Influence of noise spectra on auditory frequencies & degree of temporary threshold shift.

Influence of noise spectra on auditory frequencies of 131 audiometrically normal human volunteers was assessed. Each subject was exposed to four different types of noise on different days for a period of 30 min. Noises utilized in this study were broadband noise (100 dBA), broadband noise (BBN) mixed independently with tones of 0.5, 1.2 and 4 kHz at three intensity levels (85, 95 and 105 dBA) and noises of different bandwidths (100 dBA) around the above tones as centre frequencies. BBN produced maximum TTS2 at 4 kHz (21.42 +/- 0.61 to 26.15 +/- 1.00 dB), while concentration of sound energy around these tones, affected hearing at one-half octave above the point of concentration of sound energy. TTS2 produced by 4 kHz tonal component of 95 and 105 dBA and 2 kHz of 105 dBA were significantly higher than the one produced by BBN at 4 kHz. The single tones of 2 and 4 kHz and noise of 1/3rd octave bandwidth (cf 4 kHz) produced TTS2s which were significantly higher as compared to that of BBN at 4 kHz. At the same centre frequency, noise concentrated in thinner bands was more injurious than that in the thicker bands. Lower frequencies of hearing appears to be more resistant to noise as for the same sound pressure level the TTS2 observed in low frequencies was less as compared to higher frequencies.

Therapeutic role of carbogen in impaired hearing.

The therapeutic role of carbogen was evaluated in subjects with sensorineural hearing loss by administering carbogen, a gas mixture of 95 per cent O2 and 5 per cent CO2, for seven consecutive days (30 min/day) and monitoring puretone audiometry before and after the administration. Significant improvement was observed both in air and bone conduction threshold levels on seventh day, indicating that there was some recoverable portion in the hearing level of these subjects. The improvement in hearing may be due to action of CO2 as an otic vasodilator coupled with supplementation of the O2 requirement of degenerating hair cells. Carbogen thus appears to be useful in persons with impaired hearing, involving the inner ear.

A study of pituitary-thyroid function during exercise in man.

Exercise induced modulations in circulatory T4, T3 and TSH were monitored in 14 healthy euthyroid male volunteers undergoing exercise on a bicycle ergometer at 750 KPM for 20 minutes. TSH response to 100 micrograms TRH was also studied in 4 exercising and 4 resting subjects. Serial blood samples were obtained before, during and after the exercise. Serum T4 exhibited a significant decrease (P less than 0.05) from 9.6 +/- 0.49 microgram/dl (mean +/- SE) to 8.3 +/- 0.47 microgram/dl at 20 min after the termination of the exercise, whereas a significant decrease (P less than 0.01) in T3 levels from 158 +/- 9 ng/dl to 144 +/- 8.2 ng/dl was recorded at 40 min after the termination of the exercise. The basal TSH levels as well as the sensitivity of the pituitary thyroid axis, monitored as overall TSH response, reflected by the sum of TSH values at different time intervals and the maximum rise over the basal levels (delta TSH) remained unaltered after exercise. These observations suggest that hormone secretion by the thyroid and its responsiveness to endogenous TSH are maintained after exercise. The decrease in circulatory T4 and T3 could be due to an increase in degradation of the hormones or may reflect a generalized adaptation phenomenon. The exact mechanism and significance of these alterations remains to be elucidated.

Fitting curves to physiological data.

This paper deals with fitting of a parabola and three parameter logistic curve to relate heart output and initial index finger temperature with ambient temperature in human subjects. The coefficients of determination (R2%) between observed and estimated values of heat output and initial index finger temperature were close to 98% indicating the high percentage of variation of the total sum of squares absorbed by the fit of the curves. The superiority of the fitted curves over the other curves have been proved. Thus it is concluded that parabola and three parameter logistic curve may explain the relationships of heat output and initial index finger temperature with ambient temperature more precisely than other curves.

Gompertz curve in physiology: an application.

Gompertz curve has been successfully used to estimate mortality intensities, recovery and relapse rates for human beings suffering from specific diseases. Perhaps, no attempt has yet been made to describe statistically the phenomenon of thermoregulation efficiency of man. This paper deals with the statistical approach for describing the above mentioned phenomenon. For this purpose, Gompertz curve has been fitted to the data of recovery palm skin temperature of human subjects, which was collected after removing the hand of a subject dipped for two minutes in cold water maintained at 10 +/- 1 degree C on seven environmental situations including altitude. The coefficients of correlation between observed and estimated palm skin temperature expressed logarithmically were close to 0.99 for each situation indicating the high precision of the fitted curve. The average rates of recovery of palms skin temperature have also been compared between these seven environmental situations using analysis of covariance technique. It is concluded that recovery of palm skin temperature of sea level residents during stay at plains is much faster than their recovery at high altitude situations.