luchtzuigen, een paar fabels de wereld uit?
Geplaatst: 28-04-02 22:56
hoi allemaal, ik kom heel regelmatig allerlei hartekreten over luchtzuigers tegen op het net. Nu heb ik zelf een heel gelukkige gezonde, nooit koliek hebbende luchtzuiger en om die reden geprobeerd van alles over dat stalgebrek uit te zoeken. Ik ben ook begonnen met banden en van alles uit de stal te halen en onder de cribox te smeren. Want ze konden er koliek van krijgen, longontsteking, slechte conditie, slechte tanden en andere paarden namen het over. Affijn om een lang verhaal kort te maken: ik ben gestopt met al die hulpmiddelen. Ze werken niet echt. Mijn paard heeft dagelijks weidegang, zoveel hooi als ze wil, is zeker weten gelukkig en luchtzuigt nog steeds. In ieder geval wil ik twee fabeltjes uit de weg helpen.
1. paarden nemen het niet van haar over. Noch haar twee veulens, noch de jonge paarden op de stal (die naast haar staan) zijn ooit gaan luchtzuigen. Onderzoek (UVA) duidt eerder op slechte stalomstandigheden waardoor paarden gaan luchtzuigen (rond een jaar of twee, of rond een jaar of 12 - 15) dan op van elkaar leren.
2. Paarden hebben geen grotere kans op koliek of slechtere conditie door luchtzuigen. Ook dierenartsen zullen je dit nogal eens vertellen. Inmiddels is dit onderzoek achterhaald. En omdat ik weet dat er veel mensen een luchtzuiger hebben, zet ik hier de integrale tekst (in het Engels) op de site die ik van het web van de university of Bristol heb gehaald. Ter geruststelling. Ik hoop dat jullie er wat aan hebben. Ik zou het fijn als een dierenarts hier ook eens op wou reageren.
Het is een lang stuk, maar ik heb het maar integraal gekopieerd voor de liefhebbers.
Recent studies on cribbiting horses
J. Geoffrey Lane
University of Bristol, Depart~nent of Clinical Veterinary Science, Langford House, Langford, Bristol BS18 7DU, U.K
Introduction
There is confusion in the veterinary literature concerning the definition of oral based stereotypies "cribbiting" and "windsucking" in horses and it is a matter of semantics whether horses are "cribbiters" when they grasp fixed objects in the stable or field environment to facilitate the arching of the neck and emission of a characteristic pharyngeal sound, or "windsuckers" when the behaviour is performed without grasping objects between their incisor teeth. For the purposes of this presentation the two terms will be used as if they are synonymous. It has been widely stated that horses which exhibit either of these abnormal behavioural patterns swallow air (aerophagia) and it is also believed that the introduction of large quantities of air into the alimentary tract predisposes horses which cribite to colic and/or to poor bodily condition.
The conditions in force at the leading public auctions of thoroughbred horses in the United Kingdom and Ireland state that the sale of a horse shall be invalidated if "it is a wind sucker, i.e. habitually swallows air whether in association with grasping fixed with its incisor teeth or not, or has been operated upon for the correction of this condition, including cribbiting". Thus, there are important medicolegal reasons for accuracy in the description of the events which occur during the stereotypy.
The purpose of this presentation is to report the results of endoscopic and fluoroscopic studies of the pharyngeal structures of horses during the act of cribbiting/windsucking. The major conclusion has beenthat deglutition does not occur as part of the stereotypy and that "aerophagia" is an inappropriate synonym for this stereotypy.
Normal deglutition
Deglutition is traditionally divided into oraL pharyngeal and oesophageal stages and these are applicable to the horse. The oral phase comprises the prehension, mastication and transfer of food and fluid boluses to the base of the tongue and it is under voluntary control The presence of the bolus at the tongue triggers the complex sequence of reflexes which forms the involuntary transfer of ingesta through the pharynx to the oesophagus and eventually to the stomach. The events which occur during tthe pharyngeal phase include elevation of the soft palate to occlude the nasopharynx, adduction of the arytenoid cartilages and vocal folds, together with retroversion of the apex of the epiglottis to close tthe rime glottidis; contraction of the base of the tongue and constriction of the oro and nasopharoxy by the ciruclar muscles to propel the bolus caudally; and receptive relaxation of the cricopharyngeal sphincter to allow the bolus to enter the upper oesophagus. The oesophageal phase commences with closure of the cricopharynx shich initates a wave of primary oesophageal peristalsis which moves each bolus caudalaly towards the cardia. Secondary oesophageal persitaltic waves are irregular eventsbut result from the stretching of the oesophageal walls by residual material within the lumen.
