New Zealand Veterinary Journal
ISSN: 0048-0169 (Print) 1176-0710 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzv20
Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report G.R.G. Barnes , M. Brennan , B.E. Goulden & J. Kirkland To cite this article: G.R.G. Barnes , M. Brennan , B.E. Goulden & J. Kirkland (1979) Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report, New Zealand Veterinary Journal, 27:7, 145-146, DOI: 10.1080/00480169.1979.34629 To link to this article: http://dx.doi.org/10.1080/00480169.1979.34629
Published online: 23 Feb 2011.
Submit your article to this journal
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Citing articles: 3 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tnzv20 Download by: [University of Cambridge]
Date: 06 November 2015, At: 03:40
1979
NEW ZEALAND VETERINARY JOURNAL
145
Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report G. R. G. Barnes* M. Brennant B. E. Goulden' J. Kirklandt
N.Z. vel.J.27: 145·6
Downloaded by [University of Cambridge] at 03:40 06 November 2015
ABSTRACT
One problem in the diagnosis of subclinical roarers is that abnormal auditory signals occur only during a fast gait, and these fade quickly. This paper offers a novel technique to assist this problem. Sound recordings were obtained from five horses following exercise; two roarers, two non-roarers, and one suspected roarer. These signals were converted into spectrograms by Rayspan processing. All frequencies in the 0 to 2.25 kHz range during both inspiration and expiration, as well as occasional noises in the 2-4 kHz band, characterised roarers. Signals from non-roarers consisted of frequencies in the 0 to 2 kHz range with long quiet periods, especially during expiration. An explanation for these phenomena is offered, and supported by diagrammatic cross-sections of equine upper-respiratory tracts. It is suggested that the present technique could assist in the diagnosis of subclinical roarers, estimated to be between 20 and 40% of the competitive horse population. INTRODUCTION
For many years, veterinarians have recognised the difficulty of accurately distinguishing between the normal and abnormal respiratory sounds which horses make during exercise. In part, this di8culty arises because many abnormal respiratory noises are made only during. or immediately after, fast gaits. Additionally, the assessment of any treatments for these respiratory disorders has been subjective.
sease is known to occur in between 20 and 41.6% of the competitive horse population (2XJX4X6). Unfortunately, the amount of muscle damage is variable. It is only when a critical quantity of muscle destruction has taken place that affected animals will exhibit respiratory sounds sufficiently different from normal breathing to be recognised by horsemen(2). Most reports indicate that fewer than 5% of the competitve horse population can be identified as roarers by their abnormal respiratory sounds, though a substantial proportion may be emitting abnormal respiratory noises. However, because of the difficulty in comparing the respiratory sounds they make with those of normal horses, these affected animals remain undetected. Some method of identifying these so-called subclinical roarers is urgently required. Additionally, some means is needed of comparing sounds made by different horses and by individual horses at different times. For these reasons, a preliminary investigation of sound spectrograms obtained from both normal and abnormal animals was undertaken. MATERIALS AND METHODS
Five horses were selected (Table I); two (Nos. 1& 2) were clinical roarers which had been unsuccessfully treated by an abductor muscle prosthetic operation and a left ventriculectomy. The endoscopic view of the larynx of these animals was
TABLE I: EXPERIMENTAL ANIMALS No.
Age (in years)
Sex
Breed
Clinical Condition
Amount Exercise Given
Fitness
5
Geld.
Clydesdale x
Roarer
\0 minutes cantering
Unfit
2
3
Geld.
TB
Roarer
800 metre gallop
Fit
3
3
Filly
TB
Normal
\0 minutes cantering
Unfit
4
7
Geld.
TBX
Normal
\0 minutes cantering
Fit
5
2
Geld.
TB
Suspected roarer
800 metre gallop
Fit
TB
= Thoroughbred.
