To the Editors:

The recent article by Iregui and colleagues titled “Physicians’ Estimates of Cardiac Index and Intravascular Volume Based on Clinical Assessment Versus Transesophageal Doppler Measurements Obtained by Critical Care Nurses” (July 2003:336–342) deserves comment and very cautious interpretation because of multiple concerns with the study design and statistical analysis.

Accuracy of hemodynamic measurements obtained from transesophageal Doppler (TED) imaging is dependent on training and experience, and error can be easily introduced by inexperienced operators.1 Although nurses in this study received 2 hours of instruction about TED imaging and were supervised by investigators until they demonstrated proficiency, the authors failed to provide objective data to substantiate that proficiency in measuring hemodynamic variables with TED imaging was adequate before the study began. The authors cited research1 that validated specific objective training criteria to assess operator proficiency in obtaining cardiac output using TED imaging to ensure adequate reliability, but...

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