Carbon dioxide (CO2) is a naturally occurring gas that is a byproduct of metabolic processes in horses. It is primarily produced during cellular respiration and expelled from the body through the respiratory system. In horses, CO2 levels are indicative of respiratory efficiency and can influence acid-base balance within the bloodstream. Monitoring CO2 levels is important in assessing respiratory function and overall metabolic health in equine patients. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and physiological impact of carbon dioxide in equine biology.
Hinchcliff KW, Sams RA.To determine the effect of administration of commercially available sodium bicarbonate (NaHCO3) on carbon 13 (13C) isotopic enrichment of carbon dioxide (CO2) in serum of horses. Methods: 7 healthy Thoroughbreds. Methods: Sodium bicarbonate (450 g) was administered via nasogastric intubation to horses. Horses had been fed a diet obtained from the same source and had access to water from the same source for 3 months before the study. Blood samples were collected immediately before and at 2, 4, 6, and 24 hours after administration of NaHCO3. The concentration of total CO2 in serum was measured b...
Cruz AM, Kerr CL, Bouré LP, Sears WC.To determine the cardiovascular effects of 60 minutes of abdominal insufflation with CO2 to an intra-abdominal pressure of 15 mm Hg in standing horses receiving a constant rate infusion of detomidine. Methods: 5 horses. Methods: Horses were randomly allocated into treatment or control groups. A washout period of a minimum of 7 days separated the 2 experimental periods of the crossover study. Catheters were placed into the right atrium, pulmonary artery, jugular vein, and right transverse facial artery after lidocaine infiltration. All horses were sedated with detomidine (8.54 microg/kg/h, i.v....
Padilla DJ, McDonough P, Kindig CA, Erickson HH, Poole DC.Despite enormous rates of minute ventilation (Ve) in the galloping Thoroughbred (TB) horse, the energetic demands of exercise conspire to raise arterial Pco(2) (i.e., induce hypercapnia). If locomotory-respiratory coupling (LRC) is an obligatory facilitator of high Ve in the horse such as those found during galloping (Bramble and Carrier. Science 219: 251-256, 1983), Ve should drop precipitously when LRC ceases at the galloptrot transition, thus exacerbating the hypercapnia. TB horses (n = 5) were run to volitional fatigue on a motor-driven treadmill (1 m/s increments; 14-15 m/s) to study the ...
Koenig J, McDonell W, Valverde A.The objective of this prospective clinical study was to evaluate the accuracy of pulse oximetry and capnography in healthy and compromised horses during general anesthesia with spontaneous and controlled ventilation. Horses anesthetized in a dorsal recumbency position for arthroscopy (n = 20) or colic surgery (n = 16) were instrumented with an earlobe probe from the pulse oximeter positioned on the tip of the tongue and a sample line inserted at the Y-piece for capnography. The horses were allowed to breathe spontaneously (SV) for the first 20 min after induction, and thereafter ventilation wa...
Sander K, Deegen E, Ohnesorge B.In a placebo-controlled drug study data were collected about flow, volume and expiratory CO2-concentration in 13 horses with chronic obstructive pulmonary disease before and until 2.5 h after intravenous injection of clenbuterol. An ultrasonic flow measuring unit and an infrared-CO2-analyser (Spiroson Scientific) were used. functional deadspace and expiratory mixed volume were calculated. In addition the effect on the partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood was tested and the alveolo-arterial oxygen difference (AaDO2) determined. The volume of the functio...
Lindholm AC, Swensson U, de Mitri N, Collinder E.The clinical effects of intra-articular betamethasone together with hyaluronan (betaM/HA) and treatment with a defocalized carbon dioxide laser on acute traumatic arthritis of the fetlock joint were assessed. The horses in these studies were selected using a thorough lameness examination, including intra-articular anaesthesia abolishing the lameness. This investigation comprised an observer-blind study, including 10 sport horses (10 joints), and a prospective study, including 180 sport horses (333 joints). In both studies, the material was divided into two groups treated with either betaM/HA o...
