Radiographic evolution of the forelimb digit in Ardenner horses from weaning to 28 months of age and its clinical significance.

Ossification of collateral cartilages is a common radiographic finding in draught horses and indication of a high frequency of interphalangeal osteo-arthropathy have been found in Ardenner horses. This study first aimed at following the evolution of the digits of the forelimbs on radiographic images in a group of 32 Ardenner horses from weaning to 852 +/- 19 days and, secondly, at evaluating the clinical significance of the observed radiographic changes. At 250 +/- 21 days, only 23% of the horses presented a small separate ossification centre of collateral cartilages above the level of the distal sesamoid bone or at the level of the proximal half of the middle phalanx. At 852 +/- 19 days, 100% of the horses presented an ossification of collateral cartilages but at different stages and grades. The presence and the extent of the ossification of the lateral cartilages were not significantly associated with lameness. Phalanges changes appeared at the average age of 1 year and they were represented by entheseophytes on the dorsal surface of the middle and distal phalanges. The frequency of affected horses increased with age as well as the size of the entheseophytes. This may reflect mechanical stresses applied to the interphalangeal joints. A significant association with the presence of lameness was pointed out. The presence and the severity of phalanges changes could be of importance, in combination with a clinical examination, in improving the selection of horses able to assume work and/or leisure activities.

Validation of a portable equine metabolic measurement system.

REASONS FOR PERFORMING STUDY: In equine sports medicine, VO2 has been measured exclusively with stationary systems, in laboratories equipped with a treadmill. Measurement during exercise in field conditions has not previously been reported because of the lack of portable equipment designed for horses. OBJECTIVES: A commercially available portable metabolic measurement system, based on breath-to-breath gas analysis and flow spirometry, was adapted to the horse's physiology and morphology (Cosmed K4b2 and Equimask) and its validity tested by (1) repeatability of the measures and (2) comparing metabolic data to those obtained by a reference method (RM). METHODS: To test the reproducibility of the measurements, 5 healthy saddle horses were subjected twice at 2 day intervals to a similar submaximal standardised incremental exercise test on a treadmill. The same horses performed twice at one week interval an incremental treadmill test to fatigue: the oxygen consumption and ventilation were measured once with the K4b2 system and once with the RM. The metabolic and ventilatory data obtained with both systems were compared. RESULTS: There was a good reproducibility of the metabolic measurements obtained by the K4b2 system at any workload. The VO2 obtained by both systems at any workload was not significantly different. However, the K4b2 expired fraction in CO2 (FETCO2) and carbon dioxide production (VCO2) were significantly lower at high and at maximal workloads. As a consequence, the values of the respiratory exchange ratio were too low and incompatible with normal physiological values. CONCLUSIONS: The good reproducibility of the metabolic and ventilatory measurements and the fact that the VO2 measurements at any workload were similar to the data obtained with the reference method suggested that this system may be used for comparison of repeated VO2 measurements in practical field conditions. POTENTIAL RELEVANCE: The K4b2 system could be used to improve knowledge of the energetic cost in different equine sports disciplines and offer the opportunity to undertake performance tests with genuine track conditions, on ridden or harnessed horses, rather than under laboratory conditions.

Exercise-induced pulmonary perfusion redistribution in heaves.

This study aimed to compare exercise-induced pulmonary perfusion redistribution in healthy vs. 'heavey' horses using scintigraphy, a minimally invasive technique. Six healthy (A) and 5 'heavey' horses in remission (B(I)) and during clinical signs of disease (B(II)) were investigated. Dimensions of the exercising pulmonary perfusion (QE) images were expressed in percent of the resting perfusion (QR) images. Computed QE to QR ratios (QE/QR) images enabled the definition of the region more perfused at exercise than at rest (R1). In all groups, exercise induced a major enlargement of the Q image but a larger increase of the lung height was found in 'heavey' horses. Compared to A, 'heavey' horses showed a larger R1 region with a significantly higher QE/QR. Location of R1 pointed out the dorsal lung region as a major site of pulmonary perfusion redistribution for all groups. This work demonstrated (1) the feasibility of using scintigraphy for studying exercise-induced pulmonary perfusion redistribution; (2) perfusion redistribution to the dorsal lung with exercise and (3) an intensified redistribution in 'heavey' horses, either clinically affected or not.

