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Ann Thorac Surg 1995;59:827-828
© 1995 The Society of Thoracic Surgeons
DR LEWIS WETSTEIN (Freehold, NJ): Doctor Hill, I enjoyed your presentation, but I am not sure about the clinical applicability of your methodology. First of all, we are dealing with a different pathophysiology. Air in the chest from an atmospheric source is a self-limiting process and will resolve spontaneously rather expeditiously, ie, in a couple of days.
We, however, most frequently deal with air in the chest from a lung source, be it laceration or rupture of belbs or bullae. That is a continuous process, with persistent leakage of air and increasing positive pressure; if not managed with external drainage, ie, tube thoracostomy, it will result in a tension pneumothorax and is potentially fatal.
I probably agree with you that oxygen therapy would accelerate air resorption for scenario 1, which really is a nonclinical problem and possibly requires no treatment. But would you use oxygen therapy for scenario 2?
DR HILL: The reason that we did this experiment was because the literature had anecdotal remarks stating that oxygen may or may not be beneficial in the treatment of some pneumothoraces. We do not use it for tension pneumothoraces or anything greater than 20%. But on occasion we have patients come in with as much as 50% spontaneous pneumothoraces who refuse everything-they refuse chest tubes, they refuse operation-and we really hate to send these people home with that kind of problem. We have used oxygen in these people, and it has resolved their pneumothoraces within 48 hours. Do you want to have people at home with a 50% pneumothorax? I really do not like doing that, so I will bring them in, and if they refuse every kind of treatment-and we have had that on occasion-then we simply use oxygen.
DR F. HAMMOND COLE, JR (Memphis, TN): I particularly like this study because it provides some science to what I have been doing for years, particularly in patients with a small space or pneumothorax postoperatively that is not really bad enough to require replacement of a chest tube. Without much data we believed that oxygen hastened reexpansion of pneumothorax, so I simply want to compliment Dr Hill and his associates. I will certainly cite this to all the residents who have asked me in the past why I use this method.
DR KAMAL A. MANSOUR (Atlanta, GA): This is a nice piece of work by Dr Hill and his associates. It was carried out to prove what some authors have suggested in the past, that the administration of nasal oxygen will increase the nitrogen gradient between the pleural gas in the third space and that in the alveoli, thus speeding the absorption of pneumothorax. This therapy has a limited applicability, however, as clearly defined by Dr Hill and his associates. It should be used in patients with small pneumothoraces who refuse tube placement, or in patients with residual pneumothoraces after tube removal. It is accepted that closed tube thoracostomy is the gold standard of therapy for patients with pneumothoraces over 20% in volume, and especially those patients who are symptomatic. The tube also is good for subsequent chemical pleurodesis if deemed necessary.
My question to Dr Hill is why he chose an oxygen concentration of 60% in the resolution of the nontension pneumothoraces he created.
DR HILL: The oxygen we used was the concentration in the laboratory, basically; we took the cages and taped them to get as little air in the system as we could, and when we measured the oxygen concentration within the cage, it was 60%. With that in mind, we have now gone back and we are now doing a dose-response curve to look at whether or not 40% or 35% or 28%, which you could administer with a nasal cannula, will do as well as the 60%.
DR MANSOUR: But you proved there is no damage on electromicroscopy to the lung by your 60%?
DR HILL: At 36 hours, right.
DR JAMES W. PATE (Memphis, TN): I would like to make one suggestion for further work on this eloquent study. In these experiments, 79% nitrogen (air) was injected into the pleural space. It is not the amount of oxygen in the pleural space that is of most relevance; it is the amount of nitrogen. The nitrogen gradient between the pleural gas and the surrounding tissue, and not the oxygen gradient, is most important. It might be of more benefit to use helium rather than oxygen as a ``wash-out'' agent.
DR HILL: That is a good point. We actually did measure the washout time and the rate at which oxygen equilibrated, and when the rabbit was in a 60% cage with an oxygen concentration of 21% within the pleural space, within 20 minutes the oxygen concentration had equilibrated to 60%. But you are right, the oxygen increases the nitrogen gradient between the pleural space and the alveoli. Helium might work, but it would need some oxygen mixture with it.
DR WILLIAM A. COOK (North Andover, MA): This has been a routine part of my treatment of pneumothorax for years, and the way I have done it is to put the patients on a 50% cool mist mask, because I like to get some respiratory therapy going on these people. I would add to what you say. In the clinical setting, paradoxically, treating patients with pneumothorax with hand-held nebulization of bronchodilators and mist and incentive spirometry to clean up the airways can be a very important part of the treatment.
Related Article
Ann. Thorac. Surg. 1995 59: 825-827.
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