Using Patients’ Sensory Perception to Enhance Their Veterinary Visits

Development of sensory perception begins in utero and continues throughout the animal’s lifetime. An individual’s sensory perception is affected not only by genetics but also by learning from sensory experiences. Deprivation of sensory input during the developmental stages can lead to deficits in sensory perception. Both sensory deprivation during development and learned individual expectations affect perception. Individual variations between sensory systems and the manner in which the brain interprets sensory input can cause differences in how each patient perceives the experience of being in a veterinary hospital.

What Is Sensory Perception?

The 2 aspects of sensory perception are sensation and perception.

• Sensation is the stimulation of a sensory receptor and the resultant activation of a specific brain center, producing basic awareness of scent, taste, sound, touch, or sight (and other senses). An example of a sensation is an auditory stimulus, including its loudness, pitch, and location. For example, in a veterinary hospital, the ultrasonic sound waves from the ultrasonic dental scaler could cause a startle reaction in the patient because that sound is unfamiliar.
• Perception is the process or result of becoming aware of objects, relationships, and events by means of the senses, which includes such activities as recognizing, observing, and discriminating. An example of perception is a species-relevant auditory stimulus, such as the call of a predator, which may lead to escape or avoidance reactions. In a veterinary hospital, a cat can hear a dog barking and growling in the hospital. The cat may then perceive the dog’s vocalization as a threat and react with fear, defensive aggression, or possibly an attempt to escape.

Both sensory sensation and perception can affect how patients respond to the veterinary hospital environment. The initial sensory sensation response can change behavior, causing a patient to startle. The sensory perception response can change emotions and behavior, causing a patient to react in a seemingly unpredictable manner.

Sensory Systems

Each sensory system (olfactory, gustatory, auditory, tactile, or visual) works with other sensory systems to enhance or modify sensory perception. An example is the interaction of taste and smell. Patients with a deficient olfactory system often exhibit anorexia. Thus, it is possible to enhance taste for patients by strengthening the scent of the food.

Olfactory

Dogs and cats have 2 olfactory systems: the main olfactory epithelium where scent molecules enter through the nares and an accessory olfactory system that uses the vomeronasal organ (VNO), where pheromones and other volatile chemicals enter through a passage in the mouth or nose. Thus, olfactory information is collected through the nose as well as the mouth.¹

Although these systems separately send signals to different parts of the brain, they work together to form olfactory perception. Because dogs and cats have large olfactory sensory and perception organs, their bodies spend energy and time on this sense, which helps veterinary professionals understand how important scent messages are to patients.

Behaviors associated with the VNO also differ between dogs and cats. Cats show a flehmen response to odors by wrinkling their lips and breathing in, whereas dogs do not show a flehmen response. Both dogs and cats may place their nasal planum and/or tongue on the surface containing scent. In mice, the VNO is necessary for innate stereotypic defensive behavior and for initiating endocrine release in response to odors of predators.² Thus, the purpose of the VNO in dogs and cats, in addition to collecting pheromones associated with sexual behaviors, may possibly be to collect pheromones associated with predators and to activate defense behaviors.

Gustatory

The sensory cells for taste are the taste buds, located on the tongue. Moisture in the food and/or saliva is used to create a mixture that taste buds can collect through taste pores (small openings in the tongue epithelium that allow dissolved food to contact the taste receptors), analyze, and send information to the brain to be interpreted.

The number of taste buds per species gives an idea of the differences in taste discrimination between species. Dogs have approximately 1700 taste buds; cats, around 470; and humans, 9000. Taste buds are sensitive to the following flavors: umami (characteristic of broths and cooked meats), sweet, salty, sour, and bitter. The salty receptors encompass a smaller area than the others.³ Dogs do not have highly sensitive salt receptors, and they do not crave salt as humans do.⁴ Because cats are obligate carnivores, their taste is focused on meat due to their umami taste buds, corresponding with cats’ low number of taste buds. Because dogs are omnivores, they have a higher number of taste buds with a greater range of taste receptors for a variety of food sources.

Auditory

Cats have the largest auditory range of any known mammal, ranging from 48 to 85 000 Hz. Cats have a perforated septum in their middle ear that has a frequency-dependent effect on their ability to hear.⁵ Dogs do not have this advantage. Nonetheless, Malkemper et al concluded that dogs likely hear at a similar range⁵; the reported hearing range for dogs is 65 to 45 000 Hz.⁶ For reference, humans reportedly hear in the range of 20 to 20 000 Hz.⁶

Ear pinnae funnel the sound waves into the ear canal. Animals with erect pinnae collect sound waves more efficiently than those with dropped ear pinnae. Dogs and cats can move their pinnae to better collect sound, although dogs with dropped ears benefit less from it. Dogs and cats can move their pinnae independently from each other. Hearing can be decreased when auditory sensory cells (hair cells) are damaged by injury, disease, loud sounds, or aging⁷; damaged hair cells are not replaced. Another cause of damage to hearing is medication, such as gentamicin.

