© 2003 American Thoracic Society
Evidence-based Medical EducationCautionTo the Editor:We read with interest the study by Cox and coworkers (1). It is indeed crucial to assess the residents' knowledge of medical literature. The online supplement provides us with the questionnaire given to the medical residents. Interestingly, the second least correctly answered question is No. 12, which relates to the most appropriate next measure to take when arterial blood gas analysis of a woman mechanically ventilated under 0.6 FIO2 and 5 cm H2O positive end-expiratory pressure (PEEP) reveals: pH 7.28, PCO2 36, PaO2 55 mm Hg, and SaO2 85%. The list of possible answers is as follows: (a) Increase the FIO2 to 0.80; (b) Increase the tidal volume by 100 ml from your initial setting; (c) Increase the rate by 4 breaths per minute from your initial setting; and (d) increase the PEEP to 10 cm H2O. Only 56% of the residents provided the required answer: (d) increase PEEP to 10 cm H2O. It would have been interesting to know the percentage of residents answering the other different propositions. Our contention is that medical residents who had first increased FIO2 (and only after that increased PEEP) would have put their patient at a much lesser risk for persistent hypoxemia (and cardiac compromise) than those who had first increased PEEP. Indeed, patients may not always respond to PEEP, may sometimes increase their PaO2 only several hours after PEEP augmentation, or may even decrease their PaO2 if their cardiac output decreases as a result of increased PEEP (2). Our first concern as clinicians when treating patients with severe hypoxemia (as is the case in this vignette with PaO2/FIO2 < 92) is to avoid prolonged hypoxemia. In addition, even if one wishes to apply evidence-based medicine, then one may wish to refer to a very recent review of evidence-based medicine on adult respiratory distress syndrome (ARDS) treatment that made a grade C recommendation for the use of PEEP in ARDS treatment (3). Then it may be worthwhile to rely on physiology and consider, as stated by Lodato (4), that "the known immediate risks of systemic hypoxia and barotrauma are clearly more rapid and devastating than the potential and future risk of hyperoxia-induced lung injury." In the area of ARDS, the same caveat may be addressed to evidence-based medical education as to evidence-based medicine (5). However important it may be to assess the knowledge of medical literature of senior residents, assessing their understanding of physiology may prove to be at least as beneficial to the patient.
Hôpital Louis Mourier Colombes, France REFERENCES
From the Authors: We thank Drs. Ricard and Dreyfuss for their comments and their interest regarding our study (1). They take exception to what we considered to be the correct response to a question describing hypoxemia in a patient who is early in her course of the acute respiratory distress syndrome (ARDS). The intent of the question was to see if residents would recognize the benefits of modest levels of positive end-expiratory pressure (PEEP) in patients with ARDS with regard to improving hypoxemia. Hopefully, residents would also be aware of other benefits of recruiting collapsed alveoli such as improved lung compliance (2). The role of PEEP in avoiding ventilator-induced lung injury and improving survival from ARDS remains unproven (3). The option available to residents was to provide an additional 5 cm H2O of PEEP in a patient with plateau pressures of 24 cm H2O and an arterial oxygen saturation of 85%. Early in the course of ARDS, it is very likely that this maneuver would improve the hypoxemia, thus avoiding toxic levels of inspired oxygen while maintaining airway pressures at what are considered to be reasonably safe levels. The level of PEEP specified is at the lower end of the range of PEEP recommended by the American–European consensus conference (4), and it is consistent with FIO2/PEEP levels specified in the ARDSNet protocol (5). In designating the single best answer to this question, we chose the option that would have the most desired lasting effect. We agree, however, that temporarily increasing the FIO2 to 0.80 during the period that it would take for the PEEP to improve the hypoxemia would be safe and indicated. In that case, two answers would be appropriate for short-term management. The question could be rewritten to eliminate the confusion. This issue was not recognized during the pretesting phase. A total of 26% of residents selected increasing the FIO2 as the single best answer, but we do not know how many of them did not consider higher PEEP to be indicated as well. There is no doubt that other clinicians will disagree with some of the questions in our test, primarily because clear scientific evidence does not yet exist for much of what we do in treating critically ill patients. However, we remain concerned about how many residents were ill-informed about good clinical practice that does have sound supporting evidence.
a Duke University Durham, North Carolina REFERENCES
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