11th January 2024

A 76-year-old gentleman with severe COPD is on the respiratory ward being treated for a secondary spontaneous pneumothorax for the last 12 hours.

A 76-year-old gentleman with severe COPD is on the respiratory ward being treated for a secondary spontaneous pneumothorax for the last 12 hours. His chest drain remains in situ and is swinging and bubbling appropriately. A repeat chest x-ray 12 hours after insertion revealed an ongoing pneumothorax, so a decision to commence low-grade suction at the respiratory specialist made 10cmH20. An hour later, you are requested to review the patient as he has become significantly short of breath again and looks clinically unwell. 

His observations are respiratory rate 34 breaths/minute, oxygen saturations 89% on 10L oxygen via 40% venturi mask, HR 133bpm and BP 112/78mmHg.

Investigations: 

Arterial blood gas on 10L oxygen via 40% venturi – 

pH 7.44

pC02 7.5

p02 7.1 

HCO3 29.6 

What is the most likely cause of this patient’s deterioration? 

Select the SINGLE most appropriate option from the list below. Select ONE option only.