One condition that produces abnormal respiratory noises in horses is the disease commonly called roaring. Roaring is suspected clinically when an affected animal produces an abnormally loud respiratory noise during exercise, and when endoscopic examination reveals asymmetrical positioning and movements of the arytenoid cartilages of the larynx. The condition is associated with abnormal functioning of the left recurrent laryngeal nerve, thus effecting pathological changes to most of the muscles controlling the movements of the left laryngeal cartilages. Muscle pathology associated with this di* Department of Chemistry, Biochemistry and Biophysics,
t
~
Department of Education, Department of Veterinary Clinical Services, Massey University, Palmerston North, New Zealand.
similar to that seen in untreated roarers. One further animal was a clinically suspected roarer (No.5), and the remaining two animals were clinically normaL The respiratory noises made by these animals were recorded during and immediately after either 10 minutes of cantering or an 800 metre gallop. Sound recordings were made using a directional microphone (Sennheiser MKH 815) connected to a reel-to-reel taperecorder (Nagra IV) operating at 19.0 cm/s. Two complete respiratory cycles were taken from the first 30 seconds of each recording. Each of these cycles commenced with an inspiration. The audiotape containing these signals was Rayspan-processed.
146
NEW ZEALAND VETERINARY JOURNAL
VOL 27
Downloaded by [University of Cambridge] at 03:40 06 November 2015
RESULTS
Figure I shows five spectrograms, each consisting of three complete respiratory cycles beginning with an inspiration. Spectograms I and 2 were obtained from two roarers, that is, horses exhibiting left laryngeal hemiplegia as diagnosed by laryngoscopic examination. Spectrograms 3 and 4 were obtained from two normal horses, that is, horses free from clinical upper respiratory abnormalities. Spectrogram 5 is from a clinically suspect horse. Notable features of spectrograms I and 2 (roarers) are (a) the dense black areas between 0 and 2.25 kHz, indicating the presence of all frequencies within this range for most ofthe duration of the inspirations and much of the expirations, and (b) the occurrence of intermittent frequencies between 2 and 4kHz. This is in marked contrast with spectrograms 3 and 4 (normals) which tend to be comprised solely of frequencies within the range 0-2 kHz with long quiet periods, especially during expiration. However, spectrogram 5 (suspect roarer) differs from both the roarers and non-roarers whilst displaying characteristics of both, and with a tendency to have a noisier expiration than inspiration. Whereas the spectrograms reinforce the suspect designation of this horse, a long-term investigation will be required to determine whether it does develop into a roarer, or develops instead the symptoms of some other respiratory disease.
~
~ L
P
NC
~
"--
3
4
J
'0
4
"~~,
~~
~
3
KHz
2
5
Much of the difficulty experienced in the detection of abnormal respiratory sounds in horses is associated with the fact that these noises are usually produced at only fast gaits and for a few respirations after exercise. Thus, in most instances, an animal that is suspected to have a respiratory problem can only be satisfactorily examined during a very brief period. Attenburrow (I) attempted to overcome this problem by using a radio-stethoscope during exercise. We report a simpler method that allows respiratory noises to be recorded and subsequently examined at the clinician's leisure. It also permits simultaneous comparison of several respiratory cycles (Fig. I). During inspiration by normal horses, the maximum instan. taneous frequency remained relatively constant, indicating that a stable air-flow was occurring. In contrast, during their expiration there was a rapid decrease in the instantaneous peak freq uency. These findings support those of Gillespie et at. (5) who showed that air flow was relatively constant during inspiration but varied rapidly during expiration.
NC
2
\
I:.
DISCUSSION
Fig. 2.1
1
Right
T Left
1
2
3
time (seconds) Fig. 1. Sound spectrograms obtained/rom three respiratory cycles o/five horses. Each signal display commences with an inspiration. Spectrograms 1 and 4 show frequency calibrations ( Hz X 103).
The frequencies in the range 2-4 kHz, which are characteristic of roaring horses, may arise singly or through combinations of several processes including edge tones, vortex streets, and laryngeal tissue vibration. The likely mechanism for the production of vortex streets during inspiration is illustrated in Figure 2. The medial displacement of the left arytenoid cartilage into the airway probably increases air turbulence along the trachea and is aided by the trapping of vortices (eddies) in the piriform recess. In addition. because of the absence of proper muscle control, the reduced pressure within the laryngeal lumen (Venturi effect) will exacerbate medial displacement of the left laryngeal tissues. The higher frequencies observed in the abnormal horses may be accounted for by the irregular formation of the vortex streets. The animal with an idiopathiC disorder (Spectrogram 5) made respiratory sounds of similar frequencies to those produced by roarers, indicating that some obstruction may have been present. When the recording from this animal is compared with those obtained from roarers (Spectrograms I and 2), a relatively longer quiet period between expiration and inspiration is noticed. This may be because the possible obstruction present is less of a problem for this animal than for the roarer. ACKNOWLEDGEMENT
_h_g_._2_.2______-'~
---............ -
Right
~-~-
NC p
_ _N_C_ _ _, -
We are grateful to F. A. J. Bush, Atmospheric Physics, Physics and Engineering Laboratory, D.S.I.R., Lower Hut!, for carrying out the Rayspan processing so courteously and promptly.
