chronic%20obstructive%20pulmonary%20disease
CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Chronic obstructive pulmonary disease (COPD) is an inflammatory respiratory disease characterized by reversible airflow limitation.

The patient usually have chronic cough, sputum production or dyspnea with or without history of risk factors for the disease.

The chronic airflow limitation is caused by a combination of small airways disease and parenchymal destruction.

It is a preventable & treatable disease.

Spirometry

  • Recommended measurement of airflow limitation that confirms the diagnosis of COPD
    • A useful tool in the assessment of the severity of the pathological changes in COPD
  • Also recommended for patients at risk of COPD, especially smokers >45 years old with cough, sputum or dyspnea & for regular follow-up of patients with documented COPD
  • Measures forced vital capacity (FVC) & forced expiratory volume in 1 second (FEV1)
    • A decreased FEV1/FVC ratio is typically seen in patients with COPD
    • A post-bronchodilator FEV1/FVC <70% confirms the presence of airflow limitation
  • Spirometry services should be supported by quality control processes
  • Lung volumes are affected by process of aging & FEV1/FVC ratio depends on age, height & sex
    • The use of fixed ratio may lead to underdiagnosis in patients <45 years especially of mild disease & overdiagnosis in patients >50 years
    • There’s a proposal that diagnosis of obstructive pulmonary disease should be based on an FEV1/FVC ratio below the lower limit of normal
  • If without access to spirometry, COPD diagnosis may be suspected based on history, symptoms & physical signs
    • Peak flow measurements may be used to rule out asthma, but not to diagnose COPD
      • Has good sensitivity rate but weak specificity
  • A forced expiratory time (FET) is the time for a patient to forcefully exhale through open mouth from total lung capacity until air flow is inaudible [≥6 seconds is abnormally prolonged & >6 seconds is an acceptable guide to presence of FEV1/FVC <50% (obstructive disease)]
  • Modified Medical Research Council (mMRC) Dyspnea Scale is useful for classification, which can be used to assist in the evaluation of disease severity & functional disability

Medical research council dyspnea scale*

Grade

Description

0

Only experience breathlessness with strenuous exercise

1

There’s shortness of breath when walking up a slight hill or hurrying on the level

2

Walks slower than people of the same age on the level because of breathlessness or has to stop to catch a breath when walking at own pace on the level

3

Stops to catch a breath after walking about 100 meters or after a few minutes on the level

4

Too breathless to leave the house or breathless when dressing or undressing

*Adapted from Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2017 report.

  • COPD Assessment Test (CAT) is a short questionnaire used in routine clinical practice to gauge the health status of COPD patients
    • Measures patients’ disease severity using 8 symptoms, with scores ranging from 0-40:
  • Frequency of cough
  • Chest tightness
  • Limitations with home activities
  • Presence of sleep disturbance
  • Degree of presence of phlegm
  • Breathlessness when climbing stairs/walking uphill
  • Confidence with outdoor activities even if with COPD
  • Level of energy

Laboratory Tests

Bronchodilator Reversibility Testing

  • Usually performed only once at the time of diagnosis
  • May help rule out asthma, establish best attainable lung function, evaluate prognosis & guide treatment decisions
  • However, it may not reliably predict response to long-term bronchodilator therapy

Chest X-ray

  • Useful mainly in ruling out alternative diagnoses
  • May show signs of lung hyperinflation (eg flattened diaphragm), lungs hyperlucency & rapid tapering of the vascular markings

Computed Tomography (CT)

  • Not routinely used but may help in excluding other possible diagnosis
  • Recommended if surgical management is being contemplated

Pulse Oximetry & Arterial Blood Gas (ABG) Measurement

  • Pulse oximetry should be performed in stable patients with FEV1 <35% predicted or with signs of respiratory failure or right heart failure
  • ABG should be assessed when the peripheral saturation is <92%; should be obtained by arterial puncture