Martens A, De Moor A, Vlaminck L, Pille F, Steenhaut M.Ninety-five horses with sarcoids were subjected to three types of treatment: surgical excision (conventional or carbon dioxide laser), cryotherapy or local BCG vaccination. The type of treatment was selected on the basis of the size, location and clinical appearance of the tumours. The choice between conventional and laser excision was empirical. A successful outcome was obtained in 11 of 14 (79 per cent) of the horses treated by cryosurgery, 18 of 27 (67 per cent) treated by BCG vaccination, 18 of 22 (82 per cent) treated by conventional excision, and 20 of 28 (71 per cent) treated with a car...
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...
Geor RJ, McCutcheon LJ, Hinchcliff KW.To compare effects of low and high intensity warm-up exercise on oxygen consumption (VO2) and carbon dioxide production (VCO2) in horses. Methods: 6 moderately conditioned adult Standard-breds. Methods: Horses ran for 2 minutes at 115% of maximum oxygen consumption (VO2max), 5 minutes after each of the following periods: no warm-up (NoWU); 10 minutes at 50% of VO2max (LoWU); or 7 minutes at 50% VO2max followed by 45-second intervals at 80, 90, and 100% VO2max (HiWU). Oxygen consumption and VCO2 were measured during exercise, and kinetics of VO2 and VCO2 were calculated. Accumulated O2 deficit ...
Aguilera-Tejero E, Estepa JC, López I, Bas S, Mayer-Valor R, Rodríguez M.The acid-base status of venous blood was studied in 17 show jumpers before and after exercise using both a traditional and a quantitative approach. Partial pressure of carbon dioxide (PCO(2)), pH, haemoglobin, and plasma concentrations of sodium (Na(+)), chloride (Cl(-)), potasium (K(+)), ionized calcium (Ca(2+)), total proteins, albumin, lactate and phosphorus were measured in jugular venous blood samples obtained before and immediately after finishing a show jumping competition. Bicarbonate, anion gap and globulin concentration were calculated from the measured parameters. 'Quantitative anal...
Young LE, Marlin DJ, McMurphy RM, Walsh K, Dixon PM.Inhaled nitric oxide, a selective pulmonary vasodilator, is known to improve arterial oxygenation after cardiopulmonary bypass and during acute respiratory distress syndrome in humans. During general anaesthesia with spontaneous ventilation, healthy adult horses develop large alveolar-arterial oxygen tension differences. In this study, we have determined the effects of inhaled nitric oxide (10 parts per million (ppm)) on venous admixture and pulmonary haemodynamics in horses anaesthetized with halothane. Seven adult horses were studied twice in random sequence. After premedication with romifid...
Taylor PM.The study investigated whether hypotension in halothane-anaesthetised ponies is the stimulus inducing an endocrine stress response by assessing the effect of maintenance of normotension with a dobutamine infusion. Groups of six ponies were studied. After premedication with acepromazine (0.04 mg/kg) anaesthesia was induced with thiopentone (10 mg/kg) and maintained for 120 min with halothane (group AN). Dobutamine was infused to effect (1.1-4.4 microg/kg/min) to maintain arterial pressure at pre anaesthetic levels. The conscious group (CON) were prepared as for AN and then received only dobutam...
Kingston JK, Bayly WM.Exercise in horses is associated with a wide variety of physiological changes in fluid, electrolyte and acid base balance. The integration of physiologic and physiochemical mechanisms acts to minimize alterations in pH and enhance removal of carbon dioxide produced by exercising muscles. This article provides a description of the changes that take place during exercise and how these changes affect acid-base balance in the horse.
Donaldson LL, Trostle SS, White NA.The use of laparoscopy for the diagnosis or therapeutic management of abdominal disease in the horse has distinct advantages when it allows the horse to remain standing. However, distending the abdomen by insufflation of a biologically active gas in an anaesthetised horse may add to the physiological challenge of general anaesthesia and recumbency. The cardiopulmonary responses to abdominal insufflation with carbon dioxide (CO2) to 15 mmHg pressure were evaluated in 6 horses in dorsal recumbency anaesthetised with halothane in oxygen and subjected to laparoscopic colopexy. Vaporiser settings t...
