Definition & Description

Asthma is a chronic lung disease and a very common respiratory condition. It is also known as a reactive airway disease which is inconvenient most of the time but manageable.

Asthma is caused by inflammation and constriction of bronchial walls due to hyper-reactivity of their smooth muscle, thereby leading to a series of spasmodic attacks of wheezing and shortness of breath (SOB). Various factors can contribute to the cause of asthma: exposure to cigarette smoke, climate change, physical exertion or emotional stress. It normally begins during childhood and the disease is commonly triggered by viral infection.

Asthma can be diagnosed by the presence of the various signs and symptoms. Diagnosis is normally confirmed by presenting a response to a inhaled bronchodialator. In addition, pulmonary function tests, chest x-rays and blood tests can also be carried out to confirm the diagnosis.

In childhood, the first symptoms may appear before the age of five years. However, diagnosing asthma in young children under 5 years is difficult due to the fact that other childhood conditions may have similar symptoms. Therefore, the doctor is reliant upon the child's medical history, their symptoms and physical examinations in order to confirm a diagnosis. Moreover, the doctor could also carry out a 4-6 week asthma medication trial and monitor the child's response (US department of health and human services 2009).


According to the Global Burden of Disease Study (GBD)[1], the most recent revised global estimate of asthma suggests that as many as 334 million people worldwide have been diagnosed with the condition. The majority of people affected are in low- and middle-income countries, and its prevalence is estimated to be increasing fastest in those countries.

800px-Asthma world map - DALY - WHO2004.svg.png

In South Africa, particularly Durban and Soweto, there has been an increase in hospital admissions over the past 25 years, with reports of a 25-200 times increase [2]. For South Africa, the mortality rate was estimated to be 77.6 deaths per one million people. It has the second largest mortality rate in the world after South Korea with 86.9 deaths per one million people, followed by Georgia with an estimated 59.2 deaths per one million people after South Africa.

In the UK, approximately 5.4 million people are currently receiving treatment for asthma, this includes 1.1 million children (1 in 11) and 4.3 million adults (1 in 12) [3]. This means that asthma affects 1 in 5 households in the UK. Asthmatic conditions normally begin before the age of 5, however it can occur for the first time at any age, even in adulthood. If asthma occurs for the first time in adulthood, the condition will usually persist, whilst children often outgrow it in their teenage years [4]. On average, 3 people a day die from asthma. Although the UK still has some of the highest asthma prevalence rates in Europe, its prevalence is thought to have plateaued since the late 1990s. In Scotland, approximately 368,000 (1 in 14) people are currently receiving treatment for asthma: 72,000 children and 296,000 adults. The UK NHS spends in excess of £1 billion a year treating and caring for people with asthma, whilst in Scotland the spend is in excess of £130 million [5].


Asthma has many possible causes as the exact mechanism of onset is still unknown. This is due to asthma not being defined as a single disease, but a variety of multiple diseases with similar clinical features, resulting from different genetic and environmental causes [6] mainly developing at an early age, The complex interplay between hereditary and environmental factors which are occurring at this critical time in development, lead to the onset of the disease [7][8].

Patients who are atopic have a genetic predisposition for developing the disease due to a hypersensitivity of the airways to environmental triggers. An allergic reaction to antigens that normally do not cause a response, predisposes to asthma onset demonstrating the genetic component of the disease. Asthmatics can commonly suffer from other allergies including food, drug and skin allergies [9].
The increased prevalence of asthma in developed countries and urbanised areas [10][11] supports the theory of environmental exposure contributing to the disease. Sufferers are chronically-exposed to substances when inhaled lead to an allergic response in the airways.
The following risk factors increase possibility of disease development;


  • Family History
  • Susceptibility to Allergic Reactions


  • Tobacco Smoke/Passive Smoking
  • Prenatal Smoking
  • Dust, Dust Mites
  • Damp Homes
  • Carpets
  • Upholstered Furniture
  • Pet Hair
  • Pollens
  • Pollutants
  • Occupation (Chemical Exposure)
  • Urbanisation

Other Causes

  • Premature Birth with Ventilation Use
  • Low Birth Weight[13]
  • Early Age Antibiotic Use
  • Bronchiolitis as a Child[14][15]
  • Viral Infection [16]
  • Diet [17]

Asthma triggers initiate an asthma attack. Some causes of the manifestation of asthma may also trigger an attack.

