摘要:

SummaryAlthough bronchoalveolar lavage (BAL) has become a commonly used technique for evaluation of pulmonary cytology and there have been many reports on horses at rest and in race training, there have ben no longitudinal studies where cytological results have been assessed during a training programme which involved increases in training intensity. In this study, 10 Thoroughbred horses were trained on a treadmill for a period of 12 weeks and were divided into 2 groups, one group (FAST) being trained at intensities to produce whole blood lactate concentrations in the range 4–8 mmol/l while the other group (SLOW) were trained at half the intensity of the FAST group. The training speeds for the FAST group ranged from 8–11 m/s whereas that for the slow group ranged from 3–6 m/s. Horses were trained for 6 days/week over daily distances of 1000–3600 m. Bronchoalveolar lavage samples were collected from each horse during weeks 1, 3, 6, 8, 10 and 12. The BAL samples were analysed and compared with respect to changes in cytology occurring throughout the period of training. The results of the study indicated that intensity and duration of exercise may have an effect on the development and severity of exercise induced pulmonary haemorrhage (EIPH), as determined by the absolute count and the percentage of erythrocytes returned in a BAL sample. This appears to be especially true when training at high intensities. However, the low levels of EIPH detected in the horses were not sufficienttocause a measurable loss of exercise performance or lowering of the horses' maximal oxygen uptake during exercise. Low intensity training was noted to have very little effect on the observed BAL c

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04891.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe aim of this study was to evaluate pulmonary function in Standardbred trotters during graded exercise. The exercise test consisted of 4 work loads corresponding to 10%, 42%, 70% and 96% of the individual V̇O2max. Oxygen uptake was detected from an open bias flow system without valves. Cardiovascular and haemodynamic data were recorded at walk and during steady state exercise in 7 horses. Pulmonary gas exchange was assessed by conventional blood gas variables (arterial and mixed venous blood gas tensions) and the ventilation‐perfusion distribution V̇A|Q̇ as estimated by the multiple inert gas elimination technique. The dispersion of perfusion and ventilation distribution respectively (SDQ) and the difference between measured PaO2and that predicted on the basis of amount of ventilation‐perfusion mismatching and shunt that was observed (predicted‐measured), were determined. The latter reflects mostly diffusion limitation. At the highest work load the PaCO2increased to 50.3 torr. V̇A|Q̇ inequality increased significantly with exercise [mean log = 0.32 ± 0.03 (walk) and 0.46 ± 0.06 (heavy exercise), P<0.01]. Alveolar‐capillary diffusion limitation of oxygen was evident at and above exercise at 70% of V̇O2max. The arterial hypoxaemia seen during the highest work load was a result of a) hypoventilation, accounting for 4%, b) increase in V̇A|Q̇ mismatch, accounting for 41% and c) considerable diffusion limitation of oxygen, a

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04892.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryAmong the functional disorders of the upper respiratory tract, dorsal displacement of the soft palate (DDSP) is still a major diagnostic challenge. In this study, measurements of tracheal pressure were made in exercising horses with clinical signs of DDSP. Tracheal pressure was recorded via a percutaneously inserted tracheal catheter during exercise on a treadmill with an inclination of 6.25°, at speeds up to 9 m/s. Five horses with clinical signs of DDSP were compared to 20 earlier studied normal horses. In horses with signs of DDSP the tracheal pressure curve had a characteristic appearance. There were a number of short‐duration pressure peaks over a prolonged expiratory phase and an elevated peak expiratory pressure. The inspiratory pressure was within normal limits. These findings support the hypothesis that obstruction of the air passage in DDSP occurs mainly during expiration and the short peaks of the expiratory pressure curve may reflect the vibrations of the edge of the soft pala

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04893.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummarySeveral body systems make critical contributions to the defence of blood volume, mean arterial pressure and plasma tonicity. These mechanisms ensure adequate blood flow to the working muscles and vital tissues along with the provision of adequate fluid volume for sweating and thermoregulation. The present paper integrates data from several recent studies that examined the neuroendocrine control of cardiovascular function in exercising horses. These studies focused on the effects of exercise on plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), plasma renin activity (PRA) and aldosterone (ALDO), hormones associated with the regulation of blood pressure, the distribution of blood flow and the long term control of vascular fluid volume. Data were collected during incremental and endurance exercise, following frusemide administration and after splenectomy. Increases in ANP during exercise were associated with increased atrial pressure and stretching of the atrium. Increases in PRA and ALDO are correlated with increases in sympathetic activity during incremental exercise and with decreases in plasma Na+and CI−concentrations. Plasma AVP increases later in exercise in response to fluid losses, increases in plasma osmolality, and decreases in right atrial pressure. AVP has a minimal effect on renal function during exercise and may be more important during recovery, when it stimulates thirst and drinking. Frusemide and splenectomy decrease atrial pressure, resulting in lower plasma ANP and greater plasma AVP concentrations during steady‐state submaximal exercise. The ANP and AVP responses are part of the neuroendocrine action of the cardiopulmonary baroreflex which appears to mediate the accommodation of the mobilised splenic reserve in the horse. In summary, exercise induced increases in ANP, AVP, PRA and ALDO in the horse appear to play an important role in cardiovascular homeosta