L
....... T....... ,
.;~~-"l ~~f; ~-'
....
-----a Fig. 2. Diagrammatic horizontal cross-sections of the equine upper respiratorytract during inspiration in a normal horse (Figure 1.1) and a horse with lejt laryngeal hemiplegia (Figure 2.2.). NC: nasal cavity; P: pharynx; L: larynx; T: trachea; (a) pharyngeal recess trapping an eddy; (b) medially collapsed left arytenOid cartilage; (c) wake of(b) showing eddy formation in the air (see text).
REFERENCES (I) (2)
(3) (4) (5)
(6)
Attenburrow. D. P. (1978): The development of a radio-stethoscope for use in the horse at rest and during exercise. Equine vet. J. 10: 14-17. Cole. C. R. (1946): Changes in the equine larynx associated with laryngeal hemiplegia. Am. J. vet. Res. 7: 69-77. Cook. W. R. (1976): Idiopathic laryngeal paralysis in the horse; a clinical and pathological study with particular reference to diagnosis. aetiology and treatment. Ph.D. thesis. University of Cambridge. Duncan. I. D.; Griffiths. I. R.; McQueen. A; Baker. G. O. (1974): The pathology of equine laryngeal hemiplegia Acta neuropath. (Berl.) 27: 337-48. Gillespie. I. R.; Tyler. W. S.; Eberly. V. E. (1966): Pulmonary ventilation and resistance in emphysematous and control horses. J. appl. Physiol. 21: 416-22. Gunn. H. M. (1972): Histochemical observations on laryngeal skeletal muscle in fihres in normal horses. Equine vel. 1. 4: 144·8.
ISSN: 0048-0169 (Print) 1176-0710 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzv20
Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report G.R.G. Barnes , M. Brennan , B.E. Goulden & J. Kirkland To cite this article: G.R.G. Barnes , M. Brennan , B.E. Goulden & J. Kirkland (1979) Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report, New Zealand Veterinary Journal, 27:7, 145-146, DOI: 10.1080/00480169.1979.34629 To link to this article: http://dx.doi.org/10.1080/00480169.1979.34629
Published online: 23 Feb 2011.
Submit your article to this journal
Article views: 9
View related articles
Citing articles: 3 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tnzv20 Download by: [University of Cambridge]
Date: 06 November 2015, At: 03:40
1979
NEW ZEALAND VETERINARY JOURNAL
145
Sound spectography in the diagnosis of equine respiratory disorders: a preliminary report G. R. G. Barnes* M. Brennant B. E. Goulden' J. Kirklandt
N.Z. vel.J.27: 145·6
Downloaded by [University of Cambridge] at 03:40 06 November 2015
ABSTRACT
One problem in the diagnosis of subclinical roarers is that abnormal auditory signals occur only during a fast gait, and these fade quickly. This paper offers a novel technique to assist this problem. Sound recordings were obtained from five horses following exercise; two roarers, two non-roarers, and one suspected roarer. These signals were converted into spectrograms by Rayspan processing. All frequencies in the 0 to 2.25 kHz range during both inspiration and expiration, as well as occasional noises in the 2-4 kHz band, characterised roarers. Signals from non-roarers consisted of frequencies in the 0 to 2 kHz range with long quiet periods, especially during expiration. An explanation for these phenomena is offered, and supported by diagrammatic cross-sections of equine upper-respiratory tracts. It is suggested that the present technique could assist in the diagnosis of subclinical roarers, estimated to be between 20 and 40% of the competitive horse population. INTRODUCTION
For many years, veterinarians have recognised the difficulty of accurately distinguishing between the normal and abnormal respiratory sounds which horses make during exercise. In part, this di8culty arises because many abnormal respiratory noises are made only during. or immediately after, fast gaits. Additionally, the assessment of any treatments for these respiratory disorders has been subjective.
