a human health hazard. We evaluated the chemical immobilization with physiological measurements and blood gas analyses of 91 free-ranging feral horses () remotely immobilized with a combination of 30 mg medetomidine and 775 mg ketamine in a single disposable 6 ml dart. During immobilization, heart rate, re...
Camargo Ferreira J, Silva Amaral R, Mara Cardoso L, Panelli Marchió S, Aldrovani Rodrigues M, Fonseca Alves CE, de Meira C.Ozone (O ) therapy has been used to improve peripheral tissue oxygenation in humans and domestic animals. The goal of the present study was to characterize histological changes in the endometria of healthy equines following tissue exposure to gas mixtures enriched with different concentrations of O . Cycling mares without endometrial degeneration were divided into three groups according to treatment (n = 9 mares/group). The uteri from the O , ½O and control groups were insufflated for 3 min with gas containing 42, 21 and 0 μg O ml , respectively. Treatments were performed every three da...
Ohmura H, Mukai K, Matsui A, Takahashi T, Jones JH.Supramaximal exercise while inspiring different O gases may induce different responses in cardiopulmonary function at the same relative and/or absolute exercise intensity. The purpose of this study was to compare the effects of supramaximal exercise in hypoxia, normoxia and hyperoxia on cardiopulmonary function in Thoroughbred horses. Using a crossover design, five well-trained horses were made to run up a 6% grade on a treadmill at supramaximal speeds sustainable for approximately 110 sec (approximately 115% Omax) while breathing normoxic gas (NO, 21% O) or hypoxic gas (LO, 15.3% O) in random...
de Castro RVG, Pieri NCG, Fantinato Neto P, Grizendi BM, Dória RGS, Meirelles FV, Smith LC, Garcia JM, Bressan FF.The cellular reprogramming into pluripotency is influenced by external and internal cellular factors, such as culture conditions (e.g., environmental oxygen concentration), and the aging process. Herein, we aimed to generate and maintain equine iPSCs (eiPSCs) derived from fibroblasts of a horse older than 20 years and to evaluate the effect of different levels of oxygen tension (atmospheric 20% O, 5% O, or 20% to 5% O) on these cells. Fibroblasts were reprogrammed, and putative eiPSCs were positive for positive alkaline phosphatase detection; they were positive for pluripotency-related genes ...
Cerullo M, Driessen B, Douglas H, Hopster K. In anesthetized adult horses, changes in recumbency can influence the cardiovascular system but how arterial blood pressures and oxygen tension change in isoflurane anesthetized animals as a direct result of hoisting has not been investigated. To evaluate effects of hoisting on hemodynamic function and pulmonary gas exchange in isoflurane-anesthetized horses. Prospective, experimental study. Six adult horses were anesthetized three times using isoflurane in pure oxygen (inspired fraction 0.9-1.0), and allowed breathing spontaneously in lateral recumbency. After 45 min horses were hoisted u...
Trenholme HN, Barletta M, Quandt JE, Reed RA, Kleine SA, Hofmeister EH.Low arterial oxygen is a common complication in anesthetized horses and placing the animal in reverse Trendelenburg (RT) position may treat hypoxemia. The objective of this study was to assess the arterial partial pressure of oxygen (PaO) in horses placed in a 5-degree RT compared to horizontal (H) position. Client-owned healthy horses (n = 60) undergoing elective surgeries were enrolled in a randomized controlled clinical study. Horses were sedated with butorphanol, an α-adrenoceptor agonist, ± acepromazine and induced with ketamine combined with a benzodiazepine, propofol, or guaifenesin...
Youngblood CD, Hodgson DS, Beard WL, Song Y, Prakash P, Heflin LV.Recumbency affects respiratory mechanics and oxygenation in anesthetized horses. Changes in pleural and abdominal pressures that can impair ventilation have not been described in all recumbencies. The objective of this study was to determine the effects of patient positioning on transdiaphragmatic pressure and selected hemodynamic variables. Horses were maintained under total intravenous general anesthesia with nasal oxygen supplementation. Transnasal balloon catheters in the stomach and thoracic esophagus were used to measure intrathoracic and gastric pressures in standing horses and in anest...
Wang W, Mukai K, Takahashi K, Ohmura H, Takahashi T, Hatta H, Kitaoka Y.The aim of this study was to investigate effects of short-term hypoxic training on lactate metabolism in the gluteus medius muscle of Thoroughbreds. Using crossover design (3 months washout), eight Thoroughbred horses were trained for 2 weeks in normoxia (F O  = 21%) and hypoxia (F O  = 18%) each. They ran at 95% maximal oxygen consumption (V̇O ) on a treadmill inclined at 6% for 2 min (3 days/week) measured under normoxia. Before and after each training period, all horses were subjected to an incremental exercise test (IET) under normoxia. Following the 2-week trainings, V̇O in IET ...
Mukai K, Ohmura H, Matsui A, Aida H, Takahashi T, Jones JH.We examined the effects of high-intensity training in normobaric hypoxia on aerobic capacity and exercise performance in horses and the individual response to normoxic and hypoxic training. Eight untrained horses were studied in a randomized, crossover design after training in hypoxia (HYP; 15.0% inspired O ) or normoxia (NOR; 20.9% inspired O ) 3Â days/week for 4Â weeks separated by a 4-month washout period. Before and after each training period, incremental treadmill exercise tests were performed in normoxia. Each training session consisted of 1Â min cantering at 7Â m/s and 2Â min galloping ...
Meier M, Bettschart-Wolfensberger R, Schwarzwald CC, Portier K, Gysler A, Ringer SK.Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10 min of dobutamine infusion (2 µg kg  min ). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observe...
Jukic CC, Cowling NR, Perkins NR, van Eps AW, Ahern BJ.Laser salpingopharyngostomy has been used as an adjunct to primary medical therapy allowing for topical debridement, topical treatment or to potentially alter the guttural pouch environment in horses with guttural pouch disease. Objective: To evaluate the effect of a laser salpingopharyngostomy on the guttural pouch environment in healthy horses. Methods: Experimental study. Methods: In six adult Standardbred female horses, under standing sedation a stab incision was made ventral to the sternocephalicus tendon and a customised trocar inserted into the medial guttural pouch compartment. Baselin...
Birks EK, Ohmura H, Jones JH.Measurements of gas exchange while breathing gases of different O concentrations are useful in respiratory and exercise physiology. High bias flows required in flow-through indirect calorimetry systems for large animals like exercising horses necessitate the use of inconveniently large reservoirs of mixed gases for making such measurements and can limit the amount of equilibration time that is adequate for steady-state measurements. We obviated the need to use a pre-mixed reservoir of gas in a semi-open flow-through indirect calorimeter by dynamically mixing gases and verified the theoretical ...
Muller B, Lewis N, Adeniyi T, Leese HJ, Brison DR, Sturmey RG.Mitochondria provide the major source of ATP for mammalian oocyte maturation and early embryo development. Oxygen Consumption Rate (OCR) is an established measure of mitochondrial function. OCR by mammalian oocytes and embryos has generally been restricted to overall uptake and detailed understanding of the components of OCR dedicated to specific molecular events remains lacking. Here, extracellular flux analysis (EFA) was applied to small groups of bovine, equine, mouse and human oocytes and bovine early embryos to measure OCR and its components. Using EFA, we report the changes in mitochondr...
Zavistanaviciute P, Poskiene I, Lele V, Antanaitis R, Kantautaite J, Bartkiene E.The aim of this study was to evaluate the influence of the newly isolated Lactobacillus plantarum LUHS135 and Lactobacillus paracasei LUHS244 strains grown in potato juice (with a cell count of 8.0-9.0 log10 CFU/ml) on the blood and faeces parameters of exercising horses. The horses were classified into four different groups: a control group (which received no probiotics); the first group (which received 200 ml of L. plantarum culture in potato juice); the second group (which received 200 ml of L. paracasei culture in potato juice); and the third group (which received an L. plantarum and L. pa...
Greco-Otto P, Bond S, Sides R, Bayly W, Leguillette R.Equine water treadmills (WT) were initially designed for rehabilitation of musculoskeletal injuries, but are also commonly used for conditioning sport horses, however the effects are not well documented. The purpose of this study was to test the effect of an 18-day WT conditioning programme on peak oxygen consumption (V̇O2peak). Nine unfit Thoroughbreds were used in a randomised controlled trial. Six horses worked daily for 18 days in stifle-height water (WT group), while 3 control horses worked without water (dry treadmill group (DT)). Preconditioning and postconditioning maximal exercise ra...
