Mrs Simpson is a 74 year old lady who is concerned that over the last few months her legs appear more swollen, especially towards the end of the day. She has also noticed feeling short of breath whilst doing housework over this time. She sleeps on two pillows, which is normal for her. Past medical history includes Pulmonary fibrosis, Hypertension, raised cholesterol, Migraine and Cataracts.

Examination reveals pitting oedema to her mid-shins and bibasal lung crackles. Heart sounds are normal.

Heart rate 80 bpm

Blood pressure 145/90 mmHg

Respiratory rate 14 breaths per minute

Oxygen saturations 97% on air

What is the next most appropriate action to further investigate her symptoms?