Acute pulmonary oedema

Question 1

Describe the typical history of pulmonary oedema

Give symptoms for acute pulmonary oedema as well

Answer 1

• Dysponea (SOB)
• Paraxysmal noctural dysponea
• Orthopnea (SOB when lying down): due to increased venous return on lying down, and can be measured objectively by number of pillows required to sleep
• Cough: producing frothy, blood stained sputum

Acute presentation:

• Severe dyspnoea
• Productive cough
• Anxiety and perspiration
• Cheyne-Stokes respiration in LVF: cycling apnoea/hyperventilation due to impaired response of respiratory centre to CO₂

Question 2

Describe the pathophysiolgy of pulmonary oedema

(not an objective)

Answer 2

• Pulmonary oedea is due to an increase in fluid in the alveolar wall (pulmonary interstitium), which then affects the interstitial spaces
• The most common cause is left ventricular failure, which causes increased pressure in the alveolar capillaries and leakage of fluid into the interstitium
• This leads to subjective dyspnoea, but can remain stable for some time
• Severe LVF causes leakage of fluid from the interstitium into the alveolar spaces, leading to a severe acute impairment of respiratory function
• Capillary rupture can lead to leakage of red cells also, which are up taken by macrophages and broken down: macrophages containing iron pigment in the alveoli/interstitium are thus termed ‘heart failure cells’

Question 3

What are the clinical feature on examination of pulmonary oedema?

Answer 3

• Tachypnoea
• Tachycardia, with gallop rhythm
• Raised venous pressure
• Peripheral shutdown
• Widespread crackles/wheezes on auscultation

Question 4

What are the common causes of pulmonary oedema?

Answer 4

• Increased capillary pressure:
  
  • Cardiogenic: LVF, valve disease, arrhythmias, ventricular septal defect, cardiomyopathy, negatively inotropic drugs
  • Pulmonary venous obstruction
  • Iatrogenic fluid overload
• Increased capillary permeability
  
  • Acute respiratory distress syndrome (ARDS)
  • Infection: pneumonia/sepsis
  • Disseminated intravascular coagulation
  • Inhaled toxins
• Reduced plasma oncotic failure
  
  • Renal/liver failure: hypoalbuminaemia
• Lympathic obstruction:
  
  • Tumour/parasitic infection
• Others:
  
  • Neurogenic: raised ICP/head injury
  • PE
  • Altitude

Question 5

What are differiential diagnosis for pulmonary oedema?

Answer 5

• If no cardiac cause for pulmonary oedema is present, Acute respiratory distress syndrome should be suspected
• Chest infection may similarly produce a cough but is less likely to give pink frothy sputum and breathlessness
• Pulmonary embolism typically presents with pleuritic chest pain, cough and shortness of breath

Question 6

Outline the general principles of management of pulmonary oedema due to acute/decompensated heart failure

Answer 6

• Sit patient upright, administer 100% oxygen
• IV diamorphine 1.25-5mg
• IV furosemide 40mg-80mg
• GTN spray 2 puffs sublingual (unless systolic BP <90)
• Continue necessary investigations and history as above
• If SBP >100, start an IV infusion of nitrate
  
  • Consider non-invasive ventilation (e.g. CPAP) if not improving
• If SBP <100, treat as cardiogenic shock, alert ICU
  
  • May require invasive ventilation

Question 7

What investigations would you do in a patient with acute pulmonary oedema?

What would you expect to find?

Answer 7

• ABG:
  
  • Initial type 1 respiratory failure due to hyperventilation, with later type 2 respiratory failure due to impaired gas exchange
• Bloods:
  
  • FBC, U&E, glucose, D-dimer, CRP
• CXR:
  
  • diffuse haziness (‘bat wing oedema’) with Kerley B lines and upper zone vessel enlargement, cardiomegaly pleural effusions
• ECG:
  
  • tachycardia, arrhythmia, signs of a cardiac cause
• Echocardiography:
  
  • to demonstrate a cardiac cause, e.g. MI/valvular disease

Question 8

In a cardiac examination of a patient with pulmonary oedema what might you find?

Answer 8

• Tachycardia
• gallop rhythm
• bilateral basal crackles
• shortness of breath
• cough
• raised JVP
• peripheral oedema
• hepatomegaly may be present

Question 9

What clinical features of common heart murmers may underlie an episode of acute pulmonary oedema?

Answer 9

Valvular heart disease may lead to acute heart failure, and thus give pulmonary oedema.

Patients with hypertension may experience episodes of “flash” pulmonary oedema.

Question 10

What would you find on a CXR for a patient with pulmonary oedema?

Answer 10

• Hazy hila
• prominent vasculature (especially superiorly)
• fluid in the fissures
• Kerley B-lines.