Perfect Storm
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《新英格兰医药杂志》
To the Editor: The discussion of the rigid spine syndrome by Janssen et al. (Nov. 3 issue)1 clearly illustrates the pathophysiology of alveolar hypoventilation. However, I am somewhat puzzled by the clinical assessment. Cyanosis is generally detectable with 5 g per deciliter of deoxygenated hemoglobin. This patient had polycythemia with a hematocrit of 63 percent and a pulse oximetry reading of 55 percent. These values should translate to approximately 9.5 g per deciliter of deoxygenated hemoglobin, consistent with a very cyanotic patient, and not compatible with the statement, "A cursory physical examination showed no abnormalities."
Has modern technology eliminated our ability to detect clinical cyanosis?
Arthur M. Lam, M.D.
Harborview Medical Center
Seattle, WA 98104
artlam@u.washington.edu
References
Janssen WJ, Collard HR, Saint S, Weinberger SE. A perfect storm. N Engl J Med 2005;353:1956-1961.
The authors reply: We agree with Dr. Lam that a patient with an arterial oxygen saturation of 55 percent should have profound central cyanosis. Records from the initial assessment of the patient we described do not mention a skin examination, nor is there mention of perioral cyanosis. These omissions could reflect poor documentation, an unobservant clinician, or the fact that pulse oximetry and administration of supplemental oxygen often occur before the physician enters the room.
Lundsgaard and Van Slyke originally reported that cyanosis becomes evident when reduced hemoglobin levels are greater than 5 g per deciliter of capillary blood,1 a value roughly equivalent to 3 g of deoxyhemoglobin per deciliter of arterial blood.2 The latter value has been verified by other investigators and has high interrater reliability.3 Thus, the physical examination may be even more sensitive than Dr. Lam suggests.
Dr. Lam's comments underscore the continued importance of the physical examination.
William J. Janssen, M.D.
University of Colorado Health Sciences Center
Denver, CO 80262
william.janssen@uchsc.edu
Sanjay Saint, M.D., M.P.H.
University of Michigan
Ann Arbor, MI 48105
Steven Weinberger, M.D.
American College of Physicians
Philadelphia, PA 19106
References
Lundsgaard C, Van Slyke D. Cyanosis. Medicine (Baltimore) 1923;2:1-76.
Martin L, Khalil H. How much reduced hemoglobin is necessary to generate central cyanosis? Chest 1990;97:182-185.
Barnett HB, Holland JG, Josenhans WT. When does central cyanosis become detectable? Clin Invest Med 1982;5:39-43.
Has modern technology eliminated our ability to detect clinical cyanosis?
Arthur M. Lam, M.D.
Harborview Medical Center
Seattle, WA 98104
artlam@u.washington.edu
References
Janssen WJ, Collard HR, Saint S, Weinberger SE. A perfect storm. N Engl J Med 2005;353:1956-1961.
The authors reply: We agree with Dr. Lam that a patient with an arterial oxygen saturation of 55 percent should have profound central cyanosis. Records from the initial assessment of the patient we described do not mention a skin examination, nor is there mention of perioral cyanosis. These omissions could reflect poor documentation, an unobservant clinician, or the fact that pulse oximetry and administration of supplemental oxygen often occur before the physician enters the room.
Lundsgaard and Van Slyke originally reported that cyanosis becomes evident when reduced hemoglobin levels are greater than 5 g per deciliter of capillary blood,1 a value roughly equivalent to 3 g of deoxyhemoglobin per deciliter of arterial blood.2 The latter value has been verified by other investigators and has high interrater reliability.3 Thus, the physical examination may be even more sensitive than Dr. Lam suggests.
Dr. Lam's comments underscore the continued importance of the physical examination.
William J. Janssen, M.D.
University of Colorado Health Sciences Center
Denver, CO 80262
william.janssen@uchsc.edu
Sanjay Saint, M.D., M.P.H.
University of Michigan
Ann Arbor, MI 48105
Steven Weinberger, M.D.
American College of Physicians
Philadelphia, PA 19106
References
Lundsgaard C, Van Slyke D. Cyanosis. Medicine (Baltimore) 1923;2:1-76.
Martin L, Khalil H. How much reduced hemoglobin is necessary to generate central cyanosis? Chest 1990;97:182-185.
Barnett HB, Holland JG, Josenhans WT. When does central cyanosis become detectable? Clin Invest Med 1982;5:39-43.