asthma
ASTHMA
Asthma is a chronic inflammatory disease of the airways in the lungs of children and adults.
The patient usually complains of shortness of breath, chest tightness and coughing with wheezing.
Goals of treatment are effective symptom control with minimal or no exacerbations, minimal or no nocturnal and daytime symptoms, no limitations on activities, minimal or no need for reliever treatment, and minimal adverse effects of medication.

History

  • Personal or family history of other atopic conditions (allergic rhinitis, eczema)
  • Worsening of symptoms after exposure to common triggers (eg pollen, dust, exercise, viral infections, tobacco smoke, Aspirin or NSAID, weather changes)
    • Bronchoconstriction induced by exercise usually occurs 5-10 minutes after completing the exercise
  • Symptoms improved by appropriate antiasthmatic treatment
  • Asthma control may be assessed using different validated measures such as asthma control test (ACT), childhood asthma control test (C-Act), asthma control questionnaire (ACQ), asthma therapy assessment questionnaire (ATAQ), or asthma control scoring system
    • May improve assessment of asthma control, provide reproducible objective measures, & allow better communication between physician & patients
    • ACT is a self-administered instrument that considers frequency of patient’s activity limitations, shortness of breath & night-time symptoms, use of rescue medication & rating of overall control of the disease within the past 4 weeks
    • Sum of the factors considered will determine the level of patient’s asthma control & the management appropriate for the patient

Physical Examination

  • Because asthma symptoms are variable, physical exam may be normal
  • If patient is examined during symptomatic period, they may present with dyspnea, hyperinflation, & expiratory wheezing
    • Wheezing may be absent especially with severe attacks
  • Chronic asthma sufferers may have signs of hyperinflation with or without wheeze
  • Allergic rhinitis or nasal polyposis may also be seen during examination of the nose

Screening

Measurements of Lung Function

  • Assesses severity of airflow limitation, reversibility, & variability, & establishes the diagnosis of asthma
    • Excessive variability & documented low forced expiratory volume in 1 second (FEV1) confirms the diagnosis
  • FEV1 & peak expiratory flow (PEF) are decreased in obstructive airway diseases
  • Spirometry & PEF measurements may be used to evaluate airflow limitation in patients ≥5 years old
  • Predicted values of FEV1, forced vital capacity (FVC) & PEF based on age, gender & height may be used to base a judgment whether a value is normal or not 
    • Consider ethnic characteristics & extremes in age

Spirometry

  • Recommended technique in determining airway limitation & reversibility, & confirming asthma
  • FEV1 & FVC are measured using a spirometer
    • A more reliable equipment for FEV1 measurement as compared to PEF meters
  • Other lung diseases can result in reduced FEV1, better assessment of airflow limitation is by the ratio of FEV1 to FVC
    • In the normal lung, FEV1/FVC ratios are >75-80% & in children >90%
    • Values less than this are suggestive of airflow limitation
  • ≥12% improvement in FEV1 whether spontaneously, after inhalation of bronchodilator or after a trial of corticosteroid suggests a diagnosis of asthma
  • Spirometry may also be used in the clinic to monitor the activity of asthma & is particularly helpful in assessing progress in patients with greatly compromised lung function

PEF

  • PEF meters are important in the aid of diagnosis & the ensuing treatment of asthma
  • ≥20% improvement in PEF after inhalation of a bronchodilator suggests a diagnosis of asthma
  • PEF measurements do not always correspond with other measurements of lung function in asthma
  • PEF measurements should ideally be compared to the patient’s own previous best measurements
    • PEF measurements in children can be normal as airflow obstruction & gas trappings worsen & therefore, PEF can underestimate the degree of airflow obstruction
  • Regular PEF measurements throughout the day or over week-month can aid in the assessment of asthma severity & response to treatment
    • Severity of asthma is also reflected in its variability especially across 24 hours
  • Ideally, PEF should be measured 1st thing in the morning (when values are usually close to their lowest) & 12 hours apart in the evening (when values are usually at their highest)

Diurnal PEF

  • Diurnal PEF variability is taken as the amplitude (difference between pre-bronchodilator morning value & post-bronchodilator value from the evening before) expressed as a percentage of the mean daily PEF value
  • Another method is minimum morning pre-bronchodilator over 1 week expressed as percent of the recent best (Min%Max)
    • This method has been suggested to be the best PEF index of airway liability since it requires only once-a-day reading & correlates better than any other index with airway hyperresponsiveness
  • An average daily diurnal variation in PEF >10% in adults & >13% in children is indicative of asthma
    • Note: In mild intermittent asthma or severe retractable disease variability, PEF may not be present & only a trial of corticosteroids will show diurnal variation & reversibility

Bronchodilator (BD) Reversibility Test

  • >12 % increase in FEV1 & >200 mL from baseline, 10-15 minutes after 200-400 mcg Albuterol or its equivalent in adults, or >12% increase in FEV1 in children, confirms the diagnosis of asthma
  • Withholding administration of bronchodilators (>4 for short-acting beta2-agonists, >15 for long-acting beta2-agonists) prior to test increases this test’s effectivity

 

Other Tests

Exercise Challenge Test

  • A decrease in FEV1 by >10% & >200 mL from baseline in adults, & >12% predicted FEV1 or PEF >15% in children