Effects of inhaled ipratropium bromide on breathing mechanics and gas exchange in exercising horses with chronic obstructive pulmonary disease.

Six Warmblood horses suffering an acute exacerbation of COPD were tested to investigate whether inhalation of ipratropium bromide (IB) dry powder (2,400 microg) 30 min preexercise would improve their exercise capacity. A cross-over protocol with an inert powder placebo (P) was used. Mechanics of breathing and arterial blood gases were determined before treatment, after treatment but pre-exercise, and during an incremental exercise test. Oxygen consumption (VO2) was also measured before and during exercise, and the time to fatigue recorded. Inhalation of IB reduced total pulmonary resistance (RL) and maximum intrapleural pressure changes (deltaPpl(max)) and increased dynamic compliance before exercise. The onset of exercise was associated with a marked decrease in RL in P-treated horses but not those receiving IB, so that RL during exercise was not affected by treatment. Although deltaPpl(max) was lower at 8,9 and 10 m/s with IB, there were no treatment-related changes in VO2, blood gases, time to fatigue or any other measurement of breathing mechanics. Therefore, although inhalation of IB prior to exercise may have improved deltaPpl(max), it had no apparent impact on the horses' capacity for exercise.

Alveolar clearance in horses with chronic obstructive pulmonary disease.

OBJECTIVE: To assess sensitivity of scintigraphic alveolar clearance rate as an indicator of alveolar epithelium damage in horses. ANIMALS: 5 healthy horses (group A) and 5 with chronic obstructive pulmonary disease (COPD; group B). PROCEDURE: Horses underwent clearance rate (k [%/min]) determination. Clearance rate of group-B horses was determined after remission of the disease following 2 months at pasture (remission 1), stabling in a controlled environment (remission 2), and during crisis induced by exposure to moldy hay and straw. Methacholine challenge test was performed at each investigation period to determine nonspecific pulmonary airway hyperresponsiveness. Pulmonary function tests (PFT) also were performed, and cell populations in bronchoalveolar lavage (BAL) fluid were determined on another occasion. RESULTS: Group-B horses had significantly faster mean clearance rate during crisis (k = 4.30+/-0.95%/min), compared with that for remission 1(k = 1.98+/-0.55%/min), which did not differ from the rate in group-A horses (k = 1.95+/-0.33%/min). Despite lack of clinical signs of COPD during remission when stabled in a controlled environment, an intermediate value was found (k = 3.20+/-0.72%/min). CONCLUSIONS: This technique allowed grading of lung damage induced by COPD, whereas use of PFT and determination of BAL fluid cell populations failed to differentiate between remission 1 and remission 2. CLINICAL RELEVANCE: Determination of alveolar clearance rate by use of scintigraphy is a sensitive indicator of lung damage. A modified clearance rate was found despite the lack of clinical and functional changes.

Analysis of scintigraphical lung images before and after treatment of horses suffering from chronic pulmonary disease.

Scintigraphical analysis of the ratio of inhalation (I) to perfusion (Q) was designed to determine whether chronic pulmonary disease in horses induced mismatches in I/Q and to assess whether medical treatment would restore an I/Q distribution pattern identical to that of control horses. In addition, the results of the I/Q analysis were correlated with the alveolar-arterial PO2 difference (AaDO2). The I/Q matching found in a group of control horses was compared with the I/Q analysis of a group of diseased horses before and after their clinical signs had been treated. The analysis indicated that there was mismatching between I and Q before they were treated. The treatment improved the diseased horses, pulmonary function but there was still heterogeneity in the I/Q distribution after they had been treated. The I/Q analysis parameters were well correlated with the ratio of ventilation (VA) and pulmonary blood flow (Q), evaluated by the determination of AaDO2.

Effects of inhaled dry powder ipratropium bromide on recovery from exercise of horses with COPD.