Still J, Serteyn D, van der Merwe CA.Anaesthesia was induced in horses (n = 6) with a mixture of thiopentone and guaiphenesin and maintained by mechanical ventilation with a mixture of oxygen, air and isoflurane. Inspiratory and end-expiratory concentrations of oxygen, carbon dioxide and isoflurane were measured. Electrocardiography was used to evaluate heart rate and rhythm. Mean systemic arterial pressure (SAPm), pulmonary artery pressure (PAPm), right atrial pressure (RAPm) and pulmonary capillary wedge pressure (PCWP) were measured directly. Cardiac output was determined using the thermodilution method. Microcirculation in th...
diBella G, Scandariato G, Suriano O, Rizzo A.The dependence of blood oxygen affinity and the Bohr effect on the concentration of 2,3-diphosphoglycerate (DPG) in erythrocytes was investigated in 24 trotter horses and 24 healthy men. The oxygen tension at half saturation and standard conditions (P50st at pH 7.4, PCO2(40) mmHg and 37 degrees C) and the carbon dioxide or fixed-acid-induced Bohr effect (dlogP50/dpH) were determined. Samples of fresh blood and blood depleted of or enriched with DPG were studied. In the absence of measurable DPG, the equine and human blood had similar mean (SD) values of P50st (16.6 [0.6] and 16.2 [0.7] mmHg, r...
Bryant CE, Clarke KW, Thompson J.Medetomidine was administered intravenously to six sheep at 5, 10 and 20 micrograms kg-1 and to one horse and four ponies at 5 and 10 micrograms kg-1. In both species medetomidine resulted in significant decreases in heart rate and cardiac output and, initially, in an increase in arterial blood pressure. In the ponies this increase in blood pressure was followed by a significant and prolonged decrease, but in the sheep the secondary decrease in blood pressure was not statistically significant. In the sheep, the three doses of medetomidine resulted in profound and significant decreases in arter...
Guthrie AJ, Short CR, Swan GE, Mülders MS, Killeen VM, Nurton JP.This paper describes the use of subcutaneously-placed tissue chambers as a sterile soft-tissue inflammation model in Thoroughbred horses. Acute, non-immune inflammation was initiated by injecting a sterile lambda carrageenan solution into a tissue chamber. This model was used to study the temporal changes in oxygen and carbon dioxide tensions, pH, bicarbonate, protein, albumin, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) concentrations, cell counts and differential counts in tissue fluid from inflamed tissue chambers and control chambers. Skin temperatures over control and inflamed chamb...
Art T, Votion D, Lekeux P.The purpose of this study was 1) to measure and compare some physiological parameters in horses during a standardised treadmill exercise performed either in temperate atmospheric conditions (TC) (ambient temperature: 15 degrees C; relative humidity: 55%), or in hot and humid conditions (HHC) (ambient temperature: 30 degrees C; relative humidity: 75%) and 2) to follow the recovery of the same horses during 1 h after both tests. Five healthy fit Standardbred horses were investigated twice at 8 days interval, in TC and in HHC. Some measurements were made during a standardised treadmill exercise t...
McKane SA, Rose RJ, Evans DL.Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalve...
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...
Gauvreau GM, Wilson BA, Schnurr DL, Young SS, McDonell WN.The purpose of this study was to develop a technique to measure the oxygen cost of ventilation and the values of ventilatory parameters in seven normal horses rebreathing carbon dioxide (CO2). All the horses responded to increased inspiratory levels of CO2 by increasing their tidal volume (VT) and frequency of breathing (Vf). The mean (SE) oxygen cost litre-1 of ventilation, measured at rates of ventilation greater than 200 litres min-1 was 1.7 (0.04) ml litre-1, similar to that of normal human subjects ventilating submaximally. It was concluded that the CO2 rebreathing test is a practical, no...