Triggers for an Asthma Attack [18]
  • Exercise
  • Cold Air
  • Climate Change
  • Emotions
  • Medications (aspirin, NSAIDs, beta-blockers)
  • Respiratory Infection
  • Irritant Inhalation
  • Dust Mites
  • Pollen
  • Environmental Pollutants
  • Stress
  • Allergic Reaction



In asthma, airway constriction is caused by a combination of bronchial constriction (bronchoconstriction) and bronchial inflammation. This leads to chronic lung pathology in which the bronchial airways are prone to narrowing, causing episodes of wheezing, chest tightness, coughing and breathlessness (SOB) that range in severity from mild to potentially life threatening[19].

Entrance of allergens through the oral or nasal cavity results in swelling of an already compromised and highly sensitive airway [20]. As a result, constriction of smooth muscle in the walls of the airway and excessive release of mucus into the area causes airway narrowing and ultimately reduces the amount of air circulating in and out of the lungs [21]. Due to these differences in airway flow rate, the lungs become hyperinflated.


When the tidal volume (VT) of the lungs reaches a capacity similar to that of the pulmonary dead space, it is termed alveolar hypoventilation and results in a ventilation-perfusion (Va/Q) mismatch. This Va/Q mismatch is ultimately worsened by vasoconstriction [22]

A reduction in arterial oxygen supply (hypoxia) can result from the Va/Q mismatch. Diffusion of carbon dioxide (CO2) across the alveolar capillary membranes prevents high levels of carbon dioxide in the blood (hypercapnia) during the early stages of an acute asthmatic exacerbation/attack. Therefore, although these patients have hypoxia, the low levels of oxygen (low PaO2) trigger hyperventilation and therefore decrease PaCO2 to prevent hypercapnia and the retention of carbon dioxide. During the first stages of an acute episode, alveolar hyperventilation can result in respiratory alkalosis. However, if airway obstruction worsens and there is a further increase in Va/Q mismatch, it can lead to CO2 retention, hypercapnia and compensatory metabolic acidosis.

In asthmatic patients, chronic airway inflammation is associated with:

  • Increased in heart rate
  • Bronchospasms
  • Increased work of breathing (WOB)
  • Wheezing
  • Shortness of breath (SOB)
  • Coughing due to exposure to allergens, environmental irritants, exercise, cold air or viruses.

In some chronic asthmatic patients, limitation of airflow may only be partially reversible. This is a result of airway remodeling from the chronic untreated condition, more specifically hyperplasia and hypertrophy of smooth muscle, angiogenesis, and sub-epithelial fibrosis in the tissues of the airway.

Types of Asthma

Allergic asthma:

  • The type of asthma that is triggered by allergies(substance that is responsible to cause allergic reaction more especially in sensitive people)

Intrinsic asthma:

  • Usually develops after the age of 30 years where allergies do not play any role. It is likely triggered by respiratory irritation substances (e.g cleaning agents, perfume and smoking).

Exercise Induced Asthma:

  • It affects anyone and at any age. It is caused by lack of heat and moisture in the lungs which occurs during strenuous exercises.

Nocturnal Asthma:

  • Is the type of asthma that attacks people when they are asleep. The victims tend to sleep earlier and they wake up in the middle of the night (1-4am) due to difficulties with breathing and they will drink a glass of water to try to relieve the symptoms.[23]

Occupational Asthma:

  • Occurs as the result of inhaling chemical fumes or dust on the working environment (

Steroids Resistance Asthma:

  • Overuse of asthma medications which leads to status asthmatic and severe asthma that does not respond with any medication.

Signs and Symptoms

Asthmatics will present with varying signs and symptoms depending on disease classification and severity. Asthma attacks will exasperate symptoms leading to medication administration. Symptoms most commonly occur early morning, at night or during an attack [24].

Signs and Symptoms[25][26]

  • Wheeze
  • Dry Cough 
    • Increased with Exercise
    • Worse Early Morning/Night
  • Chest Tightness
  • Sputum (stringy, thick)
  • Fatigue
  • Itchy Throat
  • Runny Nose
  • Headache
  • Dyspnoea

These symptoms occur due to the pathophysiology of the disease. Bronchoconstriction causes an audible wheeze and subsequent cough. Chest tightness can be felt and a shortness of breath (dyspnoea) from a constriction of the bronchial walls. Sputum is produced due an inflammatory response in the airways [28] adding to the difficulty of breathing.