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04894.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryA major factor contributing to the athletic ability of the horse is exercise induced splenic contraction that augments both circulating blood volume (by about 12 litres) and haemoglobin concentration [Hb] (by a factor of 1.5–2). We examined separately the consequences of 1) splenectomy and 2) subsequent transfusion of blood at the lower post splenectomy [Hb]on pulmonary and muscle O2transport and pulmonary haemodynamics, to elucidate the separate influences of blood volume and [Hb] augmentation on these processes. We studied 6 Thoroughbreds (bwt 472 kg), (3 splenectomised, 3 controls). Splenectomy reduced V̇O2maxby 31 ± 3% (s.e.); transfusion of 11.7 litres whole blood at 42% haematocrit restored V̇O2maxto 94 ± 7% of original values. Splenectomy reduced maximal cardiac output by 15 ± 6%; transfusion increased it to 106 ± 10% of pre‐splenectomy values. The combination of splenectomy and transfusion reduced PaCO2by 14 ± 0.5 Torr, increased PaO2by 17 ± 0.4 Torr and arterial saturation by 5 ± 3% at V̇O2max. Splenectomy reduced maximal pulmonary artery pressure from 90.4 ± 1.4 to 42.4 ± 4.8 Torr; transfusion partially restored this to 71.5 ± 5.5 mmHg, despite the lower haematocrit. Splenectomy reduced muscle O2diffusional conductance (DO2) in direct proportion to the reduced maximal [Hb] while transfusion only slightly increased DO2. On the other hand, DO2was poorly related to changes in cardiac output.Although based on a small number of horses, this study suggests that 1) increased [Hb] from splenic contraction is not essential for achieving V̇O2max; a normal circulating blood volume at a moderate [Hb] is sufficient, 2) [Hb]plays an important role in overall muscle O2diffusional conductance and also affects pulmonary artery pressure and 3) splenectomy produced substantial hyperventilation (in relation to V̇O2), permitting eucapnia and increased arterial oxygenation at V̇O2max. This was still observed after transfusion despite restoration of exercise c

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04895.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryIn competitive racing, horses rapidly accelerate to their top speed and probably perform supramaximal work. Therefore, the primary objective of this study was to examine changes in pulmonary vascular pressures of Thoroughbreds with rapid acceleration to supramaximal exercise which could not be sustained for more than 90 s. Right atrial and pulmonary vascular pressures were studied at rest and during supramaximal exercise in 10 healthy, sound, exercise trained Thoroughbred horses. Exercise was performed on separate days without (control) and with frusemide administration 250 mg i.v., 4 h before exercise. The protocol consisted of a warm‐up at treadmill speeds of 2 to 6 m/s (trot) for 60 s each followed by 8 m/s (canter) for 60 s. Thereafter, the treadmill was raised to 10% uphill incline and speed accelerated from 8 to 15 m/s in 8 s. None of the horses could sustain exercise at 15 m/s + 10% incline for more than 90 s. Mean right atrial, pulmonary arterial, pulmonary artery wedge and pulmonary capillary pressures increased sharply as horses accelerated rapidly attaining their zenith as speed reached 15 m/s. Peak values of various pressures were maintained only for the first 45 s of exercise at 15 m/s +10% uphill incline. Thereafter, a declining trend emerged and all pressures decreased significantly as exercise duration increased. Although frusemide significantly lowered the magnitude of pulmonary vascular pressures both at rest and during exercise, it did not affect the rapid escalation in pulmonary vascular pressures upon rapid acceleration of horses or their unsteadiness in the latter 45 s of supramaximal exercise. It is suggested that rapid rate of rise of pulmonary capillary blood pressure during a sudden burst of supramaximal exercise may be a crucial factor in precipitating stress failure of pulmonary capillaries and onset of exercise induced pulmonary haemorrhag