There are a variety of techniques by which deglutition canbe studies ranging from observations of the movements of the structures of the pharynx and oesophagus by fluoroscopy and endoscopy to electromyographic recording of the electrical activity in the muscles of the region.
Normally, when an endoscope is placed in the nasopharynx via the nasal meatus the structures of the larynx are clearly visible. However, during deglutition the contraction of the pharyngeal walls and dorsal displacement of the soft palate completely obscure the view of the larynx until it has been restored to its intranarial position. Flexible endoscopes can be attached to a headcollar using velcro tape so that endoscopic recordings of pharyngeal activity can be made over a sustained period.
Dynamic fluoroscopic studies of deglutition can be performed during eating be offering the patient food impregnated with contrast medium. In the author's clinic such a technique is regularly used to assess horses showing signs of dsyphagia, and it has been found that a traditional bran mash impregnated with barium sulphate and with the addition of molasses to enhance palatability is an ideal material. Freshly cut or conserved herbage is less suitable, because it tends to produce uneven contrast and less consistent acceptance by the patient. Most horses are starved for 12 to 15 hours before testing to ensure an enthusiasm to participate in the investigation. Occasional patients are deterredby the noises of the radiographicmachinerybutafter one or twoperiods of familiarisationtheyarewilling to eat while the fluoroscopic records are made. The unsedated horses are stood in stocks and offered the mash from a bucket placed between the tube head and image intensifier of a system mounted on an overhead gantry for simultaneous movement.
The positive contrast in the food boluses helps to outline the structures of the oropharynx and oesophagus while the negative contrast provided by air highlights the nasopharynx and larynx. During contrast studies of deglutition the events which can be observed include the gathering of the food bolus at the base of the tongue; contraction of the pharyngeal walls and propulsion of the bolus from the pharynx the pharyngeal "stripping" wave; retroversion of the epiglottis; receptive relaxation of the upper oesophagus as the food bolus passes caudally; primary and secondary oesophageal peristalsis; and restoration of the larynx to its intranarial position.
Videotape recordings are essential for the slow motion analysis of both endoscopic and fluoroscopic images.
Endoscopic and fluoroscopic studies during cribbiting/windsucking
The investigation reported here comprised the study of a group of known cribbiters by making separate fluoroscopic and endoscopic recordings of the pharyngeal region during the performance of the oral based stereotypy. The horses were stood in stocks for both stages of the investigation and a wooden bar covered with coconut matting was placed at the front of the stocks to provide an inducement to cribbite. Complete cubes were also offered from a bucket adjacent to this bar. Fluoroscopic recordings of 6 horses performing a total of 102 stereotypic sequences were made and endoscopic records of 70 similar sequences from 4 horses, three of which had been used in the radiographic study, were also collected for analysis. In advance of the investigations the subjects had been examined by routine endoscopy and palpation to eliminate animals with identifiable structural or functional anomalies of the upper respiratory tract.
