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Air is mostly nitrogen, right?
Well, if you have a pneumothroax while breathing room air, most of the volume in the pleural space is, logically, going to be Nitrogen.
By breathing 100% oxygen, you lower the level of Nitrogen within the alveoli and, thus, the nitrogen in the pleural space will diffuse across (down the gradient).
The volume of gas within the pnuemothorax should then fall. It won't resolve the pneuomothorax completely but it's a recognised treatment for small vol collections.
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Half the answer's there. Putting someone on high flow oxygen lowers the nitrogen in the pleural space and replaces it with oxygen. Oxygen is absorbed more easily than nitrogen in the pleural space and thus the pneumothorax resolves quicker (1).
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Don't get me wrong, nitrogen washout is a crap way to treat a pneumothorax but it's always an option in those where you'd not bother treating anyway (ie, small vol of air in a healthy patient)
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Er... wouldnt really call it crap. There is evidence that it does work. If I had a 25% spontaneous pneumothorax I'd much prefer a week of O2 therapy than an FY1 sticking a needle/drain into my pleural space to save a few days (I put in around 20 drains as a PRHO in resp med, unsupervised after 2 if I recall correctly). ALL patients with pneumothoraces back when I worked on a resp firm went on high flow O2 if there was no contraindication. Every little helps! In small pneumothoraces with no breathlessness, BTS guidelines suggest discharge can be considered without any interventions with early follow up and advice to seek help if any worrying features develop (2). So your registrar's conservative management in this case is perfectly valid.
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Im a HCA on a surgerical ward (we have alot of pneumothoraces). We've just had a new registrar start on the ward who suggested we use a technique of nitrogen washout (putting patient on high flow oxygen) for treatment of a small pneumothorax. It was the first time the technique has ever been used on this ward, the nurses said.
Can anyone explain to me what a 'nitrogen washout' is exactly? And why its so uncommonly used?
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Because you're on a surgical ward where sexy drains would be reached for over a not so sexy oxygen mask? (I'm surgically inclined so I can take the piss a little!). I doubt it's the first time it's been used on that ward anyway (since the evidence is over 35 years old), it's just not often called "nitrogen washout" and people (particularly busy nurses who have other things to worry about) often don't understand the reason behind high flow O2 in a patient with a pneumothorax past the obvious.
1. Northfield TC. Oxygen therapy for spontaneous pneumothorax. BMJ
1971;4:86-88.
2. M Henry et al. BTS guidelines for the management of spontaneous pneumothorax. Thorax 2003;58:ii39.
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