摘要:

SummaryThe clinical implications of ventilatory alterations induced by left recurrent laryngeal neuropathy (LRLN) are reduced performance due to increased metabolic requirements for breathing and a reduction in peak aerobic power (V̇O2peak). To test this hypothesis, the metabolic cost of locomotion (MCL) and peak aerobic power (V̇O2peak) were measured in 4 non racing crossbred horses (low V̇O2peak) with reversibly induced LRLN using an incremental treadmill exercise test. Reversible LRLN was achieved with regional anaesthesia. These results were compared to previous measurements in 4 Thoroughbred racehorses (high V̇O2peak, Ehrlichet al.1993). No significant difference in MCL (based on V̇O2and venous lactate) was found in either group of horses at exercise intensities where V̇O2

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04881.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe compulsory respiration locomotion coupling may sometimes be broken in healthy galloping horses, leading to a ‘big respiratory cycle’ (BRC). This work is aimed at describing the ventilatory pattern of the BRC and at studying the influence of the individual horse, gallop speed and training. Eleven healthy Thoroughbred horses were studied during a 9 week period of incremental training intensity. Instantaneous respiratory airflow, tidal volume, respiratory rate and the O2and CO2fraction in inspired and expired gases were continuously obtained on a breath‐by‐breath basis during 4 standardised treadmill exercise tests (SET) performed at 3 week intervals. The inspiratory airflow of the BRC had a bi‐ or triphasic shape and its inspiratory time was 1.5‐fold longer than that of a normal breath. The expiratory flow was monophasic and lasted 2.5‐fold longer than the normal breath. The inspiratory, but not the expiratory peak flows, remained unchanged during the BRC. The inspiratory volume was 2.0‐to 1.5‐fold higher than normal, according to the gallop speed. Each BRC was followed by a ‘readjustment cycle’ (RC), which allowed the recovery of normal respiration locomotion coupling. The sum of BRC + RC times always equalled the time for 3 normal respiratory cycles. The sum of the inspiratory volumes of BRC and RC was significantly higher than the sum of their expiratory volumes. There was a highly significant effect of horse and of training on the frequency of BRC. Lastly, during the BRC and at least the 4 following respiratory cycles, the end‐tidal O2and CO2fractions were significantly lower and higher respectively. It was hypothesised that this respiratory manoeuvre could result from a negative feedback mechanism providing, at least, transiently either a readjustment of the end expiratory lung volume or an improvement of the

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04882.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe objective of the present study was to determine the effect of head and neck position on upper airway flow mechanics in exercising horses. Five Standardbred horses (452 ± 16.5 kg bwt; 4.7 ± 0.9 years [mean ± s.e.]) were exercised at 75% (Period A) and at 100% of maximal heart rate (Period B) with head and neck unrestrained, extended, or flexed. Airflow was measured using a facemask mounted pneumotachograph, while tracheal pressure during inhalation and exhalation (PUIand PUE) was measured using a nasotracheal catheter. With head and neck unrestrained, PUI, PUE, inspiratory and expiratory impedance (ZI, ZE), respiratory frequency (f) and indices describing the tidal breathing flow‐volume loops (TBFVLs) were similar to those previously reported. There were no significant changes in the extended position, except that expiratory time (Te) and ratio of peak expiratory flow and peak inspiratory flow (PEF/PIF) were significantly increased inPeriods AandB, respectively. In contrast, in the flexed position, ZIwas significantly increased inPeriod B.Also, inspiratory flow at 50% of tidal volume (IF50) was significantly decreased, and PEF/PIF and EF50/IF50were significantly increased. At period A, PUIwas increased and Te was prolonged. We conclude that during strenuous exercise head and neck extension has little effect on upper airway flow mechanics, but that head and neck flexion causes upper airway obstruc

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04883.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryWhile prolonged submaximal exercise is associated with an increase in core body temperature, the role of ventilation in the dissipation of this heat load is unclear. We examined airway mechanics in 5 horses exercising on a treadmill at 40% V̇O2maxfor 60 min or until fatigued, in order to study the ventilatory response to prolonged low intensity exercise. Respiratory tract mechanics, pH and arterial blood gases were recorded at rest and at regular intervals during exercise. Mean ± s.d. run time was 51.7 ± 5.9 min. No changes in ventilatory mechanics were seen in the first 12–15 min of exercise. Mean breathing frequency (fb) did not change during the test (109 ± 11), however, tidal volume (VT) and fbvaried considerably in individual horses over the course of the run. Some animals freely interchanged their breathing pattern between shallow tachypnoea and regular tidal breathing with fbranging from 76 to 171. Minute ventilation was not affected by breathing pattern but increased from 935 ± 119 l/min after 12–15 min to 1365 ± 343 l/min at the end of exercise. This was associated with a rise in pulmonary arterial blood temperature (BT) from 39.2 ± 0.2°C to 41.8 ± 0.4°C and an increase in work of breathing (Wrm) from 214 ± 30 to 475 ± 122 kg/cm. Wrm/min/l and kg·min increased 1.98‐, 1.28‐ and 1.87‐fold, respectively, in the same period. VTand each expression of Wrmwere logarithmically correlated with BT. PCO2decreased from 41.2 ± 1.7 Torr after 12–15 min to 30.6 ± 1.3 Torr after 57–60 min, while pH increased from 7.43 ± 0.03 to 7.56 ± 0.03 in the same period. We conclude that while the thermoregulatory role of the equine respiratory system may be unclear, horses mount a concerted hyperventilatory response during prolonged submaximal exercise. This response may be associated with rises in core temperature and intermittent tachypnoea, is characterised by increases in Wrmand may be physiolo

