Use of a novel one-nostril mask-spacer device to evaluate airway hyperresponsiveness (AHR) in horses after chronic administration of albuterol.

Inflammatory airway disease (IAD) is very common in stabled horses. Short-acting beta agonist (SABA) drugs are often used to relieve clinical signs, although long-term exposure to these drugs may result in rebound bronchoconstriction. The purpose of this study was twofold: i) to describe the deposition of radiolabeled drugs using a novel one-nostril design mask-spacer combination with a breath-activated inhaler (BAI), and ii) to determine whether treatment for 10 d with inhaled albuterol using this device would impair the ability of albuterol to prevent bronchospasm during a histamine challenge test. The percentage of radio-aerosol deposited in the total lung was 12.39% ± 5.05%. All study horses demonstrated airway hyperresponsiveness (AHR) before enrollment in the study [mean provocative concentration eliciting 35% increase in delta flow (PC35) < 6 mg/mL histamine]. There was no significant difference in airway hyperresponsiveness to post-albuterol histamine challenge before or after treatment with albuterol. A 10-d treatment with placebo, however, caused a significant increase in airway hyperresponsiveness in all horses (P < 0.001). The results of this study show that the novel mask-spacer device was effective in delivering radiolabeled aerosolized drug to the lung and that delivery of a SABA for 10 d using this device did not result in increased airway hyperresponsiveness.

La maladie inflammatoire des voies respiratoires (IAD) est très courante chez les chevaux gardés en écurie. Les médicaments agonistes bêta à courte action (SABA) sont souvent utilisés pour soulager les signes cliniques, bien qu'une exposition prolongée à ces médicaments puisse résulter en une bronchoconstriction rebond. Le but de la présente étude était double : i) décrire le dépôt de médicaments radio-marqués en utilisant un nouveau design de chambre d'inhalation pour une seule narine avec un inhalateur activé par l'haleine (BAI), et ii) déterminer si un traitement pendant 10 j avec de l'albuterol inhalé avec cet appareil compromettrait la capacité de l'albuterol à prévenir un bronchospasme durant un test défi à l'histamine. Le pourcentage d'aérosol radio-marqué déposé dans le poumon total était de 12,39 % ± 5,05 %. Tous les chevaux dans l'étude ont montré une hyperréactivité des voies respiratoires (AHR) avant l'incorporation dans l'étude [concentration moyenne induisant une augmentation de 35 % du delta flot (PC35) < 6 mg/mL d'histamine]. Il n'y avait pas de différence significative d'hyperréactivité des voies respiratoires au challenge à l'histamine post-albuterol avant ou après traitement avec de l'albuterol. Toutefois, un traitement pendant 10 j avec un placebo a causé une augmentation significative d'hyperréactivité des voies respiratoires chez tous les chevaux (P < 0,001). Les résultats de la présente étude ont montré que le nouveau design d'inhalateur était efficace pour la distribution par aérosol de médicament radio-marqué dans les poumons et que l'administration de SABA pendant 10 j à l'aide de cet appareil n'a pas causé d'augmentation de l'hyperréactivité des voies respiratoires.(Traduit par Docteur Serge Messier).

Effects of tension of the girth strap on respiratory system mechanics in horses at rest and during hyperpnea induced by administration of lobeline hydrochloride.

OBJECTIVE: To determine whether tension of the girth strap of a saddle would sufficiently affect rib motion and reduce lung volume to alter pulmonary resistance in horses. ANIMALS: 10 healthy adult horses. PROCEDURE: We used classical techniques to measure the effects of tightening a girth strap (15 kg of tension) on pulmonary dynamics during eupnea and hyperpnea in horses. Respiratory impedance was evaluated by use of oscillometry, and resistance and reactance data were partitioned into lung and chest wall components. Rib cage and abdominal contributions to tidal volume and minute ventilation were measured by use of respiratory inductance plethysmography. Effects of strap tension on functional residual capacity (FRC) were measured during eupnea by use of a helium-dilution technique. In a subgroup of 6 horses, we also measured transdiaphragmatic pressures during eupnea and hyperpnea induced by administration of lobeline hydrochloride (0.2 mg/kg, i.v.). RESULTS: Pulmonary resistance measured by use of oscillometry but not by use of classical methods was significantly increased by the tension of the girth strap. However, the increase in pulmonary resistance could not be explained by a decrease in FRC. Motion of the rib cage was significantly reduced during eupnea and hyperpnea. However, ventilatory variables (tidal volume, minute ventilation, and peak flows), FRC, and transdiaphragmatic pressures were unaltered by strap tension. CONCLUSIONS AND CLINICAL RELEVANCE: Although tension of the girth strap caused measurable changes in respiratory mechanics (loss of rib motion and increased pulmonary resistance), there was no evidence that ventilation was limited.