Pelletier N, Leith DE.Thoroughbred horses (TB) have no ventilatory response to added CO2 during near-maximal exercise. To see whether that reflects mechanical limits to ventilation or the control of breathing, we examined the effects of varying inspired O2 fraction (0.16, 0.21, or 0.30) in five normal TB standing quietly and galloping at 10 and 14 m/s on a level treadmill. We measured gas exchange (O2 consumption and CO2 production) and ventilation with a flow-through mask system. We also measured PO2, PCO2, and O2 contents in arterial and mixed venous blood and calculated cardiac output by using the Fick equation....
Johnson CB, Adam EN, Taylor PM.Hypoxaemia commonly develops during general anaesthesia and in the recovery period in horses. The Hudson demand valve has been used to increase arterial PO2, but it has been found to increase airway resistance considerably when used during spontaneous ventilation. This paper evaluates a modification of the valve designed to reduce this resistance. The effects of the valve and its modification on arterial oxygen (PaO2), and carbon dioxide (PaCO2) tensions were evaluated in four ponies anaesthetised by a total intravenous technique. The valve increased PaO2 from 8.3 +/- 1.1 to 32.7 +/- 7.6 kPa d...
Evans DL, Silverman EB, Hodgson DR, Eaton MD, Rose RJ.The relationship between gait and the respiratory response to exercise was examined in five standardbred racehorses which exercised on a treadmill at a pace and a gallop. After an initial warm-up, respiratory rate and stride frequency were measured after one and two minutes of treadmill exercise at 80 per cent of maximal oxygen consumption (VO2max), after one minute at 100 per cent VO2max and after two minutes at 100 per cent VO2max (galloping horses only). Exercise at 100 per cent VO2max continued until the horses showed signs of fatigue. Arterial blood was collected during exercise and when ...
Art T, Votion D, McEntee K, Amory H, Linden A, Close R, Lekeux P.Two randomly distributed groups of thoroughbred horses were compared during a 12-week period for their cardio-respiratory and metabolic adjustment to strenuous exercise, training and detraining. The horses were trained following the same standardized schedule and were regularly investigated using standardized treadmill exercise tests (SET) of increasing speed. After the first SET and during the whole experimental period, a group of 6 horses received a probiotic (Bioracing) once a day while a group of 5 horses received a placebo. All other conditions were similar for both groups. During each SE...
Hinchcliff KW, McKeever KH, Muir WW, Sams R.The effect of furosemide-induced weight loss on the energetic responses of horses to running was examined in a 3-way crossover study. Eight 2- to 3-year-old Standardbred mares received, in random order, 10 ml of saline solution 4 hours before running on a treadmill (control trial, C); or, during 2 trials, 1 mg of furosemide/kg of body weight, i.v., 4 hours before running. During one of the trials when the horses received furosemide, they carried weight equal to that lost over the 3.75 hours after furosemide administration while running (furosemide-loaded, FL), and during the other trial they d...
Southwood LL, Evans DL, Hodgson DR, Bryden WL, Rose RJ.The effects of roughage source on metabolism and exercise capacity were investigated using 6, previously conditioned, mature thoroughbred horses in a cross-over experiment. The horses were assigned to either non-alfalfa or alfalfa roughage diets which were isocaloric. The diets were fed for 2 weeks, after which the horses were exercise tested and then fed the alternate diet. Horses were exercised on a high-speed treadmill using a rapid incremental test. Arterial blood samples were collected for blood gas analysis and acid base measurements and venous blood samples for lactate and red blood cel...
Butler PJ, Woakes AJ, Smale K, Roberts CA, Hillidge CJ, Snow DH, Marlin DJ.A new design of flowmeter is described and used in a comprehensive study of the respiratory and cardiovascular adjustments that occur during a standardised exercise test in Thoroughbred horses. The flowmeter system and associated lightweight, fibreglass mask (total mass, 0.7 kg) have a maximum dead space of 500 ml and negligible resistance to airflow. They have no systematic effect on blood gases and, together with a rapidly responding mass spectrometer, enable an accurate computation of gas exchange to be performed together with breath-by-breath determination of other respiratory variables. A...
