Am. J. Respir. Crit. Care Med., Vol 154, No. 2, 08 1996, 424-430.
Lung sound spectra at standardized air flow in normal infants, children, and adults
H Pasterkamp, RE Powell and I Sanchez
Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, Canada.
To investigate the effect of age and body size on normal lung sounds, we
studied 10 newborn infants within 3 d after birth, nine children between 6
to 8 yr, and 10 adults between 25 and 37 yr of age. Lung sounds were
recorded with a contact transducer over the posterior right lower lobe, and
air flow was measured at the mouth. Computer analysis provided average
power spectra of lung sounds at flows of 15 ml/s/kg. In children and adults
measurements were also made at flows of 30 ml/s/kg. Lung sounds were
referenced to background noise, measured at zero air flow. The spectra in
infants contained less power below 300 Hz compared with children and
adults, resulting in significantly higher quartile and spectral edge
frequencies. Resonances of the thoracic cavity may explain some of the
differences among the study groups. Sound attenuation above 300 Hz was
similar at all ages. At increased air flows, lung sounds in children and
adults were above background noise at frequencies as high as 2,000 Hz.
High-frequency expiratory lung sounds of low intensity were present in all
children and in eight of 10 adults at increased flows. Normal lung sounds
of low intensity are present above traditionally accepted frequency limits
and warrant further investigation.