sease is known to occur in between 20 and 41.6% of the competitive horse population (2XJX4X6). Unfortunately, the amount of muscle damage is variable. It is only when a critical quantity of muscle destruction has taken place that affected animals will exhibit respiratory sounds sufficiently different from normal breathing to be recognised by horsemen(2). Most reports indicate that fewer than 5% of the competitve horse population can be identified as roarers by their abnormal respiratory sounds, though a substantial proportion may be emitting abnormal respiratory noises. However, because of the difficulty in comparing the respiratory sounds they make with those of normal horses, these affected animals remain undetected. Some method of identifying these so-called subclinical roarers is urgently required. Additionally, some means is needed of comparing sounds made by different horses and by individual horses at different times. For these reasons, a preliminary investigation of sound spectrograms obtained from both normal and abnormal animals was undertaken. MATERIALS AND METHODS
Five horses were selected (Table I); two (Nos. 1& 2) were clinical roarers which had been unsuccessfully treated by an abductor muscle prosthetic operation and a left ventriculectomy. The endoscopic view of the larynx of these animals was
TABLE I: EXPERIMENTAL ANIMALS No.
Age (in years)
Sex
Breed
Clinical Condition
Amount Exercise Given
Fitness
5
Geld.
Clydesdale x
Roarer
\0 minutes cantering
Unfit
2
3
Geld.
TB
Roarer
800 metre gallop
Fit
3
3
Filly
TB
Normal
\0 minutes cantering
Unfit
4
7
Geld.
TBX
Normal
\0 minutes cantering
Fit
5
2
Geld.
TB
Suspected roarer
800 metre gallop
Fit
TB
= Thoroughbred.
One condition that produces abnormal respiratory noises in horses is the disease commonly called roaring. Roaring is suspected clinically when an affected animal produces an abnormally loud respiratory noise during exercise, and when endoscopic examination reveals asymmetrical positioning and movements of the arytenoid cartilages of the larynx. The condition is associated with abnormal functioning of the left recurrent laryngeal nerve, thus effecting pathological changes to most of the muscles controlling the movements of the left laryngeal cartilages. Muscle pathology associated with this di* Department of Chemistry, Biochemistry and Biophysics,
t
~
Department of Education, Department of Veterinary Clinical Services, Massey University, Palmerston North, New Zealand.
similar to that seen in untreated roarers. One further animal was a clinically suspected roarer (No.5), and the remaining two animals were clinically normaL The respiratory noises made by these animals were recorded during and immediately after either 10 minutes of cantering or an 800 metre gallop. Sound recordings were made using a directional microphone (Sennheiser MKH 815) connected to a reel-to-reel taperecorder (Nagra IV) operating at 19.0 cm/s. Two complete respiratory cycles were taken from the first 30 seconds of each recording. Each of these cycles commenced with an inspiration. The audiotape containing these signals was Rayspan-processed.
146
NEW ZEALAND VETERINARY JOURNAL
VOL 27
Downloaded by [University of Cambridge] at 03:40 06 November 2015
RESULTS
Figure I shows five spectrograms, each consisting of three complete respiratory cycles beginning with an inspiration. Spectograms I and 2 were obtained from two roarers, that is, horses exhibiting left laryngeal hemiplegia as diagnosed by laryngoscopic examination. Spectrograms 3 and 4 were obtained from two normal horses, that is, horses free from clinical upper respiratory abnormalities. Spectrogram 5 is from a clinically suspect horse. Notable features of spectrograms I and 2 (roarers) are (a) the dense black areas between 0 and 2.25 kHz, indicating the presence of all frequencies within this range for most ofthe duration of the inspirations and much of the expirations, and (b) the occurrence of intermittent frequencies between 2 and 4kHz. This is in marked contrast with spectrograms 3 and 4 (normals) which tend to be comprised solely of frequencies within the range 0-2 kHz with long quiet periods, especially during expiration. However, spectrogram 5 (suspect roarer) differs from both the roarers and non-roarers whilst displaying characteristics of both, and with a tendency to have a noisier expiration than inspiration. Whereas the spectrograms reinforce the suspect designation of this horse, a long-term investigation will be required to determine whether it does develop into a roarer, or develops instead the symptoms of some other respiratory disease.
