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  • Author or Editor: Charles L. Michaux x
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Summary

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 (emg di) 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 emg di was recorded via intramuscularly placed fishhook electrodes in 5 healthy young bulls during resting and stimulated respiration. The emg di and egc signals were analyzed by use of power spectral density analysis after band-pass filtering (20 to 1,800 Hz). The emg di 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 emg di. 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.

Though the clinical relevance of fatigue in the respiratory musculature in case of ventilatory failure is currently unknown, the method described here constitutes a possible approach to detection of such phenomenon in cattle.

Free access
in American Journal of Veterinary Research

SUMMARY

The purpose of this study was to investigate the mechanism by which 5-hydroxytryptamine (5-ht) modifies respiratory function, specifically, hyperventilation, diffuse bronchoconstriction, and pulmonary arterial hypertension in cattle. We determined whether the IV response to 5-ht in calves was attributable to stimulation of 5-ht2 receptors.

Six healthy unsedated young bull calves of the Friesian (n = 4) and of the Belgian White and Blue (n = 2) breeds were used. A specific 5-ht2 antagonist (metrenperone, 0.05 mg/kg of body weight) was administered IM 30 minutes before the cattle were given a 5-minute IV 5-ht infusion. Pulmonary function values were registered before, during, and after the 5-ht challenge infusion. Minute volume increased significantly, because of an increase in respiratory rate. Conversely, lung dynamic compliance, total pulmonary resistance, and pulmonary arterial pressure were not changed.

We concluded that in cattle, 5-ht-induced ventilatory response is not mediated through activation of 5-ht2 receptors. However, the 5-ht2 receptors are involved in 5-ht-induced broncho- and pulmonary vasoconstriction.

Free access
in American Journal of Veterinary Research