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Peters CM, Dempsey JA, Hopkins SR, Sheel AW. Is the Lung Built for Exercise? Advances and Unresolved Questions. Med Sci Sports Exerc 2023; 55:2143-2159. [PMID: 37443459 DOI: 10.1249/mss.0000000000003255] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/15/2023]
Abstract
ABSTRACT Nearly 40 yr ago, Professor Dempsey delivered the 1985 ACSM Joseph B. Wolffe Memorial Lecture titled: "Is the lung built for exercise?" Since then, much experimental work has been directed at enhancing our understanding of the functional capacity of the respiratory system by applying complex methodologies to the study of exercise. This review summarizes a symposium entitled: "Revisiting 'Is the lung built for exercise?'" presented at the 2022 American College of Sports Medicine annual meeting, highlighting the progress made in the last three-plus decades and acknowledging new research questions that have arisen. We have chosen to subdivide our topic into four areas of active study: (i) the adaptability of lung structure to exercise training, (ii) the utilization of airway imaging to better understand how airway anatomy relates to exercising lung mechanics, (iii) measurement techniques of pulmonary gas exchange and their importance, and (iv) the interactions of the respiratory and cardiovascular system during exercise. Each of the four sections highlights gaps in our knowledge of the exercising lung. Addressing these areas that would benefit from further study will help us comprehend the intricacies of the lung that allow it to meet and adapt to the acute and chronic demands of exercise in health, aging, and disease.
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Affiliation(s)
| | - Jerome A Dempsey
- Population Health Science, John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin-Madison, Madison, WI
| | - Susan R Hopkins
- Department of Radiology, University of California San Diego, La Jolla, CA
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2
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Ebisuda Y, Mukai K, Takahashi Y, Ohmura H. Effect of high ambient temperature on physiological responses during incremental exercise in Thoroughbred horses. COMPARATIVE EXERCISE PHYSIOLOGY 2023. [DOI: 10.3920/cep220018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
Abstract
Several reports have suggested that the risk of exertional heat illness (EHI) in Thoroughbred racehorses increases in high ambient temperatures. Heat dissipation in horses during exercise becomes less efficient when the body temperature and ambient temperature are close. Therefore, we hypothesised that exercise at 40 °C may increase body temperature, oxygen consumption, and cardiac output during incremental exercise tests compared to 20 and 30 °C. Six trained Thoroughbred horses were studied in a randomised, crossover design at three ambient temperatures with a 6-day washout period. Using a 3% inclined treadmill, horses performed incremental exercise tests at 1.7, 3.5, 6, 8, and 10 m/s for 90 s at ambient temperatures of 20, 30, and 40 °C. The effects of ambient temperature at 10 m/s on physiological variables were analysed using mixed models (P<0.05). Pulmonary arterial temperature and rectal temperature at 40 °C were higher than those at 20 °C (P<0.001) and 30 °C (P<0.001). Similarly, oxygen consumption (vs 20 °C, P=0.009; vs 30 °C, P=0.006) and cardiac output (vs 20 °C, P=0.001; vs 30 °C, P=0.001) at 40 °C were higher than those at 20 and 30 °C. Arterial O2 partial pressure, O2 saturation, and pH at 40 °C were lower than those at 20 and 30 °C. Arterial CO2 partial pressure at 40 °C was higher than that at 20 and 30 °C. No differences were observed in arterial-mixed venous O2 concentration difference (P=0.391) and plasma lactate concentration (P=0.134) at different ambient temperatures. These results indicate that exercise at 40 °C causes excessive high body temperature, decreased running economy, and increased cardiac output compared to exercise at 20 and 30 °C. We strongly suggest that trainers and veterinarians should anticipate the occurrence of increased thermal stresses when ambient temperature is extremely high even in dry conditions and prepare to mitigate the risk of EHI from the perspective of equine welfare.
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Affiliation(s)
- Y. Ebisuda
- Sports Science Division, Equine Research Institute, Japan Racing Association, Shiba1400-4, Shimotsuke, Tochigi 329-0412, Japan
| | - K. Mukai
- Sports Science Division, Equine Research Institute, Japan Racing Association, Shiba1400-4, Shimotsuke, Tochigi 329-0412, Japan
| | - Y. Takahashi
- Sports Science Division, Equine Research Institute, Japan Racing Association, Shiba1400-4, Shimotsuke, Tochigi 329-0412, Japan
| | - H. Ohmura
- Sports Science Division, Equine Research Institute, Japan Racing Association, Shiba1400-4, Shimotsuke, Tochigi 329-0412, Japan
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Mazan M. Equine exercise physiology-challenges to the respiratory system. Anim Front 2022; 12:15-24. [PMID: 35711503 PMCID: PMC9197307 DOI: 10.1093/af/vfac035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Melissa Mazan
- Clinical Sciences, Tufts University Cummings School of Veterinary Medicine, 200 Westborough Road, North Grafton, MA 01536, USA
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Oliveira T, Bogossian P, Hilgert A, Fernandes W. Use of external nasal strip influences alveolar cell population of horses after exercise. ARQ BRAS MED VET ZOO 2021. [DOI: 10.1590/1678-4162-12325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
ABSTRACT The nasal strip is widely used in horses during exercise, but effects of using a nasal strip are controversial and little is known about its effect on horses undergoing endurance events. The aim of this study was to determine whether the use of nasal strips influences alveolar cell population assessed by bronchoalveolar lavage (BAL), tidal volume, and nasal airflow rate. Six Arabian horses were subjected to two low intensity tests on a treadmill, with and without application of a commercial external nasal strip. Tidal volumes and airflow rates were measured during the test; two hours after the test, BAL was performed to assess cytology of pulmonary secretions. The lavage fluid showed increased neutrophil count after exercise in animals with the nasal strip (P<0.05). This suggests that turbulence of airflow through the nasal cavity may have diminished with nasal strip use, thus allowing larger particles to be deposited more distally in the respiratory system, inducing a more intense neutrophilic response. No differences in tidal volumes or airflow rates were observed between groups (with or without nasal strips) during the test (P>0.05). The use of nasal strips seems to influence alveolar cell population during and after exercise in horses after low intensity exercise tests. Further studies are needed to verify whether alveolar cell population is related to poor exercise performance in horses.
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Stefanik E, Drewnowska O, Lisowska B, Turek B. Causes, Effects and Methods of Monitoring Gas Exchange Disturbances during Equine General Anaesthesia. Animals (Basel) 2021; 11:2049. [PMID: 34359177 PMCID: PMC8300395 DOI: 10.3390/ani11072049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/30/2021] [Accepted: 07/06/2021] [Indexed: 02/06/2023] Open
Abstract
Horses, due to their unique anatomy and physiology, are particularly prone to intraoperative cardiopulmonary disorders. In dorsally recumbent horses, chest wall movement is restricted and the lungs are compressed by the abdominal organs, leading to the collapse of the alveoli. This results in hypoventilation, leading to hypercapnia and respiratory acidosis as well as impaired tissue oxygen supply (hypoxia). The most common mechanisms disturbing gas exchange are hypoventilation, atelectasis, ventilation-perfusion (V/Q) mismatch and shunt. Gas exchange disturbances are considered to be an important factor contributing to the high anaesthetic mortality rate and numerous post-anaesthetic side effects. Current monitoring methods, such as a pulse oximetry, capnography, arterial blood gas measurements and spirometry, may not be sufficient by themselves, and only in combination with each other can they provide extensive information about the condition of the patient. A new, promising, complementary method is near-infrared spectroscopy (NIRS). The purpose of this article is to review the negative effect of general anaesthesia on the gas exchange in horses and describe the post-operative complications resulting from it. Understanding the changes that occur during general anaesthesia and the factors that affect them, as well as improving gas monitoring techniques, can improve the post-aesthetic survival rate and minimize post-operative complications.