Clinical Features

  • Hyperventilation/Increased Respiratory Rate
  • Increased Work of Breathing
  • Decreased Peak Expiratory Flow Rate
    • FEV1
    • FEV1/FVC
  • Decreased PaO2 (partial pressure of oxygen in blood)
  • Increased PaCO2 (partial pressure of carbon dioxide in blood)
  • Increased Heart Rate

Asthma is an obstructive lung disease. Narrowing of the airways (bronchospasm) due to constriction of the bronchial muscles in the wall, lead to decreased air flow and difficulty with breathing. Bronchospasm causes decreased peak expiratory flow rate, which in turn leads to decreased PaO2 and increased PaCO2 of the blood. Heart rate increases to compensate for a lack of oxygen being transported in the blood. To increase oxygen during inspiration, hyperventilation will occur in the patient. However work of breathing will be increased due to the narrowed bronchi which make it more difficult to breathe [29].

When does asthma become life threatening?

  • Difficulty to catch a breath
  • Difficulty talking and concentrating
  • Difficulty talking and walking
  • Cyanosis of skin especially around the mouth and finger areas
  • Nasal flaring and constant wheeze

When these signs and symptoms presents, a person should be aware and are advice to consult with your general practitioner as soon as possible.

Risk Factors and Prevention

There are a few risk factors associated with asthma that can lead to the onset of asthma, an attack or other respiratory symptoms

  • the closeness of home or work to airports, industries and shopping centers(environmental irritants)
  • the dampness level of home or work
  • being a smoker, living with a smoker or working with a smoker
  • the use of spray insecticides or insect oils
  • having pets at home, allergies and sinusitis
  • having mats or carpets that can easily trap dust particles
  • insufficient education and information

Prevention of an attack or an episode is better in the case of asthma because it cannot be cured

  • education on the disease and medication that is used
  • follow the doctor's instructions on how to use medicine and how to keep symptoms under control
  • identify the aggravating factors e.g. smoke, dust, etc.
  • keep record of recurrent symptoms and try and maintain control
  • go to doctor for regular checkups

Many substances can trigger allergies and the same applies to asthma. Common allergens that triggers asthma are pollen, mold, dust mites and pet dander. Other irritants are smoke, pollution fumes, sprays and cleaning chemicals. Asthma symptoms can therefore be reduced by avoiding exposure to known respiratory irritants and allergens.

Investigations and Diagnosis

Diagnosis of asthma is confirmed based upon various factors[30]:

  • Medical History

The patient is initially asked to explain their various symptoms, including their description, frequency, duration and aggravating factors. Substance exposure may have also lead to the onset of asthmatic symptoms, in which case exposure to tobacco smoke, chemical fumes, dust or other airborne irritants is determined. Additional questioning may include relevant health problems, the patient’s occupation and medications that may cause airway irritation.

  • Family History

If the patient has a family history of asthma or allergies, they are more likely to also suffer from asthmatic symptoms.

  • Physical Assessment

Firstly, the patient’s nose, throat and upper airways will be examined for signs of asthma or allergies. Assessment of the patient’s respiratory rate and breathing pattern will be carried out in conjunction with auscultation (using a stethoscope) in order to listen for signs of asthma or allergies that may aid diagnosis. These signs include:

  • Wheezing (high-pitched whistling sounds when the patient exhales)
  • Coughing, chest tightness
  • Shortness of breath (SOB)
  • A runny nose
  • Swollen nasal passages.

The patient’s skin will also be examined for signs of allergic skin conditions (e.g. eczema and hives)[31].

  • Diagnostic Tests

The following tests are used to assess the patient’s breathing as well as to monitor the effectiveness of asthma treatment.

Lung function tests[32]:

  • Spirometry
    Spirometry may be used to assess lung function by measuring the amount of expired air as well as the speed of expiration. It is used to confirm the presence of airway obstruction and can accurately measure the degree of lung function impairment. Spirometry is used to measure the sensitivity of the airways and lung function during physical activity, or following the inspiration of increasing doses of cold air or a special chemical However, it is only recommended for adults and children over the age of 5.
  • Peak flow testing
    Peak flow testing is a self-assessment lung function test using a peak flow meter to provide an objective measure of airway function based upon peak expiratory flow rate (PEFR). Peak flow is described as the highest airflow velocity that can be achieved, with any drop in the peak flow measurement indicating airway obstruction.

