Asthma Flashcards
Definition
Asthma is a chronic respiratory condition associated with airway inflammation and hyper responsiveness
Trigger Factors
Allergens
Allergens such as: pollen, mould, dust mites, and animal dander can be problematic. Once an individual is sensitised , both indoor and outdoor allergens can cause attacks of asthma
Air pollutants
Children with asthma who are exposed to tobacco smoke need more medication and more frequently visit hospital emergency departments as a result of asthma attacks. Exposure to traffic fumes also triggers attacks of asthma.
Diet
Allergic reactions to foods are common triggers of asthma attacks. Food preservatives, monosodium glutamate and some food colourings can cause asthma symptoms in some patients
Drugs
NSAIDs can induce asthma symptoms and beta blockers can provoke bronchoconstriction
Exercise
Exercise is the most common trigger of brief episodes of symptoms
Weather changes
Extremes of weather conditions, such as freezing, high humidity and periods of acute pollution caused by weather conditions, are all triggers of asthma attacks
Sulphur dioxide
Sulphur dioxide can trigger airflow limitation in patients with asthma, resulting in an attack of the condition
Respiratory infections
It is well established that respiratory infections can exacerbate asthma in both children and adults
Other factors
Rhinitis, sinusitis and polyposis are sometimes associated with asthma, whilst GORD can exacerbate asthma, particularly in children
Pathophysiology- airway inflammation
The clinical spectrum of asthma is highly variable and different cellular patterns have been observed but the presence of airway inflammation remains a consistent feature. The airway inflammation is persistent even though symptoms are episodic and the relationship between the severity of asthma and the intensity of inflammation is not clearly established
Pathophysiology- inflammatory cells
The characteristic pattern of inflammation found in allergic diseases is seen in asthma,
with activated mast cells and increased numbers of activated eosinophils, T cells, macrophages and neutrophils. Over 100 different inflammatory mediators are now recognised to be involved in asthma and mediate the complex inflammatory response in the airways24. Key inflammatory mediators in asthma include: chemokines (e.g. eotaxin, TARC, MDC), leukotrienes, cytokines (e.g. IL-1beta, TNF-alpha, IL-5, IL-4, IL-13), histamine, nitric oxide and prostaglandins2.
In addition to the inflammatory response, there are characteristic structural changes, often described as airway remodelling, in the airways of asthma patients. These include subepithelial fibrosis, increases in airway smooth muscle, proliferation of blood vessels in the airway walls and mucus hypersecretion2.
Airway narrowing is the final common pathway leading to symptoms and physiological changes in asthma. Several factors contribute to the development of airway narrowing in asthma: airway smooth muscle contraction, airway oedema, airway thickening and mucus hypersecretion2.
Pathophysiology- Airway hyperresponsiveness
Airway hyper-responsiveness, the characteristic functional abnormality of asthma, results in airway narrowing in response to a stimulus that would be innocuous in a person without asthma2.
BTS/SIGN clinical assessment
BTS/SIGN recommends that a structured clinical assessment should be taken to assess the initial probability of asthma, including:
* a history of recurrent episodes of symptoms, ideally corroborated by variable peak flow when symptomatic and asymptomatic
* symptoms of wheeze, cough, breathlessness and chest tightness that vary over time
* recorded observation of wheeze heard by a healthcare professional
* personal/family history of other atopic conditions, in particular, atopic eczema/dermatitis, allergic rhinitis
* no symptoms/signs to suggest alternative diagnoses7
* evidence of diurnal variability
* symptoms which are worse at night or in the early morning.
The results of diagnostic tests when a patient is asymptomatic with those undertaken when a patient is symptomatic should be compared to detect variation over time.