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04884.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryTwenty‐three Thoroughbred racehorses that were presented for a standard incremental exercise test also performed a test at an intensity equivalent to 115% V̇O2maxin an effort to evaluate their anaerobic capacity by measuring the maximal accumulated oxygen deficit (MAOD). Submaximal V̇O2values for speeds 3 to 10 m/s and V̇O2maxwere determined for horses exercising on a treadmill inclined at a 10% slope. An individual regression equation of speed and V̇O2was used to calculate the speed for each horse to exercise at 115% V̇O2maxand the energy demand for exercise at this intensity. The horses underwent a warm‐up period consisting of 5 min at 50% V̇O2maxfollowed by walking for 5 min at 1.5 m/s. The treadmill was then acclerated as rapidly as possible until a speed of 115% V̇O2maxwas attained. During the test, expired gas samples were collected at 0, 15, 30, 45, 60 s and every 30 s until fatigue. MAOD was calculated by subtracting the measured oxygen uptake from the calculated oxygen demand. A 5 min post exercise blood sample was collected for measurement of plasma [lactate]. The MAOD values ranged from 36 to 94 mlO2equivalents/kg and the V̇O2maxvalues ranged from 128 to 170 ml/kg/min. The mean ± s.e. MAOD values were 59 ± 3 mlO2equivalents/kg and mean V̇O2maxwas 146 ± 2 ml/kg/min. Mean plasma [lactate] was 23.0 ± 1.2 mmol/l. MAOD was weakly correlated with V̇O2max(r = 0.514, P<0.05), but was not correlated with run time, plasma lactate or treadmill work. The test of MAOD was suitable for use during clinical

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04885.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryWe determined the effects of exercise induced concentrations of epinephrine (E) and norepinephrine (NE) on acetylcholine (ACh) release and smooth muscle contraction. To determine ACh release, trachealis strip bundles were suspended in 2 ml tissue baths in the presence of neostigmine (10−6M), guanethidine (10−5M) and atropine (10−7M), and stimulated by electrical field stimulation (EFS; 20V, 0.5 ms, 0.5 Hz, for 15 min). EFS‐induced ACh release was measured by high‐performance liquid chromatography coupled with electrochemical detection. Concentration responses to E and NE (10−8to 10−5M) were determined. In time‐control tissues, ACh release averaged 8.2 ± 0.9 pmol/g/min. Epinephrine caused significant inhibition of ACh release at concentrations of 10−7M or greater and NE at 10−6M or greater. E‐ and NE‐induced inhibition of ACh release was attenuated by the α2‐adrenoceptor antagonist idazoxan (10−6M) but not by the α2‐antagonist prazosin (10−6M) nor the β‐antagonist propranolol (10−6M). We determined if E and NE had inhibitory actions on smooth muscle by examining their effect on the ACh concentration‐response curve of trachealis. E (10−6M) inhibited contraction only at 10−7M ACh, i.e. when muscle tension was low. NE had no effect. Exercise induced concentrations of E inhibit cholinergically mediated bronchospasm primarily by α2‐mediated prejunctional inhibition of ACh release and, to a lesser degree, by a post junctional effect on airway smooth muscle. NE only inhibits ACh release but not significantl

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04886.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe objective of this study was to determine if strenuous exercise in unconditioned horses impaired function of neutrophils and alveolar macrophages. Flow cytometry was used to assess the effects of a single bout of strenuous exercise on these cells. Bronchoalveolar lavage and venous blood sampling were performed 30 min, 1 and 5 days after exercise. Exercise consisted of 2 min at 2,4 and 6 m/s and then 1 min at 1 m/s incremental speeds until exhaustion, on a level treadmill. Intracellular oxidation of the fluorochrome dye DCFH‐DA was stimulated by PMA and detected by a flow cytometer. Size and granularity of the 2 cell preparations were also measured. The respiratory burst induced in granulocytes was significantly inhibited 30 min after exercise (480 ± 182) compared to that prior to exercise (2359 ± 456). Inhibition at 1 and 5 days after exercise was less than at 30 min and did not differ significantly from either control values. No change in size or granularity was seen as a result of exercise. The alveolar macrophage population remained unchanged in size, granularity and fluorescent responses following exercise. Several cell samples taken before exercise exhibited peripheral blood eosinophilia. In these samples, granulocyte size was markedly reduced and DCFH‐DA oxidation was depressed; viability did not alter. This study suggests that strenuous exercise impairs the respiratory burst of granulocytes for several days. Other factors associated with peripheral eosinophilia also have suppressive effects on granulo