Other tests:

Medical Management

Various medication exists that help the control of asthma by reducing inflammation of the airway and bronchial constriction, these medications are administered orally, via aerosol or an inhaler. (Cleveland Clinic. 2009)

One form of an inhaler is a bronchodilator, which allows dilatation of the bronchioles and in turn relieves some of the symptoms. It also aids in mucus removal from lungs. There are two forms of bronchodilators:

  1. Short-acting beta 2-agonists (quick acting or rescue medicine): these drugs are used best to treat sudden and severe or new asthma symptoms as they open the airways and relieve symptoms within 20 minutes and lasts four to six hours. It can also be used before physical activity about 15-20 minutes before the time to prevent exercise-induced asthma.
  2. Long-acting beta 2-agonists: these drugs are not used to for a quick relief of asthma symptoms, instead they are used to control symptoms and their effect lasts 12 hours.

Physiotherapy Management

The majority of patients suffering from asthma will seek physiotherapy for dyspnoea and hyperventilation [33] (LOE 3A). Physiotherapists treat asthma in a variety of ways with the aim to improve breathing technique. Physiotherapy techniques for asthma are in addition to medication and should never be used as a replacement to prescribed medication, however may reduce the dosage required.

Breathing Techniques

1. Breathing Retraining Techniques [34] (LOE 5)

Breathing techniques may have more benefit on mild – moderate asthma [35] (LOE 5). The aim of breathing retraining is to normalise breathing patterns by stabilising respiratory rate and increasing expiratory airflow. Instructions are given from the physiotherapist on how to complete this technique, with the following components:

  • Decreasing Breaths Taken (Reducing Respiratory Rate)
  • Taking Smaller Breaths (Reducing Tidal Volume)
  • Deep Breathing (Diaphragmatic breathing through use of abdominal muscles and lower thoracic chest movement)
  • Breathing through the Nose (Nasal Breathing)
  • Relaxation (Relaxed, controlled breathing)
  • Decreasing Air Leaving (Decreased expiratory flow through pursed lip breathing)
  • These retraining techniques help control breathing and reduce airflow turbulence, hyperinflation, variable breathing pattern and anxiety.

2. Buteyko Breathing Technique[36] (LOE 1b)

The Buteyko breathing technique is another breathing retraining technique; however it is specific to reducing hyperinflation. It was developed based on the theory that asthmatic bronchospasm is caused by hyperventilation, leading to a low PaCO2 and therefore all asthmatic symptoms are due to this. The narrowed airways induce an “air hunger” causing a switch to mouth-breathing and an increased respiratory rate leading to hyperinflation. Buteyko believes that this hyperinflation then also contributes to bronchoconstriction. The Buteyko technique aims to reduce ventilation and subsequently lung volume, as a treatment for asthma and other respiratory diseases. A qualified practitioner is necessary to train the patient [37] (LOE 5).

The Buteyko Technique[38] (LOE 5)
  • Breathe normally through the nose for 2-3 mins
  • Breathe out normally, close nose with fingers, and hold
  • Record number of seconds
  • On first need to breathe, release nose and return to nasal breathing (Control Pause)
  • Wait 3 minutes
  • Repeat and hold breath for as long as possible (Maximum Pause)

Breathing pattern retraining and relaxed breathing techniques are two approaches to physiotherapy management of asthma. The aim of breathing pattern retraining is to develop a more efficient pattern of respiration, thereby reducing breathlessness. This is usually accomplished by slowing the breathing rate, and encouraging relaxed, ‘abdominal’ breathing (Bruton, 2006). Another potential mechanism for breathing pattern retraining is that by encouraging a longer expiratory time, the effects of any static/ dynamic hyperinflation may be reduced.

Mild asthmatics can hold their breath for up to twenty seconds, moderate asthmatics for fifteen seconds and severe asthmatics for up to ten seconds. The aim of this method is to increase the control pause to 60 seconds and the maximum pause to 2 minutes. It is practiced twice a day, with the practitioner there to help with breath holding and ensure safety. Its aim is to reduce minute volume through reduction of respiratory rate, and increasing carbon dioxide levels through breath holding, reducing bronchospasm caused by hyperventilation in the asthmatic patient.

Physical Training

Physical training with asthma is advised when taking the proper precautions, and should not be avoided. The American College of Sports Medicine (ACSM) Guidelines provide tips and safety precautions for asthmatics to exercise safely[39] (LOE 5).

Physical training should be prescribed by physiotherapists for asthmatics to increase fitness and cardiorespiratory performance, reduce symptoms such as breathlessness and improve quality of life [40] (LOE 5). Breathlessness, chest tightness and wheezing can occur when exercising, deterring patients from physical exertion [41] (LOE 1b). Fear avoidance can contribute to a further deterioration of physical health and quality of life, leading to anxiety and depression. It has been shown [42] (LOE 1b) that maintaining physical training in asthmatics improves disease symptoms and quality of life, therefore making it a crucial management strategy.

