peer reviewed | 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

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peer reviewed | Although the respiratory tract of healthy and diseased cattle has been intensively studied during the past few years, only a few attempts to detect dysfunctions of bovine inspiratory muscles have been reported. Such technique would be useful in assessing the possibility of inspiratory muscle fatigue in the context of ventilatory failure. Fatigue in skeletal muscle is associated with characteristic changes in the electromyographic power spectrum. Power spectral analysis was therefore applied to cattle diaphragmatic electromyograms (EMGdi) to precisely determine the exact influence of motion and ECG artifacts, describe its basic frequency content, and extract a spectral index capable of providing an accurate warning of fatigue. The EMGdi was recorded via intramuscularly placed fishhook electrodes in 5 healthy young bulls during resting and stimulated respiration. The EMGdi and EGC signals were analyzed by use of power spectral density analysis after band-pass filtering (20 to 1,800 Hz). The EMGdi spectrum was concentrated in the band width 20 to 530 Hz. Electrode motion artifacts were absent, and it was always possible to find an electrode pair giving ECG-free EMGdi. Of the 12 power and frequency values used to quantitate the spectrum, the most stable was the centroid frequency. It was reproducible within and between calves and was only minimally altered by changing inspiratory load.(ABSTRACT TRUNCATED AT 250 WORDS)

peer reviewed | Although healthy and diseased bovine respiratory tracts have been intensively studied during the last years, to the authors' knowledge, there have been no attempts to objectively examine the inspiratory drive from the brain to the nerves and muscles and its transformation in pressure. Such technique would be useful in assessing the possibility of altered ventilatory drive or inspiratory muscle fatigue in the context of an animal with ventilatory failure. The relation among ventilation, airway opening occlusion pressure generated 100 milliseconds after onset of inspiration (Pawo100ms) and 6 indexes describing diaphragmatic electromyographic activity (EMGdi) recorded via implanted fishhooks was evaluated during free and impeded CO2 rebreathing in 6 young bulls. The best significant linear correlations (r > 0.8) with inspiratory center afferent stimulation, as judged by end-tidal CO2 concentration in expired air, were found for Pawo100ms, peak moving time average or variance EMGdi, and mean integrated EMGdi, whatever had been the respiratory impedance. However, with an inspiratory load, Pawo100ms responses systematically had greater increase for a given change in the driving EMGdi, implying dependence of the former not only on neural input, but also on configurational factors that determine inspiratory muscle excitation-pressure generation couplings. The reproducibility of EMGdi absolute values and changes was satisfactory up to 10 hours, but could not be repeated from one day to the other. It was concluded that, provided the constancy of the electrical coupling of the recording system to the tissue being studied is ensured, specific EMGdi and Pawo100ms values correlate reliably with amount of CO2 during free and loaded breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

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