DPT-402.4- Exercise Prescription: Special Considerations – Asthma

Three million people in the UK have asthma, with 700,000 of these being under 16. One in seven children has asthma and 1 in 20 adults (Strachen et al, 1994). Asthma is a respiratory disease in which the intrapulmonary airways become narrowed, obstructed or even blocked due to smooth muscle contraction and inflammation.

Pathophysiology

There are three main physiological changes that occur during an asthmatic episode (Tortora and Grabowski, 2002):

Bronchospasm:

In response to some irritants, the smooth involuntary muscle that lines the bronchioles contracts, resulting in a decrease in the diameter of the airway. In the normal mechanics of breathing, inhaling triggers a reflex relaxation of the airways to enable air to flow in. On exhalation, there is a reflex contraction of the airways to aid the expulsion of air from the lungs. Problems occur when the reflex contraction involved in exhalation is exaggerated by the bronchospasm, caused by some asthmatic triggers. This is why asthmatics experience most of their difficulties breathing out. This chain of events could, in severe asthmatic attacks, result in total obstruction.

Inflammation:

The mucus membrane lining the interior of the bronchioles functions to secrete mucus to trap particles of dust or other impurities. This membrane also acts to humidify the air and to prevent the airways drying out. However, when this membrane is irritated, it becomes inflamed and puffy, serving to further reduce the diameter of the airways.

Excess mucus production:    

When irritated, the mucus membrane secretes more mucus than usual, resulting in further restriction and congestion of the airways. The increased mucus secretion also inhibits the filtering action of the cilia lining the airways.

Clinical Features

An asthma attack is a phrase used to describe a period of breathing difficulty. The symptoms are (adapted from BTS / SIGN, 2003):

Dyspnoea (shortness of breath):

The individual exhibits laboured breathing/gasping for air. By breathing in, they are trying to facilitate the relaxation of the airways associated with inhalation. Unless some intervention is made, breathing becomes increasingly problematic until they can neither breathe in or out.

Chest tightness:

The bronchospasm involved in asthma causes feelings of ‘tightness’ especially around the sternum.

Wheezing:

Often loud enough to hear and can be the first sign of an imminent asthmatic attack. 

Excess mucus secretion:

Possibly indicated by excessive swallowing.

Coughing:

Produced by the irritant. The individual is almost trying to ‘throw out’ or expel the irritant.

Anxiety:

Asthmatics often become extremely anxious at the onset of an attack, which tends to simply make things worse.

Note – all of the above are exacerbated by smoking:

  • nicotine constricts terminal bronchioles
  • carbon monoxide binds to haemoglobin and thereby decreases an individual’s oxygen carrying capacity
  • the irritants in smoke increase mucus secretion and  inflammation of the mucus lining
  • irritants in smoke inhibit the movement of cilia so that fluid and debris is not easily removed from the airways
  • prolonged smoking leads to the destruction of the elastic fibres in the lungs and to possible emphysema

(adapted from Tortora and Grabowski, 2002)

Classification

Although the smooth muscle and the mucus membrane are involved in asthmatic episodes, as already described, there are two main types of asthmatic triggers:

Extrinsic asthma (allergic asthma):

Those who are predisposed to extrinsic asthma exhibit a hypersensitivity to certain allergens, which can trigger an attack. External irritants, such as pollen, animal dander, mould, dust and mites are inhaled, which stimulate the release of histamine and other related substances. This causes muscular contraction and increased mucus secretion. This allergenic response can also be triggered as a result of stress.

Extrinsic asthma usually occurs in children and young adults with a family history of allergic disease. Attacks tend to decrease in severity and frequency with age. 

Intrinsic asthma (chronic): 

Intrinsic asthma often occurs later in life and is not usually related to allergens, although drug hypersensitivity to aspirin and penicillin may develop. The main triggers for intrinsic asthma are exercise, respiratory infections, stress and chemical irritants.

Unless suitable treatment is given, attacks tend to increase in severity causing irreversible damage to the lungs. A severe attack after a period of poorly controlled asthma can lead to respiratory failure and death. 

Exercise induced asthma (EIA): 80% of individuals or more who have chronic asthma will develop the symptoms of asthma when they exercise at a sufficient intensity (Roberts, 1997). A cough or wheeze after exercise strongly implicates the lungs and is suggestive of EIA but sometimes, the only symptoms are shortness of breath out of proportion to the exercise intensity, poor performance, muscle cramps, nausea, chest discomfort and being ‘out of shape’.

 
Asthma and Spirometry

Spirometry assessments may group asthma as an obstructive respiratory disorder, where the forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) are reduced disproportionately (Pinnock, 1999). The FVC can be largely unaffected since the integrity of the lungs themselves is largely unaffected. The FEV1, however, is significantly reduced, since the ability to expel air forcefully is lessened as a result of the obstruction. This would lead to a reduced forced expiratory ratio (FER) reading as the following example demonstrates:

Obstructive respiratory pattern: 

FVC = 3.50 litres (98% predicted value)

FEV1 = 1.80 litres = (58% predicted value)

FER = 51% 

This may not always be the case though and an alternative diagnosis for asthma is shown below (Ryan and Pinnock, 2000):

A 15% variation (change) in peak flow or FEV1 as measured by:

  • diurnal variation over 1-2 weeks
  • improvement in PEFR after drug administration
  • a reduction in PEFR after a trigger (including exercise)

Exercise Recommendations

There was a time when advising exercise for asthmatics would have been considered irresponsible and they would probably have been advised instead to avoid undue exertion. Consequently, a fear and misunderstanding of the disease can be identified as major determinants of a lack of fitness in asthmatics rather than limitations imposed by exercise itselfExercise has the following benefits for asthmatics:

