Oximetry

Editor, – I enjoyed the review of oximetry by I. Young (Aust Prescr 2003;26:132-5), but was distressed to see the myth that 'nail polish must be removed' perpetuated in both the article and the self-test questions. An Australian woman can spend up to $1000 each year on nail care and decoration. To have to remove that polish or enamel is both inconvenient and expensive.

A study of painted and unpainted nails, in the same people, tested 10 nail colours and found no significant differences in the SpO₂ measured in the painted and unpainted fingers.¹

It has been recommended that, since some nail polishes may reduce estimates of SpO₂ by up to 6%, the probe should be rotated through 90^o and mounted transversely in patients with nail polish or long nails.² Personal observation in long endoscopy lists has shown no significant differences in saturations measured in the conventional way and measured transversely across the finger, in males or females.

We should abolish the myth of the necessity of nail polish removal once and for all and save nursing time.

John Paull
Consultant Anaesthetist
Launceston, Tasmania

Clinical Associate Professor I. Young, the author of the article, comments:

I was aware of the paper that suggests transverse mounting of the probe where nail polish is a problem and, of course, not all polish will cause a significant interference with the signal. My article does state that only strong superficial pigments are likely to be a problem.

I became aware of the Brand paper too late in the editorial process to change the article. The people in this study were normoxic individuals and some interference was found with strong blue and green pigments in vitro. However, I entirely accept Dr Paull's argument that it is not necessary to remove nail polish and regret that one of the questions attached to the article has erroneously emphasised this procedure.