cardiogenic pulmonary odema

Question 1

treatment

Answer 1

Acquire a 12 lead ECG.
* Administer 0.8 mg of GTN SL provided that:
a) The systolic BP is greater than 100 mmHg, and
b) The heart rate is greater than 40/minute and less than 150/minute.
* Continue to administer 0.8 mg GTN SL every 3-5 minutes as above if the patient is not improving.
* Apply a TTS 10 GTN patch or commence a GTN infusion IV if the patient is not rapidly improving, using the systolic BP and heart rate contraindications above.
Apply CPAP at 10 cmH2O if the patient has:
a) Severe respiratory distress despite treatment, or
b) An SpO2 less than 92% despite treatment.
* Note that a lower SpO2 threshold of less than 88% should be used if the patient also has COPD.
* Use CPAP with caution if the patient has an altered level of consciousness, vomiting or signs of shock.

Question 2

Cardiogenic pulmonary oedema is most commonly caused by

Answer 2

myocardial ischaemia involving the left ventricle.

Question 3

Cardiogenic pulmonary oedema is the likely diagnosis when

Answer 3

has been supine (for example in bed) and the wheeze is worse bilaterally in the lower zones. The patient is often hypertensive, clammy and peripherally vasoconstricted.

Question 4

The physiological effects of CPAP

Answer 4

Fluid within the airways causes areas of lung to collapse and this causes shunting of blood because these areas have blood supply but do not contribute to gas exchange. CPAP reduces shunting because the inspiratory pressure assists areas of the lung that have collapsed to expand (also called recruitment).ū Wet lungs become stiff and this increases the workload of breathing. CPAP reduces this workload because the inspiratory pressure assists inspiration.
ū The expiratory pressure assists small and medium sized airways to remain open during expiration, preventing lung collapse by splinting the airways open. Preventing areas of lung from collapsing is important because once
collapsed, significant additional pressures are required to re-expand them.
ū The positive pressure in the thoracic cavity reduces the preload (filling)
of the right ventricle by reducing venous return to the heart (this will be
further compounded by administration of GTN).
ū The positive pressure in the thoracic cavity increases the afterload of the
right ventricle and reduces venous return to the heart. This reduces blood
flow through lung vessels, reducing the amount of fluid entering the lungs.
ū The expiratory pressure increases the amount of air remaining in the lungs
at the end of expiration (also called the functional residual capacity) and this causes the lungs to be more expanded. From this more expanded resting position, less work is required to inspire as a result of the non-linear compliance of the lungs, particularly when the lungs are wet.