Different stimuli may cause different pathological changes; it is assumed that with different stimuli or in different patients, there will be heterogeneity in the involvement of different size airways as well as the airway response to these stimuli.
The primary physiological manifestation of this hyper-responsiveness is variable airway obstruction . This can take the form of spontaneous fluctuations in the severity of obstruction following bronchodilators or corticosteroids, or increased obstruction caused by
Persistent asthma : characterized by frequent symptoms (unless these are under control with treatment) and air-way abnormality as demonstrated by AHR to both direct and indirect stimuli and increased variability of daily peak flow readings at a time when the subject
Episodic asthma : characterized by episodes of symptom s of sufficient severity to require medication but during symptom-free interval there is no detectable AHR . It is the most common form of asthma in young children and in pollen-sensitive asthmatics.
Brittle asthma : is asthma that causes little or no problem on most days but that is associated with frequent severe attacks requiring unscheduled clinic or hospital visits or frequent courses of an oral corticosteroid with its attendant side-effects.
A common feature of ‘brittle asthma’ is the apparent difficulty in controlling the variability in airway function , which is usually severe at night, with near-normal lung function during the day. Attacks occur with no obvious precipitating factors and are often life-threatening.
Asthma is the most common chronic disease of childhood. It was historically viewed as a broncho-constrictive disease and is now recognized as an inflammatory disease. The triad of reversible airway obstruction, bronchial hyperresponsiveness, and airway inflammation characterize asthma.
Questions to Consider in The Diagnosis of Asthma
Has the patient had an attack or recurrent attacks of asthma?
Does the patient have troublesome cough at night?
Does the patient have a wheeze or cough after exercise?
Inhaled allergens are the strongest asthma triggers. Once triggered, the inflammatory pattern is identical from the nose to the lungs . Acute signs and symptoms include rhinorhea, itching, sneezing, congestion and/or airflow obstruction.
In late phase , a wave of mediator release occurs. This predisposes to chronic inflammation with congestion, airflow obstruction, and fatigue. The late phase reaction can lower the threshold for subsequent allergen exposure.
Respiratory infections ( early respiratory illness is defined as a respiratory illness before the age of 2 years , severe enough to have required treatment by a doctor or at a hospital. In contrast, respiratory
Infections in late childhood or adult life have not been shown to be a risk factor for the development of the disease. Viral infections in the absence of atopy are not a risk factor of importance for the development of asthma. Nevertheless, viral infections remain important triggers of attacks , especially in atopic infants.
Urban living and higher material standards of living appears to be associated with a higher prevalence of reversible airway obstruction in children. This could be due to better access to health care and increased diagnosis rates.
Childhood asthma is more prevalent in boys than in girls . This is related to narrower airways , increased airway tone , and possibly higher IgE in boys , which predisposes them to enhanced airflow limitation in response to a variety of insults.
The difference disappears after the age of 10, when the airway diameter/length ratio is the same in both sexes, probably because of changes in thoracic size that occurs with puberty in males but not in females.
Environmental pollutants such as sulfur dioxide , ozone , and nitrogen oxides can, at concentrations found in heavily polluted cities, trigger bronchoconstriction , transiently increase airway responsiveness , and enhance allergic responses.
Active smoking is associated with accelerated decline of lung function in people with asthma , greater asthma severity , and poor response to asthma treatment , supporting the concept that active smoking may contribute to asthma severity.
There is a correlation between higher body mass index and greater risk of developing asthma . Weight loss improves lung function (particularly PEF variability), symptoms, morbidity , and health status , and quality of life in obese patients with asthma.
Key indicators for asthma include the presence of history of wheeze , cough , or dyspnea ; recurrent chest tightness ; over a 20% variation in peak flow ; increased symptoms at night; increased symptoms with infection , allergens , or irritants ; weather and temperature changes ; and strong emotions.
A full enquiry into asthma symptoms is not complete until details of night - time and early morning symptoms have been sought. The presence of nocturnal asthma correlates strongly with disease activity .
Nocturnal and /or early morning symptoms with a diurnal variation in
The prevalence of chronic sinusitis in patients with asthma is high. Thus the patients should be questioned about nasal obstruction , nasal discharge, frequent colds, day and night coughing with post-nasal drip, and sore throat.
It is a very common complaint and not specific to asthma.
It is described as the only symptom in so called ‘cough variant asthma ’ where it is the sole manifestation of asthma thought to be characterized by central airways narrowing, the site at which cough receptors are most abundant.
It is not a sensitive indicator of asthma severity.
Airflow obstruction in asthma is greater during expiration than inspiration, yet only 19% of patients perceive their dyspnea to be expiratory. Dyspnea probably reflects the effort of breathing rather than airflow obstruction itself.
Reduced sensitivity to hypoxia or diminished awareness of SOB can predispose youths to a potentially fatal exacerbation. The ability to perceive signs and symptoms of hypoxia appears to vary with the individual.
Patients with a low perception of dyspnea have significantly increased ED
Nocturnal awakenings with coughing or wheezin g may be the presenting symptom especially in children. Nocturnal symptoms in a patient who has previously had only daytime symptoms represent disease progression. Circadian fluctuations in cortisol alone do not explain nocturnal symptoms.
The most common presenting symptoms in asthmatics include shortness of breath (particularly with exertion), wheezing(which may be audible to the patient but often is not), cough (often productive secondary to inspissated secretions without necessarily being related to an infectious cause), and chest
Patients with a history of current use of, or recent withdrawal from, systemic corticosteroids, hospitalization for asthma and/or emergency treatment for asthma in the past year, prior intubation for asthma, psychiatric disease or psychosocial problems and non-compliance with an asthma medication
A group of patients in whom the diagnosis of asthma is often not made or missed is the elderly.
They are susceptible to episodes of wheezing, breathlessness, and cough caused by left ventricular failure. The presence of increased symptoms with exercise and at night may add to the diagnostic confusion.
Diagnosis of asthma in children can present a particularly difficult problem, largely because episodic wheezing and cough are among the most common symptoms encountered in childhood illnesses, particularly in children under 3 years old.
In young children with frequent wheezing, a parental history of asthma along with the presence of other atopic manifestations in the child are significantly associated with the presence of asthma at age 6 years.
The factors underlying increased asthma morbidity include increased severity of the disease, under-treatment of patients with anti-inflammatory therapy, over-reliance on bronchodilators, and delay in seeking medical help during an exacerbation.