Videofluoroscopic findings: Throughout the studies the recorded events were similar for each cribbiting/windsucking sequence in all of the horses used. Initially the upper oesophageal sphincter (the cricopharynx) was closed and there was no air in the oesophagus distally. Immediatelybefore the first stereotypic sequence appetitive behaviour was noted in the form of movements by the base of the tongue and by the soft palate as the horse licked the "cribbing barn. The onset of each stereotypic sequence wa seen as retraction of the larynx caudally and slightly ventrally. Throughout each sequence the distance between the ventral border of the oesophagus and the dorsal margin of the trachea remained constant, the epiglottis remained in a resting position parallel with the tongue and the soft palate was in its normal subepiglottic position maintaining contact with the tongue rostrally. Thus continuity was invariably maintained between the nasopharynx and caudal nasal chambers. Coinciding with the emission of the characteristic noise associated with cribbiting/wind suckinth the proximal oesophagus abruptly filled with air to a maximal dorsoventral diameter approximately 80 % that of tthe diameter of the trachea. This was largely achieved by ballooning of the dorsal oesophageal wall rather than by movement of its ventral margin. The radiographic contrast provided by air in the nasopharynx and proximal oesophagus enabled observations of the palatopharyngeal arch. The caudal pillars of this structure became dorsally displaced as oesophageal distension occurred and the cricopharynx opened. The length of the cricopharynx reduced causing a further increase in the dorsoventral diameter of the rostral oesophageal sphincter. Maximal distensionof the oesophagus coincided with the initial opening fo the crico pharyngeal sphincter. During the process of eflation there was little evidence of primary or secondary oesophageal peristalsis and a ratio of 1 air bolus removed by peristalsis to 12 upper oesophageal distensions was recorded. Thus, it was concluded that the air returned to the pharynx by spontaneous deflation after most stereotypic sequences.
Endoscopic findings: Endoscopy confirmed that during each cribbite the larynx was retracted caudally and that the rime glottidis remained open with no active adduction or abduction by the arytenoid cartilages or vocal folds. The posterior pillars of the palatopharyngeal arch became visible as a curved structure which moved dorsally from its resting position caudal to the apices of the corniculate processes. The ventral border of these pillars was seen to vibrate in synchrony with opening of the oesophageal sphincter and the emission of the characteristic grunt. Again, the rostral margin of the palatopharyngeal arch was seen to remain in a subepiglottic position throughout the stereotypic sequences and there was no constriction by the pharyngeal musculature on any occasion.
Conclusions
1. Deglutition is not a feature of cribbiting/windsucking: the events recorded during the stereotypic sequences did not remotely resemble swallowing.
2. The source of the characteristic noise assoicated with this oral based stereotypy results from an inrush of air into the proximal oesophagus following dilation of the cricopharyngeal sphincter.
3. The movement of air results from pressure gradients created in the soft tissues of the throat rather than by compression of the pharyngeal lumen.
4. Only a small proportion of the air which distends the upper oesophagus is conveyed towards the stomach.
Discussion
Although the invetigation outlined above has clarified some of the events which occur in the pharynx and upper oesophagus during oral based stereotypic sequences, it has not addressed the motivation for the behaviour.Cribbiting, windsucking and grasping all include characteristic arching of the neck accompanied by contraction of the muscles on the ventral aspect of the throat. It seems likely that this muscular effort creates the pressure gradient in the oesophageal lumen and a resultant distension of the cranial oesophagus with or without the emission of a grunt. It is conjectured that is is the di stension of the viscus which is the ultimate objective of this stereotypy and that this is more likely to be the source of gratification than grasping objects between the incisor teeth. This in turn begs the question as to what physiological mechanism might render such a distension a behavioural "needn.
The efficacy of surgical procedures oriented to ablate or denervate the strap muscles in the ventral throatregioncanbe explainedby the suggestionthatitis the contraction of thesemuscleswhichcreates a pressure gradient between the oesophageal lumen and the pharynx.
Observations of cribbiting horses in the study above revealed little primary oesophageal peristalsis and only a smal1 number of air boluses conveyed towards the stomach by secondary peristalsis. In additionin order to perform the studies, cribbiting wasprovokedby offering palatable food and thus, more swallowing may have taken place than during spontaneous demonstrations of the stereotypy. Thus, why is there an accepted association between cribbiting/windsucking and tympanitis colic? One explanation may be that there the diagnosis is incorrect in the first place. In horses with fourth branchial arch defects (tBAD) the cricopharyngeus and thyropharyngeus muscles are frequently absent or vestigial. This congenital defect predisposes afflicted horses to tympanitic colic. Radiographic studies of deglutition in horses with this form of 4BAD shows a continuous column of air from the pharynx to the cervical oesophagus and the caudal propulsion of air by peristalsis is a consistent feature. This constitutes true aerophagia and the attendants of horses afflicted with this congenital disorder frequently believe that they are "windsuckersn because of the eructation noises which they occasionally emit.
