Lightfoot, JT and TS McCain. Low frequency sound during exercise testing: Impact upon auscultatory blood pressure measurements . The Physiologist 35(40): 217, 1992. (American Physiological Society meeting)
Recent articles have questioned the validity of auscultatory blood pressure measurements due to the increase in ambient sound levels during exercise, especially diastolic pressures (DBP). However, there is no data documenting the low frequency sound pressure spectrum during exercise. Using a sound pressure level (SPL) meter and signal analyzer, the low frequency sound pressure spectrum (0-100 Hz; SPL in dBA, ref=20µ Pa) was measured both ambiently and in a stethoscope tube during several exercise conditions. With the treadmill set at 94 m/min, phase IV DBP (30 dBA@50Hz) was masked both with (45 dBA@50Hz) and without (39 dBA@50Hz) a subject walking on the treadmill. Similar sound levels were observed with a 51 kg subject (45 dBA@50Hz) and a 109 kg subject (41 dBA@50Hz). During exercise on a cycle ergometer, ambient SPL increased with an increase in rpm from 50 (37 dBA@50Hz) to 90 rpm (47 dBA@50Hz) (resistance = 1.5 kp). Even though the use of a stethoscope during blood pressure cuff deflation decreased ambient sound interference, DBP was still masked during treadmill (94 m/min) and cycle (75 W) exercise (38 and 28 dBA@50Hz, respectively). Systolic blood pressure was not obscured in any condition. These data suggest that sound generated during exercise testing may impair the validity of auscultatory DBP measurements.
Supported in part by American Heart Association 90GIA/649.