Use spirometry (at the lower limit of normal to demonstrate airway obstruction) to provide a baseline for assessing response to initiation of treatment and to exclude alternative diagnoses:
* obstructive spirometry with positive bronchodilator reversibility increases the probability of asthma
* normal spirometry in an asymptomatic patient does not rule out the diagnosis of asthma7
Features that increase the probability that it is asthma
More than one of the symptoms suggest that the condition is likely to be asthma, particularly if these symptoms are variable from day to day or worse at night. Particularly if these symptoms occur in response to exercise or other triggers, or are associated with taking aspirin or beta blockers
* Wheeze
* Breathlessness
* Chest tightness
* Cough
Other suggestive symptoms
* Personal history of atopy
* Family history of atopy and/or asthma
* Widespread wheeze heard on auscultation
* Otherwise unexplained low FEV1 or PEF
Otherwise unexplained peripheral blood eosinophilia
Features that lower the probability of asthma
- Dizziness, light headedness, peripheral tingling
- Chronic productive cough in the absence of wheeze or breathlessness
- Repeatedly normal physical examination of chest when symptomatic
- Voice disturbance
- Symptoms with colds only
- Significant smoking history
- Presence of cardiac disease
Normal spirometry or PEF when symptomatic
Asthma in Children
- Dizziness, light headedness, peripheral tingling
- Chronic productive cough in the absence of wheeze or breathlessness
- Repeatedly normal physical examination of chest when symptomatic
- Voice disturbance
- Symptoms with colds only
- Significant smoking history
- Presence of cardiac disease
Normal spirometry or PEF when symptomatic
History and examination
NICE recommends that a structured clinical history should be undertaken in adults, young people and children with suspected asthma specifically checking for:
* wheeze, cough or breathlessness and any daily or seasonal variation in these symptoms
* any triggers that make symptoms worse
* a personal or family history of atopic disorders.
A history of atopic diseases alone should not be used to diagnose asthma. Similarly the presence of symptoms without the use of an objective test should not be used to diagnose asthma.
A physical examination to identify expiratory polyphonic wheeze and signs of other causes of respiratory symptoms should be undertaken in cases of suspected asthma. However, even where results of the examination are normal the possibility of asthma should not be ruled out
Acutely unwell patient
For patients who are acutely unwell at presentation, treatment should be initiated immediately and objective tests for asthma undertaken e.g fractional exhaled nitric oxide [FeNO], spirometry and peak flow variability where equipment is available and testing does not compromise treatment of the acute episode.
If objective tests cannot be done immediately for these patients, testing should be carried out when acute symptoms have been controlled and patient advised to contact their healthcare professional immediately if they become unwell while waiting to have objective tests.
Be aware that the results of spirometry and FeNO tests may be affected in people who have been treated empirically with inhaled corticosteroids
Children under 5
For children under 5 years of age with suspected asthma, treat symptoms based on observation and clinical judgement and review the child on a regular basis. If they still have symptoms when they reach 5 years of age, objective tests should be carried out.
If a child is unable to perform objective tests when they are aged 5 years:
* continue treatment based on observation and clinical judgement
* try doing the tests again every 6 to 12 months until satisfactory results are obtained
consider referral for specialist assessment if the child repeatedly cannot perform objective tests and is not responding to treatment
occupational asthma
In adults (ages 17 years and over), check for possible occupational asthma by asking employed people with suspected new-onset asthma or established asthma that is poorly controlled (making sure all answers are recorded for later review):
* are symptoms better on days away from work?
* are symptoms better when on holiday i.e. any longer time away from work than the usual breaks at weekends or between shifts?
Refer people with suspected occupational asthma to an occupational asthma specialist
Objective tests
NICE outlines a number of assessment methods that can be used to determine the likelihood of asthma including:
* lung function tests aimed at
* measuring airflow obstruction using spirometry and peak flow or
* the ability to reverse an obstruction in the airways using drugs that widen the airways i.e. bronchodilatory reversibility testing
* measuring for airways hyperactivity using direct bronchial challenge test with histamine or methacholine
* testing for airway inflammation using FeNO.
Fractional exhaled nitric oxide (FeNO) is a non‑invasive marker of airway inflammation in asthma. Nitric oxide which is present in exhaled breath has been implicated in the pathophysiology of lung diseases, including asthma. FeNO increases as eosinophilic inflammation in the airways increases and so FeNO can be used as a way of measuring this inflammation27.
NICE recommends that those responsible for planning diagnostic service support to primary care should consider establishing asthma diagnostic hubs to achieve economies of scale and improve the practicality of implementing the recommendations in this guideline
NICE suspected asthma
Before starting or adjusting medicines for asthma in adults, young people and children, clinicians should take into account other possible reasons for uncontrolled asthma including:
* alternative diagnoses
* lack of adherence
* suboptimal inhaler technique
* smoking (active or passive)
* occupational exposures
* psychosocial factors
* seasonal or environmental factors.