Accurate definitions in this area of behaviour are necessary in the context of horse sales and the results reported here confirm that the Conditions of Sale currently in use at public auctions require amendment if unnecessary litigation is to be avoided.
1. paarden nemen het niet van haar over. Noch haar twee veulens, noch de jonge paarden op de stal (die naast haar staan) zijn ooit gaan luchtzuigen. Onderzoek (UVA) duidt eerder op slechte stalomstandigheden waardoor paarden gaan luchtzuigen (rond een jaar of twee, of rond een jaar of 12 - 15) dan op van elkaar leren.
2. Paarden hebben geen grotere kans op koliek of slechtere conditie door luchtzuigen. Ook dierenartsen zullen je dit nogal eens vertellen. Inmiddels is dit onderzoek achterhaald. En omdat ik weet dat er veel mensen een luchtzuiger hebben, zet ik hier de integrale tekst (in het Engels) op de site die ik van het web van de university of Bristol heb gehaald. Ter geruststelling. Ik hoop dat jullie er wat aan hebben. Ik zou het fijn als een dierenarts hier ook eens op wou reageren.
Het is een lang stuk, maar ik heb het maar integraal gekopieerd voor de liefhebbers.
Recent studies on cribbiting horses
J. Geoffrey Lane
University of Bristol, Depart~nent of Clinical Veterinary Science, Langford House, Langford, Bristol BS18 7DU, U.K
Introduction
There is confusion in the veterinary literature concerning the definition of oral based stereotypies "cribbiting" and "windsucking" in horses and it is a matter of semantics whether horses are "cribbiters" when they grasp fixed objects in the stable or field environment to facilitate the arching of the neck and emission of a characteristic pharyngeal sound, or "windsuckers" when the behaviour is performed without grasping objects between their incisor teeth. For the purposes of this presentation the two terms will be used as if they are synonymous. It has been widely stated that horses which exhibit either of these abnormal behavioural patterns swallow air (aerophagia) and it is also believed that the introduction of large quantities of air into the alimentary tract predisposes horses which cribite to colic and/or to poor bodily condition.
The conditions in force at the leading public auctions of thoroughbred horses in the United Kingdom and Ireland state that the sale of a horse shall be invalidated if "it is a wind sucker, i.e. habitually swallows air whether in association with grasping fixed with its incisor teeth or not, or has been operated upon for the correction of this condition, including cribbiting". Thus, there are important medicolegal reasons for accuracy in the description of the events which occur during the stereotypy.
The purpose of this presentation is to report the results of endoscopic and fluoroscopic studies of the pharyngeal structures of horses during the act of cribbiting/windsucking. The major conclusion has beenthat deglutition does not occur as part of the stereotypy and that "aerophagia" is an inappropriate synonym for this stereotypy.
Normal deglutition
Deglutition is traditionally divided into oraL pharyngeal and oesophageal stages and these are applicable to the horse. The oral phase comprises the prehension, mastication and transfer of food and fluid boluses to the base of the tongue and it is under voluntary control The presence of the bolus at the tongue triggers the complex sequence of reflexes which forms the involuntary transfer of ingesta through the pharynx to the oesophagus and eventually to the stomach. The events which occur during tthe pharyngeal phase include elevation of the soft palate to occlude the nasopharynx, adduction of the arytenoid cartilages and vocal folds, together with retroversion of the apex of the epiglottis to close tthe rime glottidis; contraction of the base of the tongue and constriction of the oro and nasopharoxy by the ciruclar muscles to propel the bolus caudally; and receptive relaxation of the cricopharyngeal sphincter to allow the bolus to enter the upper oesophagus. The oesophageal phase commences with closure of the cricopharynx shich initates a wave of primary oesophageal peristalsis which moves each bolus caudalaly towards the cardia. Secondary oesophageal persitaltic waves are irregular eventsbut result from the stretching of the oesophageal walls by residual material within the lumen.