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Affiliation(s)
- Elżbieta Stefanik
- Department of Large Animals Diseases and Clinic, Institute of Veterinary Medicine, Warsaw University of Life Sciences, Nowoursynowska 100, 02-797 Warsaw, Poland;
| | - Olga Drewnowska
- Department of Large Animals Diseases and Clinic, Institute of Veterinary Medicine, Warsaw University of Life Sciences, Nowoursynowska 100, 02-797 Warsaw, Poland;
| | - Barbara Lisowska
- National Geriatrics, Rheumatology and Rehabilitation Institute, Spartańska 1, 02-637 Warsaw, Poland;
| | - Bernard Turek
- Department of Large Animals Diseases and Clinic, Institute of Veterinary Medicine, Warsaw University of Life Sciences, Nowoursynowska 100, 02-797 Warsaw, Poland;
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Reef VB, Davidson EJ, Slack J, Stefanovski D. Hypercapnia and hyperlactatemia were positively associated with higher-grade arrhythmias during peak exercise in horses during poor performance evaluation on a high-speed treadmill. Vet J 2020; 266:105572. [PMID: 33323171 DOI: 10.1016/j.tvjl.2020.105572] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 10/09/2020] [Accepted: 11/02/2020] [Indexed: 01/21/2023]
Abstract
Cardiac arrhythmias are common in horses during exercise, especially immediately post-exercise. The objectives of this study were to: (1) describe the frequency and type of cardiac arrhythmias detected in horses during incremental high-speed treadmill exercise testing (ITET); (2) determine if arterial blood gas (ABG) changes at peak and immediately post-exercise were associated with arrhythmias; and (3) determine whether upper or lower airway disease was associated with exercising cardiac arrhythmias. Horses (n = 368) presenting for an ITET underwent resting and exercising upper airway endoscopy, resting, exercising and post-exercise electrocardiography, resting and post-exercise echocardiography and exercising ABG. Arrhythmias were graded by the most severe arrhythmia present. Grade 1 arrhythmias were defined as one or two atrial (APCs) or ventricular premature complexes (VPCs), or one APC and one VPC, detected in 6.9% at peak and 16% at 0-2 min post exercise.. Grade 2 arrhythmias were >2 APCs or VPCs, or both, detected in 5.8% at peak and 16.6% at 0-2 min post exercise. Grade 3 included complex arrhythmias (couplets, triplets, R on T, multiform complexes or paroxysmal atrial or ventricular tachycardia), detected in 4.4% at peak and 7.3% at 0-2 min post exercise. Both partial pressure of arterial CO2 (PaCO2; P = 0.008) and lactate (P = 0.031) were significantly associated with arrhythmias occurring at peak exercise, but not immediately post-exercise. As PaCO2 and lactate increased, arrhythmia severity increased. Blood pH was significantly associated with grades 2 and 3 arrhythmias at 0-2 min post ITET (OR = 0.0002; P < 0.001). There was no significant association between grades 2 and 3 cardiac arrhythmias, inflammatory airway disease (IAD), or exercise-induced pulmonary hemorrhage (EIPH). When adjusted for lactate concentration (P = 0.06), higher PaCO2 concentrations in horses with and without exercising upper respiratory tract (URT) obstruction were associated with higher likelihood of grades 2 and 3 arrhythmias (P < 0.01). This study demonstrated that at peak exercise, with severe hypercapnia and hyperlactatemia, there was increased risk for grades 2 or 3 cardiac arrhythmias and, as the PaCO2 and lactate values increased further, the severity of those arrhythmias increased.
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Affiliation(s)
- V B Reef
- Department of Clinical Studies, New Bolton Center, University of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA.
| | - E J Davidson
- Department of Clinical Studies, New Bolton Center, University of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA
| | - J Slack
- Department of Clinical Studies, New Bolton Center, University of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA
| | - D Stefanovski
- Department of Clinical Studies, New Bolton Center, University of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA
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Dempsey JA, La Gerche A, Hull JH. Is the healthy respiratory system built just right, overbuilt, or underbuilt to meet the demands imposed by exercise? J Appl Physiol (1985) 2020; 129:1235-1256. [PMID: 32790594 DOI: 10.1152/japplphysiol.00444.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In the healthy, untrained young adult, a case is made for a respiratory system (airways, pulmonary vasculature, lung parenchyma, respiratory muscles, and neural ventilatory control system) that is near ideally designed to ensure a highly efficient, homeostatic response to exercise of varying intensities and durations. Our aim was then to consider circumstances in which the intra/extrathoracic airways, pulmonary vasculature, respiratory muscles, and/or blood-gas distribution are underbuilt or inadequately regulated relative to the demands imposed by the cardiovascular system. In these instances, the respiratory system presents a significant limitation to O2 transport and contributes to the occurrence of locomotor muscle fatigue, inhibition of central locomotor output, and exercise performance. Most prominent in these examples of an "underbuilt" respiratory system are highly trained endurance athletes, with additional influences of sex, aging, hypoxic environments, and the highly inbred equine. We summarize by evaluating the relative influences of these respiratory system limitations on exercise performance and their impact on pathophysiology and provide recommendations for future investigation.
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Affiliation(s)
- Jerome A Dempsey
- John Robert Sutton Professor of Population Health Sciences, John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Andre La Gerche
- Clinical Research Domain, Baker Heart and Diabetes Institute, Melbourne, Australia.,National Center for Sports Cardiology, St. Vincent's Hospital, Melbourne, Fitzroy, Australia
| | - James H Hull
- Department of Respiratory Medicine, Royal Brompton Hospital, London, United Kingdom.,Institute of Sport, Exercise and Health (ISEH), University College London, United Kingdom
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Katz LM, Stallard J, Holtby A, Hill EW, Allen K, Sweeney J. Inspiratory muscle training in young, race-fit Thoroughbred racehorses during a period of detraining. PLoS One 2020; 15:e0225559. [PMID: 32275657 PMCID: PMC7147778 DOI: 10.1371/journal.pone.0225559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/25/2020] [Indexed: 11/19/2022] Open
Abstract
Although inspiratory muscle training (IMT) is reported to improve inspiratory muscle strength in humans little has been reported for horses. We tested the hypothesis that IMT would maintain and/or improve inspiratory muscle strength variables measured in Thoroughbreds during detraining. Thoroughbreds from one training yard were placed into a control (Con, n = 3 males n = 7 females; median age 2.2±0.4 years) or treatment group (Tr, n = 5 males, n = 5 females; median age 2.1±0.3 years) as they entered a detraining period at the end of the racing/training season. The Tr group underwent eight weeks of IMT twice a day, five days per week using custom-made training masks with resistance valves and an incremental threshold of breath-loading protocol. An inspiratory muscle strength test to fatigue using an incremental threshold of breath-loading was performed in duplicate before (T0) and after four (T1) and eight weeks (T2) of IMT/no IMT using a custom-made testing mask and a commercial testing device. Inspiratory measurements included the total number of breaths achieved during the test, average load, peak power, peak volume, peak flow, energy and the mean peak inspiratory muscle strength index (IMSi). Data were analysed using a linear mixed effects model, P≤0.05 significant. There were no differences for inspiratory measurements between groups at T0. Compared to T0, the total number of breaths achieved (P = 0.02), load (P = 0.003) and IMSi (P = 0.01) at T2 had decreased for the Con group while the total number of breaths achieved (P<0.001), load (P = 0.03), volume (P = 0.004), flow (P = 0.006), energy (P = 0.01) and IMSi (P = 0.002) had increased for the Tr group. At T2 the total number of breaths achieved (P<0.0001), load (P<0.0001), volume (P = 0.02), energy (P = 0.03) and IMSi (P<0.0001) were greater for the Tr than Con group. In conclusion, our results support that IMT can maintain and/or increase aspects of inspiratory muscle strength for horses in a detraining programme.