Moore RM, Trim CM.Facial artery pressure, central venous pressure, heart rate, and lateral ventricle cerebrospinal fluid (CSF) pressure (LV-CSFP) were measured in 10 pentobarbital-anesthetized horses at arterial partial pressure of carbon dioxide (PaCO2) values of 40, 60, and 80 mm Hg, produced by varying the inspired carbon dioxide concentration. Variables were recorded at 5-minute intervals for 15 minutes at each level of PaCO2. Arterial blood gas analysis was performed at the end of the 15-minute time period for each level of PaCO2. Lateral ventricle CSF pressure was significantly increased (p < .05) at a...
Wong DM, Hepworth-Warren KL, Sponseller BT, Howard JM, Wang C.OBJECTIVE To assess multiple central venous and arterial blood variables that alone or in conjunction with one another reflect global oxygenation status in healthy neonatal foals. ANIMALS 11 healthy neonatal foals. PROCEDURES Central venous and arterial blood samples were collected from healthy neonatal foals at 12, 24, 36, 48, 72, and 96 hours after birth. Variables measured from central venous and arterial blood samples included oxygen saturation of hemoglobin, partial pressure of oxygen, lactate concentration, partial pressure of carbon dioxide, and pH. Calculated variables included venous-...
Hinchcliff KW, McKeever KH, Muir WW, Sams R.The effect of furosemide-induced weight loss on the energetic responses of horses to running was examined in a 3-way crossover study. Eight 2- to 3-year-old Standardbred mares received, in random order, 10 ml of saline solution 4 hours before running on a treadmill (control trial, C); or, during 2 trials, 1 mg of furosemide/kg of body weight, i.v., 4 hours before running. During one of the trials when the horses received furosemide, they carried weight equal to that lost over the 3.75 hours after furosemide administration while running (furosemide-loaded, FL), and during the other trial they d...
Littlejohn A, Bowles F.The haemoglobin concentration, the partial pressures of oxygen and carbon dioxide, the oxygen content and the pH were determined in the arterial and mixed venous blood of 5 normal and 3 horses with chronic obstructive pulmonary disease (COPD) at 3 stages of an exercise distance of 1200 m. Arterial and mixed venous samples were collected simultaneously by means of an automatic technique during the walk, trot and gallop at 0-100 m, at 500-600 m and at 1100-1200 m. The standard bicarbonate and the lactic and pyruvic acid concentrations were also determined in arterial and mixed venous blood. High...
Evans DL, Rose RJ.The effects of a respiratory gas collection mask on arterial blood gases, acid base values, oxygen content, respiratory frequency and heart rate, were investigated in standardbred horses during treadmill exercise at speeds up to 10 m sec-1 and a treadmill slope of 10 per cent. The mask had no significant effect on heart rates during exercise, but respiratory frequency was lower when the mask was used. The increase in respiratory frequency as treadmill velocity increased was also significantly slower with the mask operative. Arterial carbon dioxide tensions were significantly higher during exer...
Sainas G, Melis S, Corona F, Loi A, Ghiani G, Milia R, Tocco F, Marongiu E, Crisafulli A.The purpose of the present investigation was to study the metabolic demand and cardiovascular response during a typical horse riding session. Methods: To this aim, 19 (9 male, 10 female) riders, regularly participating in competitions, were enrolled. They underwent a preliminary, incremental exercise test on a cycle-ergometer to assess their anaerobic threshold (AT) and VO2max. Then, participants underwent a riding training session, which comprised periods of walking, trotting, and cantering for a total of 20 min. Oxygen uptake (VO2), carbon dioxide production (VCO2), and heart rate (HR) were...
Wright BD, Hildebrand SV.To compare arterial oxygen and carbon dioxide tensions in apneic and spontaneously ventilating horses recovering from anesthesia. Methods: Randomized clinical trial. Methods: Forty-two healthy horses averaging 466 ± 106 kg and 6 ± 5 years of age. Methods: Anesthetized horses undergoing a variety of surgical procedures and receiving positive pressure ventilation (IPPV) were divided into two equal groups. One group was allowed to return to spontaneous ventilation prior to disconnection from the anesthetic circuit (weaned). The other group remained apneic during transport to a recovery stall. A...
