Showing papers by "Rambam Health Care Campus published in 1995"

Spectral characteristics of chest wall breath sounds in normal subjects.

Abstract: BACKGROUND--This study was carried out to establish a reliable bank of information on the spectral characteristics of chest wall breath sounds from healthy men and women, both non-smokers and smokers. METHODS--Chest wall breath sounds from 272 men and 81 women were measured using contact acoustic sensors, amplifiers, and fast Fourier transform (FFT) based spectral analysis software. Inspiratory and expiratory sounds were picked up at three standard locations on the chest wall during breathing at flows of 1-2 l/s and analysed breath by breath in real time. RESULTS--The amplitude spectrum of normal chest wall breath sounds has two linear parts in the log-log plane--low and high frequency segments--that are best characterised by their corresponding regression lines. Four parameters are needed and are sufficient for complete quantitative representation of each of the spectra: the slopes of the two regression lines plus the amplitude and frequency coordinates of their intersection. The range of slopes of the high frequency lines was -12.7 to -15.2 dB/oct during inspiration and -13.4 to -20.3 dB/oct during expiration. The frequency at which this line crossed the zero dB level--that is, the amplitude resolution threshold of the system--was designated as the maximal frequency (Fmax) which varied from 736 to 999 Hz during inspiration and from 426 to 796 Hz during expiration with higher values in women than in men. The mean (SD) regression coefficient of the high frequency line was 0.89 (0.05). CONCLUSIONS--These data define the boundaries of normal chest wall breath sounds and may be used as reference for comparison with abnormal sounds.

Suppression of insulin secretion by C-peptide infusion in humans.

Abstract: A role for insulin in the regulation of its own secretion has been established; however, no such effect of C-peptide has been demonstrated. In order to reexamine the role of C-peptide and insulin in regulating beta cell secretion, we infused C-peptide as a primed continuous infusion of 1 ng/min per kg for 45 min to 7 healthy volunteers, and insulin in a similar manner at rates of 1 and 10 mU/min per kg for 2 h to 14 healthy subjects using the euglycemic insulin clamp technique. Plasma insulin and C-peptide were measured before and during the infusions. During C-peptide infusion, C-peptide levels rose from 1.8 +/- 0.2 to 2.3 +/- 0.2 ng/ml, and insulin levels fell from 14.5 +/- 0.8 to 11.0 +/- 1.0 microU/ml (P < 0.01). During low and high rate insulin infusions, insulin levels rose to 70 +/- 8 and 1,020 +/- 105 microU/ml, while C-peptide levels fell significantly from 1.9 +/- 0.2 to 1.5 +/- 0.2 and to 1.3 +/- 0.1 ng/ml, respectively. Thus 5- and 70-fold increases in circulating insulin levels caused 15% and 33% drops in serum C-peptide, respectively. However, a 30% increase in C-peptide levels caused a significant approximately 24% decrease in the levels of plasma insulin. We conclude that insulin induces a dose-dependent inhibition of beta cell secretion, which is even more sensitive to inhibition by C-peptide. These data suggest a physiological role for C-peptide in regulating human insulin secretion in vivo.