The present study evaluated ventilatory, cardiovascular and metabolic parameters during recovery from strenuous exercise in horses suffering from a crisis of chronic obstructive pulmonary disease (COPD) and to determine whether ipratropium dry powder inhalation (DPI) before exercise has an effect on these parameters. When 6 saddle horses, affected with COPD, developed airway obstruction, they inhaled placebo and ipratropium (2400 microg/horse), the order being randomly chosen. Pulmonary function tests were then recorded 15 min after inhalation. Following these tests, the horses underwent a strenuous treadmill exercise, followed by a recovery period that consisted of a 10 min walk. Measurements were made at the first and tenth min of recovery. Respiratory flow, O2 and CO2 fractions in the respired gas, pleural pressure changes and heart rate were recorded. Arterial and mixed venous blood samples were analysed for gas tensions, haemoglobin and plasma lactate concentrations. Oxygen consumption (VO2), CO2 production, tidal volume, alveolar oxygen tension (PAO2), alveolar ventilation, the alveolar-pulmonary capillary oxygen difference ((A-a)dO2) and total pulmonary resistance (RL) were measured. The PAO2 was the only parameter significantly improved during recovery following ipratropium DPI. This improvement was not accompanied by evidence of improvement of other ventilatory or cardiorespiratory parameters. The results showed that in horses suffering from a crisis of COPD, recovery is characterised by an exercise-induced bronchodilation. Secondly, ipratropium DPI at a dose of 2400 microg/horse is an effective bronchodilator in these horses at rest but it has little effect on the airway calibre during the recovery period. It is suggested that the short term recovery period is still influenced by exercise-induced adjustments that may exceed the bronchodilatory effect of inhaled ipratropium that are observed before exercise.

Scintigraphical evaluation of alveolar clearance in horses.

This study proposed a standardized method for measuring alveolar epithelium membrane permeability in the horse. The normal rate of clearance (%.min-1) from lung into blood of nebulized 99mTc-DTPA has been established for healthy horses (Group A) compared with values obtained with horses suffering from chronic obstructive pulmonary disease (COPD; Group B). The 99mTc-DTPA clearance was measured in the caudoventral (R1) and in the half caudal (R2) parts of the left lung during different time intervals. The two regions aimed to define the influence of the airways on measured clearance (R2 contained proportionally more conducting airways than R1). It was concluded that a comparison of groups of subjects may be performed in R2 and on data collected during a 20 min period. The normal clearance rate in R2 was 1.80 +/- 0.46%.min-1 (T1/2R2 = 40.99 +/- 12.45 min) in Group A. In Group B, a significantly faster 99mTc-DTPA transfer rate was found (4.17 +/- 0.83%.min-1 or T1/2R2 = 17.17 +/- 3.38min). Bronchoalveolar lavage (BAL) suggested that the increased permeability measured in Group B could be the result of lung inflammatory responses. Our results have demonstrated the ability of the 99mTc-DTPA clearance test to detect alveolar epithelial damage in horses. Furthermore, we were able to show that a regional analysis of the alveolar-capillary barrier integrity may be performed satisfactorily in the equine patient.

Effect of a set stabled environmental control on pulmonary function and airway reactivity of COPD affected horses.

The aim of this study was to evaluate the respiratory function of horses affected with chronic obstructive pulmonary disease (COPD) when maintained in a barn on wood shavings and fed grass silage for a period of 6 weeks. The mechanics of breathing, blood gas analysis and bronchial reactivity were examined on five horses with COPD at the end of the environment-controlled period (Period B) and the results compared with values obtained after 2 months at pasture (Period A) and after the onset of clinical signs of acute crisis (Period C). The results showed that clinical and functional parameters were similar in healthy horses and in COPD horses placed on pasture or stabled and fed grass silage. Moreover, the bronchial reactivity of COPD horses at pasture was similar to the bronchial reactivity of healthy horses. COPD horses fed grass silage however presented a bronchial reactivity intermediate between those measured after Period A and Period C which suggested they would be more susceptible to develop bronchoconstriction when in contact with inhaled irritants.

Does an acute COPD crisis modify the cardiorespiratory and ventilatory adjustments to exercise in horses?