Bronchial Provocation Testing

  • An alternative test to assess airway hyperresponsiveness
  • A decrease from FEV1 baseline of >20% with standard doses of methacholine or histamine, or >15% with standardized hyperventilation, hypertonic saline, or Mannitol challenge
    • Positive test with methacholine, histamine or Mannitol can occur in patients with allergic rhinitis, bronchiectasis, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF)

Allergy Tests

  • Atopy, which is the most likely cause of respiratory symptoms in allergy-induced asthmatic patients, may be tested by skin prick testing or by measurement of specific immunoglobulin E (IgE) in serum
    • sIgE measurement may be preferred for patients who are uncooperative, with widespread skin disease, or if history suggests an anaphylaxis risk

Fractional Concentration of Exhaled Nitric Oxide (FENO) Measurement

  • Increased in eosinophilic conditions (eg eosinophilic asthma, eosinophilic bronchitis, atopy, allergic rhinitis)
  • Further studies are needed to prove use in the diagnosis of asthma
    • Levels are elevated in non-asthma conditions (allergic rhinitis, atopic dermatitis, eosinophilic bronchitis); lower in smokers, during bronchoconstriction, & early-onset allergic reactions

Presence of Infrequent Symptoms

  • The above tests may fail to support asthma diagnosis
  • Surveillance & periodic re-evaluation should be maintained until the diagnostic situation is clearer
  • Consider patient’s family history, age & asthma triggers before deciding on diagnostic & therapeutic course of action
  • If in doubt, trial of treatment with short-acting beta2-agonists as needed & inhaled corticosteroids assists in establishing the diagnosis of asthma especially if combined with PEF monitoring

Assessment

  • Asthma attacks are events characterized by increased dyspnea, cough, wheezing, or chest tightness
    • Described as having a reduction in expiratory airflow that is measured & monitored by lung function
  • Goal of management is to immediately relieve airflow obstruction & hypoxemia, & to prevent further deterioration

Home Management Assessment

Mild-Moderate Exacerbations:

  • Adults & children >5 years old: Talks in phrases, prefers to sit, calm, RR increased, 100-120 bpm pulse rate, 90-95% O2 saturation, PEF >50% personal best
  • Children <5 years old: Breathless, agitated, ≤200 bpm (0-3 yr)/≤180 bpm (4-5 yr) pulse rate, ≥92% O2 saturation

Indications for Immediate Hospital Transfer (Severe Exacerbations)

  • Adults & children >5 years old: RR >30/min, >120 bpm pulse rate, <90% O2 saturation, PEF ≤50% predicted/best, accessory muscles in use, talks in words, hunched forward while sitting, agitated
  • Children <5 years old: (any of the following) cyanosis, <92% O2 saturation, chest silent on auscultation, not able to speak, subcostal retractions present, >200 bpm (0-3 years old)/>180 bpm (4-5 years old) pulse rate, >6 puffs of inhaled bronchodilator is needed within the first 2 hours to achieve symptom relief, confusion/drowsiness, persistent tachypnea even after 3 doses of short-acting beta2-agonist (inhaled), unresponsive to 6 puffs of short-acting beta2-agonist (inhaled) over 1-2 hours

Emergency Department Assessment

  • Brief history & physical exam should be conducted while therapy is initiated

History

  • Symptom severity
  • Time of onset & cause
  • Risks for possible asthma-related death, which necessitates closer medical supervision
    • History of asthma attack that needed intubation & mechanical ventilation
    • Hospitalized or emergency visit in the past year
    • Using oral/inhaled corticosteroid currently or recently stopped
    • Using >1 canister of inhaled rapid-acting beta2-agonists monthly
    • With psychiatric or psychosocial problem
    • Noncompliant to management plan

Physical Exam

  • Assess severity of exacerbation
  • Mild-Moderate Exacerbations:
    • Adults & children >5 years old: Prefers sitting, talks in phrases, no accessory muscles used, not agitated, RR increased, 100-120 bpm pulse rate, 100-120 bpm pulse rate, 90-95% O2 saturation, PEF >50% predicted or best
    • Children <5 years old: conscious, >95% O2 saturation, speaks in sentences, <100 bpm pulse rate, cyanosis absent
  • Severe Exacerbations:
    • Adults & children >5 years old: RR >30/min, >120 bpm pulse rate, <90% Osaturation, PEF ≤50% predicted/best, accessory muscles in use, talks in words, hunched forward while sitting, agitated
    • Children <5 years old: cyanotic, agitated, confused/drowsy, <92% O2 saturation, speaks in words, >200 bpm (0-3 year)/>180 bpm (4-5 year) pulse rate, silent chest upon auscultation
  • Examine for other factors that may complicate the condition (eg pneumonia, pneumothorax, atelectasis)

Functional Assessments

  • PEF or FEV1
    • If possible, obtain baseline prior to treatment w/o unduly delaying therapy, & until improvement is observed
  • O2 saturation
    • Preferably obtained by pulse oximetry
    • Helpful in childn where lung function measurement is not reliable

Chest X-ray

  • Requested only if there are suspected complicating factors, patient is for admission & not responding to treatment

Arterial Blood Gas

  • Recommended in patients w/ PEF of 30-50% predicted, unresponsive to treatment, & signs of deterioration
    • Respiratory failure is indicated if results show PaO2 <60 mmHg & normal or increased PaCO2 (>45 mmHg)
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