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Asthma is a major cause of impairedquality of life with impact on workand recreational, as well as physicalactivities, and emotions.
"a chronic inflammatory disorder of the airways” caused by reversible airways obstruction. 3
• Inflammatory airways disorder involving mast cells, eosinophils, PMN’s, epithelial cells, macrophages and T cells.• This inflammation leads to clinical sequelae of episodic bronchospasm (wheezing), breathlessness, chest tightness and cough.• Episodes are usually associated with variable airflow obstruction that is reversible.
is "a chronic inflammatory disorder of the airways inwhich many cells and cellular elements play a role.The chronic inflammation is associated with airwayresponsiveness that leads to recurrent episodes ofwheezing, breathlessness, chest tightness, andcoughing, particularly at night or in the earlymorning. These episodes are usually associated withwidespread, but variably, airflow obstruction withinthe lung that is often reversible eitherspontaneously or with treatment.
1. Episodic or chronic symptoms of airflow obstruction: breathlessness, chest tightness, wheezing, and cough.2. Complete or partial reversibility of airflow obstruction, either spontaneously or following bronchodilator therapy.3. Symptoms frequently worse at night or in the early morning. 6
4. Prolonged expiration and diffuse wheezes on physicalexamination.5. Limitation of airflow on pulmonary function testingor positive bronchoprovocation challenge.
1. Bronchial muscle contraction, triggered by a variety of stimuli.2. Mucosal swelling/inflammation, caused by mast cell and basophil degranulation resulting in the release of inflammatory mediators.3. Increased mucus production.
Airflow limitation which is usually reversible spontaneously or with treatment. Airway hyperresponsiveness to a wide range of stimuli. Inflammation of the bronchi with T lymphocytes, mast cells, eosinophils with associated plasma exudation, oedema, smooth muscle hypertrophy, matrix deposition, mucus plugging and epithelial damage.
GENDER:• From childhood till 20 : more in male.• From 20 till 40 : approximately equal.• After 40 : more in females.
Explanations :• greater prevalence of atopy in young boys.• smaller airway size in young boys compared to girls.
Classification:Asthma is a complex disorder of the conducting airways that most simply can be classified as:■ extrinsic – implying a definite external cause.■ intrinsic – when no causative agent can be identified.
Extrinsic asthma:1) Occurs most frequently in atopic individualswho show positive skin-prick reactions tocommon inhalant allergens such as dustmite, animal danders, pollens and fungi.2) Positive skin-prick tests to inhalant allergensare shown in 90% of children and 70% of adultswith persistent asthma. 14
3) Childhood asthma is often accompanied by eczema (atopic dermatitis).4) A frequently overlooked cause of late- onset asthma in adults is sensitization to chemicals or biological products in the workplace.
Intrinsic asthma:1) Often starts in middle age (‘late onset’).2) Nevertheless, many patients with adult-onset asthma show positive allergen skin tests and on close questioning give a history of respiratory symptoms compatible with childhood asthma.
• Non-atopic individuals may develop asthma in middle age fromextrinsic causes such as sensitization tooccupational, intolerance to nonsteroidal anti-inflammatory drugs (NSAID’S) such as aspirin orbecause they were given β-adrenoceptor-blocking agents for concurrent HTN or anginathat block the protective effect of endogenousadrenergic agonists.
Extrinsic causes must beconsidered in all cases of asthma and, where possible, avoided.
HISTORY AND PHYSICAL EXAMINATION :• Asthma may develop at any age although new-onset asthma is less frequent in the elderly compared to other age groups.• Asthma is diagnosed before the age of seven years in approximately 75 percent of cases.
• Thus, clinicians treating adolescents and adults will often encounter patients whose diagnosis of asthma was made (correctly or incorrectly) years earlier.• Many adolescents experience a remission of childhood asthma symptoms around the time of puberty, with recurrence several years later.
Historical information:Some patients will report or present with theclassic triad of symptoms:1) Wheeze (high-pitched whistling sound, usuallyupon exhalation).2) Cough (typically worsening at night).3) Shortness of breath or difficulty breathing.
• "Wheezing" does not have a standard meaning for patients and may be used by those without a medical background to describe a variety of sounds, including upper airway noises from the nose or throat.
• Cough may be dry or productive of mucoid or pale yellow sputum (made discolored by the presence of eosinophils).
• Some describe chest tightness or a band-like constriction. In contrast, chest pain is uncommonly used to describe the sensation of asthma.
• Because the symptoms of asthma are also seen in a myriad of other respiratory diseases, it may be difficult to be certain of the diagnosis of asthma based upon history alone.
1) Episodic symptoms: Asthmatic symptoms characteristically come and go, with a time course of hours to days, resolving spontaneously with removal from the triggering stimulus or in response to anti-asthmatic medications.
2) Characteristic triggers: Respiratory symptoms triggered by exercise, cold air, and exposure to allergens are suggestive of asthma.
3) Personal or family history of atopy: A strong family history of asthma and allergies or a personal history of atopic diseases (specifically, atopic dermatitis, seasonal allergic rhinitis and conjunctivitis, or hives) favors a diagnosis of asthma in a patient with suggestive symptoms.
4) History of asthmatic symptoms as a child: As previously mentioned, recollection of childhood symptoms of chronic cough, nocturnal cough in the absence of respiratory infections, or a childhood diagnosis of "chronic bronchitis" or "wheezy bronchitis" favors asthma.
Allergens that typically trigger asthma symptoms include:• Dust, molds, furred animals, cockroaches, and pollens.• Other irritant-type exposures (eg, cigarette smoke, strong fumes, changes in weather, airborne chemicals or dusts) are non- specific and do not favor a diagnosis of asthma over other respiratory diseases.• Similarly, viral infections are common triggers for asthma, although they can trigger exacerbations in other chronic respiratory conditions as well.
historic features lessen the prior probabilityof asthma. • Onset of symptoms after age 50 • Lack of improvement following anti- asthmatic medications: • History of cigarette smoking
Symptoms: Intermittent dyspnoea. Wheeze. Cough (often nocturnal) and sputum.
Ask specifically about?1. Precipitants? Cold air, exercise, emotion, allergens (house dust mite, pollen, animal fur), infection, drugs (eg: aspirin, NSAID’s, B-blockers).2. Diurnal variation in symptoms or peak flow? Marked morning dipping of peak flow is common and can tip the balance into a serious attack, despite having normal peak flow at other times.
3. Exercise? Quantify the exercise tolerance. 4. Disturbed sleep? Quantify as nights per week (a sign of severe asthma).5. Acid reflux? This has a known association with asthma. 36
6. Other atopic disease? Eczema, hay fever, allergy, or family history. 7. The home (especially the bedroom)? Pets? Carpet? Feather pillows or duvet? Floor cushions and other soft furnishing?37
8. Occupation? If symptoms remit at weekends or holidays, something at work may be a trigger. Ask the patient to measure his peak flow at intervals at work and at home (at the same time of day) to confirm this.9. Days per week off work or school? 38
1- Widespread, high-pitched, musical wheezes are characteristic of asthma, although these findings are not specific. 2- Wheezes are heard most commonly on expiration, but can also occur during inspiration.41
3- Asthmatic wheezing usually involves sounds of multiple different pitches, starting and stopping at various points in the respiratory cycle and varying in tone and duration over time.42
4- It is different from the monophasic wheezing of a local bronchial narrowing (eg, due to an aspirated foreign body or bronchogenic cancer), which has single pitch and repeatedly begins and ends at the same point in each respiratory cycle.43
5- Transmission of expiratory noises from the upper airway (eg, larynx, pharynx) can mimic wheezing and is often described as wheezing by patients. However, these noises are typically loudest over the neck and greatly diminished over the chest.44
6- A history of intermittent symptoms typical of asthma (as described above) plus the finding on physical examination of characteristic musical wheezing (present in association with symptoms and absent when symptoms resolve) strongly point to a diagnosis of asthma.45
7- Importantly, the presence or absence of wheezing on physical examination is a poor predictor of the severity of airflow obstruction in asthma.46
8- Wheezing may be heard in patients with mild, moderate, or severe airway narrowing, while widespread airway narrowing may be present in individuals without wheezing. Thus, the presence of wheezing alerts one to the likely presence of airway narrowing, but not its severity.47