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04887.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryWe tested the hypothesis that training would result in more rapid increase in V̇O2and V̇CO2following the onset of submaximal exercise. Six Standardbred horses were used and trained at submaximal intensities for 5 weeks. Horses were trained 6 days per week on an inclined treadmill (10% slope) at intensities between 40 and 70% V̇CO2max. At the onset of training horses ran 2600 m/day which progressively increased to 4500 m/day by week 5. Testing was carried out before training and after weeks 3 and 5 of training. The test involved exercise at 2 speeds, 4 m/s and 8 m/s, both for 3 min with one h recovery between the 2 speeds. All horses performed at both speeds but the initial speed was randomly allocated. An open flow gas collection system was used to measure V̇O2and V̇CO2every 15 s for the first min of exercise and every 30 s thereafter. After 5 weeks training, mean body weight and V̇O2max(mean ± s.e.) of the group had altered from 433 ± 5 kg to 430 ± 8 kg (P>0.05) and from 104 ± 5 ml/kg/bwt/min to 116 ± 6 ml/kg/bwt/min (P<0.05), respectively. There were no significant training effects on the rate of change of V̇O2or V̇CO2at either of the test speeds. By 45 s, the V̇O2and V̇CO2values had reached 85 to 95% of mean steady state values at both intensities of exercise. In general, steady state V̇O2and V̇CO2values were evident by 60 s of exercise. We conclude that horses have rapid increases in gas exchange at the start of exercise and these are not influenced by low in

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04888.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe purpose of the present work is to report the feasibility, humaneness and reliability of a method for measurement of diaphragm performance in intact, awake horses. Phrenic nerves were activated through thevena cavaby repeated transvenous stimulations (40 to 80V, 100 to 200 μs square‐wave pulses), using an electrode‐catheter advanced from the jugular vein. Twitches were produced that caused changes in gastric and oesophageal pressures, abdominal and rib cage motion and airflow tracings, suggesting that the diaphragm was activated. Four sites were selected over each hemithorax for placement of surface electrodes able to detect and to ensure constancy of evoked compound diaphragmatic action potentials (CDAP). Trains of repeated pulses applied to nerves (10 to 100 Hz) gave repeatable diaphragmatic force‐frequency relationships. Nerve stimulation produced no visible signs of discomfort and increases in Cortisol and β‐endorphins similar to those produced by nasogastric intubation. Transvenous single and repeated activations of the phrenic nerves in ponies is feasible, free of iatrogenic risks and ethically acceptable, recording reliable evoked potentials via surface electrodes is possible, and force‐frequency characteristics of the diaphragm can be conveniently obtained from simultaneous oesophageal and gastric pressures m

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04889.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe objective of this study was to determine the effects of 2 different gas collection systems on locomotor and ventilatory responses to exercise in a group of 8 Standardbred pacers. Each horse completed the same incremental treadmill exercise test (8, 9, 10 and 11 m/s on a 3° incline) using an open (flow‐through) system (OS) and a closed system (CS) incorporating one way valves. Only 2 horses completed the final (11 m/s) step using the CS. Peak values for V̇O2, O2pulse, plasma lactate and respiratory exchange ratio (RER) were significantly higher for the OS compared with the CS. There was no change in breathing frequency (Vf) or stride frequency (Sf) (mean ± s.e. 128 ± 2 strides/min) throughout either exercise test, however Vfwas significantly lower when horses exercised in the CS (68 ± 6 breaths/min) when compared to the OS (100 ± 3 breaths/min). There was a linear increase in stride length (SL) with speed (3.8 ± 0.1 m/stride at 8 m/s to 5.0 ± 0.2 m at 11 m/s) but no difference in SLbetween systems. There was also a linear increase in VTmeasured in the CS. Incremental exercise did not alter the Sf:Vfratio, however Sf:Vfwas significantly lower in the OS (1.3:1) when compared to the CS (2.1:1). There was a significant difference between systems for PaO2and PaCO2values at all increments of exercise. The lower Vfmeasured in the CS was associated with marked hypercapnia (59 ± 7 mmHg at 10 m/s) and hypoxaemia (45 ± 3 mmHg at 10 m/s). The higher Vfmeasured in the OS was associated with hypocapnia (35 ± 2 mmHg) at 8 m/s. It was concluded that although Vfvaried between OS and CS, Vfand Sfdid not change during incremental exercise with either system. Therefore the increase in speed was achieved solely by an increase in SL. Although the CS did not alter locomotor parameters or V̇O2at lower increments of exercise, the altered Vfappeared to limit

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04890.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY