Chronic Obstructive Pulmonary Disease

COPD is a chronic, progressive inflammatory disease characterised by persistent respiratory symptoms with incompletely reversible airflow limitation. COPD:

Epidemiology and Risk Factors

Common comorbidity:

  • 10% of >40s worldwide
  • 4th most common cause of death
  • Associated with:
    • CAD
    • Malignancy
    • Depression

Risk factors:

  • Environmental exposures:
    • Smoking
      • Cigarettes
      • Pipes/cigars
      • Water pipe
      • Marijuana
        Greater ↑ in bullous emphysema due to holding hot inhaled smoke.
    • Occupational exposures
      • Dusts
      • Chemical agents
      • Fumes
    • Indoor air pollution
      • Cooking fuels
    • Outdoor air pollution
      Relatively small effect.
  • Genetic factors:
    • FAM13A associated with development

Degree of decline in FEV1 with age varies with the duration of smoking, timing of quitting smoking, and susceptibility to COPD.

Pathophysiology

Expiratory airflow limitation via:

  • ↑ Airway resistance:
    • Obstructive bronchiolitis
      Small airway inflammation leads to gas trapping and dynamic hyperinflation.
    • ↑ Secretion production
    • Bronchospasm
    • Parenchymal destruction
      Leading to emphysema, which reduces:
      • Pulmonary capillary bed volume
      • Lung surface area for gas exchange
      • V/Q matching
  • Loss of elastic recoil
    Combination of elastin destruction and fall in alveolar surface tension.
    • ↓ Expiratory air flow

Air flow limitation leads to:

  • Prolonged expiration
  • Pulmonary hyperinflation
  • ↑ work of breathing
  • Dyspnoea

Aetiology

Assessment

Key symptoms are:

  • Chronic cough or sputum production
  • History of exposures
  • Dyspnoea
    Graded using the mMRC scale.
Modified Medical Research Council (mMRC) Scale
MRC Grade Breathlessness
Grade 0 Only with strenuous exercise
Grade 1 Hurrying or a slight incline
Grade 2 Slower than people of same age; stopping due to shortness of breath on flat ground
Grade 3 After ~100m or a few minutes on flat ground
Grade 4 Too breathless to leave the house; breathless when dressing/undressing

GOLD Criteria

Global Initiative for Obstructive Lung Disease Criteria:

  • Used clinically to determine severity of disease in order to prognosticate and guide therapeutic interventions
  • Not appropriate for diagnosis
  • Are based upon:
    • Symptom burden
      mMRC score.
    • Number of exacerbations and hospital admissions
    • FEV1

Treatment recommendations:

  • GOLD A
    Bronchodilator (LABA or SABA) offered, and continued if effective.
  • GOLD B
    LABA or long-acting methacholine antagonist should be offered as initial therapy.
  • GOLD C
    LAMA as initial therapy, and benefit may be seen with LAMA & LABA & inhaled corticosteroids.
  • GOLD D
    LAMA & LABA as initial therapy, with inhaled corticosteroids for patients with frequent exacerbations.

Diagnostic Approach and DDx

Diagnosis should be considered in:

  • Smokers
  • Age >35
  • Exertional breathlessness
  • Chronic cough
  • Frequent winter bronchitis or wheeze

Differentials include:

  • Chronic asthma
    Long-term dyspnoea from childhood, with obvious precipitants. Normal TLCO with reversibility.
  • Late-onset asthma
    Associated with GORD. Normal TLCO with reversibility.
  • Broncholitis obliterans

Investigations

Laboratory:

  • Bloods
    • α-1 antitrypsin
      All patients should be screened once for α1 antitrypsin deficiency. ⩽20% is suggestive of homozygous deficiency.
    • ABG/VBG
      Evaluate degree of chronic hypercapnoea and metabolic compensation.

Imaging:

  • CXR
    Hyperinflation if >=10 posterior ribs visible.

Other:

  • Respiratory Function Tests
    • Diagnostic
    • Used to grade severity:
      • FEV1FVC/ of ⩽0.7
        • Reversibility is not required
          Differentiated from asthma on clinical grounds.
      • Severity graded by FEV1
        Multiple grading systems, the GOLD 2008/NICE 2010 system:
        • FEV1 ⩾80% predicted
          Mild.
        • FEV1 50-79% predicted
          Moderate.
        • FEV1 30-49% predicted
          Severe.
        • FEV1 ⩽30% predicted
          Very severe.