Bardell D, Mosing M, Cripps PJ.Arterial hypoxaemia is common in anaesthetised horses, but little information exists regarding restoration of arterial oxygen tension (PaO ) during recovery from anaesthesia, or if intra-operative management factors exert any longer-term effect. Objective: To evaluate PaO in horses recovering from general anaesthesia up to 1Â h after resuming standing. Methods: Prospective observational clinical cohort study. Methods: Systemically healthy adult horses undergoing inhalational general anaesthesia for elective surgical procedures were studied. Arterial blood samples were obtained anaerobically pr...
Varner KM, Hopster K, Driessen B.To assess effects of nitrogen and helium on efficacy of an alveolar recruitment maneuver (ARM) for improving pulmonary mechanics and oxygen exchange in anesthetized horses. Methods: 6 healthy adult horses. Methods: Horses were anesthetized twice in a randomized crossover study. Isoflurane-anesthetized horses in dorsal recumbency were ventilated with 30% oxygen and 70% nitrogen (treatment N) or heliox (30% oxygen and 70% helium; treatment H) as carrier gas. After 60 minutes, an ARM was performed. Optimal positive end-expiratory pressure was identified and maintained for 120 minutes. Throughout ...
Auckburally A, Grubb TL, Wiklund M, Nyman G.OBJECTIVE To determine the impact of mechanical ventilation (MV) and perfusion conditions on the efficacy of pulse-delivered inhaled nitric oxide (PiNO) in anesthetized horses. ANIMALS 27 healthy adult horses. PROCEDURES Anesthetized horses were allocated into 4 groups: spontaneous breathing (SB) with low ( 70 mm Hg. Data were collected after a 60-minute equilibration period and at 15 and 30 minutes during PiNO administration. Variables included Pao, arterial oxygen saturation and content, oxygen delivery, and physiologic dead space-to-tidal volume ratio. Data were analyzed with Shapiro-Wilk, ...
Alsobayil FA, El-Shafaey ES, Sadan M, Alshoshan AA.Sevoflurane is a volatile anesthetic agent that has become popular in the field of large animal anesthesia. The aim of this study was to evaluate the use of sevoflurane in adult healthy donkeys. Six male, adult, healthy donkeys were premedicated with xylazine (1Â mg/kg IV), induced with thiopental (5Â mg/kg IV), and then maintained for 90Â minutes with sevoflurane in 100% oxygen at a flow rate of 6Â L/min with spontaneous breathing. Rectal temperature (RT), respiratory rate, heart rate (HR), oxygen hemoglobin saturation (OHS), and mean arterial blood pressure (MBP) were measured before and 20Â...
Jones T, Bracamonte JL, Ambros B, Duke-Novakovski T.To evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals. Methods: Prospective, experimental study. Methods: A group of six healthy foals [median (range) 11 (8-33) days] undergoing abdominal surgery. Methods: Intravenous (IV) dexmedetomidine (3-7μgkg) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg) and maintained with alfaxalone (6mgkghour), dexmedetomidine (1μgkghour) and remifentanil (3μgkghour). Foals were endotracheally intubated and lung...
Hopster K, Dï¿® 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...
Schauvliege S, Binetti A, Duchateau L, van Dijk JJ, Gasthuys F.To evaluate the cardiorespiratory effects of a 7° reverse Trendelenburg position (RTP) in anaesthetized horses. Methods: Randomized, non-blinded clinical trial. Methods: A total of 125 horses undergoing elective surgery in dorsal recumbency. Methods: Horses were allocated to one of three weight classes and assigned to be positioned either on a horizontal table or on a table in 7° RTP, according to a randomized block design. In all horses, anaesthesia was maintained with isoflurane in oxygen and a constant rate infusion of romifidine. All horses were mechanically ventilated throughout anaesth...
Wickler SJ, Hoyt DF, Clayton HM, Mullineaux DR, Cogger EA, Sandoval E, McGuire R, Lopez C.It is well known that adding a load to a horse's back increases its energetic costs of locomotion, but the magnitude of increase obtained by loading the most distal portion of limb has not been measured. Objective: To measure oxygen consumption in horses with mass added to the back and hooves. Because such mass distribution alters inertial parameters of the limbs, kinematic measurements were made to quantify the magnitude of change in limb movement. Methods: Steady-state oxygen consumption was measured in 6 horses with a load of 2.4 kg. The load was either carried on the back or distributed eq...