Hillidge CJ, Lees P.Respiratory function and acid-base variables were studied in Welsh Mountain ponies before and at predetermined times after the intravenous injection of Immobilon and Revivon.A marked depression of respiratory rate was accompanied by large reductions in arterial blood oxygen tension and saturation and the development of a mild respiratory acidosis following the injection of Immobilon. It was concluded that at least three factors contributed to the hypoxic hypoxia produced by Immobilon; the posture of lateral recumbency, the decrease in respiratory rate and the laboured character of the respirat...
Art T, Votion D, McEntee K, Amory H, Linden A, Close R, Lekeux P.Two randomly distributed groups of thoroughbred horses were compared during a 12-week period for their cardio-respiratory and metabolic adjustment to strenuous exercise, training and detraining. The horses were trained following the same standardized schedule and were regularly investigated using standardized treadmill exercise tests (SET) of increasing speed. After the first SET and during the whole experimental period, a group of 6 horses received a probiotic (Bioracing) once a day while a group of 5 horses received a placebo. All other conditions were similar for both groups. During each SE...
Moore RM, Trim CM.Facial artery pressure, central venous pressure, heart rate, and lateral ventricle cerebrospinal fluid (CSF) pressure (LV-CSFP) were measured in 10 pentobarbital-anesthetized horses at arterial partial pressure of carbon dioxide (PaCO2) values of 40, 60, and 80 mm Hg, produced by varying the inspired carbon dioxide concentration. Variables were recorded at 5-minute intervals for 15 minutes at each level of PaCO2. Arterial blood gas analysis was performed at the end of the 15-minute time period for each level of PaCO2. Lateral ventricle CSF pressure was significantly increased (p < .05) at a...
Art T, Votion D, Lekeux P.The purpose of this study was 1) to measure and compare some physiological parameters in horses during a standardised treadmill exercise performed either in temperate atmospheric conditions (TC) (ambient temperature: 15 degrees C; relative humidity: 55%), or in hot and humid conditions (HHC) (ambient temperature: 30 degrees C; relative humidity: 75%) and 2) to follow the recovery of the same horses during 1 h after both tests. Five healthy fit Standardbred horses were investigated twice at 8 days interval, in TC and in HHC. Some measurements were made during a standardised treadmill exercise t...
Jansson N.To evaluate the use of carbon dioxide (CO(2)) gas for joint distention during arthroscopy for removal of osteochondral (OC) fragments of the palmar/plantar aspect of the metacarpo (MCP)/metatarsophalangeal (MTP) joints in horses. Methods: Clinical study. Methods: Horses (26) with OC fragment(s) of palmar/plantar aspect of 1 or 2 MCP/MTP joint(s). Methods: OC fragments were removed using arthroscopic technique. Joint distention was maintained by isotonic Ringer's acetate at the beginning and at the end of the procedure but during fragment removal, CO(2) was used for joint distention. After surg...
Sutton GJ, Cawley A, Murphy C, Lau ML, Hibbert DB.Horse racing authorities impose a limit on the concentration of plasma 'total carbon dioxide' (TCO2), typically 36 mM with action taken above 37 mM, as measured by an electrochemical gas analyzer. It is of interest to understand the distribution of TCO2 in a 'normal' population of racehorses and determine probabilities of members of this population exceeding these current regulatory and action limits. TCO2 levels in equine plasma samples have been modelled for 12 months (2011-2012) of thoroughbred (3076 measurements) and standardbred (3788 measurements) data in Australia. The two populations h...
Blaze CA, Robinson NE.Apneic oxygenation was studied in six ponies for 30 minutes, and six horses for 10 minutes. Arterial blood was sampled at regular intervals for measurement of oxygen and carbon dioxide tensions (PaO2 and PaCO2) and calculation of alveolar-arterial oxygen tension difference (PAO2-PaO2). In both groups of animals, PaO2 decreased rapidly during the first 3 minutes of apnea, then more slowly. Although the mean value was above 100 mmHg at 10 minutes, there was considerable inter-animal variability. Before apnea, PAO2-PaO2 was slightly, but not significantly, larger in horses than in ponies and incr...
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. ...
