Three Part Question
In [patients with spontaneous pneumothorax] does [treatment with oxygen] increase [resolution rate]?
A 15-year-old boy is admitted with sudden onset chest pain and breathlessness. Chest x-ray shows a small pneumothorax. He has no background health problems. He is treated conservatively with high-flow oxygen, as the registrar has been taught this can improve the resolution rate of pneumothoraces. The consultant questions the biological plausibility of this treatment.
Medline (1950 to present) was searched via the Ovid interface on 6 July 2009.
Medline:Pneumothorax’ [MeSH] and ‘oxygen inhalation therapy’ [MeSH] with no limits produced 113 results, two of which were relevant.
Embase:‘spontaneous pneumothorax’ [MeSH] and ‘oxygen therapy’ [MeSH] with no limits producing 23 results, none of which were relevant.
The reference list of the British Thoracic Society (BTS) guidelines on the management of spontaneous pneumothoraces was searched. In addition to one of the references found on Medline, a further relevant reference was found.
|Author, date and country
||Study type (level of evidence)
|England et al,|
|40 rabbits with experimentally induced complete unilateral pneumothoraces exposed to different concentrations of inhaled oxygen (21–50%)||Prospective randomised trial||Pneumothorax resolution rate||Resolution rate per O2 concentration: 21% FiO2 61.65±12.3 h, 30% FiO2 42.90±5.97 h, 40% FiO2 35.8±4.26 h, 50% Fi02 33.80±4.66 h ||Each rabbit had a 100% pneumothorax. Pneumothorax induced by injection of air into the pleural space—is this applicable to spontaneous pneumothoraces? Unblinded trial. Oxygen levels in cages monitored but arterial oxygen levels not measure|
|10 adult patients with spontaneous pneumothoraces of varying volumes treated with intermittent high-flow oxygen||Prospective trial with retrospective control group||Pneumothorax resolution rate||Mean resolution rate in air=4.8 cm2 day, with oxygen=17.9 cm2/day the resolution rate was increased if occupying >30% of the hemi-thorax (25.2 cm2/day) compared to <30% of hemi-thorax (10.4 cm2/day) while breathing oxygen ||Resolution rate in air taken from mean of retrospective control group treated with bed-rest only with inherent bias. Varying lengths of time exposed to oxygen 9–38 h|
It is suggested that inhaling gas with a higher oxygen concentration than room air improves rate of resolution of pneumothorax. This has been incorporated into BTS Guidelines on the treatment of spontaneous pneumothoraces(Henry). The biological mechanism is proposed to be air from the pneumothorax is re-absorbed by diffusion from the pleural space to the alveolar space via pleural capillaries. Administering oxygen reduces the partial pressure of nitrogen in the alveolus compared to the pleural space and a diffusion gradient for nitrogen is increased, resulting in faster resolution of the pneumothorax.
An increase in pneumothorax resolution rates has been observed in rabbits inhaling high oxygen concentrations. In a prospective randomised trial comparing resolution rates of experimentally induced complete unilateral pneumothoraces in 40 rabbits, England et al demonstrated a dose-dependent improvement in the rate of resolution of pneumothoraces.
The only prospective human trial studied 10 participants with spontaneous pneumothoraces of varying volumes treated with intermittent high-flow oxygen for between 9 and 38 h at a time (only detail of treatment duration given).3 The concentration of oxygen delivered was not measured but frequently observed to be around 33% at 8 l/min.4 Each patient had a daily chest x-ray from which the pneumothorax area was calculated. The resolution rate was then compared to a cohort of patients who had been treated with bed-rest only, whose resolution rate had been computed retrospectively. When in air, the resolution rate of pneumothoraces was 4.8 cm2/day, but increased with oxygen administration to 17.9 cm2/day. The rate of resolution was dependent on pneumothorax size, with larger pneumothoraces having a significantly greater reduction in area when on oxygen. There were no side effects recorded from the high concentration oxygen therapy in this small study.
Oxygen therapy is not used without cost or adverse effects. High-flow oxygen apparatus is uncomfortable to wear (Chanques), has been associated with pulmonary toxicity (Stogner) and the patient would be limited to bed. For these reasons its use in a paediatric population may not be desirable.
Oxygen has been demonstrated to increase the resolution rate of spontaneous pneumothoraces in animals. The evidence for its effect in humans is poor but would suggest that in small pneumothoraces, oxygen may double the rate at which pneumothoraces are re-absorbed and increase the rate by up to fivefold in large pneumothoraces. Although oxygen may increase pneumothorax recovery rates, the limited evidence for its benefit does not outweigh the short-term disadvantages and potential long-term toxicities of unnecessary oxygen therapy and oxygen should be reserved for those who are hypoxic.
Clinical Bottom Line
There is weak evidence that high-flow oxygen use causes faster re-absorption of pneumothoraces (grade c).
The benefits of high-flow oxygen do not outweigh the risks and difficulties of its use unless the patient is hypoxic (grade d).
- Henry M, Arnold T, Harvey J. BTS guidelines for the management of spontaneous pneumothorax. Thorax 2003;58(Suppl II):ii39–52.
- England GJ, Hill RC, Timberlake GA, et al. Resolution of experimental pneumothorax in rabbits by graded oxygen therapy. J Trauma 1998;45:333–4.
- Northfield TC. Oxygen therapy for spontaneous pneumothorax. Br Med J 1971;4:86–8.
- Catterall M, Snow M. The polymask as a means of administering oxygen. BMJ 1960;1:1255–6.
- Chanques G, Constantin JM, Sauter M, et al. Discomfort associated with underhumidified high-flow oxygen therapy in critically ill patients. Intensive Care Med 2009;35:996–1003.
- Stogner SW, Payne DK. Oxygen toxicity. Ann Pharmacother 1992;26:1554–62.