Management

Specific therapy:

  • Pharmacological:
    • Inhaled therapies
      Mainstay of day-to-day treatment. Includes: * Short-acting bronchodilators
      For breathlessness and exercise limitation. * Long-acting bronchodilators
      For persistent breathlessness.
      • Oral therapy
        Regular oral corticosteroids may be requried in advanced disease.
      • Vaccination
        Influenza and pneumococcal vaccines ↓ LRTI rate.
  • Procedural
    • Lung volume reduction surgery
      Improves survival in severe upper-lobe emphysema and low post-rehabilitation exercise capacity.
    • Bullectomy
      Improves dyspnoea, lung function, and exercise tolerance is selected patients.
    • Lung transplantation
      Improves quality of life in selected patients with very severe COAD.
    • Bronchoscopic interventions
      Includes coils and endobronchial valves, and improves exercise tolerance and lung function at 6-12 months following treatment.
  • Physical
    • Smoking cessation
      Vital, and will slow down deterioration and disability before death occurs.
    • NIV
      Reduces chronic hypercarbia, survival, and readmission rates.
    • Home oxygen
      Indicated in patients with severe resting hypoxia (PaO2 <60mmHg, or ⩽55mmHg with cor pulmonale or pulmonary hypertension).

Acute Exacerbation of COPD

Acute change in degree of dyspnoea, cough, or sputum production. Acute exacerbations are:

  • The most common admission diagnosis in the UK (~16%)
  • Usually survivable in the short term but a poor prognostic sign for survival in the medium-long term
    Up to 90% hospital survival, but significantly impaired 2-3 year survival.

Common precipitants:

  • Infection
    • Most commonly bacterial:
      80% caused by:
      • S. Pneumoniae
      • H. Influenze
    • Viral isolated in 20-30%:
      • Rhinovirus
      • Influenze
      • Parainfluenzae
  • Sputum retention
  • Cardiac failure
  • Other respiratory disease
    • Pneumothorax
  • Uncontrolled oxygen therapy
    Relative hyperoxia (>92%) may adversely affect V/Q matching, reduce hypoxic drive, and ↑ CO2 dissociation via the Haldane effect.

Specific therapy:

  • Physical
    • Oxygen
      Target SpO2 88-92%.
    • HFNO
    • NIV
      Preferred over invasive ventilation, and indicated when:
      • Uncompensated respiratory acidosis
      • Severe dyspnoea with signs of fatigue
      • Persistent hypoxaemia despite supplemental oxygen
    • Chest physio
      • Encourage coughing
      • Bubble PEEP
    • Invasive ventilation
      Reasonable in patients without end-stage lung disease - 80-90% wean successfully. Avoid breath stacking.
      • Suggested initial settings to avoid breath stacking
        • PEEP 3-8cmH2O
        • Psup 8-15cmH2O
        • RR <14
          Aim MV <115mL/kg.
      • Minimise dynamic hyperinflation by:
        • Watching the flow-volume loop
        • Measuring end-inspiratory pause
          Target <25cmH2O. flow-volume loop to minimise dynamic hyperinflation
  • Pharmacological:
    • Bronchodilators
      Many patients have a small response, and this assists in sputum clearance.
      • Ipratropium 500ug Q2H
        Anticholinergic agents have a greater effect compared to beta-agonists.
      • Salbutamol 5mg Q2H
    • Steroids
      Prednisolone 0.5mg/kg (or equivalent) for 5 days.
    • Antibiotics
      Amoxycillin usually first line for S. pneumoniae and H. influenzae cover.
    • Electrolyte correction
    • DVT prophylaxis

Anaesthetic Considerations

  • B
    • Smoking cessation
      Patients are more receptive to smoking cessation perioperatively, and this should be encouraged.
    • Disease severity
      • Exercise tolerance
      • Number of exacerbations
      • Most recent course of antibiotics or steroids
      • Previous requirement for NIV or intubation
    • Wheezing
      If present needs aggressive treatment with bronchodilators +/- steroids.
    • Active respiratory infection
      Consider treatment and postponing surgery.
    • Consider CXR if:
      • Current infection
      • Recent deterioration in symptoms
    • Ventilator settings
      Aim to minimise gas trapping:
      • ↑ the I:E ratio to prolong expiratory time
        Suggest 1:3-1:5.
        • May require ↑ inspiratory flow rate and higher Pip
      • Consider PEEP
        Aim to splint open small airways, and if ePEEP < iPEEP then worsening of CV effects will not occur.
      • Bronchospasm
  • C
    • Pulmonary hypertension
    • Concomitant IHD
  • D
    • General anaesthesia
      ↑ Risk, particularly with intubation and IPPV, of:
      • Laryngospasm
      • Bronchospasm
      • Barotrauma
      • Hypoxaemia
      • Cardiovascular instability
    • Regional anaesthesia
  • E
    • Neuromuscular blockade
      • Ensure complete reversal prior to extubation
      • Consider extubation directly onto NIV
        Reduces need for post-operative reintubation.

Marginal and Ineffective Therapies

Complications

  • Death:
    • 8% in-hospital mortality
    • 15% 90-day mortality
    • Up to 50% 1-year mortality
  • B
    • Recurrent infection
      ↑ With Pseudomonas colonisation

Prognosis

  • Lung cancer is frequently seen and is the major cause of death

Key Studies

References

  1. Lumb A, Biercamp C. Chronic obstructive pulmonary disease and anaesthesia. Contin Educ Anaesth Crit Care Pain. 2014 Feb 1;14(1):1–5.
  2. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.