Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a non-reversible, long term deterioration in air flow through the lungs caused by damage to lung tissue. This lung damage is almost always the result of smoking. The damage to the lung tissues causes an obstruction to the flow of air through the airways making it more difficult to ventilate the lungs and making them prone to developing infections.

Unlike asthma, this obstruction is not significantly reversible with bronchodilators such as salbutamol. Patients are susceptible to exacerbations during which there is worsening of their lung function. Exacerbations are often triggered by infections and these are called infective exacerbations.

 

Presentation

Suspect COPD in a long term smoker presenting with chronic shortness of breath, cough, sputum production, wheeze and recurrent respiratory infections, particularly in winter.

Always consider differential diagnoses such as lung cancer, fibrosis or heart failure. COPD does NOT cause clubbing. It is unusual for it to cause haemoptysis (coughing up blood) or chest pain. These symptoms should be investigated for a different cause.

 

MRC (Medical Research Council) Dyspnoea Scale

This is a 5 point scale that NICE recommend for assessing the impact of their breathlessness:

Grades:

  • Grade 1 – Breathless on strenuous exercise
  • Grade 2 – Breathless on walking up hill
  • Grade 3 – Breathless that slows walking on the flat
  • Grade 4 – Stop to catch their breath after walking 100 meters on the flat
  • Grade 5 – Unable to leave the house due to breathlessness

 

Diagnosis

Diagnosis is based on clinical presentation plus spirometry.

Spirometry will show an “obstructive picture”. This means that the overall lung capacity is not as bad as their ability to quickly blow air out of their lungs. The overall lung capacity is measured by forced vital capacity (FVC) and their ability to quickly blow air out is measured by the forced expiratory volume in 1 second (FEV1). Being able to blow air out is limited by the damage to their airways causing airway obstruction. Therefore in COPD:

  • FEV1/FVC ratio <0.7

The obstructive picture does not show a dramatic response to reversibility testing with beta-2 agonists such as salbutamol during spirometry testing. If there is a large response to reversibility testing them consider asthma as an alternative diagnosis.

 

Severity

The severity of the airflow obstruction can be graded using the FEV1:

  • Stage 1: FEV1 >80% of predicted
  • Stage 2: FEV1 50-79% of predicted
  • Stage 3: FEV1 30-49% of predicted
  • Stage 4: FEV1 <30% of predicted

 

Other Investigations

There are a number of other investigations that can be considered to help with diagnosis and management and to exclude other conditions:

  • Chest xray to exclude other pathology such as lung cancer.
  • Full blood count for polycythaemia or anaemia. Polycythaemia (raised haemoglobin) is a response to chronic hypoxia.
  • Body mass index (BMI) as a baseline to later assess weight loss (e.g. cancer or severe COPD) or weight gain (e.g. steroids).
  • Sputum culture to assess for chronic infections such as pseudomonas.
  • ECG and echocardiogram to assess heart function.
  • CT thorax for alternative diagnoses such as fibrosis, cancer or bronchiectasis.
  • Serum alpha-1 antitrypsin to look for alpha-1 antitrypsin deficiency. Deficiency leads to early onset and more severe disease.
  • Transfer factor for carbon monoxide (TLCO) is decreased in COPD. It can give an indication about the severity of the disease and may be increased in other conditions such as asthma.

 

Long Term Management

It is essential for people to stop smoking. Continuing to smoke will progressively worsen their lung function and prognosis. They can be referred to smoking cessation services for support to stop.

Patients should have the pneumococcal and annual flu vaccine.

STEP 1:

Short acting bronchodilators: beta-2 agonists (salbutamol or terbutaline) or short acting antimuscarinics (ipratropium bromide).

STEP 2:

If they do not have asthmatic or steroid responsive features they should have a combined long acting beta agonist (LABA) plus a long acting muscarinic antagonist (LAMA). “Anoro Ellipta”, “Ultibro Breezhaler” and “DuaKlir Genuair” are examples of combination inhalers.