Tactile

Tactile sensations, or somatosensory signals, come from the skin, muscles, and joints, where sensory cells collect mechanical, chemical, and thermal stimuli.⁸ Some of these signals are felt consciously and others subconsciously. Some conscious signals are temperature sensations (thermoreceptors), pain (nociceptors), and pressure/touch (including vibrations). Some unconscious signals are blood pressure levels and oxygen levels in the blood.⁸

Hairs have free nerve endings surrounding the hair follicles within the skin, which measure hair bending and releasing.⁸ Whiskers are specialized sensory hairs called vibrissae. Cats have facial and carpal vibrissae. Cats are believed to use their vibrissae to assess air currents, small vibrations, and object locations; protect the face; and direct food and prey into the mouth. Removal of vibrissae results in loss of tactile information.

Visual

Pupils let light into the eye; a larger pupil lets more light in, allowing more visual sensation. Elliptical pupils change size faster than round pupils, which enables cats to adjust quickly to dappled light at dusk and dawn. The lens forces light onto the retina and changes shape to accommodate changes in distance viewing, a limited ability for dogs and cats.

The 2 types of sensory cells in the retina are rods and cones. Rods function best in low light; they absorb light wave information about movement and contrast between objects.¹⁰ Rods are more numerous in cat and dog eyes than in human eyes. Cones function best in high light by absorbing information about color and acuity.¹⁰ Dogs and cats have 2 types of cones while humans have 3; thus, dogs and cats cannot distinguish between red, yellow, and green, making their color vision similar to red–green color blindness in humans.

Visual acuity is the ability to see the details of an object, separately from adjacent objects and not blurred. Visual acuity in cats is 0.2 times that of humans, 0.33 times that of horses, and 0.5 times that of dogs.¹⁰ To look at visual acuity another way, think of the vision charts for which you have to cover 1 eye and read the letters you see on various lines. Humans without vision impairment have a visual acuity of 20/20 (i.e., an object 20 feet away can be seen sharply). Among animals, visual acuity differs among individuals and breeds. Some dogs have 20/20 vision; however, visual acuity for most dogs is 20/75 (i.e., the dog must be 20 feet away to clearly see an object that a human can see at 75 feet away). The range of cats’ visual acuity is 20/100 to 20/200.

The tapetum lucidum is a shiny membrane located behind the retina in the choroid and enhances visual contrast and brightness.¹¹ The tapetum lucidum is more effective in cats than in dogs, creating higher contrast between sky and objects.^10,12

Dogs and cats can see light in the ultraviolet (UV) range because they lack UV shielding on the cornea and they have a type of ocular media (aqueous humor) that transmits UV energy. Humans cannot see UV light because we have a UV light filter within our cornea that blocks the light from entering our eyes.

Dogs and cats can detect flickering (and buzzing) in electric lights that humans cannot, depending on the speed of the flicker. With a flicker fusion rate of 70 to 89 Hz,¹⁰ dogs and cats can detect flickering lights that humans, with their flicker fusion rate of 45 Hz,¹⁰ cannot. However, if the flicker is very fast, dogs and cats will not notice it.

Visual field (the entire area that can be seen when the eyes are directed forward) is associated with placement of the animal’s eyes on the head. Animals can have binocular vision (visual fields from both eyes overlap) and monocular vision (information from only 1 eye is used to create visual perception). Variation of eye placement in dogs of different breeds affects their visual fields. When eyes are on the front of the head facing forward, as in humans, there is a large binocular field of vision (directly related to depth perception) and smaller monocular fields on each side. Cats have a similar or larger binocular field than humans. The monocular field of dogs and cats is larger than that of humans.

Using Patients’ Sensory Perception To Enhance Veterinary Visits

The value of reducing stress-causing sensations and perceptions in the veterinary hospital is directly associated with the damaging effects of stress, especially in cats (TABLE 1). Because sensory perception in humans can differ from that of dogs and cats, the veterinary team may be unaware that their patients may be experiencing stress.

Stress has both short- and long-term effects that reduce an animal’s ability to function within homeostasis. Common behaviors that change when animals are feeling stress include appetite, grooming, elimination, social interactions, and physical activity.¹³ With regard to the effects on hospitalized animals, stress (or illness) can cause them to lose their appetite and also prevents their immune system from working at an optimal level, creating opportunities for infection.