Respiratory Muscle Training

Hyperinflation in asthma causes increased lung volume, leading to altered inspiratory muscle mechanics. Inspiratory muscles are shortened resulting in a sub-optimal length-tension relationship for contraction. There is a decreased capacity for tension generation when breathing, resulting in accessory muscles of inspiration being utilised [43] (LOE 1a)

Breathing exercises are carried out using an external device to make breathing more difficult. This helps to strengthen the inspiratory muscles, making it easier to breathe in everyday life ( ).
A breathing device is used (, which sets up a load to breathe against. During inspiration air is only released if enough effort is used to force open the valves of the device. Respiratory muscles are forced to work harder, increasing their strength, leading to diaphragmatic breathing becoming easier, reducing hyperinflation.

[44] (LOE 5)

The following physiotherapy management techniques would also be beneficial:

Removal of secretions

  • Percussions
  • Shaking
  • Vibrations,
  • Postural drainage and
  • Effective coughing

Range of motion exercises for patients who need hospitalisation.


  • About condition
  • On use of a bronchodilator and any other medication
  • How to prevent chest infection from occurring
  • Correct posture in standing and sitting which assists in the management of asthma attacks by allowing the chest to expand appropriately and the lungs to function optimally

Unfortunately, there is no cure for this illness but there are ways of effectively managing the disease. However, this should involve the active participation of both the person suffering from the disease and his/her doctor.

Other Health Professional Management

Asthma patients will be involved with a multidisciplinary team to manage their condition. Other health professionals treating the patient include:

  • Doctor
    • Initial diagnosis and treatment.
  • Consultant
    • Specialised in asthma, to help with reducing symptoms and recognising triggers.
  • Specialised Nurse
    • To provide help, education, medication advice and general information.
  • Pharmacist
    • Medication distribution.
  • Dietitian
    • Advice on proper to diet to not induce symptoms.
  • Health Psychologist
    • To help with anxiety/depression associated with symptoms

Prevention and Physiotherapist Role In Prevention

Asthma may not be fully preventable due to the pathology progression and the differing possible causes of onset. However, there are ways of avoiding triggers for the disease and reducing symptoms. Being aware of triggers is vital on an individual basis as these will differ amongst sufferers.

Before the onset of disease, a child should avoid causes of asthma such as passive smoking, damp and dusty living environment and allergen exposure, as well as all possible causes for the disease. However, development can be hereditary and may not be preventable.

Some triggers to be avoided include:

  • Cold Air
  • Allergens
  • Tobacco smoke

To prevent asthma attacks, precautions should be made to avoid exacerbations of symptoms and to be aware of the signs of an attack.[45]

  • Vaccination against flu and pneumonia
  • Learn to recognise warning signs of an attack
  • Identify signs of attack and treat early
  • Use medication as prescribed

A physiotherapist works with the patient to promote a healthy lifestyle benefiting the patient in identifying triggers, reducing symptoms and preventing disease progression. Education, advice and physiotherapy techniques help in the overall outcome of the disease.

Educate on:

Advice on:

  • Appropriate living environment
  • For family members to stop smoking, or not smoke around children
  • Promoting a healthy lifestyle, free of air pollution and inhalation irritants

Disease Progression:

  • Identifying triggers
  • Medication management
  • Physiotherapy techniques to manage disease