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Affiliation(s)
- Lisa M. Katz
- UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland
- * E-mail:
| | - Jessica Stallard
- UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland
| | | | - Emmeline W. Hill
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, Ireland
| | - Kate Allen
- School of Veterinary Sciences, University of Bristol, Bristol, United Kingdom
| | - James Sweeney
- Department of Mathematics & Statistics, University of Limerick, Limerick, Ireland
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9
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Léguillette R, Greco-Otto P, Sides R, Bond S, El Alami S, Bayly W. Relative aerobic and anaerobic energy contribution in race fit endurance and Thoroughbred racehorses during strenuous exercise. COMPARATIVE EXERCISE PHYSIOLOGY 2019. [DOI: 10.3920/cep190019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective was to compare fit Arabian endurance and Thoroughbred racehorses’ responses to a maximal intensity standardised incremental treadmill test (MaxSIT) with respect to: (1) their relative aerobic contributions during maximal exercise; and (2) selected physiological parameters related to performance. Six high-level endurance Arabians and six race-ready Thoroughbreds performed a MaxSIT starting at 8 m/s and increasing by 1 m/s increments 60 s until maximum oxygen consumption (V̇O2max) was reached. Heart rate (HR), blood lactate concentration (BLac), haematocrit (Hct), minute ventilation (V̇E) and oxygen consumption (V̇O2) were measured. V̇O2max, the speeds at which the HR were 200 and 160 bpm, respectively (V200, V160), the speed at which the BLac reached 4 mmol/l (VLa4) and lactate at HR200 (BLa200) were calculated. The relative aerobic energy input was determined using ΔBLacPeak-Resting increase as previously described. Data were expressed as median with interquartile range and analysed with a Wilcoxon rank sum test (P<0.05). Endurance horses had greater V̇O2max (202.5 ml/(kg.min) (190.3-211) vs 152.7 ml/(kg.min) (140.5-158.3); P<0.001) and had a greater aerobic energy contribution to total exercise effort (89.9% (87.0-96) vs 82.8% (81.1-84.1); P=0.009) than Thoroughbreds. Endurance horses reached HR>200 bpm on the treadmill, but had a lower HRmax (210 bpm (205-217) vs 226 bpm (219-228); P=0.008), BLa200 (3.8 mmol/l (2.7-5.5) vs 4.8 mmol/l (3.6-5.2); P<0.001) and Hctmax (56.4% (54.9-57.5) vs 61.5% (59-64); P=0.002). Endurance horses median VLa4 was 11.6 m/s (11.0-13.0); V200=11.9 m/s (10.9-12.3) and V160=8.5 m/s (7.2-8.6). Because of the HR and speed characteristics of modern endurance races, we proposed BLa200 as a new calculated parameter with which to assess endurance horses. Trained endurance horses accumulate less lactate, have a greater V̇O2max and relative aerobic contribution to their energy requirements at maximal intensity exercise despite a lower blood haematocrit.
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Affiliation(s)
- R. Léguillette
- Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - P. Greco-Otto
- Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - R. Sides
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
| | - S.L. Bond
- Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - S. El Alami
- Al Reef Stables, Abu Dhabi, United Arab Emirates
| | - W. Bayly
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
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Meir JU, York JM, Chua BA, Jardine W, Hawkes LA, Milsom WK. Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose ( Anser indicus). eLife 2019; 8:e44986. [PMID: 31478481 PMCID: PMC6721836 DOI: 10.7554/elife.44986] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 07/25/2019] [Indexed: 11/16/2022] Open
Abstract
The bar-headed goose is famed for migratory flight at extreme altitude. To better understand the physiology underlying this remarkable behavior, we imprinted and trained geese, collecting the first cardiorespiratory measurements of bar-headed geese flying at simulated altitude in a wind tunnel. Metabolic rate during flight increased 16-fold from rest, supported by an increase in the estimated amount of O2 transported per heartbeat and a modest increase in heart rate. The geese appear to have ample cardiac reserves, as heart rate during hypoxic flights was not higher than in normoxic flights. We conclude that flight in hypoxia is largely achieved via the reduction in metabolic rate compared to normoxia. Arterial [Formula: see text] was maintained throughout flights. Mixed venous PO2 decreased during the initial portion of flights in hypoxia, indicative of increased tissue O2 extraction. We also discovered that mixed venous temperature decreased during flight, which may significantly increase oxygen loading to hemoglobin.
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Affiliation(s)
- Jessica U Meir
- NASA Johnson Space CenterHoustonUnited States
- University of British ColumbiaVancouverCanada
| | - Julia M York
- University of British ColumbiaVancouverCanada
- University of Texas at AustinAustinUnited States
| | - Bev A Chua
- University of British ColumbiaVancouverCanada
| | | | - Lucy A Hawkes
- Hatherly Laboratories, College of Life and Environmental SciencesUniversity of ExeterExeterUnited Kingdom
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Bond S, Greco-Otto P, Sides R, Léguillette R, Bayly W. Assessment of high-intensity over-ground conditioning and simulated racing on aerobic and anaerobic capacities in racehorses. COMPARATIVE EXERCISE PHYSIOLOGY 2019. [DOI: 10.3920/cep190002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A prospective, randomised study assessed the impact of high-intensity racetrack conditioning on aerobic and anaerobic capacities in seasoned Thoroughbred racehorses. The effect of 10 weeks race conditioning and two simulated races on V̇O2maxand maximum accumulated oxygen deficit (MAOD) were evaluated. An incremental treadmill test to determine V̇O2max, followed by three supramaximal runs to fatigue (at speeds (V105%, V115%, V125%) corresponding to oxygen requirements 105%, 115% and 125% of V̇O2max, in randomised order) were performed at each timepoint (T1 [pre-conditioning] and T2 [post-conditioning]). Prior to T1, racehorses were briefly de-trained for four-six weeks and given low-level treadmill conditioning to prepare them for the more strenuous race conditioning after T1. Paired variables between T1 and T2 were analysed using a paired t-test. A 2-way RM ANOVA compared variables with >1 measurement. Speed at V̇O2max(P=0.04) and V̇O2max(P=0.01) increased with conditioning. Calculated speeds for the supramaximal runs increased for V105% (P=0.02) and V115% (P=0.03) but not for V125% (P=0.08). There was no conditioning effect on time to fatigue (P=0.34), although it was different between all intensities (2.8, 2.2 and 1.4 mins at V105%, V115% and V125% respectively at T2). O2demand increased with conditioning (P=0.02) for each supramaximal intensity. On average, horses’ aerobic capacity improved 4.43% after conditioning. MAOD was unchanged with conditioning (P=0.25) and unaffected by exercise intensity. Fit racehorses that have undergone repeated intensive training programs, experience smaller, incremental improvement than completely unfit horses. The anaerobic capacity of previously trained racehorses is relatively stable, despite brief periods of de-training.
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Affiliation(s)
- S. Bond
- Faculty of Veterinary Medicine, Department of Veterinary Clinical and Diagnostic Services, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - P. Greco-Otto
- Faculty of Veterinary Medicine, Department of Veterinary Clinical and Diagnostic Services, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - R. Sides
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6610, USA
| | - R. Léguillette
- Faculty of Veterinary Medicine, Department of Veterinary Clinical and Diagnostic Services, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - W.M. Bayly
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6610, USA
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Dempsey JA. Respiratory Determinants of Exercise Limitation: Focus on Phrenic Afferents and the Lung Vasculature. Clin Chest Med 2019; 40:331-342. [PMID: 31078213 DOI: 10.1016/j.ccm.2019.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We examine 2 means by which the healthy respiratory system contributes to exercise limitation. These include the activation of respiratory and locomotor muscle afferent reflexes, which constrain blood flow and hasten fatigue in both sets of muscles, and the excessive increases in pulmonary vascular pressures at high cardiac outputs, which constrain O2 transport and precipitate maladaptive right ventricular remodeling in endurance-trained subjects.
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Affiliation(s)
- Jerome A Dempsey
- Department Population Health Sciences, University of Wisconsin-Madison, 707 WARF Building, 610 N. Walnut Street, WI 53726, USA.
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BROXTERMAN RYANM, CRAIG JESSEC, RICHARDSON RUSSELLS. The Respiratory Compensation Point and the Deoxygenation Break Point Are Not Valid Surrogates for Critical Power and Maximum Lactate Steady State. Med Sci Sports Exerc 2018; 50:2379-2382. [DOI: 10.1249/mss.0000000000001699] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Joyner MJ, Dempsey JA. Physiological Redundancy and the Integrative Responses to Exercise. Cold Spring Harb Perspect Med 2018; 8:cshperspect.a029660. [PMID: 28490539 DOI: 10.1101/cshperspect.a029660] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The biological responses to acute and chronic exercise are marked by a high level of physiological redundancy that operates at various levels of integration, including the molecular, cellular, organ-system, and whole-body scale. During acute exercise, this redundancy protects whole-body homeostasis in the face of 10-fold or more increases in whole-body metabolic rate. In some cases, there are "trade-offs" between optimizing the performance of a given organ or system versus whole-body performance. Physiological redundancy also plays a key role in the adaptive responses to exercise training and high levels of habitual physical activity, including the positive effects of regular exercise on health. Appreciation of the general principles of physiological redundancy is critical to (1) gain an overall understanding of short- and long-term responses to exercise, and (2) place physiological responses occurring at various levels of integration in perspective.