Tracey AK, Alcott CJ, Schleining JA, Safayi S, Zaback PC, Hostetter JM, Reinertson EL.Topical oxygen therapy (TOT) has been used in human medicine to promote healing in chronic wounds. To test the efficacy and safety of TOT in horses, an experimental wound model was created by making 1 standardized dermal wound on each limb of 4 healthy horses (n = 16). Each wound was fitted with an oxygen delivery cannula and covered with a bandage. One limb of each front and hind pair was randomly assigned to the treatment group (fitted with an oxygen concentrator device), with the contralateral limb assigned to the control group (no device). Wound area, epithelial area, and contraction were ...
Honess NA, Gibson JS, Cossins AR.The effects of oxygen tension (PO2) upon the K influx pathways of equine red cells have been studied using 86Rb+ as congener for K. Equilibration of cells in 100% nitrogen led to a low and Cl-independent K flux. Change to an atmosphere of 100% air led to a rapid sixfold increase in K flux. The oxygen-activated flux was entirely Cl dependent and was maintained for up to 3 h. Oxygenation-evoked activation was dependent upon PO2 over the physiological range with little effect up to 70% saturation of haemoglobin with oxygen but significant effects between 70 and 100%. K flux at low PO2 was unaffec...
Auckburally A, Nyman G.To discuss how hypoxaemia might be harmful and why horses are particularly predisposed to developing it, to review the strategies that are used to manage hypoxaemia in anaesthetized horses, and to describe how successful these strategies are and the adverse effects associated with them. Methods: Google Scholar and PubMed, using the search terms horse, pony, exercise, anaesthesia, hypoxaemia, oxygen, mortality, morbidity and ventilation perfusion mismatch. Conclusions: Although there is no evidence that hypoxaemia is associated with increased morbidity and mortality in anaesthetized horses, mos...
Westerling D.Thirteen experienced riders and three elite riders underwent bicycle ergometer tests at submaximal and maximal workloads. Oxygen uptake, pulmonary ventilation and heart rate were also studied during riding at a walk, a trot and a canter. The mean maximal oxygen uptake of the experienced riders in the ergometer test (2.71 . min-1) was superior to the average maximal oxygen uptake of other groups of the same age and sex. The average oxygen uptake of the experienced riders in trot sitting was 1.701 . min-1, trot rising 1.681 . min-1 and in canter 1.801 . min-1. The experienced riders used at leas...
Gollnick PD, Bertocci LA, Kelso TB, Witt EH, Hodgson DR.The effect of high-intensity exercise on the respiratory capacity of skeletal muscle was studied in horses which ran five 600-m bouts on a track with 2 min of rest between exercise bouts, or once to fatigue on a treadmill at an intensity that elicited the maximal oxygen uptake. Venous blood and biopsy samples of the middle gluteal muscle were collected at rest, after each exercise bout, and 30 and 60 min post-exercise. Blood samples were analyzed for lactate concentration and pH and muscle samples for metabolites, pH, and respiratory capacity. Venous blood and muscle pH declined to 6.91 +/- 0....
Nagata S, Takeda F, Kurosawa M, Mima K, Hiraga A, Kai M, Taya K.The responses of plasma adrenocorticotropin (ACTH), cortisol, noradrenaline and adrenaline in 5 Thoroughbred horses to an incremental exercise and 2 relative workload exercises, at 105 and 80% maximal oxygen consumption (VO2max), on a treadmill were examined. These hormone concentrations increased (P < 0.05) with each exercise and the maximal plasma concentrations of ACTH, cortisol were observed between 5 and 30 min after the end of the exercise, while maximal catecholamine concentrations occurred just at exhaustion time. The plasma ACTH, noradrenaline and adrenaline responses during exerci...
Schott HC, Hodgson DR, Bayly WM.The effects of exercise on urinary excretion of red blood cells, pigments (haemoglobin and myoglobin) and protein were studied in 8 mares performing treadmill exercise at speeds eliciting 40, 60 and 95% of the maximal oxygen consumption (VO2max). Gross haematuria and pigmenturia were observed in all horses during exercise at the 2 higher intensities, while these findings were detected in only one of 8 mares during exercise at 40% of the VO2max. For the remaining 7 mares exercised at 40% of the VO2max, increased urinary excretion of red blood cells (RBCs) and pigments was evident after centrifu...