Olfactory

Animals use scent to communicate. Scent causes emotions and memories. In the veterinary hospital, patients leave their scent on every surface they touch. Odors are contained in many substances, including urine, sebaceous gland secretions, sweat, saliva, anal sac secretions, and feces. Odor is rubbed onto surfaces from sebaceous glands located on the face, chin, dorsal neck, paws, rump, and tail area of cats and the dorsal neck, paws, rump, and tail area of dogs.¹⁴ These oily deposits contain long-lasting odors. When patients urinate or defecate in the hospital because they are fearful, these odors can be left behind on the surface and in the air.

Patients may feel threatened or excited by the scent of their own or other species, and they may find the scent of other species stressful. When veterinary patients smell odors left by a fearful patient, they may feel fear themselves. Both excited and fearful patients pose their own challenges by making them more likely to resist handling, diagnostics, and treatment. More employees will be needed to complete the veterinary procedures, which may take longer to accomplish and could result in pet and/or handler injury.

Removing Scents

Scent can be removed from objects by using odor eliminators, including products containing bacteria and/or enzymes. Dogs and cats can discriminate between odors well; odors cannot be masked with fragrance as they can be for humans. Some products remove odor from the air if sprayed; other products can be used on objects by coating the surface, waiting a certain amount of time (depending on the product), and then removing the liquid. Staff can also wash their hands with an odor-eliminating soap. We may neglect to remove odors because our olfactory system does not function at the same level as that of dogs and cats, which can easily identify odors that we may not notice.

Adding Scents

Scent can be placed on an object by having clients bring an object from home that smells like the patient and/or the client. To help the patient feel calmer and more relaxed while in the veterinary hospital, the object can be placed on the floor in the examination room, on the scale, on the examination table, on the table in the treatment room, or in the patient’s cage or run. Familiar scents can be used to calm patients (e.g., species-specific pheromones, lavender). Scent can also be used to excite patients (e.g., peppermint).

Gustatory

Taste can be useful when interacting with a patient. Veterinary professionals can use taste to their advantage by associating procedures with food, causing the patient to feel a positive emotional valence (a pleasant emotional state associated with a stimulus) during the procedure. Veterinary team members can use a trail of food to entice a patient to walk onto a scale, and then reinforce this behavior by offering the patient food when on the scale to keep the patient still while obtaining its weight. If the patient does not readily follow and eat the food, desensitization and counterconditioning are indicated (see Additional Resources).

To facilitate medicating patients, veterinary compounding pharmacies can create medications with a better taste. Bitter tastes are associated with toxic substances and can cause animals to associate the entire oral medicating procedure with a negative emotion through classical conditioning. Because taste buds act independently, masking taste can be a challenge. When bitter medications are forced on patients, they learn to anticipate the bitter taste and unpleasant oral medicating, which increases stress and fear associated with receiving the medication. When patients respond with stress and fear, client compliance is affected and medication may not be given as directed.

Taste and smell are intimately connected. If the sense of smell is blunted by disease or physical damage, the sense of taste will be affected. To increase the patient’s ability to smell food, moisture can be added to the food (adding water helps the odor molecules readily escape from the food). Heating food helps it release a pleasant aroma. Adding fats or oils changes the food’s texture and enhances palatability. As obligate carnivores, cats have a strong preference for meat and meat tastes; adding meat to their food can be used to entice them to eat while hospitalized. Cats are sensitive to flavor changes associated with meat freshness and protein quality. Meat oxidizes over time, becoming rancid.¹⁵ Cats are sensitive to this process and will refuse to eat food that is not fresh.

When patients are hospitalized, they may stop eating and drinking because their environment is stressful. They may need to have a person near them when they eat or have a person hand feed them by placing the food on a spoon or the fingers and allow the patient to lick it off. This works better for dogs because of their sociation facilitation (presence of others improves performance) associated with eating. Dogs also eat more if another dog is eating near them and will eat faster if a dog near them is eating faster.

Another taste issue is related to nausea. If a patient feels nauseated and is offered food, it will associate that food with the nausea and will learn not to eat it because of its association with feeling nauseated. The association between the food and nausea is stronger if the food is novel. For example, a cat with renal failure may feel nauseated, and if fed a new diet while hospitalized may quickly learn to avoid that food.