The present study was conducted to understand better the mechanisms leading to the decrease in exercise capacity observed in horses suffering from chronic obstructive pulmonary disease (COPD). Five COPD horses were submitted to a standardized submaximal treadmill exercise test while they were in clinical remission or in acute crisis. Respiratory airflow, O2 and CO2 fractions in the respired gas, pleural pressure changes and heart rate were recorded, and arterial and mixed venous blood were analyzed for gas tensions, hemoglobin, and plasma lactate concentrations. O2 consumption, CO2 production, expired minute ventilation, tidal volume, alveolar ventilation, cardiac output, total pulmonary resistance, and mechanical work of breathing were calculated. The results showed that, when submaximally exercised, COPD horses in crisis were significantly more hypoxemic and hypercapnic and that their total pulmonary resistance and mechanical work of breathing were significantly higher and their expired minute ventilation significantly lower than when they were in remission. However, their O2 consumption remained unchanged, which was probably due to the occurrence of compensatory mechanisms, i.e., higher heart rate, cardiac output, and hemoglobin concentration. Last, their net anaerobic metabolism seemed to be more important.

Environmental control to maintain stabled COPD horses in clinical remission: effects on pulmonary function.

The objective of this study was to test the hypothesis that stabled COPD horses can be maintained in clinical remission by replacing hay by grass silage and bedding made of wood shavings (Period B) and of wheat straw (Period C) during 6 weeks, respectively. At the end of these different periods, the pulmonary function of the horses was assessed by mechanics of breathing and arterial blood analyses. These results were compared to those measured in clinical remission obtained after 2 months in pasture (Period A). No significant difference was observed between these 3 periods neither to values obtained for healthy horses placed during 6 weeks in a hay environment. For all that, COPD horses placed in contact with hay in the same barn developed within mean +/- s.d. 8+/-3 days clinical signs of heaves and significant alterations of pulmonary function parameters.

Technical validation of a face mask adapted for dry powder inhalation in the equine species.

Development of dry powder inhalation (DPI) for horses requires the use of an adapted face mask. In experiment I, 4 masks (A, B, C and D) were tested and factors influencing the delivery of the dry powder were determined. Mask A was one which is commercially available for metered-dose inhalation. Mask B had the same shape as Mask A but an airtight rubber seal was added for the connection between the mask and horse's head. Mask C was a prototype adapted for DPI with connection for the DPI device between the nostrils, airtight expiratory valves in front of each nostril and airtight rubber seal to attach the mask on the horse's head. Mask D was the same as Mask C but the airtight expiratory valve was situated in front of one nostril and the connection for the DPI device was placed in front of the other nostril. Inhalet emptying and peak inspiratory pressure were measured on 5 healthy horses with each face mask. Both Masks A and B gave a low rate of inhalet emptying. Inspiratory pressures created in Masks C and D were negative enough to ensure inhalet emptying rates of mean +/- s.d. 98.28 +/- 1.79% and 100% respectively. In experiment 2, the face masks giving the greatest inhalet emptying were used to test the therapeutic efficacy of ipratropium bromide DPI. This was tested on 6 horses suffering from acute exacerbation of chronic obstructive pulmonary disease (COPD). At a dose of 200 micrograms/100 kg bwt, ipratropium administered with Mask D improved significantly pulmonary function measurements compared to baseline values and placebo inhalation. With Mask C, a double dose of ipratropium (400 micrograms/100 kg bwt) was necessary to improve these parameters compared to baseline values. This indicated the importance of locating the DPI device in front of one nostril. It was concluded that inhalet emptying is correlated to inspiratory pressures measured in the face masks. Secondly, these pressures are in turn dependent on the air-tightness of the mask, i.e. air-tightness of the expiratory valve and close connection between the horse's head and the mask. Thirdly, position of the DPI device in front of a nostril allows bronchodilation at a dose half that required when the device is placed between the nostrils. Finally DPI using Mask D (EquiPoudre) is a rapid, effective and well tolerated inhalation treatment for COPD horses.

Aerosol deposition in equine lungs following ultrasonic nebulisation versus jet aerosol delivery system.

