Topic 2.2 Cardiovascular and Respiratory Systems

The cardiovascular and respiratory systems work together to deliver oxygen and nutrients to every cell in the body while removing carbon dioxide and other metabolic waste products. These systems are fundamental to life and play a critical role in maintaining the endurance, stamina and physical capacity required of working assistance animals.

Assistance animals often work for extended periods in a variety of environments, including shopping centres, schools, workplaces, airports and outdoor settings. They may be required to walk considerable distances, negotiate stairs and uneven terrain, remain attentive for prolonged periods and respond quickly to their handler’s needs. To perform these tasks safely, the heart, lungs and circulatory system must function efficiently to meet the body’s increased oxygen demands during activity.

Occupational therapists are not expected to diagnose cardiovascular or respiratory disease. However, understanding how these systems normally function enables therapists to recognise early signs of illness, appreciate how disease may affect an animal’s occupational performance and make appropriate referrals for veterinary assessment.

The Cardiovascular System

The cardiovascular system consists primarily of the heart, blood vessels and blood. Together, these structures circulate oxygen, nutrients, hormones and immune cells throughout the body while removing waste products generated by normal metabolism.

The heart is a specialised muscular organ divided into four chambers. The right side receives deoxygenated blood returning from the body and pumps it to the lungs, where oxygen is absorbed. Oxygen-rich blood then returns to the left side of the heart before being pumped throughout the body via the arterial system.

Blood vessels form an extensive transport network. Arteries carry oxygenated blood away from the heart, veins return blood to the heart, and microscopic capillaries allow oxygen and nutrients to diffuse into surrounding tissues while collecting waste products for removal.

The cardiovascular system also contributes to temperature regulation, immune function, blood pressure maintenance and healing following injury.

For an assistance animal, efficient cardiovascular function ensures adequate endurance during prolonged work and supports rapid recovery following physical exertion.

The Respiratory System

The respiratory system is responsible for exchanging oxygen and carbon dioxide between the body and the environment. Oxygen is essential for cellular respiration, the process by which cells produce energy required for movement, organ function and tissue repair.

Air enters through the nose or mouth before passing through the pharynx, larynx and trachea into progressively smaller bronchi and bronchioles within the lungs. At the end of these airways are millions of tiny air sacs called alveoli. These delicate structures are surrounded by microscopic blood vessels where oxygen enters the bloodstream and carbon dioxide is removed.

Healthy lungs provide an enormous surface area for gas exchange while maintaining efficient airflow during both rest and exercise.

Breathing is controlled automatically by the brainstem and adjusts continuously according to the body’s oxygen demands. During exercise, respiratory rate and depth increase to deliver additional oxygen to working muscles.

Cardiovascular Fitness in Assistance Animals

Unlike many companion animals, assistance animals require sustained cardiovascular fitness throughout their working lives. Physical conditioning allows the heart and lungs to work more efficiently, reducing fatigue and improving endurance during prolonged activity.

Good cardiovascular fitness contributes to:

• improved stamina;
• faster recovery following exercise;
• more efficient oxygen delivery;
• reduced fatigue;
• improved thermoregulation; and
• better overall health.

Fitness develops gradually through regular, appropriately structured exercise. Sudden increases in workload without adequate conditioning may increase the risk of injury, heat stress or exhaustion.

Occupational therapists should appreciate that an assistance animal’s workload extends beyond formal exercise. Walking throughout a shopping centre, navigating public transport, accompanying a handler to work or university and remaining constantly attentive all contribute to the animal’s daily physical and mental demands.

Common Cardiovascular Conditions

Heart disease is relatively common in ageing companion animals and may affect an assistance animal’s ability to work safely.

One of the most frequently diagnosed cardiac conditions in dogs is myxomatous mitral valve disease, particularly in smaller breeds. Degeneration of the mitral valve allows blood to leak backwards within the heart, gradually reducing cardiac efficiency. Early stages may produce few obvious clinical signs, while more advanced disease may result in coughing, exercise intolerance, fatigue or collapse.

