Wed3November0919PM 8

A 71-year-old patient with known COPD phones the ambulance with chest pain and tightness.

On their arrival the paramedics note he is cyanosed and commence oxygen via a reservoir bag. On arrival at hospital he is no longer cyanosed but noted to be drowsy.

His arterial blood gas is as follows:

FiO2 0.85 (estimated)

pH 7.26

pO2 29.1 kPa

pCO2 11.3 kPa

The nursing staff recognise this as an indication for NIV and quickly leave him unattended to retrieve the NIV mask.

What should you do during this time?

(Please select 1 option)

Switch to a slightly lower percentage venturi mask and recheck the saturations This is the correct answer

Leave the current reservoir mask with 15 litres oxygen in place and await NIV

Reduce the reservoir bag flow to 6 litres and recheck the saturations

Remove the oxygen immediately, as it is contributing to the hypercapnia

Drop to a 24% venturi mask and recheck the saturations Incorrect answer selected

Explanation

The oxygen has taken away this patient's hypoxic drive, but sudden withdrawal of oxygen can also prompt rebound hypoxaemia,

Rebound hypoxaemia is a major risk and may be more dangerous than the hypercapnic respiratory failure itself. Consequently, the current BTS oxygen guidelines recommend that oxygen therapy be stepped down gradually through sequential Venturi devices while monitoring saturation continuously.

Sudden cessation of supplementary oxygen therapy can cause rebound hypoxaemia with a rapid fall in oxygen tension to below the tension that was present prior to the commencement of supplementary oxygen therapy, which could lead to respiratory arrest itself.

Reference:

O'Driscoll BR, Howard LS, Davison AG. BTS guideline for emergency oxygen use in adult patients. Thorax. 2008;63:vi1-68.

Answer Statistics

1

43%

2

2%

3

6%

4

12%

5

39%

Times answered: 303