The Journal of physiologyMarch 24, 2005
Volume 565, Issue Pt 3 1019-1030 doi: 10.1113/jphysiol.2004.078469
Giussani DA, Forhead AJ, Fowden AL.In mammals, the mechanisms regulating an increase in fetal arterial blood pressure with advancing gestational age remain unidentified. In all species studied to date, the prepartum increase in fetal plasma cortisol has an important role in the maturation of physiological systems essential for neonatal survival. In the horse, the prepartum elevation in fetal cortisol and arterial blood pressure are delayed relative to other species. Hence, the mechanisms governing the ontogenic increase in arterial blood pressure in the horse fetus may mature much closer to term than in other fetal animals. In ...
Sørensen MA, Petersen LJ, Bundgaard L, Toft N, Jacobsen S.As in other fibroproliferative disorders, hypoxia has been suggested to play a key role in the pathogenesis of exuberant granulation tissue (EGT). The purpose of this study was to investigate metabolism and blood flow locally in full-thickness wounds healing with (limb wounds) and without (body wounds) formation of EGT. Microdialysis was used to recover endogenous metabolites from the wounds, and laser Doppler flowmetry was used to measure blood flow. Measurements were performed before wounding and 1-28 days after wounding. Blood flow was consistently lower in limb wounds than in body wounds t...
Constantinopol M, Jones JH, Weibel ER, Taylor CR, Lindholm A, Karas RH.Because the maximal rate of O2 consumption (VO2max) of the horse is 2.6 times larger than that of steers of equal size, we wondered whether their pulmonary gas exchanger is proportionately larger. Three Standardbred racehorses [body mass (Mb) = 447 kg] and three domestic steers (Mb = 474 kg) whose cardiovascular function at VO2max had been thoroughly studied (Jones et al. J. Appl. Physiol. 67: 862-870, 1989) were used to study their lungs by morphometry. The basic morphometric parameters were similar in both species. The nearly 2 times larger lung volumes of the horses caused the gas exchange ...
Wagner PD, Erickson BK, Seaman J, Kubo K, Hiraga A, Kai M, Yamaya Y.Although the horse is considered an elite athlete with a specific VO2max some 2-4 times higher than man, maximal O2 transport is compromised both by moderately severe arterial desaturation and by failure to extract all O2 from blood perfusing exercising muscle. This prompted the present study to ascertain whether correction of arterial desaturation would proportionally augment VO2max and, if so, would O2 extraction behave in a manner predicted by diffusional transport limitation. Six two year old thoroughbreds were exercised to VO2max on a treadmill each on three separate occasions breathing g...
Thomas DP, Fregin GF, Gerber NH, Ailes NB.The cardiorespiratory and metabolic responses to various levels of tethered-swimming were evaluated in 5 sedentary horses. Cardiac output (Q) and heart rate (HR) correlated highly (r = 0.89 and 0.94 respectively) with work effort (WE) expressed as kg pulled . kg body wt-1 . 10-2. While swimming, stroke volume (SV) was reduced at the lowest workloads, but increased with increasing WE so that at the highest workloads it had returned to the on-land standing SV. Pressures in the pulmonic as well as on both sides of the systemic circulation were considerably elevated by this form of exercise, altho...
Hubbell JA, Aarnes TK, Bednarski RM, Lerche P, Muir WW.The purpose of this study was to compare the effects of 0.5 fraction of inspired oxygen (FiOâ‚‚) and >0.95 FiOâ‚‚ on pulmonary gas exchange, shunt fraction and oxygen delivery (DOâ‚‚) in dorsally recumbent horses during inhalant anesthesia. The use of 0.5 FiOâ‚‚ has the potential to reduce absorption atelectasis (compared to maximal FiOâ‚‚) and augment alveolar oxygen (Oâ‚‚) tensions (compared to ambient air) thereby improving gas exchange and DOâ‚‚. Our hypothesis was that 0.5 FiOâ‚‚ would reduce ventilation-perfusion mismatching and increase the fraction of pulmonary blood flow that is ox...
Dane DM, Hsia CC, Wu EY, Hogg RT, Hogg DC, Estrera AS, Johnson RL.The spleen acts as an erythrocyte reservoir in highly aerobic species such as the dog and horse. Sympathetic-mediated splenic contraction during exercise reversibly enhances convective O2 transport by increasing hematocrit, blood volume, and O2-carrying capacity. Based on theoretical interactions between erythrocytes and capillary membrane (Hsia CCW, Johnson RL Jr, and Shah D. J Appl Physiol 86: 1460-1467, 1999) and experimental findings in horses of a postsplenectomy reduction in peripheral O2-diffusing capacity (Wagner PD, Erickson BK, Kubo K, Hiraga A, Kai M, Yamaya Y, Richardson R, and Sea...