Larger breeds may develop dilated cardiomyopathy (DCM), a disease in which the heart muscle becomes weakened and enlarged, reducing its ability to pump blood effectively. Affected animals may demonstrate reduced stamina, weakness, rapid breathing or fainting episodes.

Cardiac arrhythmias, congenital heart defects and heartworm disease may also impair cardiovascular function depending on geographic location and parasite prevention practices.

Because assistance animals often maintain a strong desire to work despite illness, subtle reductions in endurance or willingness to perform physical tasks may be among the earliest signs of cardiovascular disease.

Common Respiratory Conditions

Respiratory disease may significantly impair an animal’s ability to tolerate exercise or safely perform assistance work.

Infectious respiratory diseases, including canine infectious respiratory disease complex (“kennel cough”), are relatively common among dogs attending training classes, boarding facilities or public events. Although many cases are mild and self-limiting, affected animals should not continue working while infectious or clinically unwell.

Chronic lower airway disease, including chronic bronchitis, may result in persistent coughing, reduced exercise tolerance and increased respiratory effort.

Some breeds are predisposed to anatomical airway abnormalities. Brachycephalic obstructive airway syndrome (BOAS) affects many flat-faced breeds, including Bulldogs, French Bulldogs and Pugs. Narrowed nostrils, elongated soft palates and other anatomical abnormalities reduce airflow, making breathing more difficult, particularly during exercise or hot weather.

Because of these significant welfare concerns and reduced exercise tolerance, brachycephalic breeds are generally considered unsuitable for most assistance animal roles requiring prolonged physical activity.

Heat Regulation

Unlike humans, dogs possess relatively few sweat glands and rely primarily on panting to dissipate excess body heat. Efficient respiratory function therefore plays an essential role in temperature regulation.

When environmental temperatures rise or exercise intensity increases, panting allows heat to evaporate from moist surfaces within the respiratory tract. Any condition that impairs breathing may also reduce the animal’s ability to regulate body temperature, increasing the risk of heat stress or heat stroke.

Occupational therapists should recognise that hot weather, humidity, poor ventilation and prolonged work may all increase physiological stress, particularly in animals with underlying respiratory or cardiovascular disease.

Recognising Cardiovascular and Respiratory Disease

Cardiovascular and respiratory disorders often develop gradually. Early recognition allows veterinary intervention before disease progresses to advanced stages.

Changes that may warrant veterinary assessment include persistent coughing, noisy breathing, exercise intolerance, rapid fatigue, reduced willingness to work, excessive panting unrelated to environmental temperature, breathing difficulty, blue or pale gums, collapse, fainting episodes or prolonged recovery following exercise.

Subtle changes in endurance may be particularly significant in assistance animals. A dog that previously completed a full day of work comfortably but now tires easily or begins refusing familiar routes may be demonstrating early signs of underlying disease rather than behavioural change.

Supporting Cardiovascular and Respiratory Health

Maintaining cardiovascular and respiratory health requires a combination of preventative healthcare, appropriate exercise, nutrition and routine veterinary assessment.

Healthy body weight, regular physical conditioning, parasite prevention, vaccination against respiratory disease where appropriate and routine veterinary examinations all contribute to long-term health. Workloads should be adjusted according to the animal’s age, fitness level, environmental conditions and any diagnosed medical conditions.

Occupational therapists should also consider environmental factors that may influence respiratory health, including exposure to smoke, dust, allergens, extreme temperatures and poor air quality during community access activities.

Occupational Therapy Considerations

The cardiovascular and respiratory systems directly influence an assistance animal’s endurance, stamina and ability to safely participate in daily occupations. Occupational therapists should recognise that reduced exercise tolerance, excessive fatigue or changes in breathing may reflect underlying medical conditions rather than behavioural problems or inadequate training.

When planning interventions involving prolonged walking, community mobility or physically demanding tasks, therapists should consider the animal’s age, fitness, environmental conditions and overall health. Activities may require modification during periods of illness, hot weather or recovery from medical treatment.

Through careful observation during functional activities and close collaboration with veterinarians, trainers and handlers, occupational therapists can help identify early indicators of cardiovascular or respiratory disease, promote appropriate workload management and support the long-term health, welfare and working longevity of assistance animal teams.