July 18, 2012Volume 7 - Issue 29

DynaMed Weekly Update

For the week ending July 13, 2012

Last week 424 articles were evaluated via DynaMed's Systematic Literature Surveillance and 238 were added to DynaMed content.   


Based on the editors' criteria of selecting "articles most likely to change clinical practice," one article of significant interest was selected for the DynaMed Weekly Update.

Feature Article

Pulse Oximetry Algorithm for Preflight Evaluation May Identify Patients with COPD Who Can Fly without Further Assessment


Due to reduced cabin pressure, air travel can increase the risk of hypoxemia in patients with COPD. The gold standard for preflight risk assessment in these patients is the hypoxia-altitude simulation test (HAST), which requires arterial blood gas measurement after breathing a gas mixture with 15.1% oxygen (simulating cabin pressure at 8,000 feet altitude). Supplemental in-flight oxygen is recommended for patients with arterial oxygen pressure (PaO2) < 6.6 kPa (49.5 mm Hg) on HAST. Guidelines from the British Thoracic Society (BTS) recommend this test for any patient with resting oxygen saturation (SpO2) at sea level < 95% (Thorax 2011 Sep;66 Suppl 1:i1). The HAST is mildly invasive, relatively difficult to perform, and not widely available. A recent study derived and validated a new algorithm to simplify assessment of the need for supplemental oxygen based on resting and exercise pulse oximetry.


The algorithm was derived in a cohort of 100 patients (mean age 65 years) with moderate to very severe COPD who had been referred for preflight testing. All patients had both HAST evaluation and SpO2 measurement by pulse oximetry at rest and during exercise (6-minute walk test). According to the new algorithm, supplemental oxygen is required if resting SpO2 < 92% or resting SpO2 = 92%-95% AND exercise SpO2 < 84%. Supplemental oxygen would not be required if resting SpO2 > 95% AND exercise SpO2 ≥ 84%. For patients with other pulse oximetry results, the algorithm recommends performing HAST assessment.


The algorithm was validated in an independent cohort of 50 similar patients. All 16 patients who were classified by the algorithm as not needing supplemental oxygen were correctly identified (confirmed by HAST). There were 4 patients who were incorrectly classified as needing oxygen. By the BTS guideline, 27 patients would have required HAST evaluation, but the algorithm indicated HAST for only 20 patients, a reduction of 26%. For predicting the need for in-flight supplemental oxygen, the algorithm had 100% sensitivity and 80% specificity (Thorax 2012 Jul 6 early online). One caveat regarding this algorithm is that pulse oximetry may not accurately reflect arterial oxygenation in certain patients, such as those with hemoglobinopathies.


For more information, see the COPD topic in DynaMed.

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About DynaMed Weekly Update

Prepared by the clinician members of the DynaMed Editorial Team, DynaMed Weekly Update is a compilation of one to five articles selected from DynaMed's Systematic Literature Surveillance as articles most likely to change clinical practice.

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CME Information


0.25 AMA PRA Category I Credit(s)™
Family Physicians: 0.25 Prescribed credits
Nurse Practitioners: 0.25 Contact hours
Release Date: July 18, 2012
Expiration Date: July 18, 2013
Estimated Completion Time:
15 minutes
There is no fee for this activity.

To Receive Credit 
In order to receive your certificate of participation, you should read the information about this activity, including the disclosure statements, review the entire activity, take the post-test, and complete the evaluation form. You may then follow the directions to print your certificate of participation. To begin, click the CME icon at the end of the article.

Program Overview

Learning Objectives

Upon successful completion of this educational program, the reader should be able to:
1. Discuss the significance of this article as it relates to your clinical practice.
2. Be able to apply this knowledge to your patient's diagnosis, treatment and management.
Faculty Information
Alan Ehrlich, MD - Assistant Clinical Professor in Family Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; Deputy Editor, DynaMed, Ipswich, Massachusetts, USA

Michael Fleming, MD, FAAFP - Assistant Clinical Professor of Family Medicine and Comprehensive Care, LSU Health Science Center School of Medicine, Shreveport, Louisiana, USA; Assistant Clinical Professor of Family Medicine, Department of Family and Community Medicine, Tulane University Medical School, New Orleans, Louisiana, USA; Chief Medical Officer, Amedisys, Inc. & Antidote Education Company

Dr. Ehrlich, Dr. Fleming, DynaMed Editorial Team members, and the staff of Antidote Education Company have disclosed that they have no relevant financial relationships or conflicts of interest with commercial interests related directly or indirectly to this educational activity.
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AAFPEnduring Material activity, DynaMed Weekly Update, has been reviewed and is acceptable for up to 13 Prescribed credits by the American Academy of Family Physicians. AAFP certification begins March 7, 2012. Term of approval is for one year from this date with the option of yearly renewal. Each Weekly Update is worth .25 Prescribed credits. Physicians should claim only the credit commensurate with the extent of their participation in the activity.


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