Marntell S, Nyman G, Hedenstierna G.To compare pulmonary function and gas exchange in anaesthetized horses during and after breathing either O2-rich gas mixtures or air. Methods: Six healthy standard bred trotters (age range 3-12 years; mass range 423-520 kg), four geldings and two mares. Study design Randomized, cross-over experimental study. Methods: Horses were anaesthetized on two occasions with tiletamine-zolazepam after pre-anaesthetic medication with acepromazine, romifidine and butorphanol. After endotracheal intubation and positioning in left lateral recumbency, animals were allowed to breathe spontaneously. One of two,...
Jones JH.Taylor and Weibel's principle of symmorphosis hypothesized optimal design of the mammalian respiratory system, with no excess structure relative to its maximal O2 flux, VO2max. Although they found symmorphosis not to be a general principle of design, it might apply to a highly adapted aerobic athlete, e.g. the Thoroughbred racehorse. Using a mathematical model based on empirical data of the equine O2 transport system at normoxic VO2max, the fraction of the total limitation to O2 flux contributed by each of the respiratory transport steps is calculated as either the fractional change (F) in VO2...
Art T, Anderson L, Woakes AJ, Roberts C, Butler PJ, Snow DH, Lekeux P.The changes induced by exercise on the mechanics of breathing, as well as the simultaneous changes occurring in arterial blood gas tensions and in respiratory gas exchange were investigated in 6 healthy thoroughbred horses, performing a treadmill exercise of increasing intensity. Respiratory airflow and tidal volume (VT) were measured with ultrasonic flowmeters. Pleural pressure changes were measured by an oesophageal balloon catheter. Gas concentration of the expired air was analysed with a mass spectrometer; the oxygen consumption (VO2) and the carbon dioxide output (VCO2) were computed brea...
Reichert C, Kästner SB, Hopster K, Rohn K, Rötting AK.To evaluate the use of a micro-lightguide tissue spectrophotometer for measurement of tissue oxygenation and blood flow in the small and large intestines of horses under anesthesia. Methods: 13 adult horses without gastrointestinal disease. Methods: Horses were anesthetized and placed in dorsal recumbency. Ventral midline laparotomy was performed. Intestinal segments were exteriorized to obtain measurements. Spectrophotometric measurements of tissue oxygenation and regional blood flow of the jejunum and pelvic flexure were obtained under various conditions that were considered to have a potent...
Mukai K, Hiraga A, Eto D, Takahashi T, Hada T, Tsubone H, Jones JH.To determine whether warm-up exercise at different intensities alters kinetics and total contribution of aerobic power to total metabolic power in subsequent supramaximal exercise in horses. Methods: 11 horses. Methods: Horses ran at a sprint until fatigued at 115% of maximal oxygen consumption rate (VO(2max)), beginning at 10 minutes following each of 3 warm-up protocols: no warmup (NoWU), 1 minute at 70% VO(2max) (moderate-intensity warm-up [MoWU]), or 1 minute at 115% VO(2max) (high-intensity warm-up [HiWU]). Cardiopulmonary and blood gas variables were measured during exercise. Results: Th...
Art T, Lekeux P.Five healthy, fit Standardbreds (mean +/- SEM, 490.4 +/- 15.0 kg, 4.0 +/- 0.5 years) were studied during a standardized test carried out on a treadmill. The test consisted of an 8-minute warm-up and a 9-minute exercise period (1 minute at 1.7, 4, 7, 8, 9, and 10 m/s; 2 minutes at 4 m/s; and a 1-minute walk at a 6% slope). Respiratory airflow, tidal volume (V(T)), and respiratory frequency (f) were continuously recorded, using 2 ultrasonic pneumotachographs connected to a face mask and mass spectrometer. Oxygen uptake, carbon dioxide output, and expired minute volume (V(E)) were obtained on a b...
Schneider N, Mouithys-Mickalad A, Lejeune JP, Duyckaerts C, Sluse F, Deby-Dupont G, Serteyn D.We investigated the oxygen (O(2)) uptake of equine articular chondrocytes to assess their reactions to anoxia/re-oxygenation. They were cultured under 5% or 21% gas phase O(2) and at glucose concentrations of 0, 1.0 or 4.5g/L in the culture medium (n=3). Afterwards, the O(2) consumption rate of the chondrocytes was monitored (oxymetry) before and after an anoxia period of 25min. The glucose consumption and lactate release were measured at the end of the re-oxygenation period. The chondrocytes showed a minimal O(2) consumption rate, which was hardly changed by anoxia. Independently from the O(2...
