- Diseases, Disorders & Conditions
All You Should Know about Asthma
Asthma is a disease of small airways characterized by obstruction to the airflow which may be partially or completely reversible for a considerable period (evidenced by recurrent attacks of remissions and exacerbations). It is a disease with a long term course with intermittent acute attacks. The number of asthma patients has increased with urbanization and geographical variations are seen. The disease is seen to affect teenagers commonly and is likely to affect 20% of the work force if exposed to sensitizers.
Risk factors to develop asthma can be categorized into the factors of the individual (host factors) and the factors of the environment. Host factors include any close (1st degree) relations with the disease (positive family history), presence of atopy (rhinitis, conjunctivitis, dermatitis in response to an allergen), less number of infections during childhood (the more an individual acquires infections during childhood lesser becomes the likely hood of developing asthma in later life), infections during pregnancy, male sex and race. Environmental factors may also act like precipitating and aggravating factors (factors that may worsen the disease) and include
1. Chest infection – viral RTI (bronchiolitis)
2. Exercise and rapid deep breathing
3. Cold dry air
4. Air pollution
5. Tobacco smoke (including smoking by the mother during pregnancy)
6. Stress and emotions
7. Drugs – NSAIDs (e.g.- Aspirin), beta blockers (e.g.- Propanolol)
8. Diet – Cow’s milk
9. Fungi (mould), Pollen
10. Domestic mites
11. Animal allergens
12. Cockroach allergens
- Lung Pressures and Lung Compliance
Air flow between the lungs and the environment occurs via a pressure gradient. This hub is on the changes in alveolar and pleural pressure changes in a breathing cycle and the resulting volume changes
Asthma is a disease that is easy to suspect and diagnose but difficult to treat, especially in children. The main clinical features seen are the wheeze, cough, chest tightness and shortness of breath. Severity of these symptoms tends to have a variation with the time of the day, usually being severe towards the night and the early morning and becoming mild towards the afternoon. Triggering factors and precipitating factors are present in most of the cases. On examination, the respiratory rate may be high and diffuse rhonchi may be heard over both lung fields.
Though quite rare, the diagnosis of asthma may be confused with other diseases of the lungs as well as generalized illnesses. Inhalation of a foreign body, a tumour in the airways, chronic obstructive airway disease, viral infections and cystic fibrosis may mimic asthma. In addition, left heart failure, pulmonary embolism, excessive rapid breathing (e.g.-hysteria) and vocal cord dysfunction may also be confused with asthma. Usually investigations are not necessary to confirm the diagnosis of asthma, but incase of suspicion of the diagnosis, peak expiratory flow rate or spirometry and its variability with time of the day or with the administration of a drug can be used as a diagnostic test. Chest X-rays are seldom required and are usually ordered to look for complications rather than to diagnose.
- Non-respiratory Functions of the Respiratory System
In addition to serving the function of respiration, the respiratory system is involved in providing immunity, in olfaction, in phonation, as a reservoir and a filter for CVS and as a metabolic ground
- Lung Volumes and Capacities
Breathing (inspiration and expiration) occurs in a cyclical manner due to the movements of the chest wall and the lungs. The resulting changes in pressure, causes changes in lung volumes.
To assessment of the severity of an attack is based on clinical judgment and is categorized into mild, moderate, severe and life-threatening as the management of the acute attack defers for each category. The more sever the attack is, more aggressive and quicker is the treatment. As asthma is a disease going on for a long time, it is important to assess the control of the disease. Drugs are always prescribed to increase the level of control, which can be categorized into mild intermittent, mild persistent, moderate persistent and severe persistent based on the frequency of the symptoms and attacks. Poorer the level of control is, higher becomes the number of drugs and the doses prescribed.
Management of asthma is complex and is described in detail in a separate article by the author. However, it should be clearly understood that asthma is only a controllable disease and with poor compliance, it can always be worsened. It is important to identify the risk factors and reduce the exposure to such factors. The severity as well as the control of the disease can be monitored by a symptom diary or a peak expiratory flow meter at home and they are important in making decisions about altering drugs and their doses. The drugs should be administered at the prescribed times and in correct doses. If the patient is on an inhaler with or without a spacer device, always the accuracy of the inhaler techniques should be checked with the help of an experienced health care worker. There should be a proper plan to hospitalize the patient in an acute attack and there should be at least one person other than the patient aware of such facts. Finally it would always be better to have a tag or a card with the patient indicating that the patient is asthmatic with the contact details, incase the patient develops an attack while alone.
- Lung Volumes and Lung Capacities in Health and Respiratory Diseases
Lung volumes and capacities tend to vary with age, sex, ethnicity and built. Alterations in the lung volumes are used to diagnose obstructive and restrictive lung diseases.
- Respiratory Physiology - Introduction
The respiratory physiology is on the process of incorporation of oxygen in the environment for the utilization of energy from the organic compounds and for the elimination of carbon dioxide