There are a variety of techniques by which deglutition canbe studies ranging from observations of the movements of the structures of the pharynx and oesophagus by fluoroscopy and endoscopy to electromyographic recording of the electrical activity in the muscles of the region.
Normally, when an endoscope is placed in the nasopharynx via the nasal meatus the structures of the larynx are clearly visible. However, during deglutition the contraction of the pharyngeal walls and dorsal displacement of the soft palate completely obscure the view of the larynx until it has been restored to its intranarial position. Flexible endoscopes can be attached to a headcollar using velcro tape so that endoscopic recordings of pharyngeal activity can be made over a sustained period.
Dynamic fluoroscopic studies of deglutition can be performed during eating be offering the patient food impregnated with contrast medium. In the author's clinic such a technique is regularly used to assess horses showing signs of dsyphagia, and it has been found that a traditional bran mash impregnated with barium sulphate and with the addition of molasses to enhance palatability is an ideal material. Freshly cut or conserved herbage is less suitable, because it tends to produce uneven contrast and less consistent acceptance by the patient. Most horses are starved for 12 to 15 hours before testing to ensure an enthusiasm to participate in the investigation. Occasional patients are deterredby the noises of the radiographicmachinerybutafter one or twoperiods of familiarisationtheyarewilling to eat while the fluoroscopic records are made. The unsedated horses are stood in stocks and offered the mash from a bucket placed between the tube head and image intensifier of a system mounted on an overhead gantry for simultaneous movement.
The positive contrast in the food boluses helps to outline the structures of the oropharynx and oesophagus while the negative contrast provided by air highlights the nasopharynx and larynx. During contrast studies of deglutition the events which can be observed include the gathering of the food bolus at the base of the tongue; contraction of the pharyngeal walls and propulsion of the bolus from the pharynx the pharyngeal "stripping" wave; retroversion of the epiglottis; receptive relaxation of the upper oesophagus as the food bolus passes caudally; primary and secondary oesophageal peristalsis; and restoration of the larynx to its intranarial position.
Videotape recordings are essential for the slow motion analysis of both endoscopic and fluoroscopic images.
Endoscopic and fluoroscopic studies during cribbiting/windsucking
The investigation reported here comprised the study of a group of known cribbiters by making separate fluoroscopic and endoscopic recordings of the pharyngeal region during the performance of the oral based stereotypy. The horses were stood in stocks for both stages of the investigation and a wooden bar covered with coconut matting was placed at the front of the stocks to provide an inducement to cribbite. Complete cubes were also offered from a bucket adjacent to this bar. Fluoroscopic recordings of 6 horses performing a total of 102 stereotypic sequences were made and endoscopic records of 70 similar sequences from 4 horses, three of which had been used in the radiographic study, were also collected for analysis. In advance of the investigations the subjects had been examined by routine endoscopy and palpation to eliminate animals with identifiable structural or functional anomalies of the upper respiratory tract.
Videofluoroscopic findings: Throughout the studies the recorded events were similar for each cribbiting/windsucking sequence in all of the horses used. Initially the upper oesophageal sphincter (the cricopharynx) was closed and there was no air in the oesophagus distally. Immediatelybefore the first stereotypic sequence appetitive behaviour was noted in the form of movements by the base of the tongue and by the soft palate as the horse licked the "cribbing barn. The onset of each stereotypic sequence wa seen as retraction of the larynx caudally and slightly ventrally. Throughout each sequence the distance between the ventral border of the oesophagus and the dorsal margin of the trachea remained constant, the epiglottis remained in a resting position parallel with the tongue and the soft palate was in its normal subepiglottic position maintaining contact with the tongue rostrally. Thus continuity was invariably maintained between the nasopharynx and caudal nasal chambers. Coinciding with the emission of the characteristic noise associated with cribbiting/wind suckinth the proximal oesophagus abruptly filled with air to a maximal dorsoventral diameter approximately 80 % that of tthe diameter of the trachea. This was largely achieved by ballooning of the dorsal oesophageal wall rather than by movement of its ventral margin. The radiographic contrast provided by air in the nasopharynx and proximal oesophagus enabled observations of the palatopharyngeal arch. The caudal pillars of this structure became dorsally displaced as oesophageal distension occurred and the cricopharynx opened. The length of the cricopharynx reduced causing a further increase in the dorsoventral diameter of the rostral oesophageal sphincter. Maximal distensionof the oesophagus coincided with the initial opening fo the crico pharyngeal sphincter. During the process of eflation there was little evidence of primary or secondary oesophageal peristalsis and a ratio of 1 air bolus removed by peristalsis to 12 upper oesophageal distensions was recorded. Thus, it was concluded that the air returned to the pharynx by spontaneous deflation after most stereotypic sequences.
