Decreasing sound and vibration during ground transport of infants with very low birth weight.

OBJECTIVE: To measure the effectiveness of modifications to reduce sound and vibration during interhospital ground transport of a simulated infant with very low birth weight (VLBW) and a gestational age of 30 weeks, a period of high susceptibility to germinal matrix and intraventricular hemorrhage. STUDY DESIGN: Researchers measured vibration and sound levels during infant transport, and compared levels after modifications to the transport incubator mattresses, addition of vibration isolators under incubator wheels, addition of mass to the incubator mattress and addition of incubator acoustic cover. RESULT: Modifications did not decrease sound levels inside the transport incubator during transport. The combination of a gel mattress over an air chambered mattress was effective in decreasing vibration levels for the 1368 g simulated infant. CONCLUSION: Transport mattress effectiveness in decreasing vibration is influenced by infant weight. Modifications that decrease vibration for infants weighing 2000 g are not effective for infants with VLBW. Sound levels are not affected by incubator covers, suggesting that sound is transmitted into the incubator as a low-frequency vibration through the incubator's contact with the ambulance. Medical transportation can apply industrial methods of vibration and sound control to protect infants with VLBW from excessive physical strain of transport during vulnerable periods of development.

Subretinal neovascularization in children and adolescents.

Subretinal neovascular membranes (SRNVM) in the pediatric population are rare. The clinical presentation, etiology, course, and management of SRNVM in 25 children (27 eyes) were studied retrospectively. Inflammatory or infectious conditions predominated (10 of 25). Eleven of 19 untreated SRNVM (58%) spontaneously involuted, with 9 of these 11 achieving a final visual acuity of 20/50 or better. A hyperpigmented ring on fluorescein angiography was associated with 9 of the 11 involuted SRNVM. The presence of this pigmented ring may help to identify those cases with a better visual prognosis.

Effects of intensity on speech recognition in high- and low-frequency bands.

OBJECTIVE: This study investigated the intensive effects of a low-frequency (200 to 400 Hz) and a high-frequency (1000 to 5000 Hz) band of speech presented jointly and in isolation. DESIGN: Each band was presented at a reference intensity level equivalent to the average normal conversational level. To investigate intensive effects, the low-frequency band was presented at 20 dB and 36 dB, and the high-frequency band at 20 dB above the reference level. Each band was presented at a fixed signal-to-noise ratio. Subjects were four normal-hearing adult females. The AI was used to predict performances and to determine audibility of each band. RESULTS: The best performance occurred for a joint band presentation with each band at the reference level. Increasing intensity of one band by 20 dB, for joint band conditions, did not significantly affect performance. However, increasing the low-frequency band by 36 dB or both bands by 20 dB resulted in a significant decrease in performance. CONCLUSIONS: Reduced performance with the low-frequency band at 36 dB and the high-frequency band at the reference level is attributed primarily to upward spread of masking by speech. Performance decrements for other joint band conditions are attributed to combined effects of high intensity.

Auditory reaction times for functional and nonfunctional hearing loss.

Differences in decision processes as measured by auditory reaction times of simulated or actual functional hearing-loss subjects and nonfunctional subjects were investigated. Sensation level data are presented that reflect marked differences between such individuals with regard to probability of response, and means and standard deviations of auditory reaction times. Means and standard deviations of auditory reaction times for nonfunctional subjects are greatly reduced when compared with results obtained by simulated or actual functional subjects. Probability of response data was less effective in differentiating functional from nonfunctional subjects. Individuals who were trained to simulate hearing loss responded in a manner similar to functional patients. The results of this study suggest that auditory reaction time measures can be employed to determine the existence or nonexistence of functional hearing loss with considerable accuracy.