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04896.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThis study was designed to evaluate the influence of pleural pressure on mean pulmonary vascular pressures in exercising horses. Pulmonary artery (Pa), pulmonary wedge (Pw) and oesophageal pressures (Pes) were measured with transducer tip catheters in 6 Standardbred horses at rest and during treadmill exercise at 75, 90 and 100% of maximal heart rate. Oesophageal pressure (Pes) measurements were used to estimate pleural pressure. Vascular pressures were determined in 4 ways: 1) mean transmural vascular pressure (Ptm) at Pesequal to resting end expiratory pressure; 2) mean Ptmat Pesequal to mean Pesfor the data collection period; 3) mean Ptmwithout selection of specific data points and 4) mean pulmonary vascular pressure relative to atmospheric pressure (conventional method). Despite large fluctuations associated with breathing, mean Pesduring exercise remained close to zero, suggesting that pleural pressure fluctuates equally about zero. The swings in Peswere associated with approximately equal swings in vascular pressure so that, despite the marked fluctuations, mean Paand Pwdetermined with the 4 methods were not significantly different. The results indicate that during exercise it is valid to report mean pulmonary vascular pressures without accounting for the fluctuations in pleural pressure.

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04897.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryExercise induced pulmonary haemorrhage (EIPH) is thought to result from capillary stress failure associated with high pulmonary vascular pressures during heavy exercise. One possible mechanism for the caudodorsal distribution of haemorrhage is preferential distribution of blood flow to affected regions due to regional differences in pulmonary vascular regulation. Endothelial cells (EC) are known controllers of vascular smooth muscle tone and could play a role in regional distribution of blood flow. The present study investigated relaxation responses to the endothelium‐dependent and independent vasodilators, methacholine (MCh) and nitroglycerin (NTG) in pulmonary arteries from the caudodorsal (top) and cranioventral (bottom) regions of the lung. Pulmonary arteries (7 mm diameter) from 6 horses were isolated from top and bottom regions of the lung and vessels with and without endothelium were mounted in 15 ml tissue baths. Vessels were pre‐contracted with norepinephrine (10−6M) and changes in isometric tension in response to MCh (10−6M) and NTG (10−6M) were compared. MCh consistently relaxed, and never contracted, endothelium‐intact top vessels. In top vessels, relaxation was abolished by removal of EC, suggesting an obligatory role of EC in MCh relaxation. However, in bottom vessels, a small transient relaxation was followed by a profound contraction, enhanced by EC removal. Relaxation to NTG was similar in all vessels. Therefore, in response to MCh, top vessels relax in an endothelium‐dependent manner, while bottom vessels contract. Similar regional differences in endothelium dependent flow mediated vasodilation may result in higher blood flow to the caudodorsal regions of the lung and hence be responsible in part for the loc

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04898.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe purposes of this study were to test whether a relatively steady state with respect to the blood lactate pool can prevail during a prolonged exercise test (PET) at Vla4, to study the kinetics of the flux of lactate between plasma and cells in relation to lactate concentration [LA] and haematocrit and to test the interrelationships between plasma [PLA], whole blood [BLA] and erythrocyte lactate [ELA]. The study used 7 Standardbred trotters. In the PET they ran at their respective pre‐established Vla4for 12 min. Before, every 2 min during and 0, 2, 5, 10 and 15 min after exercise, [PLA] and [BLA]as well as packed cell volume (PCV) were determined. [ELA] was calculated from [PLA], [BLA] and PCV. Heart rate was monitored continuously and remained at a relatively steady state of approximately 200 beats/min throughout the PET.Lactate concentrations increased exponentially during PET, [PLA] more rapidly than [BLA]and [ELA]. The diverging curves during exercise and converging declining curves after exercise suggested a delay in attainment of an equilibrium between plasma and cells. The close relationship between [PLA]and [BLA] (r = 0.98) allows derivations from regression equations. As the [LA]accumulation over time is exponential, it is likely that the increase during the first 2 min at any speed up to that causing a [BLA] of 4 mmol/l is marginal and insignificant and a submaximal incremental exercise test using 2 min step intervals could still be used for determination of Vla

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04899.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe reproducibility of a standardised exercise test was evaluated in 2 conditions with 2 groups of Standardbred horses: 1) the first condition was a test and a re‐test performed with a 1 week interval by 11 trotters on their usual training track (2) the second condition was a test and a re‐test performed with another group of 8 horses on 2 different tracks with a 9 day interval, in order to assess the influence of changing the place of the test. The test was composed of 3 steps, conducted at an increasing speed. The duration of each step was 3 min with a 1 min rest between 2 steps at a walking pace. The speed level used for each step depended on the age and fitness of the horses. Mathematic treatment of the collected data, speed, heart rate and venous blood lactate measured after each step, allowed the estimation of 5 fitness parameters: V200, V4, V2, HR2and HR4. The Spearman rank correlation coefficients calculated for these indicators between the 2 tests measured during the experiment (1) and the experiment (2) were higher than 0.79 (P<0.05) for V200, V4, V2and HR2.The standardised exercise test proposed in the present work, was demonstrated to be reliable in field conditions for Standardbred hor

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04900.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY