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Investigation of Asthma

Investigation of Asthma

Why we investigate asthma patients?

  • For classification and assessment of severity
  • For diagnosis of concomitant illness
  • For exclusion of other causes of cough, wheeze dyspnoea or chest tightness

What are the investigations for asthma?

We should do four basic investigations of all patients.

1. Blood for TC, DC, ESR,
Hb% and : 

To exclude Tropical
pulmonary eosinophilia
Total circulating
Eosinophil (TCE)  (where eosinophil count > 20%).		  
   
2. Sputum for AFB and
Eosinophil :		  To exclude Pulmonary
tuberculosis & for the diagnostic evidence of Pulmonary eosinophilia/Asthma.
   
3. Chest X-ray P/A view : To exclude Pulmonary
tuberculosis, Consolidation, Pneumothorax, Pulmonary oedema, Tumor, FB in
airway etc.
   
4. Pulmonary Function
Tests (P.F.T) :		 Spirometric analysis to
differentiate obstructive from restrictive disorders and asthma from COPD.

After 40 years of age or in suspected cases we should also advise:

5. Blood glucose to exclude Diabetes mellitus.

6. ECG/Echocardiography to exclude cardiac diseases.

CFT/IFAT for filaria is suggestive but not confirmatory for the diagnosis of tropical pulmonary eosinophilia.

What other concomitant illnesses of an asthma patient should be investigated?

The following problems, which may be present in association with asthma, should be investigated properly.

  1. Atopic dermatitis (Eczema)
  2. Allergic rhinoconjunctivitis
  3. Chronic bronchitis or COPD
  4. Cor-pulmonale
  5. Diabetes mellitus
  6. Hypertension
  7. Ischemic Heart Disease (IHD)

Spirometry

Spirometry is a method of assessing lung function by measuring the volume of air that the patient is able to expel from the lungs after a maximal inspiration. It is a reliable method of differentiating between obstructive airway disorders (e.g. COPD, Asthma) and restrictive diseases (e.g. ILD). Spirometry can also be used to determine the severity of COPD. This is important because the severity of COPD can not be predicted simply from the clinical signs and symptoms.

Spirometry gives 3 important measures:

FEV1: The volume of air that the patient is able to exhale in the first-second of forced expiration.

FVC: The total volume of air that the patient can forcibly exhale in one breath.

FEV1/FVC: The ratio of FEV1 to FVC expressed as a percentage.

Values of FEV1 and FVC are expressed as a percentage of predicted normal for a person of the same sex, age and height.

Slowly progressive respiratory symptoms in a middle aged and elderly smoker are likely to indicate COPD. However, such patients may also have asthma. Patients whose symptoms started before the age of 40 years are more likely to be asthmatic, particularly if they are non-smokers with symptoms that vary in severity. Serial peak flow monitoring, looking for diurnal variation of greater than 20%, may help to differentiate these conditions.

Alternatively bronchodilator reversibility tests can be used. A change in FEV1, that is, both a >12% increase and >200 ml over pre-bronchodilator levels indicates positive reversibility test. COPD patients with smaller changes are likely to benefit from bronchodilator therapy symptomatically.

Spirometry indicates the presence of an abnormality if any of the following are recorded:
- FEV1Obstructive disorder shows :

- FEV1 reduced (Restrictive disorder shows:

- FEV1 reduced (<80% of predicted value)

- FVC reduced (<80% of predicted value)

- FEV1/FVC ratio normal (>70%)

Broncho- Provocation test:

Fall of FEV1 >20% after inhalation of methacholine or hypertonic saline is used for diagnosis of hyper-responsiveness of airways in susceptible patients with normal spirometry. Susceptible patients are: (i) Patient with cough variant asthma, (ii) Mild intermittent asthma, (iii) Chronic Bronchitis.

Exercise Challenge test:

Fall of FEV1 or PEFR >15% after vigorous exercise indicates Exercise Induced Asthma. The fall starts at 5 to 10 minutes after exercise and peaks at 20 to 30 minutes and then resolves.

See Also:

Definition of Asthma

Etiology of Asthma

Classification of Asthma

Diagnosis of Asthma

Medicines of Asthma

Further Reading:

Topics:

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  • Misconception about Asthma

    There are some common concerns about Asthma prevailing in the society. In majority of cases, these are misconceptions or baseless fears. For optimum control of asthma, these points should be dealt with proper care. Otherwise the management plan may go in vain. It the physicians responsibility to eradicate such worries, if present, from the patient’s mind. Some common concerns and suggested clinicians responses are listed below. Model answers to some frequently asked questions (FAQs) are also given. These will help the physician to deal with such situations more confidently.

  • Hospital Based Care of Asthma

    Management of Asthma Attacks :

    Hospital-Based Care

    Initial Assessment:

    History, Physical examination (auscultation, use of accessory muscles, heart rate, respiratory rate) and Investigations (PEF or FEV1, Oxygen saturation SaO2, arterial blood gas analysis and other tests)

    Initial Treatment:

    • Inhaled short-acting b2-agonist, usually by nebulization, one dose every 20 minutes for 1 hour
    • Oxygen to achieve O2 saturation >90% (95% in children)
  • Asthma Control Plan

    Name of Patient ........................................ Prepared by Dr. .........................................

    This plan will help a patient control his asthma and know what to do if he has an asthma episode. Keeping a patient’s asthma under control will help to :

    • Be active without having asthma symptoms. This includes being active in exercise and sports.
    • Sleep through the night without having asthma symptoms.
    • Prevent asthma episodes (attacks).
    • Have the best possible peak flow number - lungs that work well.
  • Definition of Asthma

    Why do we define asthma?

    We define asthma to identify the disease correctly and to differentiate it from other diseases. To fulfill this goal, definition of asthma has been changing over last 40 years. The clinician, physiologist, immunologist, pathologist or epidemiologist - all have different perspective of asthma.

    In the year 1997, the following working definition has been formulated by Expert Panel-2 of National Asthma Education and Prevention Program, USA.

    Asthma is a chronic inflammatory disorder of the airways:

  • Use of Peak Flow Meter

    A peak flow meter is a device that measures how well air moves out of a patient's lungs. During an asthma episode, the airways of the lungs begin to narrow slowly. The peak flow meter can be used to find out if there is narrowing in the airways, hours - even days - before the patient has any symptoms of asthma. By taking the medicine early (before symptoms), your patient may be able to stop the episode quickly and avoid a serious episode of asthma. So its role in preventing severe asthma attack is very important.

    The peak flow meter can also be used to help you:

  • Medicines for Asthma

    What are the medicines used to treat asthma?

    There are basically three kinds of medicines:

    Relievers (Bronchodilators) are medicines that relax smooth muscles that have tightened around the airways. They relieve asthma symptoms. Short acting b2-agonists, short acting aminophylline, and ipratropium are bronchodilators or relievers.

  • Home Management of Asthma

    Why management at home ?

    Since asthma is a chronic disease, it can be and should be managed at home up to a certain level. If home management plan is applied intelligently and skillfully, most asthmatics can lead symptom free normal life, avoid hospitalization thereby cutting down the financial expenditure significantly. All patients of asthma, except those with acute exacerbation, should be treated at home.

    What are the components of home management plan ?