  • builds muscular strength and endurance. This is especially important to respiratory muscles
  • produces greater efficiency in extracting oxygen and thereby increasing the body’s work capabilities
  • decreases sensitivity to dyspnoea
  • reduces the occurrence of EIA
  • makes the airways less sensitive to triggers, resulting in less exacerbations
  • reduces the dependence on medication

ACSM recommendations (Cooper, 1997) for those with pulmonary disease include:

Aerobic Exercise Recommendations
Frequency1-2 sessions 3-7 x/week
Intensitycomfortable pace, RPE 11-13, light to moderate activity
Time30 minutes maximum per session (shorter intermittent sessions may be necessary initially)
Typeaerobic physical activity (walking, cycling, swimming)
Resistance Training Exercise Recommendations
Frequency2-3 x/week
Intensityform failure – 15-20 repetitions
Time1-2 sets per exercise, 6-8 exercises
Typeall major muscle groups
Flexibility Recommendations
Frequencyminimum of 2-3 x/week
Intensityto a position of mild discomfort
Time10-30 seconds per hold for maintenance10-30 seconds repeated with 6-second contractions for development3-4 repetitions for each stretch
Typeall major muscle groups used in the sessions

Additional recommendations:

  • emphasise progression of duration over intensity
  • ensure a thorough warm up is given. This will reduce the likelihood of subsequent bronchospasm
  • RPE and dyspnoea are the preferred methods of monitoring intensity 

Special exercise precautions:

Exercising in dusty (keep your gyms dust free!) or cold conditions (e.g. early mornings) should be avoided, since fewer problems have been identified with exercise in warm conditions when the air is moist. In cold conditions, covering the mouth or nose with a scarf may reduce airway temperature fluctuations. With the above in mind, swimming has been proposed as the best environment for exercise because of the warm and humid air, although care must be taken because some asthmatics are sensitive to chlorine.

The American Council on Exercise (Roberts, 1997) recommends the following precautions for asthmatics:

  • reduce the intensity if asthmatic symptoms occur
  • use an inhaler several minutes before training to reduce the chances of an attack
  • ensure adequate hydration before, during and after training
  • avoid exercise areas with poor ventilation, high pollen counts, high or low temperatures, and heavy air pollution
  • monitor dyspnoea
  • only stable asthmatics should exercise

Clients usually respond best to exercise in mid-to late morning (Cooper, 1997).

Other precautions:

  • during an attack, no exercise should be undertaken
  • when the asthmatic has a cold or respiratory tract infection, no exercise should be undertaken
  • asthmatics should always have their medication available when beginning an exercise session

Summary of Exercise Recommendations

Additional Lifestyle Recommendations


Effective management involves:

  • avoiding all known triggers
  • collaborating with the GP to obtain most suitable form of treatment
  • relaxation techniques
  • maintaining general fitness
  • treatment during an attack
Emergency procedures during an attack

The individual must have discussed what to do in case of an attack with their GP or practice nurse.

  1. Use the reliever immediately. This will have an immediate effect although the full effect will not be felt for 20-30 minutes. An inhaler must be in easy reach throughout the exercise session. In recognised cases of EIA, two puffs of ventolin may be used 10-15 minutes before exercise. This usually works within 2-10 minutes and will last 2-6 hours. 
  • Calm the client and reassure them.
  • Place them in a seated position with their hands on their knees (don’t lie them down).
  • Encourage them to slow their breathing down.
  • If symptoms fail to subside after 10 minutes, call a doctor or an ambulance.
  • Keep taking the inhaler every few minutes until help arrives.
  • If the client is currently taking steroid tablets, take the prescribed amount.

Point of interest: It is good practice to encourage the client to take their peak flow reading before, during and after exercise. If a low reading is shown, the client should use their inhaler and take another reading 10-15 minutes later. If the reading hasn’t increased, the safe option should be taken and the client referred to the GP. 

Medication

Medications are generally administered by means of an inhaler. There are two main types of inhaler (BUPA, 2003):

Relievers:

Usually blue inhalers to be taken in the event of an asthmatic attack, immediately as symptoms appear. The main medications used are salbutamol (Ventolin), which is the most popular, and terbutaline (Bricanyl). These medications are anti-spasmodic and act to relax the smooth muscle of the airways. They have an immediate effect and hence are often referred to as ‘rescue relievers’.

Preventers:

These take the form of white, red, brown or orange inhalers. They function to protect the lining of the airways by reducing the swelling and inflammation of the mucus membrane and decreasing their sensitivity to allergens. These inhalers are usually used in both the morning and evenings, even when there are no symptoms. They do not have an immediate effect but act over a period of regular use.

Chronic Bronchitis and Emphysema

Continued insult to the respiratory system through smoking and pollution, results in the bronchial tubes becoming inflamed and secreting too much mucus. The airways become constricted and the person is short of breath and frequently coughing.  Chronic bronchitis often leads to pulmonary emphysema. Again, smoking is the primary cause and leads to a rapid deterioration of the alveoli. They lose their elasticity and the surface area of the lungs is reduced.  Air is not expelled effectively and stale air accumulates in the lungs. The emphysema victim struggles for every breath and, to compensate; the right ventricle pumps harder and becomes enlarged. Emphysema patients frequently die of heart failure.

Treatment and exercise prescription:

Both these diseases are serious and should be treated with care depending on the severity. Always consult the patient’s doctor before prescribing exercise. One of the most effective measures in combating these diseases is to quit smoking.

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