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Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Jerome A Dempsey
- John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706
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Hines MT. Clinical Approach to Commonly Encountered Problems. EQUINE INTERNAL MEDICINE 2018. [PMCID: PMC7158300 DOI: 10.1016/b978-0-323-44329-6.00007-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Dedar R, Kumar V, Bala P, Singh J, Pal Y, Legha R, Gupta A. Effect of electrolyte supplementation on electrolyte profile in Marwari horses during 20 km moderate intensity riding exercise. COMPARATIVE EXERCISE PHYSIOLOGY 2017. [DOI: 10.3920/cep160024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effect of electrolyte supplementation on plasma electrolyte profile in horses in hot environmental conditions was studied using sweat loss and sweat electrolyte concentration. Eleven adult Marwari mares were selected for the study. To develop an electrolyte supplement, 7 mares were given a preliminary 20 km moderate intensity exercise and the electrolyte supplement was designed on basis of their body weight loss and sweat electrolyte concentration during exercise. In the subsequent trials, 4 mares were kept in an exercise control group that did not receive the supplement (ECG), while 3 mares were kept in the exercise supplementation group (ESG) that received the supplement. Four other mares were used as resting controls (RG). ESG mares were daily fed 50 g electrolyte supplement and 150 g supplement orally 1 h before the 20 km trial. Mares of ESG and ECG groups were conferred 3 km trot + canter riding every day in the morning and a 20 km trot + canter ride on every 10th day of the total trial period of 40 days. Blood analysis revealed a significant (P<0.05) decline in plasma calcium and chloride concentrations immediately after exercise in both groups. There was significant less post-exercise decrease of plasma calcium and chloride concentration in ESG mares. Post-exercise plasma sodium concentration was higher (P<0.05) and plasma potassium concentration was lower only in ESG mares (P<0.05) compared to pre-exercise concentrations. The supplement did not affect the physiological responses (heart rate and rectal temperature). However, the changes in plasma sodium, potassium, calcium and chloride concentration were in favour of better performance in supplemented (ESG) mares and advocate sweat-developed electrolyte supplementation in riding mares.
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Affiliation(s)
- R.K. Dedar
- National Research Center on Equines, Bikaner, Rajasthan 334001, India
| | - V. Kumar
- National Research Center on Equines, Bikaner, Rajasthan 334001, India
| | - P.A. Bala
- National Research Center on Equines, Bikaner, Rajasthan 334001, India
| | - J. Singh
- National Research Center on Equines, Bikaner, Rajasthan 334001, India
| | - Y. Pal
- ICAR – National Research Center on Equines, Sirsa Road, Hisar, Haryana 125001, India
| | - R.A. Legha
- National Research Center on Equines, Bikaner, Rajasthan 334001, India
| | - A.K. Gupta
- ICAR – National Research Center on Equines, Sirsa Road, Hisar, Haryana 125001, India
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Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles. Animals (Basel) 2017; 7:ani7060041. [PMID: 28587125 PMCID: PMC5483604 DOI: 10.3390/ani7060041] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/22/2017] [Accepted: 05/23/2017] [Indexed: 01/05/2023] Open
Abstract
Simple Summary Horses have superior athletic capabilities due largely to their exceptional cardiorespiratory responses during exercise. This has particular relevance to horses’ potential to experience breathlessness, especially when their athletic performance is reduced by impaired respiratory function. Breathlessness, incorporating three types of unpleasant experiences, has been noted as of significant animal welfare concern in other mammals. However, the potential for breathlessness to occur in horses as usually ridden wearing bitted bridles has not yet been evaluated in detail. Accordingly, key physiological responses to exercise and the consequences of impaired respiratory function are outlined. Then the physiological control of breathing and the generation of the aversive experiences of breathlessness are explained. Finally, the potential for horses with unimpaired and impaired respiratory function to experience the different types of breathlessness is evaluated. This information provides a basis for considering the circumstances in which breathlessness may have significant negative welfare impacts on horses as currently ridden wearing bitted bridles. Potential beneficial impacts on respiratory function of using bitless bridles are then discussed with emphasis on the underlying mechanisms and their relevance to breathlessness. It is noted that direct comparisons of cardiorespiratory responses to exercise in horses wearing bitless and bitted bridles are not available and it is recommended that such studies be undertaken. Abstract Horses engaged in strenuous exercise display physiological responses that approach the upper functional limits of key organ systems, in particular their cardiorespiratory systems. Maximum athletic performance is therefore vulnerable to factors that diminish these functional capacities, and such impairment might also lead to horses experiencing unpleasant respiratory sensations, i.e., breathlessness. The aim of this review is to use existing literature on equine cardiorespiratory physiology and athletic performance to evaluate the potential for various types of breathlessness to occur in exercising horses. In addition, we investigate the influence of management factors such as rein and bit use and of respiratory pathology on the likelihood and intensity of equine breathlessness occurring during exercise. In ridden horses, rein use that reduces the jowl angle, sometimes markedly, and conditions that partially obstruct the nasopharynx and/or larynx, impair airflow in the upper respiratory tract and lead to increased flow resistance. The associated upper airway pressure changes, transmitted to the lower airways, may have pathophysiological sequelae in the alveolae, which, in their turn, may increase airflow resistance in the lower airways and impede respiratory gas exchange. Other sequelae include decreases in respiratory minute volume and worsening of the hypoxaemia, hypercapnia and acidaemia commonly observed in healthy horses during strenuous exercise. These and other factors are implicated in the potential for ridden horses to experience three forms of breathlessness—”unpleasant respiratory effort”, “air hunger” and “chest tightness”—which arise when there is a mismatch between a heightened ventilatory drive and the adequacy of the respiratory response. It is not known to what extent, if at all, such mismatches would occur in strenuously exercising horses unhampered by low jowl angles or by pathophysiological changes at any level of the respiratory tract. However, different combinations of the three types of breathlessness seem much more likely to occur when pathophysiological conditions significantly reduce maximal athletic performance. Finally, most horses exhibit clear behavioural evidence of aversion to a bit in their mouths, varying from the bit being a mild irritant to very painful. This in itself is a significant animal welfare issue that should be addressed. A further major point is the potential for bits to disrupt the maintenance of negative pressure in the oropharynx, which apparently acts to prevent the soft palate from rising and obstructing the nasopharynx. The untoward respiratory outcomes and poor athletic performance due to this and other obstructions are well established, and suggest the potential for affected animals to experience significant intensities of breathlessness. Bitless bridle use may reduce or eliminate such effects. However, direct comparisons of the cardiorespiratory dynamics and the extent of any respiratory pathophysiology in horses wearing bitted and bitless bridles have not been conducted. Such studies would be helpful in confirming, or otherwise, the claimed potential benefits of bitless bridle use.
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Allen KJ, van Erck-Westergren E, Franklin SH. Exercise testing in the equine athlete. EQUINE VET EDUC 2015. [DOI: 10.1111/eve.12410] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- K. J. Allen
- Equine Sports Medicine Centre; University of Bristol; Langford UK
| | | | - S. H. Franklin
- School of Animal and Veterinary Sciences; University of Adelaide; Roseworthy South Australia Australia
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Joyner MJ, Casey DP. Regulation of increased blood flow (hyperemia) to muscles during exercise: a hierarchy of competing physiological needs. Physiol Rev 2015; 95:549-601. [PMID: 25834232 DOI: 10.1152/physrev.00035.2013] [Citation(s) in RCA: 404] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This review focuses on how blood flow to contracting skeletal muscles is regulated during exercise in humans. The idea is that blood flow to the contracting muscles links oxygen in the atmosphere with the contracting muscles where it is consumed. In this context, we take a top down approach and review the basics of oxygen consumption at rest and during exercise in humans, how these values change with training, and the systemic hemodynamic adaptations that support them. We highlight the very high muscle blood flow responses to exercise discovered in the 1980s. We also discuss the vasodilating factors in the contracting muscles responsible for these very high flows. Finally, the competition between demand for blood flow by contracting muscles and maximum systemic cardiac output is discussed as a potential challenge to blood pressure regulation during heavy large muscle mass or whole body exercise in humans. At this time, no one dominant dilator mechanism accounts for exercise hyperemia. Additionally, complex interactions between the sympathetic nervous system and the microcirculation facilitate high levels of systemic oxygen extraction and permit just enough sympathetic control of blood flow to contracting muscles to regulate blood pressure during large muscle mass exercise in humans.
