Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report

Factors influencing variation in locomotor-respiratory coupling in Standardbred Trotters in the field

REASONS FOR PERFORMING STUDY

A close relationship between limb and respiratory rhythms has been shown in clinically healthy galloping horses due to mechanical constraints in the thoracic region. This synchronisation leads to a 1/1 ratio between stride frequency (SF) and respiratory frequency (RF) during galloping. Very little is known about locomotor-respiratory coupling (LRC) during fast trot.

OBJECTIVES

To investigate stride and respiratory rates during a standardised exercise test on the track in Standardbred Trotters.

METHODS

Forty-four French trotters age 2-10 years performed a standardised exercise test consisting of three 3 min steps at constant speeds. Speed (V) of exercise varied between 500 and 750 m/min. Variables measured during exercise: SF, heart rate, RF using a microphone between the nostrils, blood lactate concentration. Physiological variables V4 and V200 were calculated and race performance index recorded.

RESULTS

There was no age-related difference in RF or in LRC. Two LRC strategies were found: around 1/1 ratio and 3/2 ratio between SF and RF, respectively. A relationship between SF/RF ratio and physiological parameters showed a higher LRC in good performers because of a lower RF during submaximal and maximal exercise.

CONCLUSION

RF is significantly lower and LRC significantly higher in good compared to poor performers.

POTENTIAL RELEVANCE

Investigation is required to ensure that the breathing techniques of trotters may be used in the selection process of racehorses.

The displaced equine soft palate as a source of abnormal respiratory noise during expiration

REASONS FOR PERFORMING STUDY

To develop the technique of respiratory sound analysis for the diagnosis of dorsal displacement of the equine soft palate.

OBJECTIVES

To show that 1) the displaced soft palate can spontaneously vibrate in the presence of expiratory airflow; 2) the observed frequency of vibration can be detected in respiratory sound recordings; and 3) the frequency of vibrations measured in cadaveric specimens are similar to those obtained from audio spectra in exercising horses with DDSP.

METHODS

Palatal movements and respiratory sounds were recorded from artificially ventilated cadaveric heads. The fundamental mode of palate vibrations calculated from high-speed videoendoscopic recordings was compared with frequencies detected in the audio spectra and with data collected from exercising horses with DDSP.

RESULTS

Palate vibrations occurred when air was blown through the trachea. The fundamental mode of vibrations was present in the audio spectra and was not significantly different from those recorded in vivo.

CONCLUSIONS

Vibrations of the soft palate are the probable source of expiratory sounds recorded in horses with DDSP.

POTENTIAL RELEVANCE

This study strengthens the case for the application of respiratory sound analysis in the diagnosis of DDSP in exercising horses.