Therapeutic aerosols pay an increasing role in the treatment of equine respiratory disorders. This route of delivery permits concentration of significant amounts of drugs at the site of action without unwanted high systemic concentration and resultant side effects. The efficiency of such a topical therapy depends on the quantity of inhaled drugs deposited in the lungs and, for some drugs, on the proportion retained in specific parts of the lungs. The objective of this study was to define and to compare quantitative (dose deposited) and qualitative (regional distribution) deposition of an aerosol in the equine lungs, using either a ultrasonic nebuliser (UN) currently used in human medicine or a high pressure jet nebuliser (JN) especially developed for the equine species. This comparison was possible owing to gamma-scintigraphy, a noninvasive technique ideally suited to give information about both total and regional deposition of inhaled drugs in the respiratory tract. The quantitative study did not point out any difference between the 2 systems concerning the activity released from the nebuliser proportionally to the initial loaded dose (mean +/- s.d. 45.95 +/- 4.93% for the UN vs. 46.47 +/- 8.49% for the JN). By contrast, the percentage of the dose released reaching the lungs was significantly lower with the UN compared to the JN (5.09 +/- 0.66% vs. 7.35 +/- 1.96%). The qualitative analysis did not show any significant difference in size of aerosol deposition image between the 2 nebulisers. However peripheral deposition was significantly higher with JN compared to UN. In conclusion, both nebulisers may be used for aerosol therapy in the equine species. The ultrasonic and pneumatic nebulisation achieved drug deposition in the peripheral part of the lungs (i.e. small airways and lung parenchyma).

Airway response of horses with COPD to dry powder inhalation of ipratropium bromide.

To determine the effects of the dry powder inhalation (DPI) of ipratropium bromide (ipratropium) on the airways of health horses and the dose-response curve in horses suffering from chronic obstructive pulmonary disease (COPD) by means of pulmonary function tests, five healthy horses were first studied. Ipratropium (2400 micrograms ipratropium horse-1) was contained in gelatine capsules and administered using a dry powder device connected to an adapted face mask. Pulmonary function tests were recorded before inhalation and 15 and 60 min after inhalation. No modification of pulmonary function was observed. The airway response to ipratropium DPI was then determined in six horses suffering from COPD. To induce airway obstruction, the horses were bedded on straw and fed hay. When the maximal change in pleural pressure during tidal breathing exceeded 1.96 kPa, pulmonary function tests were recorded before DPI, and 15 and 60 min post-inhalation. Placebo (six capsules horse-1) or ipratropium (600, 1200 and 2400 micrograms horse-1) was administered in a randomized order to each horse using the dry powder device and the adapted face mask. Neither ipratropium nor placebo DPI affected respiratory frequency (f) or tidal volume (VT). Inhalation of 600 micrograms ipratropium horse-1 resulted in a delayed decrease of total pulmonary resistance (RL) whereas dynamic compliance (Cdyn) was improved (although not significantly) at both times of measurement when compared with values following placebo inhalation. Simultaneous decreased RL and increased Cdyn, was observed within 15 min after DPI of 1200 micrograms ipratropium horse-1 and persisted for the 1 h duration of the experiment. Doubling the dose also improved pulmonary function but not significantly more than following inhalation of 1200 micrograms ipratropium. No systemic side effects were observed in either group of horses.

Evaluation of some parameters influencing the drug delivery from a dry powder inhalation device using an in vitro model of the horse airways.

The aim of this study was to determine the effect of breathing pattern, air humidity and position of the device on the delivery of an aerosol generated by a dry powder inhalation (DPI) device (Inhalator M). The in vitro inhalation study was performed using the cascade impaction method (Andersen Sampler) adapted to imitate nasal breathing. The amount of ipratropium found in the device, the artificial upper airways and the six stages of the Andersen Sampler was measured using high precision liquid chromatography. Stage 1 of the Andersen Sampler was considered to be the respirable fraction and stages 2 to 6 to be the non-respirable fraction. It was concluded that the theoretical respirable fraction of ipratropium obtained after DPI through Inhalator M was influenced by relative air humidity, air flow and the position of the device, whereas the number of successive inspirations and the duration of inspiration did not affect this fraction of the drug.

Aerosol therapy in the equine species.

Inhalation therapy plays an increasing role in the management of equine respiratory disorders. This alternative to systematic treatment permits a high concentration of medication to act locally while minimizing side effects and residues. In human medicine, literature in this field is prolific and continuously renewed, whereas in veterinary medicine, applications of aerosol therapy are less extensive. This review considers the principles of action of the different types of devices used for inhalation, i.e., nebulization, metered-dose inhalation and dry powder inhalation, describes the technical and practical requirements for their use in the equine species and considers the advantages and disadvantages of each inhalation device. The pharmacological agents currently administered to horses by inhalation are also discussed. Perspectives of aerosol therapy in the equine species, including aerosols already used in human medicine and their potential applications for horses are described.