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Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Darren P Casey
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
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Hubbell JAE, Muir WW. Oxygenation, oxygen delivery and anaesthesia in the horse. Equine Vet J 2014; 47:25-35. [DOI: 10.1111/evj.12258] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 02/26/2014] [Indexed: 11/30/2022]
Affiliation(s)
- J. A. E. Hubbell
- The Department of Veterinary Clinical Sciences; College of Veterinary Medicine; The Ohio State University; Columbus USA
| | - W. W. Muir
- Veterinary Clinical Pharmacology Consulting Services; Columbus Ohio USA
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Abstract
Muscular exercise requires transitions to and from metabolic rates often exceeding an order of magnitude above resting and places prodigious demands on the oxidative machinery and O2-transport pathway. The science of kinetics seeks to characterize the dynamic profiles of the respiratory, cardiovascular, and muscular systems and their integration to resolve the essential control mechanisms of muscle energetics and oxidative function: a goal not feasible using the steady-state response. Essential features of the O2 uptake (VO2) kinetics response are highly conserved across the animal kingdom. For a given metabolic demand, fast VO2 kinetics mandates a smaller O2 deficit, less substrate-level phosphorylation and high exercise tolerance. By the same token, slow VO2 kinetics incurs a high O2 deficit, presents a greater challenge to homeostasis and presages poor exercise tolerance. Compelling evidence supports that, in healthy individuals walking, running, or cycling upright, VO2 kinetics control resides within the exercising muscle(s) and is therefore not dependent upon, or limited by, upstream O2-transport systems. However, disease, aging, and other imposed constraints may redistribute VO2 kinetics control more proximally within the O2-transport system. Greater understanding of VO2 kinetics control and, in particular, its relation to the plasticity of the O2-transport/utilization system is considered important for improving the human condition, not just in athletic populations, but crucially for patients suffering from pathologically slowed VO2 kinetics as well as the burgeoning elderly population.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology, Anatomy, and Physiology, Kansas State University, Manhattan, Kansas, USA.
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Abstract
Evolutionary forces drive beneficial adaptations in response to a complex array of environmental conditions. In contrast, over several millennia, humans have been so enamored by the running/athletic prowess of horses and dogs that they have sculpted their anatomy and physiology based solely upon running speed. Thus, through hundreds of generations, those structural and functional traits crucial for running fast have been optimized. Central among these traits is the capacity to uptake, transport and utilize oxygen at spectacular rates. Moreover, the coupling of the key systems--pulmonary-cardiovascular-muscular is so exquisitely tuned in horses and dogs that oxygen uptake response kinetics evidence little inertia as the animal transitions from rest to exercise. These fast oxygen uptake kinetics minimize Intramyocyte perturbations that can limit exercise tolerance. For the physiologist, study of horses and dogs allows investigation not only of a broader range of oxidative function than available in humans, but explores the very limits of mammalian biological adaptability. Specifically, the unparalleled equine cardiovascular and muscular systems can transport and utilize more oxygen than the lungs can supply. Two consequences of this situation, particularly in the horse, are profound exercise-induced arterial hypoxemia and hypercapnia as well as structural failure of the delicate blood-gas barrier causing pulmonary hemorrhage and, in the extreme, overt epistaxis. This chapter compares and contrasts horses and dogs with humans with respect to the structural and functional features that enable these extraordinary mammals to support their prodigious oxidative and therefore athletic capabilities.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS, USA.
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Meir JU, Milsom WK. High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose. ACTA ACUST UNITED AC 2013; 216:2172-5. [PMID: 23470665 DOI: 10.1242/jeb.085282] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The bar-headed goose (Anser indicus) crosses the Himalaya twice a year at altitudes where oxygen (O2) levels are less than half those at sea level and temperatures are below -20°C. Although it has been known for over three decades that the major hemoglobin (Hb) component of bar-headed geese has an increased affinity for O2, enhancing O2 uptake, the effects of temperature and interactions between temperature and pH on bar-headed goose Hb-O2 affinity have not previously been determined. An increase in breathing of the hypoxic and extremely cold air experienced by a bar-headed goose at altitude (due to the enhanced hypoxic ventilatory response in this species) could result in both reduced temperature and reduced levels of CO2 at the blood-gas interface in the lungs, enhancing O2 loading. In addition, given the strenuous nature of flapping flight, particularly in thin air, blood leaving the exercising muscle should be warm and acidotic, facilitating O2 unloading. To explore the possibility that features of blood biochemistry in this species could further enhance O2 delivery, we determined the P50 (the partial pressure of O2 at which Hb is 50% saturated) of whole blood from bar-headed geese under conditions of varying temperature and [CO2]. We found that blood-O2 affinity was highly temperature sensitive in bar-headed geese compared with other birds and mammals. Based on our analysis, temperature and pH effects acting on blood-O2 affinity (cold alkalotic lungs and warm acidotic muscle) could increase O2 delivery by twofold during sustained flapping flight at high altitudes compared with what would be delivered by blood at constant temperature and pH.
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Affiliation(s)
- Jessica U Meir
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4.
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Franklin SH, Van Erck-Westergren E, Bayly WM. Respiratory responses to exercise in the horse. Equine Vet J 2012; 44:726-32. [DOI: 10.1111/j.2042-3306.2012.00666.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. H. Franklin
- School of Animal and Veterinary Sciences; University of Adelaide; South Australia; Australia
| | | | - W. M. Bayly
- Office of the Provost; Washington State University; Washington; USA
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A comparative meta-analysis of maximal aerobic metabolism of vertebrates: implications for respiratory and cardiovascular limits to gas exchange. J Comp Physiol B 2012; 183:167-79. [DOI: 10.1007/s00360-012-0688-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 06/13/2012] [Accepted: 06/18/2012] [Indexed: 10/27/2022]
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Ponganis PJ, Meir JU, Williams CL. In pursuit of Irving and Scholander: a review of oxygen store management in seals and penguins. J Exp Biol 2011; 214:3325-39. [DOI: 10.1242/jeb.031252] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Since the introduction of the aerobic dive limit (ADL) 30 years ago, the concept that most dives of marine mammals and sea birds are aerobic in nature has dominated the interpretation of their diving behavior and foraging ecology. Although there have been many measurements of body oxygen stores, there have been few investigations of the actual depletion of those stores during dives. Yet, it is the pattern, rate and magnitude of depletion of O2 stores that underlie the ADL. Therefore, in order to assess strategies of O2 store management, we review (a) the magnitude of O2 stores, (b) past studies of O2 store depletion and (c) our recent investigations of O2 store utilization during sleep apnea and dives of elephant seals (Mirounga angustirostris) and during dives of emperor penguins (Aptenodytes forsteri). We conclude with the implications of these findings for (a) the physiological responses underlying O2 store utilization, (b) the physiological basis of the ADL and (c) the value of extreme hypoxemic tolerance and the significance of the avoidance of re-perfusion injury in these animals.