  2. Jeena,P., Luyt, D., Morris,A. (2004). What is Asthma? Department of Health. Retrieved on April,11, 2009, from
  4. Jeena,P., Luyt, D., Morris,A. (2004). What is Asthma? Department of Health. Retrieved on April,11, 2009, from
  5. Mome, M., Gupta, R., Farr, A., Heaven, M., Stoddart, A., Nwaru, B.I., Fitzsimmons, D., et al, 2014, "Estimating the incidence, prevalence and true cost of asthma in the UK: secondary analysis of national stand-alone and linked databases in England, Northern Ireland, Scotland and Wales—a study protocol." BMJ open 4, no. 11: e006647.
  6. Ober C, Yao T. The genetics of asthma and allergic disease: a 21st century perspective. Immunol Rev 2011;242(1):10-30.
  7. LeSouef P. Genetics of asthma: What do we need to know? Pediatr Pulmonol 1997;24(S15):3-8.
  8. Ober C, Hoffjan S. Asthma genetics 2006: the long and winding road to gene discovery. Genes Immun 2006;7(2):95-100.
  9. Ober C, Yao T. The genetics of asthma and allergic disease: a 21st century perspective. Immunol Rev 2011;242(1):10-30.
  10. Beasley R, Crane J, Lai CK, Pearce N. Prevalence and etiology of asthma. J Allergy Clin Immunol 2000;105(2):S466-S472.
  11. Shimwela M, Mwita JC, Mwandri M, Rwegerera GM, Mashalla Y, Mugusi F.Asthma prevalence, knowledge, and perceptions among secondary school pupils in rural and urban coastal districts in Tanzania. BMC Public Health. 2014; 14: 387. doi: 10.1186/1471-2458-14-387
  12. Hough A. Physiotherapy in Respiratory and Cardiac Care: An Evidence-Based Approach. Nelson Thornes; 2013.
  13. Mu M, Ye S, Bai MJ, Liu GL, Tong Y, Wang SF, Sheng J. Birth weight and subsequent risk of asthma: a systematic review and meta-analysis. Heart Lung Circ. 2014;23(6):511-9. doi: 10.1016/j.hlc.2013.11.018.
  14. Koponen P, Helminen M, Paassilta M, Luukkaala T, Korppi M. Preschool asthma after bronchiolitis in infancy. European Respiratory Journal. 2012; 39: 76-80; DOI: 10.1183/09031936.00040211
  15. Backman K, Nuolivirta K, Ollikainen H, Korppi H, Piippo-Savolainen E. Low eosinophils during bronchiolitis in infancy are associated with lower risk of adulthood asthmaPediatric Allergy and Immunology, 2015; 26 (7): 668 DOI: 10.1111/pai.12448
  16. Lemanske RF, Jackson DJ, Gangnon RE, Evans MD, Li Z, Shult PA, et al. Rhinovirus illnesses during infancy predict subsequent childhood wheezing. J Allergy Clin Immunol 2005;116(3):571-577.
  17. Fogarty A, Britton J. The role of diet in the aetiology of asthma. Clinical and Experimental Allergy 2000;30(5):615-627.
  27. toms weisiong. Understanding Asthma - 360p [Animation]. Available from: [last accessed 18/5/15]
  28. Evans CM, Kim K, Tuvim MJ, Dickey BF. Mucus hypersecretion in asthma: causes and effects. Curr Opin Pulm Med 2009 Jan;15(1):4-11.
  29. Anees W, Moore VC, Burge PS. FEV1 decline in occupational asthma. Thorax 2006 September 2006;61(9):751-755.
  33. Thomas M, Bruton A. Breathing exercises for asthma. Breathe 2014;10(4):312-322. (level of evidence 3a)
  34. Bott J, British Thoracic Society Physiotherapy Guideline Development Group. Guidelines for the physiotherapy management of the adult, medical, spontaneously breathing patient. BMJ Publ. Group; 2009. (level of evidence 5)
  35. Lord of Physiotherapy. Postural Drainage. Available from:[last accessed 08/02/13] (level of evidence 5)
  36. Cowie RL, Conley DP, Underwood MF, Reader PG. A randomised controlled trial of the Buteyko technique as an adjunct to conventional management of asthma. Respir Med 2008;102(5):726-732. (level of evidence 1b)
  37. Hough A. Physiotherapy in Respiratory and Cardiac Care: An Evidence-Based Approach. Nelson Thornes; 2013. (level of evidence 5)
  38. (level of evidence 5)
  39. (level of evidence 5)
  40. Bott J, British Thoracic Society Physiotherapy Guideline Development Group. Guidelines for the physiotherapy management of the adult, medical, spontaneously breathing patient. BMJ Publ. Group; 2009. (level of evidence 5)
  41. Turner S, Eastwood P, Cook A, Jenkins S. Improvements in symptoms and quality of life following exercise training in older adults with moderate/severe persistent asthma. Respiration 2011;81(4):302-310. (level of evidence 1b)
  42. Fanelli A, Cabral ALB, Neder JA, Martins MA, Carvalho CRF. Exercise training on disease control and quality of life in asthmatic children. Med Sci Sports Exerc 2007;39(9):1474. (level of evidence 1b)
  43. Silva IS, Fregonezi GA, Dias FA, Ribeiro CT, Guerra RO, Ferreira GM. Inspiratory muscle training for asthma. The Cochrane Library 2013. (level of evidence 1a)
  44. POWERbreatheUK. POWERbreathe - How it works. Available from: [last accessed 18/5/15] (level of evidence 5)