Alpha-1 Antitrypsin Deficiency (AATD) Screening

  • Recommended procedure by the WHO for all patients diagnosed with COPD especially in AATD-prevalent areas
  • May be useful in young patients (<45 years) who develop COPD
  • Positive results may lead to family screening & counseling
  • Alpha-1 antitrypsin serum concentration of <15-20% of the normal value is highly suggestive of homozygous AATD

COPD Exacerbation

Definition of COPD Exacerbation

  • An acute event wherein the patient’s symptoms worsen beyond normal daily variations that leads to change in medication
  • Viral & bacterial respiratory tract infections are the common causes
    • Exacerbations caused by bacterial etiology in 50% of patients
  • Other causes: air pollution, interruption of maintenance medications, other comorbidities (GERD)

Signs & Symptoms of COPD Exacerbation

  • Increased breathlessness, wheezing, chest tightness
  • Increased cough & sputum, change in color &/or tenacity of sputum
  • Fever, malaise, fatigue, depression, confusion, sleep disturbances, decreased exercise tolerance
  • Respiratory rate >25 breaths/minute, heart rate >110/minute, use of accessory muscles for breathing &/or dyspnea at rest may indicate severe acute exacerbation

Assessment

Severity of COPD is classified based on patient’s symptoms, spirometry results, presence of complications & future risk of exacerbations

Classification of airflow limitation1*

Stage

Characteristics

I: Mild COPD

  • FEV1 ≥80% predicted

II: Moderate COPD

  • 50% ≤ FEV1 <80% predicted

III: Severe COPD

  • 30% ≤ FEV1 <50% predicted

IV: Very Severe COPD

  • FEV1 <30% predicted
1Classification is based on post-bronchodilator FEV1 in patients with FEV1/FVC <0.7
The use of fixed ratio may lead to underdiagnosis in patients <45 years especially of mild disease & overdiagnosis in patients >50 years

SYMPTOM/RISK EVALUATION OF COPD*

Patient Category

Airflow Limitation Classification

Characteristics

A

I-II

  • mMRC 0-1
  • Low risk, less symptoms
  • CAT (COPD Assessment Test) <10
  • ≤1 exacerbations/year (without hospitalization)

B

I-II

  • mMRC ≥2
  • Low risk, more symptoms
  • CAT ≥10
  • ≤1 exacerbations/year (without hospitalization)

C

III-IV

  • mMRC 0-1
  • High risk, less symptoms
  • CAT <10
  • ≥2 exacerbations/year (with hospitalization)

D

III-IV

  • mMRC ≥2
  • High risk, more symptoms
  • CAT ≥10
  • ≥2 exacerbations/year (with hospitalization)
*Adapted from Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2017 report.


The following are used to assess the severity of a COPD exacerbation:
  • History, symptoms
  • Physical exam
  • Lab tests

Lab Tests

ABG Measurement

  • PaO2 <60 mmHg &/or SaO2 <90% with or without PaCO2 >50 mmHg on room air are indicative of respiratory failure
  • If there are no facilities to measure blood gases, SaO2 should be measured

Chest X-ray

  • Helpful in patients with suspected pneumonia
  • May be useful in identifying alternative diagnoses that can mimic symptoms of exacerbation

Electrocardiogram (ECG)

  • Helpful in diagnosing right ventricular hypertrophy, arrhythmias & ischemic episodes
  • Aids in the diagnosis of pulmonary embolism from COPD exacerbation, as right ventricular hypertrophy & large pulmonary arteries may lead to confusing radiographic & ECG findings

Complete Blood Count (CBC)

  • May show polycythemia (hematocrit >55%) or bleeding
  • White blood cells (WBC) may be elevated in patients with respiratory infection

Biochemical Tests

  • May be helpful in determining the cause of exacerbation & in diagnosing other comorbid conditions (eg electrolyte imbalances, diabetic crisis, poor nutrition, acid-base disorders)

Sputum Culture

  • Presence of purulent sputum during an exacerbation is sufficient basis for starting antibiotics
  • Culture & sensitivity testing of sputum must be done if the patient does not respond to initial antibiotic therapy
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