THE TRUTH ABOUT BITS - PART 5 : ABOUT THE AIRWAY...

Horses can only breathe through their nose, unlike us humans who have two options - the nose or the mouth. When the body supplies only one option to sustain life, it is extremely important that this airway is not compromised in anyway. A horse, just like a human cannot breathe and swallow at the same time. While these two functions seem like they occur simultaneously, they are in fact separate and work cooperatively because of highly refined and complex reflexes.

The nasal cavity of a horse is the first of the respiratory organs and consists of a large irregular space divided into two equal passages by a septum and is known as the organ of smell. Nerve endings located within the nose, are stimulated by various substances and the nerve impulses are then sent to the brain, where the sensation of smell is perceived. The nasal cavity contains a large amount of blood vessels, and is lined with mucus secreting membranes. Inspiration is initiated by contraction of the diaphragm and chest muscles which allows the lungs to expand. Air is sucked in through the nose, where it is warmed, moistened and filtered on its way to the lungs.

The roof, floor and hard palate of the mouth are formed by various bones, with the soft palate made up of a flap of tissue or involuntary muscle which lies deep within the throat. When the horse is breathing, the soft palate lies in a tight seal over the oral cavity which both prevents a horse even when in extreme respiratory distress, from breathing through it's mouth. It directs air efficiently through the nasal cavity where it flows into the trachea [windpipe] and lungs. When a horse swallows the soft palate elevates thus closing off the nasal cavity so that no air can be drawn into the nose. By doing this it opens the oral cavity and allows food to travel from the mouth into the pharynx and oesophagus [food tube].

The pharynx is around 15 cm and divided, for descriptive purposes into three parts - the nasopharynx, oropharynx and laryngopharynx. In general terms, the location of parts of the pharynx describe the area where the nose, mouth and voice box all converge. The pharynx area is composed of a mucous membrane lining, fibrous tissue and involuntary muscle tissue, and structures within the pharynx are activated in the complex mechanism of swallowing.

The larynx or voice box is made up of cartilage, and is located by the trachea where it assists in controlling the volume of air inhaled, and also enables the horse to vocalise. When the horse is breathing the larynx lies open to allow air to flow through the nasal cavity, through the pharynx and into the trachea and lungs and by so doing also effectively forms a tight seal which blocks off the oesophagus. However when a horse swallows, the larynx closes and forms a tight seal over the trachea, which both prevents food from entering into the trachea, and directs food into the oesophagus.

AIRWAY CLOSED - SWALLOWING Swallowing means all other routes are closed When a horse eats, food is taken into the mouth where it is chewed and moved backwards by the teeth, tongue, cheeks and mouth grooves until it is swallowed and passed into the oesophagus. To enable this to happen, the soft palate which usually lies lowered against the oral cavity - elevates and prevents air from being drawn in through the nose. The larynx which usually lies open, closes and forms a tight seal over the trachea, thus preventing food from entering the trachea and efficiently directing food into the oesophagus. When a horse is eating they are relaxed and usually stationery or moving very slowly. The head is down and the mind is at rest. The lips are open, the jaw is moving and the salivary glands are discharging. The breathing is shallow and pulse rate slow.

AIRWAY OPEN - BREATHING Breathing means all other routes are closed When a horse breathes, air is taken in through the nasal cavity, and passes efficiently through the pharynx into the trachea and lungs. To enable this to happen, the soft palate lies lowered in a tight seal over the oral cavity, preventing air from being drawn in through the mouth. The larynx lies open, effectively closing the oesophagus which prevents air from entering the stomach. When a horse is breathing lightly at rest or deeply and quickly when moving or being exercised, the head is up and the mind is alert. The lips are sealed closed, the jaw is stationary and there is minimal saliva being produced in the mouth. The breathing and pulse rate is elevated and every breath is in harmony with the horse’s gait.

The effect of a bit in relation to the airway

Although the action of breathing and swallowing seem simultaneous, it is anatomically impossible for a horse and a human to breath and swallow at the same time, although the actions between the two different mechanisms are of split second timing. When a horse is asked to exercise with a bit in the mouth, digestive responses are triggered, as the horse senses something is in it's mouth. As well, respiratory, cardiovascular and musculoskeletal systems engage as the body prepares for exercise. Horses do not ever eat and exercise at the same time and these conflicting messages are relayed from the sensory organs via the nervous system to the brain and then back to the body which in turn responds. Although a horse understands a bit is not food, these messages are automatic physiological reflexes which the mind cannot stop by an act of will. An example of this is when a human sits in the dentist's chair. The mouth is open and the dentist's tools are placed in the mouth. Salivation becomes profuse, the tongue automatically retracts which lifts the root of the tongue, as well as various other reflexes being initiated. A human, like a horse, cannot wilfully stop these reflexes, even though the patient knows food is not in the mouth.

The conflicting nerve impulses and messages relayed to the brain is that a demand for increased respiration to fuel the demands of an exercising body is required, but also that food is going to be swallowed. Thus the soft palate which usually sits lowered against the oral cavity elevates, partially or even fully which closes the trachea and allows saliva to enter. The larynx which should remain open to block the oesophagus partially closes which also closes the trachea and allows air to enter the oesophagus.

The conflicting messages cause different reflex responses to become so confused that they operate only partially or become dysfunctional, and so at the crucial time the horse requires more air - when exercising - less air is being delivered to the lungs, and therefore to the muscles and body systems which require it.