Auditory

Reducing Unavoidable Noise

Many sounds within the hospital are not heard by humans but are heard by dogs and cats, which hear within the ultrasonic frequency (high-frequency sound inaudible to humans, generally >20 kHz). Ultrasonic wavelengths come from electronic machines and electric light fixtures. These sounds can cause patients to feel stress because they are novel, predictive of unpleasant interactions with veterinary personnel, and unpleasant to hear. To reduce ultrasonic sound, light bulbs can be changed from fluorescent bulbs to light-emitting diode (LED) bulbs. Ultrasonic scalers create a noise that humans can hear but also an ultrasonic noise that we cannot hear but dogs and cats can. Conscious patients can be moved farther away from the dental sink area, and strategies to muffle the sound can include closing doors and using sound baffles.

Loud and sudden sounds can cause patients to startle (an example of sensation) and become fearful (an example of perception).Take time to keep the latches of cages and kennels aligned and in good repair. Close cage/kennel doors quietly. For areas in the hospital with primarily hard surfaces, sound can bounce around and increase in intensity. Blankets and pads can be used in metal cages and kennels to reduce sound. Sound baffles can be used on hard walls to muffle sound, and white noise machines can be used to mask some sounds.

Minimizing Noise Sources

Canine patients can be taught to rest quietly instead of barking when exposed to sound or other sensory stimuli in kennels. For patients that are vocalizing, try to find the reason and resolve the issue. For example, if your hospital uses an anesthetic protocol that causes patients to wake up vocalizing and thrashing, which is stressful for that patient and can upset other patients, switch to a new protocol from which patients wake more calmly and quietly. For patients that vocalize because they are in pain, ask if pain medication can be given. For patients that vocalize because they have to eliminate, take them out for a walk to reduce their discomfort.

Veterinary team members should keep their voices low and speak to patients in a tone that induces positive emotional valence. Certain tonal qualities of sound have intrinsic meanings for our patients: high-frequency pure tones are associated with care soliciting and appeasement; low-frequency noisy tones are threat and alarm signals. No matter where you are, speak in tones to keep your patients calm. There are commercial sound products for calming dogs and cats. These musical sounds are based on scientific information regarding the tonal sounds that produce calm behavior in dogs and cats. Slow, simple, solo piano music is the basis of many of the products that can be used to create a calming wall of sound in the hospital (see Additional Resources for more information).

Tactile

Touch can change patients’ emotional state to a positive emotional valence. Animals enjoy touch from people they accept and trust. However, keep in mind that patients are individuals and may enjoy different types of touch (e.g., stroking, scratching, different degrees of pressure) due to their genetics and learning history.

Reading and Projecting Body Language

Animals do not usually enjoy manipulation of their whiskers because these vibrissae are very sensitive and collect sensory information about pressure, object identification and location, and prey capture.¹⁶ All hairs on the patient’s body are connected to sensory cells that detect which way the hair is bending. Most animals prefer to have your touch move with the lay of the hair instead of against it. Animals that do not know the veterinary team member well may not allow some sorts of touch (e.g., scratching their ventrum).

Veterinary team members can build patients’ trust by tossing them treats while obtaining a history from the client. This interaction will associate veterinary staff and the environment with a desired taste leading to a positive emotion. It can encourage the patient to approach you for touch, which enables you to engage with the patient on a more intimate level. It is important to use body language to communicate that you are a friendly person by staying at a distance, turning your side to the animal, and keeping your arms close to your body. As you build trust, patients then need to give consent for you to touch them. After the patient approaches you, you can assess whether it wants the tactile component.

Some patients may approach you to investigate you. They may even rub on you but not want you to touch them. It is important to observe their behavior and body language closely to decide your next move. One way to interact with a cat that rubs against you is to place your hand so the cat can rub against it. When the cat exhibits pleasure, you can try scratching just behind the ear pinna or the side of the neck. Soennichsen and Chamove found that cats prefer to be petted in their temporal area, between the eye and ear.¹⁷ This area contains scent glands, and it may innately feel better to be touched there. When stroking patients, use firm long strokes as these are calming strokes that reduce arousal. When scratching patients, use slow scratches, as fast scratches increase arousal, and increased arousal (even if the animal is happy) can reduce the veterinary team’s effectiveness when interacting with them to complete tasks and procedures.

Animals generally enjoy dorsolateral touch because it is considered to be less of a threat than touch on the dorsal body and head. Using 1 hand, touch patients on the dorsolateral aspects of their body with a firm stroke or scratch, which may increase the chance for a successful pleasant touch interaction. Watch behavior and body language for confirmation that the patient is enjoying the type of touch you are using (TABLE 2).