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Affiliation(s)
- Paul J. Ponganis
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA
| | - Jessica U. Meir
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Cassondra L. Williams
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, 92697, USA
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Vengust M, Stämpfli H, De Moraes AN, Teixeiro-Neto F, Viel L, Heigenhauser G. Effects of chronic acetazolamide administration on gas exchange and acid-base control in pulmonary circulation in exercising horses. Equine Vet J 2011:40-50. [PMID: 21058981 DOI: 10.1111/j.2042-3306.2010.00240.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
REASONS FOR PERFORMING STUDY Carbonic anhydrase (CA) catalyses the hydration/dehydration reaction of CO(2) and increases the rate of Cl(-) and HCO(3)(-) exchange between the erythrocytes and plasma. Therefore, chronic inhibition of CA has a potential to attenuate CO(2) output and induce greater metabolic and respiratory acidosis in exercising horses. OBJECTIVES To determine the effects of Carbonic anhydrase inhibition on CO(2) output and ionic exchange between erythrocytes and plasma and their influence on acid-base balance in the pulmonary circulation (across the lung) in exercising horses with and without CA inhibition. METHODS Six horses were exercised to exhaustion on a treadmill without (Con) and with CA inhibition (AczTr). CA inhibition was achieved with administration of acetazolamide (10 mg/kg bwt t.i.d. for 3 days and 30 mg/kg bwt before exercise). Arterial, mixed venous blood and CO(2) output were sampled at rest and during exercise. An integrated physicochemical systems approach was used to describe acid base changes. RESULTS AczTr decreased the duration of exercise by 45% (P < 0.0001). During the transition from rest to exercise CO(2) output was lower in AczTr (P < 0.0001). Arterial PCO(2) (P < 0.0001; mean ± s.e. 71 ± 2 mmHg AczTr, 46 ± 2 mmHg Con) was higher, whereas hydrogen ion (P = 0.01; 12.8 ± 0.6 nEq/l AczTr, 15.5 ± 0.6 nEq/l Con) and bicarbonate (P = 0.007; 5.5 ± 0.7 mEq/l AczTr, 10.1 ± 1.3 mEq/l Con) differences across the lung were lower in AczTr compared to Con. No difference was observed in weak electrolytes across the lung. Strong ion difference across the lung was lower in AczTr (P = 0.0003; 4.9 ± 0.8 mEq AczTr, 7.5 ± 1.2 mEq Con), which was affected by strong ion changes across the lung with exception of lactate. CONCLUSIONS CO(2) and chloride changes in erythrocytes across the lung seem to be the major contributors to acid-base and ions balance in pulmonary circulation in exercising horses.
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Affiliation(s)
- M Vengust
- Firestone Equine Respiratory Research Laboratory, University of Guelph, Ontario, Canada.
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Dempsey JA, Adams L, Ainsworth DM, Fregosi RF, Gallagher CG, Guz A, Johnson BD, Powers SK. Airway, Lung, and Respiratory Muscle Function During Exercise. Compr Physiol 2011. [DOI: 10.1002/cphy.cp120111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Kaufman MP, Forster HV. Reflexes Controlling Circulatory, Ventilatory and Airway Responses to Exercise. Compr Physiol 2011. [DOI: 10.1002/cphy.cp120110] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Rowell LB, O'Leary DS, Kellogg DL. Integration of Cardiovascular Control Systems in Dynamic Exercise. Compr Physiol 2011. [DOI: 10.1002/cphy.cp120117] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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RAMSEYER A, SIDES R, SLINKER B, EVANS D, BAYLY W. Evaluation of a mask for breath-by-breath respirometry during exercise in horses. Equine Vet J 2010:240-5. [DOI: 10.1111/j.2042-3306.2010.00250.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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GEOR RJ, STAEMPFLI HR, MCCUTCHEON LAURAJ, PRINGLE J, YOUNG S. Effect of gas collection system on respiratory and stride frequency and stride length. Equine Vet J 2010. [DOI: 10.1111/j.2042-3306.1995.tb04890.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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CARLSON GP. Interrelationships between fluid, electrolyte and acid-base balance during maximal exercise. Equine Vet J 2010. [DOI: 10.1111/j.2042-3306.1995.tb04933.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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NYMAN G, BJÖRK M, FUNKQUIST P, PERSSON SGB, WAGNER PD. Ventilation-perfusion relationships during graded exercise in the Standardbred trotter. Equine Vet J 2010. [DOI: 10.1111/j.2042-3306.1995.tb04892.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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LEÓN LASOSA, DAVIE AJ, HODGSON DR, EVANS DL, ROSE RJ. Effects of oral fluid on cardiorespiratory and metabolic responses to prolonged exercise. Equine Vet J 2010. [DOI: 10.1111/j.2042-3306.1995.tb04936.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Durando MM, Martin BB, Davidson EJ, Birks EK. Correlations between exercising arterial blood gas values, tracheal wash findings and upper respiratory tract abnormalities in horses presented for poor performance. Equine Vet J 2010:523-8. [PMID: 17402477 DOI: 10.1111/j.2042-3306.2006.tb05598.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
REASONS FOR PERFORMING STUDY There are limited data on the correlations between arterial blood gas (ABG) values, tracheal wash (TW) cytology and upper respiratory tract (URT) abnormalities. OBJECTIVES To identify horses with abnormal exercising ABG, and compare the proportions of horses with abnormal ABG and TW cytology, mucus or URT dysfunction with those with normal ABG results and abnormal TW cytology, mucus or URT dysfunction. METHODS Medical records of 813 horses presenting to the treadmill facility that had a complete treadmill examination, including ABG analysis, TW and URT endoscopy were selected. Diagnoses, ABG results, TW cytology and URT endoscopy were compared. RESULTS Two hundred and eleven horses met the study criteria of a complete treadmill examination and could have ABG evaluated. There were no significant differences in the age distribution of horses having normal and abnormal ABG or upper respiratory tract (URT) examinations. There was a significantly higher percentage of geldings with abnormal ABG analysis. In the horses with abnormal URT examinations, there were no differences in the proportion of horses having mucus vs. no mucus. However, in the horses with normal URT, there were a higher percentage of horses with visible mucus in the group with abnormal ABG analysis. The majority of horses had abnormal TW cytology and evidence of prior EIPH, with no differences in proportions between the groups. CONCLUSIONS Because such a large percentage of horses had evidence of inflammation and/or evidence of prior EIPH on TW cytology, it was not possible to determine the effect of these findings on gas exchange. Mucus was present in a larger percentage of cases with abnormal ABG analysis and normal URT examinations, suggesting that the presence of mucus may affect gas exchange. Standardbreds may be more likely to have abnormal gas exchange than Thoroughbreds. A larger number of horses is needed to determine the significance of these findings. POTENTIAL RELEVANCE Abnormal TW cytology and endoscopic visualised mucus may contribute to impairment of gas exchange, but they do not specifically predict abnormal ABG analysis.
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Affiliation(s)
- M M Durando
- Department of Clinical Studies, New Bolton Centre, University of Pennsylvania, 382 West Street Road, Kennett Square, Pennsylvania 19348, USA
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KRONFELD DS, FERRANTE PAMELAL, TAYLOR LYNNE, CUSTALOW SELIZABETH. Blood hydrogen ion and lactate concentrations during strenuous exercise in the horse. Equine Vet J 2010. [DOI: 10.1111/j.2042-3306.1995.tb04934.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Meir JU, Champagne CD, Costa DP, Williams CL, Ponganis PJ. Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals. Am J Physiol Regul Integr Comp Physiol 2009; 297:R927-39. [PMID: 19641132 DOI: 10.1152/ajpregu.00247.2009] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Species that maintain aerobic metabolism when the oxygen (O(2)) supply is limited represent ideal models to examine the mechanisms underlying tolerance to hypoxia. The repetitive, long dives of northern elephant seals (Mirounga angustirostris) have remained a physiological enigma as O(2) stores appear inadequate to maintain aerobic metabolism. We evaluated hypoxemic tolerance and blood O(2) depletion by 1) measuring arterial and venous O(2) partial pressure (Po(2)) during dives with a Po(2)/temperature recorder on elephant seals, 2) characterizing the O(2)-hemoglobin (O(2)-Hb) dissociation curve of this species, 3) applying the dissociation curve to Po(2) profiles to obtain %Hb saturation (So(2)), and 4) calculating blood O(2) store depletion during diving. Optimization of O(2) stores was achieved by high venous O(2) loading and almost complete depletion of blood O(2) stores during dives, with net O(2) content depletion values up to 91% (arterial) and 100% (venous). In routine dives (>10 min) Pv(O(2)) and Pa(O(2)) values reached 2-10 and 12-23 mmHg, respectively. This corresponds to So(2) of 1-26% and O(2) contents of 0.3 (venous) and 2.7 ml O(2)/dl blood (arterial), demonstrating remarkable hypoxemic tolerance as Pa(O(2)) is nearly equivalent to the arterial hypoxemic threshold of seals. The contribution of the blood O(2) store alone to metabolic rate was nearly equivalent to resting metabolic rate, and mean temperature remained near 37 degrees C. These data suggest that elephant seals routinely tolerate extreme hypoxemia during dives to completely utilize the blood O(2) store and maximize aerobic dive duration.
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Affiliation(s)
- Jessica U Meir
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla 92093-0204, USA.
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Donovan DC, Jackson CA, Colahan PT, Norton N, Hurley DJ. Exercise-induced alterations in pro-inflammatory cytokines and prostaglandin F2α in horses. Vet Immunol Immunopathol 2007; 118:263-9. [PMID: 17617470 DOI: 10.1016/j.vetimm.2007.05.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 04/20/2007] [Accepted: 05/24/2007] [Indexed: 11/25/2022]
Abstract
Using an established standardized exercise test on a high-speed treadmill, thirteen Thoroughbred racehorses were exercised to fatigue (failure); blood samples were obtained before exercise, at failure, and at 2, 6, 24, 48, and 72 h after exercise. The exercise test induced a systemic inflammatory response characterized by a mild transient endotoxemia, leukocytosis, increased leukocyte expression of mRNA for tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, and IL-6, and increased circulating concentrations of TNF-alpha and prostaglandin F2 alpha (PGF 2 alpha), with the most pronounced changes being evident at failure and 2h after exercise. Expression of mRNA for IL-6, TNF-alpha, and IL-1 beta was increased by 120-fold, three-fold, and four-fold, respectively, when compared to pre-exercise values. Plasma concentrations of 6-keto-PGF1alpha and PGE2 did not change in response to the exercise test. Collectively, these findings indicate that brief, strenuous exercise induces endotoxemia and a systemic pro-inflammatory response in horses that persists for at least 2h.
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Affiliation(s)
- Douglas C Donovan
- Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30605, USA
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Vengust M, Staempfli H, Viel L, Heigenhauser G. Effects of chronic acetazolamide administration on fluid flux from the pulmonary vasculature at rest and during exercise in horses. Equine Vet J 2007:508-15. [PMID: 17402475 DOI: 10.1111/j.2042-3306.2006.tb05596.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
REASONS FOR PERFORMING STUDY Horses develop high pulmonary pressures during exercise, which force fluid out of pulmonary capillaries. Specific airway diseases in horses, especially those associated with hypoxaemia, hypercapnoea and acidosis may influence pulmonary haemodynamics and pulmonary interstitial fluid equilibrium. OBJECTIVES This study was designed to determine fluid flux (J(V-A) l/min) across the lung in exercising horses treated chronically with acetazolamide. METHODS Six horses were exercised on a treadmill until fatigue without (Con) and with chronic carbonic anhydrase (CA) inhibition (AczTr) and associated hypercapnoea and acidosis. Carbonic anhydrase inhibition was achieved with administration of acetazolamide (Acz). Arterial and mixed venous blood were sampled, and VCO2 and VO2 measured. Blood volume changes across the lung (deltaBV%) were calculated from changes in plasma protein, haemoglobin and packed cell volume (PCV). Cardiac output (Q) was calculated using Fick principle. J(V-A) across the alveolar-capillary barrier was then quantified based on Q and deltaBV. Variables were analysed using 2-way repeated-measures ANOVA (P<0.05). A significant F ratio was further analysed using Tukey post hoc analysis. RESULTS Treatment had a significant effect on J(V-A) (P = 0.002). At rest there was no J(V-A) in Con (0.63 +/- 0.6 l/min) and AczTr (0.84 +/- 0.3 l/min). During exercise Con fluid moved from the pulmonary circulation into the pulmonary interstitium (mean +/- s.e. J(V-A) 9.4 +/- 2.4 l/min). This was different from AczTr (mean +/- s.e. J(V-A) 1.8 +/- 1.9 l/min), where no transvascular fluxes from pulmonary circulation were present during exercise (P = 0.008). CONCLUSIONS Chronic Acz treatment with associated hypercapnoea and acidosis affects J(V-A) in lungs of exercising horses. Lung fluid dynamics adapted to hypercapnoea and acidosis with reduction of fluid flow from the pulmonary circulation. POTENTIAL RELEVANCE The current data provide comprehensive evidence of in vivo fluid homeostasis in lungs of exercising horses without and with CA inhibition.
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Affiliation(s)
- M Vengust
- Veterinary Faculty, University of Ljubljana, Ljubljana SI- 115, PO Box 3425, Slovenia
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Tennent-Brown BS, Goetz TE, Manohar M, Hassan AS, Freeman DE, Bundy JS, Evans MR. Pre-exercise hypervolaemia is not detrimental to arterial oxygenation of horses performing a prolonged exercise protocol simulating the second day of a 3-day equestrian event. Equine Vet J 2007:495-501. [PMID: 17402473 DOI: 10.1111/j.2042-3306.2006.tb05594.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
REASONS FOR PERFORMING STUDY Hyperhydration, prior to prolonged moderate-intensity exercise simulating the 2nd day of a 3-day equestrian event (E3DEC), may induce arterial hypoxaemia detrimental to performance. OBJECTIVES Because moderate-intensity exercise does not induce arterial hypoxaemia in healthy horses, the effects of pre-exercise hypervolaemia on arterial oxygenation were examined during a prolonged exercise protocol. METHODS Blood-gas studies were carried out on 7 healthy, exercise-trained Thoroughbred horses in control and hyperhydration experiments. The study conformed to a randomised crossover design. The sequence of treatments was randomised for each horse and 7 days were allowed between studies. Hyperhydration was induced by administering 0.425 g/kg bwt NaCl via nasogastric tube followed by free access to water. The exercise protocol was carried out on a treadmill set at a 3% uphill grade and consisted of walking at 2 m/sec for 2 min, trotting for 10 min at 3.7 m/sec, galloping for 2 min at 14 m/sec (which elicited maximal heart rate), trotting for 20 min at 3.7 m/sec, walking for 10 min at 1.8 m/sec, cantering for 8 min at 9.2 m/sec, trotting for 1 min at 5 m/sec and walking for 5 min at 2 m/sec. RESULTS NaCl administration induced a significant mean +/- s.e. 15.5 +/- 1.1% increase in plasma volume as indicated by a significant reduction in plasma protein concentration. In either treatment, whereas arterial hypoxaemia was not observed during periods of submaximal exercise, short-term maximal exertion caused significant arterial hypoxaemia, desaturation of haemoglobin, hypercapnoea, and acidosis in both treatments. However, the magnitude of exercise-induced arterial hypoxaemia, desaturation of haemoglobin, hypercapnoea, and acidosis in both treatments remained similar, and statistically significant differences between treatments could not be demonstrated. CONCLUSIONS It was concluded that significant pre-exercise expansion of plasma volume by this method does not adversely affect the arterial oxygenation of horses performing a prolonged exercise protocol simulating the 2nd day of an E3DEC.
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Affiliation(s)
- B S Tennent-Brown
- Department of Veterinary Clinical Medicine and Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA
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Katz LM, Bayly WM, Hines MT, Sides RH. Ventilatory responses of ponies and horses to exercise. ACTA ACUST UNITED AC 2007. [DOI: 10.1079/ecp200570] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
AbstractBecause athletic horses become hypoxaemic and hypercapnoeic during high-intensity exercise but ponies do not, six Thoroughbred horses and five ponies performed an incremental exercise test at speeds with calculated energy requirements that were 40, 60, 80 and 115% of V˙O2max, with the objective of comparing their blood gas and ventilatory responses to exercise. Expired gas and blood samples were taken and breathing mechanics were assessed before exercise and during the last 15 s at each intensity. Maximal V˙O2and V˙CO2in horses were 153±5 (SEM) and 187±4 ml kg−1min−1, respectively, while corresponding values in ponies were 92±4 and 112±7 ml kg−1min−1. During heavy and supramaximal exercise, horses, but not ponies, became hypoxaemic and hypercapnic. There was no significant difference for V˙Ekg−1between groups during maximal exercise, but PAO2, PaO2and PvO2were lower and PaCO2and [(A−a)O2D] were greater in horses than in ponies. Additionally, the horses' maximal transpulmonary pressure difference was higher and their total pulmonary resistance and ventilatory equivalent lower than in ponies. Flow-volume loops suggested that horses experienced expiratory flow limitation but that ponies did not. These results indicated that horses like Thoroughbreds appear to be expiratory flow-limited and become hypoxaemic and hypercapnic when the demand for gas exchange associated with their high V˙O2maxand V˙CO2maxis greater than can be met by their ventilatory system. Ponies, which are less capable athletes, could better match their ventilatory response with their metabolic capabilities and so were able to maintain PaO2in the pre-exercise range and decrease PaCO2to a tension that was more compatible with acid–base homeostasis.
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Watanabe M, Thomassian A, Teixeira Neto F, Alves A, Hussni C, Nicoletti J. Alterações do pH, da P O2 e da P CO2 arteriais e da concentração de lactato sangüíneo de cavalos da raça Árabe durante exercício em esteira de alta velocidade. ARQ BRAS MED VET ZOO 2006. [DOI: 10.1590/s0102-09352006000300006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
Avaliaram-se as alterações do pH, da P O2 e da P CO2 do sangue arterial e da concentração de lactato sangüíneo de 11 cavalos adultos da raça Árabe, submetidos a exercício progressivo em esteira de alta velocidade. Antes do exercício, no intervalo dos 15 segundos finais de cada mudança de velocidade e aos 1, 3 e 5 minutos após o término do exercício foram coletadas amostras de sangue arterial e venoso para a mensuração dos gases sangüíneos e da concentração de lactato. O exercício resultou em diminuição do pH, da pressão parcial de O2 (P O2) e da pressão parcial de CO2 (P CO2). A concentração de lactato sangüíneo elevou-se exponencialmente a partir da velocidade de 8,0m/s até os momentos após término do exercício.
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Lovering AT, Haverkamp HC, Eldridge MW. Responses and limitations of the respiratory system to exercise. Clin Chest Med 2005; 26:439-57, vi. [PMID: 16140137 DOI: 10.1016/j.ccm.2005.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
During maximal exercise, the gas exchange function of the lung is challenged because of the major cardiopulmonary changes that must occur to meet the increased metabolic demands imposed by exercise. In healthy untrained young adults, the respiratory system is able to meet these demands imposed on it during maximal exercise by implementing several key mechanisms. Nonetheless, there are several exceptional cases in which the lung is unable to accommodate the demands of exercise because of vascular or airway limitations.
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Affiliation(s)
- Andrew T Lovering
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin at Madison, Madison, WI 53706-1532, USA.
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Manohar M, Goetz TE. Intrapulmonary arteriovenous shunts of >15 microm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses. J Appl Physiol (1985) 2005; 99:224-9. [PMID: 15774703 DOI: 10.1152/japplphysiol.01230.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study examined whether Thoroughbred horses performing strenuous exercise exhibit intrapulmonary arteriovenous shunting that may contribute to the observed arterial hypoxemia. Experiments were carried out on seven healthy, exercise-trained Thoroughbreds at rest, maximal exercise (galloping at 14 m/s on a 3.5% uphill grade for 120 s), and submaximal exertion (8 m/s on a 3.5% uphill grade for 150 s). Along with blood gas/hemodynamic parameters, intrapulmonary arteriovenous shunting was studied by injecting 15-microm-diameter microspheres, labeled with different stable isotopes, into the right atrium while simultaneous blood samples were being withdrawn at a constant rate from the pulmonary artery and the aorta. Arterial hypoxemia was observed only during maximal exercise. Also, despite significant pulmonary arterial hypertension during submaximal and maximal exertion, 15-microm microspheres did not traverse the pulmonary microcirculation to appear in the aortic blood. Thus our findings did not support a role for intrapulmonary arteriovenous shunts of >15 microm in diameter in the exercise-induced arterial hypoxemia in racehorses. Interestingly, our observation that, in going from 30 to 120 s of maximal exertion, arterial O2 tension had remained unchanged despite significant reductions in mixed venous blood O2 tension, hemoglobin-O2 saturation, and O2 content also discounts the importance of intrapulmonary arteriovenous shunts in causing arterial hypoxemia. This is because, assuming that a constant fraction of total pulmonary blood flow bypasses the gas-exchange areas of the equine lungs via intrapulmonary arteriovenous shunts during 30-120 s of maximal exertion, the observed significant reductions in mixed venous blood oxygenation should cause a significant reduction in arterial O2 tension, which was not the case in our horses. Thus it is suggested that intrapulmonary arteriovenous shunting probably does not contribute to the exercise-induced arterial hypoxemia in racehorses.
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Affiliation(s)
- Murli Manohar
- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
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Art T, Lekeux P. Exercise-induced physiological adjustments to stressful conditions in sports horses. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.livprodsci.2004.11.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Padilla DJ, McDonough P, Kindig CA, Erickson HH, Poole DC. Ventilatory dynamics and control of blood gases after maximal exercise in the Thoroughbred horse. J Appl Physiol (1985) 2004; 96:2187-93. [PMID: 14766783 DOI: 10.1152/japplphysiol.00998.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Despite enormous rates of minute ventilation (V̇e) in the galloping Thoroughbred (TB) horse, the energetic demands of exercise conspire to raise arterial Pco2(i.e., induce hypercapnia). If locomotory-respiratory coupling (LRC) is an obligatory facilitator of high V̇e in the horse such as those found during galloping (Bramble and Carrier. Science 219: 251–256, 1983), V̇e 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 dynamic control of breath-by-breath V̇e, O2uptake, and CO2output at the transition from maximal exercise to active recovery (i.e., trotting at 3 m/s for 800 m). At the transition from the gallop to the trot, V̇e did not drop instantaneously. Rather, V̇e remained at the peak exercising levels (1,391 ± 88 l/min) for ∼13 s via the combination of an increased tidal volume (12.6 ± 1.2 liters at gallop; 13.9 ± 1.6 liters over 13 s of trotting recovery; P < 0.05) and a reduced breathing frequency [113.8 ± 5.2 breaths/min (at gallop); 97.7 ± 5.9 breaths/min over 13 s of trotting recovery ( P < 0.05)]. Subsequently, V̇e declined in a biphasic fashion with a slower mean response time (85.4 ± 9.0 s) than that of the monoexponential decline of CO2output (39.9 ± 4.7 s; P < 0.05), which rapidly reversed the postexercise arterial hypercapnia (arterial Pco2at gallop: 52.8 ± 3.2 Torr; at 2 min of recovery: 25.0 ± 1.4 Torr; P < 0.05). We conclude that LRC is not a prerequisite for achievement of V̇e commensurate with maximal exercise or the pronounced hyperventilation during recovery.
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Affiliation(s)
- Danielle J Padilla
- Department of Anatomy and Physiology, 228 Coles Hall, Kansas State University, Manhattan, KS 66506, USA
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Dempsey JA, Sheel AW, Haverkamp HC, Babcock MA, Harms CA. [The John Sutton Lecture: CSEP, 2002]. Pulmonary system limitations to exercise in health. ACTA ACUST UNITED AC 2004; 28 Suppl:S2-24. [PMID: 14768314 DOI: 10.1139/h2003-066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is commonly held that the structural capacity of the normal lung is "overbuilt" and exceeds the demand for pulmonary O2 and CO2 transport in the healthy, exercising human. On the other hand, the adaptability of pulmonary system structures to habitual physical training is substantially less than are other links in the O2 transport system. Accordingly, in some highly fit, and even in some not so fit habitually active individuals, the lung's diffusion surface, airways, and/or chest-wall musculature are underbuilt relative to the demand for maximal O2 transport. Two specific pulmonary limitations to exercise performance are proposed: (1) exercise-induced arterial hypoxemia secondary to excessive widening of the alveolar to arterial O2 difference, inadequate hyperventilation, and metabolic acidosis; and (2) highly fatiguing levels of respiratory muscle work which effectively steals blood flow from locomotor muscles via sympathetically mediated reflexes and heightens the perception of limb discomfort and dyspnea. In this brief review, we describe the characteristics and causes of each of these proposed pulmonary limitations and their consequences to maximal O2 uptake and exercise performance.
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Affiliation(s)
- Jerome A Dempsey
- Dept. of Population Health Sciences, John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
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