Endoscopic findings: Endoscopy confirmed that during each cribbite the larynx was retracted caudally and that the rime glottidis remained open with no active adduction or abduction by the arytenoid cartilages or vocal folds. The posterior pillars of the palatopharyngeal arch became visible as a curved structure which moved dorsally from its resting position caudal to the apices of the corniculate processes. The ventral border of these pillars was seen to vibrate in synchrony with opening of the oesophageal sphincter and the emission of the characteristic grunt. Again, the rostral margin of the palatopharyngeal arch was seen to remain in a subepiglottic position throughout the stereotypic sequences and there was no constriction by the pharyngeal musculature on any occasion.
Conclusions
1. Deglutition is not a feature of cribbiting/windsucking: the events recorded during the stereotypic sequences did not remotely resemble swallowing.
2. The source of the characteristic noise assoicated with this oral based stereotypy results from an inrush of air into the proximal oesophagus following dilation of the cricopharyngeal sphincter.
3. The movement of air results from pressure gradients created in the soft tissues of the throat rather than by compression of the pharyngeal lumen.
4. Only a small proportion of the air which distends the upper oesophagus is conveyed towards the stomach.
Discussion
Although the invetigation outlined above has clarified some of the events which occur in the pharynx and upper oesophagus during oral based stereotypic sequences, it has not addressed the motivation for the behaviour.Cribbiting, windsucking and grasping all include characteristic arching of the neck accompanied by contraction of the muscles on the ventral aspect of the throat. It seems likely that this muscular effort creates the pressure gradient in the oesophageal lumen and a resultant distension of the cranial oesophagus with or without the emission of a grunt. It is conjectured that is is the di stension of the viscus which is the ultimate objective of this stereotypy and that this is more likely to be the source of gratification than grasping objects between the incisor teeth. This in turn begs the question as to what physiological mechanism might render such a distension a behavioural "needn.
The efficacy of surgical procedures oriented to ablate or denervate the strap muscles in the ventral throatregioncanbe explainedby the suggestionthatitis the contraction of thesemuscleswhichcreates a pressure gradient between the oesophageal lumen and the pharynx.
Observations of cribbiting horses in the study above revealed little primary oesophageal peristalsis and only a smal1 number of air boluses conveyed towards the stomach by secondary peristalsis. In additionin order to perform the studies, cribbiting wasprovokedby offering palatable food and thus, more swallowing may have taken place than during spontaneous demonstrations of the stereotypy. Thus, why is there an accepted association between cribbiting/windsucking and tympanitis colic? One explanation may be that there the diagnosis is incorrect in the first place. In horses with fourth branchial arch defects (tBAD) the cricopharyngeus and thyropharyngeus muscles are frequently absent or vestigial. This congenital defect predisposes afflicted horses to tympanitic colic. Radiographic studies of deglutition in horses with this form of 4BAD shows a continuous column of air from the pharynx to the cervical oesophagus and the caudal propulsion of air by peristalsis is a consistent feature. This constitutes true aerophagia and the attendants of horses afflicted with this congenital disorder frequently believe that they are "windsuckersn because of the eructation noises which they occasionally emit.
Accurate definitions in this area of behaviour are necessary in the context of horse sales and the results reported here confirm that the Conditions of Sale currently in use at public auctions require amendment if unnecessary litigation is to be avoided.