Hubbell JA, Muir WW.The rate of rise of arterial partial pressure of carbon dioxide (PaCO2) was determined in 49 apneic halothane-anesthetized horses following controlled ventilation. Drugs given for induction of anesthesia did not affect the rapid rate of rise of PaCO2 during the first minute after controlled ventilation, the PaCO2 at 1 minute after controlled ventilation, or the PaCO2 at which spontaneous ventilation began. Horses given xylazine-ketamine for induction of anesthesia had a significantly (P less than 0.05) faster rate of rise of PaCO2 after 1 minute following controlled ventilation than did horses...
Noël PG, Couëtil L, Constable PD.Plastic heparinised vacutainer tubes are used for blood gas analysis in horses. This collection method may not be ideal because influx of atmospheric O(2) through the permeable plastic wall of the vacutainer tube and loss of CO(2) into the gas phase above the blood sample should increase blood PO(2) and decrease PCO(2), respectively. Objective: To determine the effects of collecting blood into plastic vacutainer tubes and storage conditions on blood gas analysis values. Methods: Blood was obtained from 6 healthy horses and tonometered at 37 °C with 12% O(2) and 5% CO(2). Three ml aliquots of ...
Johnson CB, Adam EN, Taylor PM.Hypoxaemia commonly develops during general anaesthesia and in the recovery period in horses. The Hudson demand valve has been used to increase arterial PO2, but it has been found to increase airway resistance considerably when used during spontaneous ventilation. This paper evaluates a modification of the valve designed to reduce this resistance. The effects of the valve and its modification on arterial oxygen (PaO2), and carbon dioxide (PaCO2) tensions were evaluated in four ponies anaesthetised by a total intravenous technique. The valve increased PaO2 from 8.3 +/- 1.1 to 32.7 +/- 7.6 kPa d...
Beazley SG, Focken A, Fernandez-Parra R, Thomas KL, Adler A, Duke-Novakovski T.To determine changes in distribution of lung ventilation with increasing intra-abdominal pressure (IAP) from carbon dioxide (CO) insufflation in standing sedated horses. Methods: Prospective experimental study. Methods: A group of six healthy adult horses. Methods: Each horse was sedated with acepromazine, detomidine and butorphanol and sedation maintained with a detomidine infusion. The horse was restrained in a stocks system and a 32 electrode electrical impedance tomography (EIT) belt was wrapped around the thorax at the fifth-sixth intercostal space. EIT images and arterial blood samples f...
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 ...
Cribb PH.Forty-five horses were maintained on halothane or isoflurane anesthesia for at least 90 minutes and received positive pressure ventilation after the first 30 minutes of anesthesia. Parameters monitored included end-tidal partial pressure of carbon dioxide (ETPCO2), arterial blood pressure, and arterial blood gases and pH. There was a statistically significant correlation between end-tidal carbon dioxide and arterial partial pressure of carbon dioxide (PaCO2) for both halothane and isoflurane anesthesia. There was no significant correlation between end-tidal carbon dioxide and either body weigh...
McKane SA, Rose RJ, Evans DL.Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalve...
Cruz AM, Coté N, McDonell WN, Geor RJ, Wilson BA, Monteith G, Li R.In this study, we aimed to define the effects of anesthesia and surgery on the resting energy expenditure of horses in experimental conditions. Six horses were used in a longitudinal study with 2 study periods: before and after anesthesia and surgery. Every horse underwent a standard 90-min ventral midline exploratory laparotomy. Oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured, with the use of a closed-circuit spirometry system, on 5 consecutive days immediately before and after the surgery. In 3 consecutive 5-min periods each day, the expired air was collected in a Collins ...
Cruz AM, Kerr CL, Bouré LP, Sears WC.To determine the cardiovascular effects of 60 minutes of abdominal insufflation with CO2 to an intra-abdominal pressure of 15 mm Hg in standing horses receiving a constant rate infusion of detomidine. Methods: 5 horses. Methods: Horses were randomly allocated into treatment or control groups. A washout period of a minimum of 7 days separated the 2 experimental periods of the crossover study. Catheters were placed into the right atrium, pulmonary artery, jugular vein, and right transverse facial artery after lidocaine infiltration. All horses were sedated with detomidine (8.54 microg/kg/h, i.v....