Throughout your interaction with the patient, its emotions and reactions can change. Those that like the touch will lean into the touch, loosen their posture, have a contented facial expression, and come back for more when you stop. Areas that dogs and cats might not want to be touched are the top of the head (i.e., eyes, ears, and mouth), dorsum, ventrum, tail, anus, and genitals.

Cats may indicate that they do not want your touch by vocalizing rather than purring. There are touch techniques used specifically for calming, massage, and Tellington TTouch (ttouch.com). These techniques can help relax dogs and cats and can be used when an animal is hospitalized or receiving treatment.

If veterinary team members need to touch a patient for diagnostics and treatments, allow the patient to approach by using your body language to make you less of a threat. Examples include turning sideways, squatting down a short distance from the patient, and keeping arms close to the body. When patients get close and allow you to pet them, you can start touching them where they like to be touched and keep your hand in contact instead of removing it and touching again; putting your hand repeatedly on and off patients can cause them to startle and feel stressed. Once contact has been initiated, move your hand to the area that needs to be touched for the veterinary procedure. For example, if you needed to complete a nail trim, you could start scratching the dog on the side of the neck and then work your way down to the paw instead of grasping the paw immediately. Food can be used to create a positive association with the procedure. Every time you touch, no matter what the patient does, offer food. If the animal stops being relaxed, modify the touch to make it less intense. For cats, Hunt and McIntyre found that repeated touching and long-duration touching decreased touch sensitivity to a specific area; they also found that warming and cooling the skin decreased touch sensitivity.¹⁸ (For more information on how to desensitize and countercondition patients to veterinary procedures, see Additional Resources.)

Modifying the Environment

Modifying surfaces can also support patients’ positive emotional valence. Consider the tactile aspects of standing, sitting, and lying down. The surface should support patients physically while maintaining their comfort and homeostasis. Thermoregulation should be considered. A cold, slippery surface can make patients feel threatened because they cannot get their footing, and hypothermia is a threat for patients that have trouble thermoregulating. The environmental temperature range considered acceptable for dogs is
10 °C to 29 °C (50 °F to 84 °F), although 10 °C seems too cold for many dogs, including sight hounds. Cats prefer temperatures of 30 °C to 36 °C (86 °F to 97 °F), and some say the upper range is 38 °C (100 °F). The ambient temperature of most hospitals is probably comfortable for some dogs and very few cats. Consider adding a heating device or blankets for hospitalized cats. Comfortable surfaces are more likely to make patients feel relaxed.

Some animals with tactile sensory discrimination deficits (difficulty identifying touch) will also exhibit social interaction deficits,¹⁹ which could mean that if patients dislike touch even from people they trust, they may also have trouble interacting appropriately with all people. For these patients, medication may be necessary before examining or administering treatment.

Visual

To create and maintain positive emotional valence for patients, adjust your movements and proximity accordingly. Quick movements can elicit fear and fighting behaviors. Steady and calm movements can elicit trust. Sometimes remaining still will enable patients to calm themselves by acclimating to the environment. Some dogs and most cats are myopic (nearsighted) and unable to see the visual detail that people do¹⁰; they rely on movement and contrast to identify some objects and live beings. Use this information about their perception to think about how to introduce objects used for veterinary care to enable patients to become comfortable with them before moving the items toward their body.

Modify lighting to create a more relaxing environment for patients. Consider the brightness and type of lighting. A light source that does not produce a visible flicker for dogs and cats is ideal. At a flicker rate of 70 to 80 Hz, dogs and cats cannot see the flicker of the light.¹⁰ Light bulbs have this information on the packaging to help you find appropriate bulbs. Some LED lighting has no visible flicker and can be dimmed. Dimmers are useful for creating bright light when needed for veterinary procedures and dimmer light for patient comfort. Cats especially prefer dimmer light because what they see appears brighter; however, brightness is not as likely to affect dogs. Compared with humans, brightness detection in cats is about 6 times better and brightness detection in dogs is about 2 times worse.²⁰

Monitor patient responses to objects and images within the hospital associated with animal images or other images perceived as a threat or prey. For some patients, images of animals (e.g., pictures on the wall, models of animals used to help explain procedures to clients) may lead to increased arousal, fear, anxiety, and stress. Some dogs may react to life-sized stuffed dogs by lunging and biting them; for other patients, such items do not cause a problem. When items become a consistent problem, they should be removed from the patient area.

Summary

As healthcare professionals, our perception of being in a veterinary hospital differs from that of our patients. If we understand and appreciate how our patients perceive the experience, we will be better able to modify our behavior and the hospital environment to improve their veterinary experience.