Wickler SJ, Hoyt DF, Cogger EA, Hall KM.Horses have a tendency to utilize a relatively narrow set of speeds near the middle of a much broader range they are capable of using within a particular gait, i.e., a preferred speed. Possible explanations for this behavior include minimizing musculoskeletal stresses and maximizing metabolic economy. If metabolic economy (cost of transport, CT) and preferred speeds are linked, then shifts in CT should produce shifts in preferred speed. To test this hypothesis, preferred speed was measured in trotting horses (n = 7) unloaded on the level and loaded with 19% of their body weight on the level. T...
Ringer SK, Schwarzwald CC, Portier KG, Ritter A, Bettschart-Wolfensberger R.The objective of this study was to compare the cardiopulmonary effects of a xylazine or romifidine loading-dose, followed by a constant rate infusion (CRI) of the same α(2)-agonist. Nine research horses were treated in a randomized, blinded, crossover design with xylazine or romifidine. After instrumentation, a loading dose of intravenous xylazine (1mg/kg) or romifidine (80μg/kg) was administered, immediately followed by a CRI of xylazine (0.69mg/kg/h) or romifidine (30μg/kg/h) for a duration of 2h. Cardiopulmonary variables were recorded before bolus administration, during CRI, and for 1h ...
Roy TK, Popel AS.Characterizing the resistances to O2 transport from the erythrocyte to the mitochondrion is important in understanding potential transport limitations. A steady-state model of this process was developed to predict the minimum (critical) end-capillary PO2 required to prevent hypoxia at maximal O2 consumption (VO2max) in a circular region of tissue surrounding the venular end of a capillary. Capillary density was used as a measure of O2 delivery, and mitochondrial density was used as a measure of O2 consumption. The effects of oxyhemoglobin dissociation kinetics and diffusion facilitation by hem...
Speake PF, Gibson JS.The effect of urea and its interactions with oxygen tension (PO2), cell volume and inhibitors of protein phosphatases/kinases (PP/PK) on the K influx into equine red blood cells were studied. K influx was measured using 86Rb as a radioactive tracer for K. As in other species, Cl-dependent K influxes were stimulated by urea, with peak fluxes occurring at about 750 mM. This effect was not mediated via changes in cell volume or following formation of cyanate, the hydrolysis product of urea. Stimulation by urea was prevented by pre-treatment with calyculin A (100 nM) at all urea concentrations tes...
Gehr P, Erni H.The lungs of two half-bred geldings were fixed in situ by instillation of a glutaraldehyde solution into the airways during deep anaesthesia. The body weight of both animals was 510 kg and their average lung volume about 38 l. Stratified random samples from 22 regions were morphometrically analysed from electron microscopic films. Eighty-six per cent of the total lung volume was gas exchange parenchyma. It contained 26.9 l air space and 5.6 l interalveolar septa which were composed of equal parts of capillaries and tissue. The average alveolar and capillary surface areas were 2457 m2 and 1663 ...
Conley KE, Jones C.We test the hypothesis that myoglobin is important for O2 supply near the oxidative capacity of muscle. This hypothesis is evaluated with a simple model that incorporates the properties of heart and skeletal muscle tissue taken from steers and horses exercising at their maximum O2 consumption rate. These tissue samples allowed us to set the bounds on oxidative demand and O2 flux from red blood cells to the core of the muscle fiber, to estimate the blood and tissue capacities for O2 diffusion, and to define the capillary blood PO2 driving this O2 flux. A model combining blood convection with ti...
Langsetmo I, Weigle GE, Fedde MR, Erickson HH, Barstow TJ, Poole DC.The horse is a superb athlete, achieving a maximal O2 uptake (approximately 160 ml . min-1 . kg-1) approaching twice that of the fittest humans. Although equine O2 uptake (VO2) kinetics are reportedly fast, they have not been precisely characterized, nor has their exercise intensity dependence been elucidated. To address these issues, adult male horses underwent incremental treadmill testing to determine their lactate threshold (Tlac) and peak VO2 (VO2 peak), and kinetic features of their VO2 response to "square-wave" work forcings were resolved using exercise transitions from 3 m/s to a below...