Wong DM, Alcott CJ, Wang C, Bornkamp JL, Young JL, Sponseller BA.To determine agreement between indirect measurements of end-tidal partial pressure of carbon dioxide (PetCO(2)) and saturation of hemoglobin with oxygen as measured by pulse oximetry (SpO(2)) with direct measurements of PaCO(2) and calculated saturation of hemoglobin with oxygen in arterial blood (SaO(2)) in conscious healthy and ill foals. Methods: Validation study. Methods: 10 healthy and 21 ill neonatal foals. Methods: Arterial blood gas analysis was performed on healthy and ill foals examined at a veterinary teaching hospital to determine direct measurements of PaCO(2) and PaO(2) along wit...
diBella G, Scandariato G, Suriano O, Rizzo A.The dependence of blood oxygen affinity and the Bohr effect on the concentration of 2,3-diphosphoglycerate (DPG) in erythrocytes was investigated in 24 trotter horses and 24 healthy men. The oxygen tension at half saturation and standard conditions (P50st at pH 7.4, PCO2(40) mmHg and 37 degrees C) and the carbon dioxide or fixed-acid-induced Bohr effect (dlogP50/dpH) were determined. Samples of fresh blood and blood depleted of or enriched with DPG were studied. In the absence of measurable DPG, the equine and human blood had similar mean (SD) values of P50st (16.6 [0.6] and 16.2 [0.7] mmHg, r...
Savage KA, Colahan PT, Tebbett IR, Rice BL, Freshwater LL, Jackson CA.To determine the effects of a dose of caffeine (2.5 mg/kg, IV) administered to physically fit Thoroughbreds during incremental exercise testing to fatigue on a treadmill. Methods: 10 conditioned Thoroughbreds. Methods: Horses were randomly assigned to receive caffeine or a control solution. Each horse received both treatments in a crossover design with a 3-week interval between treatments. Each horse was administered caffeine (2.5 mg/kg) or an equivalent amount of a control solution IV. One hour after injection, each horse performed an incremental exercise test to exhaustion. Hematologic value...
Bozorgmanesh R, Sutton-Burges JW, Tablin F.Equine whole blood collection and storage methods have been evaluated to assess red blood cell viability; however, platelet (PLT) viability has not been comprehensively assessed. Objective: The purpose of the study was to compare viability of PLTs collected in whole blood into 2 different anticoagulants. Methods: Whole blood from 6 healthy adult Thoroughbred horses was collected into citrate-phosphate-dextrose-adenine (CPDA) or acid-citrate-dextrose (ACD). Platelet count, pH, and concentrations of glucose, lactate, carbon dioxide, oxygen, bicarbonate, sodium, potassium, and chloride were measu...
Guthrie AJ, Short CR, Swan GE, Mülders MS, Killeen VM, Nurton JP.This paper describes the use of subcutaneously-placed tissue chambers as a sterile soft-tissue inflammation model in Thoroughbred horses. Acute, non-immune inflammation was initiated by injecting a sterile lambda carrageenan solution into a tissue chamber. This model was used to study the temporal changes in oxygen and carbon dioxide tensions, pH, bicarbonate, protein, albumin, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) concentrations, cell counts and differential counts in tissue fluid from inflamed tissue chambers and control chambers. Skin temperatures over control and inflamed chamb...
Krzywanek H, Milne DW, Gabel AA, Smith LG.Blood gases, lactic acid concentrations, and pH were measured in arterial and mixed venous blood in moderately conditioned Standardbred horses after a standardized exercise load of 1.6 km in 2 minutes, 40 seconds. Samples were obtained at rest, immediately after exercise, and at 3, 6, 15, 30, and 60 minutes after exercise. Arterial oxygen tension and mixed venous oxygen tension increased after exercise, reaching peak values at 6 minutes. Arterial oxygen tension returned to the resting (preexercise) value by 15 minutes, and mixed venous oxygen tension by 30 minutes. Arterial carbon dioxide tens...