The nose, which is the primary external organ for inspiration of air is often partially obstructed by the use of a tight noseband and even tighter flash. The lips which usually form a tight seal in a closed mouth at exercise, are slightly open at the corners from the bit's encroachment in the mouth, or more so if the horse is avoiding bit pain by opening it's mouth. The seal of the mouth is broken, and together with the partial elevation of the soft palate allows air to enter into the oral cavity. The soft palate then elevates even further and flutters at each breath. As well, if the neck is held unnaturally in any kind of flexion or hyper flexion, this creates even further obstruction in airflow.

A bit in the mouth causes the tongue to automatically retract and elevate at the root, which causes further obstruction of the airway. The nervous system relays the message that salivation should be increased thus with the obstruction of the airway, saliva becomes air filled and frothy. As the act of swallowing is impaired by having a bit in the mouth, this frothy saliva drools from the open mouth of the horse - which at exercise should be sealed. It is often mentioned in equestrian instruction that this frothy drool is a sign that the horse is relaxing at the poll or accepting the bit. This is just one of many preposterous fabrications, that the equestrian world accepts without question! Salivation is actually encouraged, with little knowledge and even less regard for the physiological and emotional stress which the horse suffers. Frothy drool resulting from excess salivation and an obstructed airway means only one thing - that the horse is being asphyxiated. This is a fact.

When the airway is either partially or fully obstructed even for small amounts of time, the body is deprived of crucial oxygen, and even more so when demand is placed on it at exercise. From the deprivation of oxygen, organs, muscles and body systems start to fail and dysfunction. The horse slows, becomes fatigued as oxygen deprivation reaches unbearable and unsustainable limits. The horse is whipped and kicked to keep going, resulting in an extremely dangerous situation developing, with often fatal consequences for both horse and rider. Insufficient oxygen at any time, let alone at times of maximum exercise not only causes physical incapacitation, but must be a terrifying experience for the horse. Over time, this repetitive dysfunction paves the way for chronic diseases to manifest in the upper respiratory area and the horse becoming unmanageable. Some physical effects of obstruction of the airway, caused by displacement of the soft palate, elevation of the tongue and poll flexion are :

• Airway deformity and diseases [common] : Airway deformities and disease are very common occurrences due to repetitive dysfunction of the upper respiratory area. Due to the displacement of the soft palate so often during exercise, together with collapse of the cartilage supporting the airway, the airway becomes deformed and often permanently damaged. Permanent airway deformities cause breathing to become laboured and noisy - for example roaring on inspiration, and there is a higher incidence of acute and chronic airway disorders and diseases. Obstructed breathing or chronic airway problems are often diagnosed by veterinarians as simply genetically narrow airways, however this is questionable to say the least, especially when the horse has been healthy for the early part of it's life. A more plausible explanation is that over time, deformities of the airway have been caused directly from use of a bit


• Sprains, strains, dislocations and fractures [common] : When a horse is exercised there is more demand for oxygen to supply the muscles, heart, lungs and other organs. Because the airway is partially obstructed by the displacement of the soft palate etc, there is insufficient oxygen to meet the requirements of these organs. This deficient supply causes muscles and body systems to fatigue and fail, which in turn causes incorrect striding to breath ratio, stumbling, tripping, falling, sprains, strains, dislocations, and in more serious cases fractures and organ failure which may result in injuries, accidental death of either horse and|or rider or euthanasia for the horse


• Asphyxia and suffocation [common in sporting events] : Because the horse is not able to breathe normally, and especially so during demanding exercise, an insufficient supply of oxygen in the blood is created, which increases the amount of carbon dioxide. This creates extreme shortness of breath, dizziness and confusion usually resulting in the horse being unable to continue. Asphyxia, however, manifests to differing degrees and whilst most horses suffer only partially, with virtually no detectable signs, and seemingly complete recovery, there is actually tremendous and widespread impairment and dysfunction of body systems at the biological level which manifest over time as chronic diseases and unwilling or unmanageable behaviour.
  
  For other horses who are not so 'lucky' in suffering from only partial asphyxia - this becomes total asphyxia. The detection of gurgling respiration [the noise created from the fluttering and obstruction of the soft palate] quickly accelerates to multiple organ failure, periods of unconsciousness, bleeding from the nose resulting from pulmonary edema and haemorrhage to finally unconsciousness and a torturous death.
  
  Multiple organ failure, unconsciousness and ultimate death is very common in disciplines such as horse racing, cross country and show jumping events, and although the majority of horses do not express auditory signs of airway obstruction, or bleeding from the nose, over 80% of sport horses experience some form of asphyxia.

Simulated airway obstruction exercise

As an example of this increased requirement of air, and decreased supply, try squeezing your nose slightly together with your fingers as you walk around normally. Breathe naturally through your nose, keeping your mouth closed. You will feel not only an increase in the rate of your breathing, but also an increase of suction pressure in the nose and in the chest. The work of the nasal passages becomes more intense, although the air flow will be less. You may feel an intense desire to move your cheek, nose or lips in an effort to generate more air. Another feeling that you may experience is one of slight panic. Not being able to draw enough air for the demands of your body, even at a walk, is a most unpleasant experience.

Remember when completing this exercise, you are the one that has complete control of when your fingers are released, thereby allowing the freedom to breathe normally again. A horse does not have this freedom. One can only imagine the torture a horse experiences, not only because of the physical damage and malfunctioning airway and lungs caused from an obstructed airway, but also the profound psychological terror of not being able to breathe properly, and particularly so, at times of enforced and often extremely challenging exercise.