Ultrasound ‘simple, accurate’ predictor of mortality risk in COPD
Posted May 12 2009 6:06pm
By Philip Ford
Ultrasound is a simple and reliable tool for assessing muscle strength and, therefore, risk for death in patients with chronic obstructive pulmonary disease (COPD), UK scientists believe.
“Even in non-cachectic patients with COPD, quadriceps strength is typically reduced by up to 30% compared with healthy elderly subjects,” write John Seymour (King’s College Hospital, London) and fellow researchers in the introduction to their report.
Of note, this loss of quadriceps strength has been shown to independently predict increased use of healthcare resources and mortality in COPD. However, methods for measuring muscle strength are typically difficult or expensive to perform or require significant exertion from patients.
For the present study, Seymour and team used ultrasound to measure quadriceps strength and fat-free mass in 30 patients with COPD and 26 volunteers.
“Ultrasound equipment is available in most hospitals and, in principle, trained non-specialists could perform scans rapidly at the bedside,” the researchers explain.
Specifically, the investigators used ultrasound to measure the cross-sectional area of the rectus femoris muscle, one of the four quadriceps muscles, and found that it was typically 25% smaller in patients with COPD than in those without the condition.
Importantly, the authors demonstrated that the cross-sectional area of the rectus femoris muscle was significantly predictive of maximum voluntary contraction strength, a measure that is commonly used to assess muscle mass in COPD.