~
~ L
P
NC
~
"--
3
4
J
'0
4
"~~,
~~
~
3
KHz
2
5
Much of the difficulty experienced in the detection of abnormal respiratory sounds in horses is associated with the fact that these noises are usually produced at only fast gaits and for a few respirations after exercise. Thus, in most instances, an animal that is suspected to have a respiratory problem can only be satisfactorily examined during a very brief period. Attenburrow (I) attempted to overcome this problem by using a radio-stethoscope during exercise. We report a simpler method that allows respiratory noises to be recorded and subsequently examined at the clinician's leisure. It also permits simultaneous comparison of several respiratory cycles (Fig. I). During inspiration by normal horses, the maximum instan. taneous frequency remained relatively constant, indicating that a stable air-flow was occurring. In contrast, during their expiration there was a rapid decrease in the instantaneous peak freq uency. These findings support those of Gillespie et at. (5) who showed that air flow was relatively constant during inspiration but varied rapidly during expiration.
NC
2
\
I:.
DISCUSSION
Fig. 2.1
1
Right
T Left
1
2
3
time (seconds) Fig. 1. Sound spectrograms obtained/rom three respiratory cycles o/five horses. Each signal display commences with an inspiration. Spectrograms 1 and 4 show frequency calibrations ( Hz X 103).
The frequencies in the range 2-4 kHz, which are characteristic of roaring horses, may arise singly or through combinations of several processes including edge tones, vortex streets, and laryngeal tissue vibration. The likely mechanism for the production of vortex streets during inspiration is illustrated in Figure 2. The medial displacement of the left arytenoid cartilage into the airway probably increases air turbulence along the trachea and is aided by the trapping of vortices (eddies) in the piriform recess. In addition. because of the absence of proper muscle control, the reduced pressure within the laryngeal lumen (Venturi effect) will exacerbate medial displacement of the left laryngeal tissues. The higher frequencies observed in the abnormal horses may be accounted for by the irregular formation of the vortex streets. The animal with an idiopathiC disorder (Spectrogram 5) made respiratory sounds of similar frequencies to those produced by roarers, indicating that some obstruction may have been present. When the recording from this animal is compared with those obtained from roarers (Spectrograms I and 2), a relatively longer quiet period between expiration and inspiration is noticed. This may be because the possible obstruction present is less of a problem for this animal than for the roarer. ACKNOWLEDGEMENT
_h_g_._2_.2______-'~
---............ -
Right
~-~-
NC p
_ _N_C_ _ _, -
We are grateful to F. A. J. Bush, Atmospheric Physics, Physics and Engineering Laboratory, D.S.I.R., Lower Hut!, for carrying out the Rayspan processing so courteously and promptly.
L
....... T....... ,
.;~~-"l ~~f; ~-'
....
-----a Fig. 2. Diagrammatic horizontal cross-sections of the equine upper respiratorytract during inspiration in a normal horse (Figure 1.1) and a horse with lejt laryngeal hemiplegia (Figure 2.2.). NC: nasal cavity; P: pharynx; L: larynx; T: trachea; (a) pharyngeal recess trapping an eddy; (b) medially collapsed left arytenOid cartilage; (c) wake of(b) showing eddy formation in the air (see text).
REFERENCES (I) (2)
(3) (4) (5)
(6)
Attenburrow. D. P. (1978): The development of a radio-stethoscope for use in the horse at rest and during exercise. Equine vet. J. 10: 14-17. Cole. C. R. (1946): Changes in the equine larynx associated with laryngeal hemiplegia. Am. J. vet. Res. 7: 69-77. Cook. W. R. (1976): Idiopathic laryngeal paralysis in the horse; a clinical and pathological study with particular reference to diagnosis. aetiology and treatment. Ph.D. thesis. University of Cambridge. Duncan. I. D.; Griffiths. I. R.; McQueen. A; Baker. G. O. (1974): The pathology of equine laryngeal hemiplegia Acta neuropath. (Berl.) 27: 337-48. Gillespie. I. R.; Tyler. W. S.; Eberly. V. E. (1966): Pulmonary ventilation and resistance in emphysematous and control horses. J. appl. Physiol. 21: 416-22. Gunn. H. M. (1972): Histochemical observations on laryngeal skeletal muscle in fihres in normal horses. Equine vel. 1. 4: 144·8.