Physical findings that suggest severe airflowobstruction in asthma, include:1. Tachypnea.2. Tachycardia.3. Prolonged expiratory phase of respiration (decreased I:E ratio).4. A seated position with use of extended arms to support the upper chest ("tripod position"). 48
5. Use of the accessory muscles of breathing (eg, sternocleidomastoid) during inspiration. AND 6. A pulsus paradoxus (greater than 12 mmHg fall in systolic blood pressure during inspiration) are usually found only during acute asthmatic attacks.49
• However, these signs are insensitive manifestations of severe airflow obstruction; as their absence does not exclude the possibility of a severe asthmatic attack.50
Acute severe asthma: • The term ‘status asthmaticus’ was defined as asthma that had failed to resolve with therapy in 24 hours. • Although this term is still used occasionally, it has been mainly discarded and replaced by ‘acute severe asthma’, i.e. severe asthma that has not been controlled by the patient’s use of medication.51
Patients with acute severe asthma typically have: 1- Inability to complete a sentence in one breath. 2- Respiratory rate ≥ 25 breaths per minute. 3- Tachycardia ≥ 110 beats/min (pulsus paradoxus, is not useful as it is only present in 45% of cases) 4- PEFR < 50% of predicted normal or best.52
Features of life-threatening attacks are:1- A silent chest, cyanosis or feeble respiratory effort.2- Exhaustion, confusion or coma.3- Bradycardia or hypotension.4- PEFR < 30% of predicted normal or best (approximately 150 L/min in adults).
• Arterial blood gases should always be measured in asthmatic patients requiring admission to hospital. • Pulse oximetry is useful in monitoring oxygen saturation during the admission and reduces the need for repeated arterial puncture.54
Features suggesting very severe life- threatening attacks are: • A high Paco2 > 6 kPa. • Severe hypoxaemia Pao2 < 8 kPa despite treatment with oxygen. • A low and falling arterial pH.55
1- A pale, swollen nasal lining on otoscopic examination of the nasal cavities suggests associated allergic rhinitis.57
2- Nasal polyps, which appear as glistening, gray, mucoid masses within the nasal cavities, should prompt questioning about concomitant aspirin sensitivity and chronic sinusitis. Since triad asthma (asthma, nasal polyps, and aspirin sensitivity) is uncommon in childhood, the finding of nasal polyps in an adolescent with similar respiratory symptoms should lead to consideration of alternative diagnoses, specifically cystic fibrosis.58
Nasal polyps in nostril Nasal polyps appear as fixed, glistening, gray or white, mucoid masses in the nasal cavities.59
3- Clubbing is not a feature of asthma; its presence should direct the clinician toward alternative diagnoses such as interstitial lung disease, lung cancer, and cystic fibrosis.60
PULMONARY FUNCTION TESTING• Pulmonary function tests are critical tools in the diagnosis of asthma.• Measurement of peak expiratory flow rate and spirometry are the two pulmonary function tests most often used in the diagnosis of asthma.
Peak expiratory flow rate:The peak expiratory flow rate (PEFR) is •measured during a brief, forceful exhalation.Simple and inexpensive (approximately $20) •equipment can be used to measure the PEFR;the patient can be taught to monitor PEFRroutinely at home.
• However, the resulting measurements are highly dependent upon the patients expiratory effort and technique. • Thus, it is important that the clinician assess the patients use of the monitor and effort level and correct any mistakes.63
• In addition, the patients peak flow values may vary depending upon the particular brand of peak flow meter. • The PEFR maneuver can be performed sitting or standing.64
• Proper technique involves taking a maximally large breath in, putting the peak flow meter quickly to the mouth and sealing the lips around the mouthpiece, and blowing as hard and fast as possible into the meter.65
• For PEFR, the effort does not need to be sustained beyond one to two seconds. • The patient should perform the maneuver three times and record the highest of the three measurements.66
• A peak flow meter is small, inexpen sive, and easy for most patients to use.67
• Personal best PEFR: Peak flow monitoring can be used to establish a patients "personal best" peak flow. Each patient must establish his or her own personal best PEFR value, ideally by recording measurements at least twice daily for two weeks (or more). If possible, this should be done when the patient is feeling well and free from asthma symptoms.
• The personal best PEFR is used to define the patients normal peak flow range, which is between 80 and 100 percent of the personal best. Readings below this range indicate airway narrowing, a change that often occurs before the onset of symptoms and can alert the patient to a change in asthma control.69
• Interpretation of PEFR variability : There is some variability inherent in measurements of peak flow. This may be as much as 15 to 20 % with repeated measurements, even in individuals without asthma. PEFR results that vary little over time (less than 20 % of the maximal value) argue against the diagnosis of asthma, particularly if reported symptoms are associated with unchanging peak flow measurements. In contrast, peak flow values that repeatedly fall by more than 20 % when symptoms are present and return to baseline as symptoms resolve are consistent with asthma. 70
• A single peak flow determination made in the doctors office at the time that a patient is experiencing respiratory symptoms, if reduced from the normal predicted value, is suggestive of asthma. However, it is not diagnostic, because a reduced peak flow is not specific for airflow obstruction and can be seen with other pulmonary processes. A reduced peak flow that improves by more than 20 % approximately 10 minutes after administration of a quick-acting bronchodilator (eg, inhaled albuterol) is also confirmatory evidence favoring the diagnosis of asthma. 71
ASTHMA MONITORING RECOMMENDATIONS: The NAEPP recommend that patients use a peak flow meter to: Regularly monitor lung function and response to treatment over the short- and long-term. Determine the severity of an asthma attack. Assess response to treatment during an attack.
• Patients should use an asthma diary to record their daily peak flow meter readings, exposure to potential asthma triggers, asthma medication use, and asthma symptoms.73
HOW TO USE A PEAK FLOW METER:• PEFR monitoring should be performed on a regular basis, even when asthma symptoms are not present.• PEFR should also be checked if symptoms of coughing, wheezing, or shortness of breath develops.• Patients should demonstrate PEFR measurement with their healthcare provider to verify that their technique is accurate. 75
Getting the best readings:Several steps are important to make sure the peak flowmeter records an accurate value: 1. The peak flow meter should read zero or its lowest reading when not in use. 2. Use the peak flow meter while standing up straight. 3. Take in as deep a breath as possible. 4. Place the peak flow meter in the mouth, with the tongue under the mouthpiece.
5. Close the lips tightly around the mouthpiece.6. Blow out as hard and fast as possible; do not throw the head forward while blowing out.7. Breathe a few normal breaths and then repeat the process two more times. Write down the highest number obtained. Do not average the numbers. 77
• Normal values for men and women are based upon height and age. • Normal values for adolescents are based upon height.78
Limitations of PEFR: Despite its usefulness, there are several shortcomings of the PEFR that should be kept in mind.79
1. Mild airflow obstruction may be present when the peak flow remains within the normal range.2. Reduced peak flow measurements may be seen in both obstructive and restrictive diseases. Spirometry and lung volumes are necessary to distinguish the two. 80
3. Peak flow measurements are not sufficient to distinguish upper airway obstruction (eg, vocal cord dysfunction) from asthma. Spirometry is needed for this. 4. The validity of PEFR measurements depends entirely upon patient effort and technique. Errors in performing the test frequently lead to underestimation of true values, and occasionally to overestimation.81
5. Home PEFR monitoring is unsupervised. Patients may produce higher values with appropriate coaching. 6. Peak flow meters cannot be routinely calibrated, unlike spirometers. Thus, results will vary somewhat among different instruments.82
A zone scheme similar to a traffic light system be used to illustrate a plan upon which patients can base self-management decisions.83
• GREEN (80 to 100 % of personal best) signals "all clear". When readings are within this range and symptoms are not present, the patient is advised to adhere to his or her regular maintenance regimen.84
• YELLOW (50 to 80 % of personal best) signals "caution", since the airways are somewhat obstructed. The patient should implement the treatment plan decided upon with the clinician to reverse airway narrowing and regain control. The wide range represented by the yellow zone can be subdivided above and below the 65 percent level if desired.85
• RED (below 50 % of personal best) signals "medical alert". Bronchodilator therapy should be started immediately, and the clinician should be contacted if PEFR measures do not return immediately to the yellow or green zones.86
Spirometry:• Spirometry, which includes measurement of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), provides additional information that is useful in the diagnosis of asthma.• Spirometry can be completed in 10 to 15 minutes with no risk to the patient.
The results of spirometry can be used to determine the following:1. Distinguish normal from abnormal lung function.2. Categorize abnormalities into obstructive or restrictive patterns.3. Characterize the severity of the abnormality.4. Assess the reversibility of the obstructive abnormality if the testing is repeated after administration of a bronchodilator.
• The forced vital capacity (FVC), which is the total volume of air exhaled. • The FEV1, which is the volume exhaled in the first second of expiration. • The ratio of FEV1 to FVC, or FEV1/FVC ratio.90
Bronchodilator response (baseline spirometry):• Administer bronchodilator (at least 400mcg salbutamol or bricanyl, e.g. 4 puffs using a spacer device e.g. volumatic spacer or 5mg by nebuliser). Then perform spirometry again after 15 minutes. An increase in FEV1 of >12% and >200mls suggests significant reversible airflow obstruction) with 95 % certainty.• A steroid trial (30 - 40mg prednisolone daily for 2 weeks or 1,000 μg of inhaled corticosteroid for three months) may also be appropriate to assess bronchodilator reversibility if asthma is still suspected.
• Having identified the presence of airflow obstruction by a reduction in FEV1/FVC, the severity of airflow obstruction is then categorized by the degree of reduction of the FEV1 below normal and is graded as mild, moderate, severe, and very severe according to the following categories. (Note: these are categories used for pulmonary function interpretation and are NOT the same as categories used to stage asthma severity):92
• FEV1 80 to 99 % : mild obstruction. • FEV1 51 to 79 % : moderate obstruction. • FEV1 36 to 50 % : severe obstruction. • FEV1 less than 35 % : very severe obstruction.93
Flow-volume curves in obstructive and restrictive lung disease Sample flow-volume curves during a maximal forced expiration in normals and in obstructive and restrictive lung disease. The normal expiratory portion of the flow volume curve is characterized by a rapid rise to the peak flow rate, followed by a nearly linear fall in flow as the patient exhales toward residual volume. With obstructive disease, maximal expiration begins and ends at higher lung volumes and lower flow rates than normal. With restrictive disease, the lung volumes and flow rates are reduced but the flow in relation to lung volume is actually higher than normal.94
OTHER LABORATORY TESTS Other laboratory studies, including chest radiography, blood tests, and tests for allergy, are sometimes useful in the diagnosis of asthma.96
Chest radiography:• The chest radiograph is almost always normal in patients with asthma.• Many clinicians favor obtaining a chest radiograph for new-onset asthma in the adult, for the purpose of excluding the occasional alternative diagnosis (eg, the mediastinal mass with tracheal compression or congestive heart failure). 97
In contrast, CXR is definitely recommended in the evaluation of severe or "difficult-to-control" asthma, for the detection of co-morbid conditions (eg, ABPA, eosinophilic pneumonia, or atelectasis due to mucus plugging). In addition, CXR is indicated in patients presenting with features that are atypical for asthma, including any of the following:98
• Fever. • Chronic purulent sputum production. • Localized wheezing. • Hemoptysis. • Weight loss. • Clubbing. • Inspiratory crackles. • Significant hypoxemia. • Airflow obstruction that does not reverse with bronchodilators.99
Blood tests: • No blood tests are available that assess the presence or absence of asthma or gauge its severity. However, a complete blood count (CBC) with differential white blood cell analysis to screen for eosinophilia or significant anemia may be helpful in certain cases.100
• An elevated eosinophil percentage by automated cell sorter is best confirmed by manual differential (to exclude erroneous classification of neutrophils as eosinophils). Markedly elevated eosinophil percentages (>15 percent) should prompt consideration of alternative diagnoses, including parasitic infections (eg, Strongyloides), drug reactions, and syndromes of pulmonary infiltrates with eosinophilia.
• Significant anemia can cause dyspnea that is unresponsive to asthma therapies and would require further evaluation to determine the causative process. • A one-time measurement of the serum alpha-1 antitrypsin level is recommended in the lifelong non-smoker with persistent and irreversible airflow obstruction, to exclude emphysema due to alpha-1 antitrypsin deficiency.102