If they have asthmatic or steroid responsive features they should have a combined long acting beta agonist (LABA) plus an inhaled corticosteroid (ICS). “Fostair“, “Symbicort” and “Seretide” are examples of combination inhalers. If these don’t work then they can step up to a combination of a LABA, LAMA and ICS. “Trimbo” and “Trelegy Ellipta” are examples of LABA, LAMA and ICS combination inhalers.

In more severe cases additional options are:

  • Nebulisers (salbutamol and/or ipratropium)
  • Oral theophylline
  • Oral mucolytic therapy to break down sputum (e.g. carbocisteine)
  • Long term prophylactic antibiotics (e.g. azithromycin)
  • Long term oxygen therapy at home

Long term oxygen therapy is used for severe COPD that is causing problems such as chronic hypoxia, polycythaemia, cyanosis or heart failure secondary to pulmonary hypertension (cor pulmonale). It can’t be used if they smoke as oxygen plus cigarettes is a significant fire hazard.

 

Exacerbation of COPD

An exacerbation of COPD presents as acute worsening of symptoms such as cough, shortness of breath, sputum production and wheeze. It is usually triggered by a viral or bacterial infection.

Arterial blood gas:

Remember that CO2 makes blood acidotic by breaking down into carbonic acid (H2CO3). Low pH (acidosis) with a raised pCO2 suggests they are acutely retaining (not able to get rid of) more CO2 and their blood has become acidotic. This is a respiratory acidosis.

Raised bicarbonate indicates they chronically retain CO2 and their kidneys have responded by producing more bicarbonate to balance the acidic CO2 and maintain a normal pH. In an acute exacerbation, the kidneys can’t keep up with the rising level of CO2 so they become acidotic despite having a higher bicarbonate than someone without COPD.

It is important to distinguish the type of respiratory failure:

  • Low pO2 indicates hypoxia and respiratory failure
  • Normal pCO2 with low pO2 indicates type 1 respiratory failure (only one is affected)
  • Raised pCO2 with low pO2 indicates type 2 respiratory failure (two are affected)

Other investigations:

  • Chest xray to look for pneumonia or other pathology
  • ECG to look for arrhythmia or evidence of heart strain (heart failure)
  • FBC to look for infection (raised white cells)
  • U&E to check electrolytes which can be affected by infection and medications
  • Sputum culture if significant infection is present
  • Blood cultures if septic

 

Oxygen therapy in COPD

Too much oxygen in someone that is prone to retaining CO2 can depress their respiratory drive. This slows down their breathing rate and effort and leads to them retaining more CO2. Therefore in someone who retains CO2 the amount of oxygen that is given needs to be carefully balanced to optimise their pO2 whilst not increasing their pCO2. This is guided by oxygen saturations and repeat ABGs.

Venturi masks are designed to deliver a specific percentage concentration of oxygen. They allow some of the oxygen to leak out of the side of the mask and normal air to be inhaled along with oxygen. This means the percentage of inhaled oxygen can be carefully controlled to balance how much oxygen they get. Environmental air contains 21% oxygen. Venturi masks deliver 24% (blue), 28% (white), 31% (orange), 35% (yellow), 40% (red) and 60% (green) oxygen.

A general rule regarding target oxygen saturations in COPD is:

  • If retaining CO2 aim for oxygen saturations of 88-92% titrated by venturi mask
  • If not retaining CO2 and their bicarbonate is normal (meaning they do not normally retain CO2) then give oxygen to aim for oxygen saturations > 94%

 

Medical Treatment of an Exacerbation

Typical treatment if they are well enough to remain at home:

  • Prednisolone 30mg once daily for 7-14 days
  • Regular inhalers or home nebulisers
  • Antibiotics if there is evidence of infection

In hospital:

  • Nebulised bronchodilators (e.g. salbutamol 5mg/4h and ipratropium 500mcg/6h)
  • Steroids (e.g. 200mg hydrocortisone or 30-40mg oral prednisolone)
  • Antibiotics if evidence of infection
  • Physiotherapy can help clear sputum

Options in severe cases not responding to first line treatment:

  • IV aminophylline
  • Non-invasive ventilation (NIV)
  • Intubation and ventilation with admission to intensive care
  • Doxapram can be used as a respiratory stimulant where NIV or intubation is not appropriate

 

Last updated March 2019
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