Yiming Zhao

Application of the kurtosis statistic to the evaluation of the risk of hearing loss in workers exposed to high-level complex noise.

Objective: Develop dose-response relations for two groups of industrial workers exposed to Gaussian or non-Gaussian (complex) types of continuous noises and to investigate what role, if any, the kurtosis statistic can play in the evaluation of industrial noise-induced hearing loss (NIHL). Design: Audiometric and noise exposure data were acquired on a population (N = 195) of screened workers from a textile manufacturing plant and a metal fabrication facility located in Henan province of China. Thirty-two of the subjects were exposed to non-Gaussian (non-G) noise and 163 were exposed to a Gaussian (G) continuous noise. Each subject was given a general physical and an otologic examination. Hearing threshold levels (0.5–8.0 kHz) were age adjusted (ISO-1999) and the prevalence of NIHL at 3, 4, or 6 kHz was determined. The kurtosis metric, which is sensitive to the peak and temporal characteristics of a noise, was introduced into the calculation of the cumulative noise exposure metric. Using the prevalence of hearing loss and the cumulative noise exposure metric, a dose-response relation for the G and non-G noise-exposed groups was constructed. Results: An analysis of the noise environments in the two plants showed that the noise exposures in the textile plant were of a Gaussian type with an Leq(A)8hr that varied from 96 to 105 dB whereas the exposures in the metal fabrication facility with an Leq(A)8hr = 95 dB were of a non-G type containing high levels (up to 125 dB peak SPL) of impact noise. The kurtosis statistic was used to quantify the deviation of the non-G noise environment from the Gaussian. The dose-response relation for the non-G noise-exposed subjects showed a higher prevalence of hearing loss for a comparable cumulative noise exposure than did the G noise-exposed subjects. By introducing the kurtosis variable into the temporal component of the cumulative noise exposure calculation, the two dose-response curves could be made to overlap, essentially yielding an equivalent noise-induced effect for the two study groups. Conclusions: For the same exposure level, the prevalence of NIHL is greater in workers exposed to non-G noise environments than for workers exposed to G noise. The kurtosis metric may be a reasonable candidate for use in modifying exposure level calculations that are used to estimate the risk of NIHL from any type of noise exposure environment. However, studies involving a large number of workers with well-documented exposures are needed before a relation between a metric such as the kurtosis and the risk of hearing loss can be refined.

Effect of cigarette smoking on noise-induced hearing loss in workers exposed to occupational noise in China.

Excessive exposure to high noise level environments has the potential to cause noise-induced hearing loss (NIHL), and cigarette smoking has also been shown to have a potential adverse effect on hearing. The aim of this study was to determine whether smoking interacts with noise in the development of hearing loss, and if so, the extent of the contribution from smoking on NIHL. A cross-sectional study was designed to assess the effect of smoking on NIHL in 517 male workers (non-smokers: N = 199; smokers: N = 318) exposed to a high-level industrial noise environment in China. Shift-long temporal waveforms of the noise that workers were exposed to for evaluation of noise exposures, and audiometric threshold measures were obtained on all selected subjects. The subjects used hearing protection devices only within the last 1-2 years. The results suggest that smoking has an adverse effect on NIHL in workers exposed to high level industrial noise, i.e., the median high frequency hearing thresholds were significantly greater in smokers than non-smokers exposed to noise for more than 10 years. This effect was observed at 4.0 and 6.0 kHz. Smoking did not have an adverse effect on NIHL in workers exposed to noise less than 10 years. Multivariate regression analysis revealed that the odds ratio (OR) for high frequency hearing loss (i.e., hearing threshold greater than 40 dB at 4.0 kHz) were 1.94 for smokers in comparison to non-smokers. The results suggest that: (1) smokers have a higher risk of developing high frequency hearing loss than non-smokers with a similar occupational noise exposure, and (2) the interaction between cigarette smoking and high-level noise exposure may be additive. There is a need to develop and analyze a larger database of workers with well-documented exposures and smoking histories for better understanding of the effect of smoking on NIHL incurred from high-level industrial noise exposures. A better understanding of the role of smoking may lead to its incorporation into hearing risk assessment for noise exposure.

Investigation of road-traffic noise and annoyance in Beijing: a cross-sectional study of 4th Ring Road.

The authors aimed to evaluate traffic noise level and noise annoyance in Beijing and the impact of the noise on the quality of life of the residences. The authors performed a cross-sectional study in a 12-floor college dormitory near 4th Ring Road in Beijing, China. The north-side rooms of the building were noisy and had windows facing the road. The authors measured both indoor and outdoor noise. Using both a 5-item verbal scale and a 0-10 numerical scale, they questioned a sample of 1,293 college students living in the dormitory about road-traffic noise annoyance. The results showed that the average outdoor day-to-night noise level was 79.2 dB(A) in the noisy rooms and 64.0 dB(A) in the quiet rooms. Nearly 39% of the respondents living in the noisy rooms indicated that they were highly annoyed by traffic noise according to the response on the verbal scale, and 50% of the respondents living in the noisy rooms were highly annoyed according to the numerical scale.

Evaluation of Individual Susceptibility to Noise-Induced Hearing Loss in Textile Workers in China

The authors applied noise exposure and audiometry information collected on 156 Chinese textile workers to develop a method of identifying individuals susceptible to noise-induced hearing loss. They estimated noise-induced hearing threshold shift (NIHTS) by averaging the adjusted hearing thresholds at 3, 4, and 6 kHz of both ears, and they fitted a quadratic model to describe the dose-response relationship between cumulative noise exposure and NIHTS. The residual between the actual NIHTS and the model-predicted NIHTS indicated susceptibility. A comparison of the 20% of the subjects with the greatest residuals (those who were susceptible to hearing loss) with the 20% of the subjects with the smallest residuals (those who were resistant to hearing loss) revealed that the former had poorer hearing, although the noise exposures were similar. The identified susceptible individuals also had the poorest hearing thresholds within each subgroup of homogenous noise exposures. With their model-based procedure, the authors were able to identify individuals susceptible to noise-induced hearing loss from subjects with heterogeneous noise exposures.

The use of the kurtosis metric in the evaluation of occupational hearing loss in workers in China: implications for hearing risk assessment.

This study examined: (1) the value of using the statistical metric, kurtosis [β(t)], along with an energy metric to determine the hazard to hearing from high level industrial noise environments, and (2) the accuracy of the International Standard Organization (ISO-1999:1990) model for median noise-induced permanent threshold shift (NIPTS) estimates with actual recent epidemiological data obtained on 240 highly screened workers exposed to high-level industrial noise in China. A cross-sectional approach was used in this study. Shift-long temporal waveforms of the noise that workers were exposed to for evaluation of noise exposures and audiometric threshold measures were obtained on all selected subjects. The subjects were exposed to only one occupational noise exposure without the use of hearing protection devices. The results suggest that: (1) the kurtosis metric is an important variable in determining the hazards to hearing posed by a high-level industrial noise environment for hearing conservation purposes, i.e., the kurtosis differentiated between the hazardous effects produced by Gaussian and non-Gaussian noise environments, (2) the ISO-1999 predictive model does not accurately estimate the degree of median NIPTS incurred to high level kurtosis industrial noise, and (3) the inherent large variability in NIPTS among subjects emphasize the need to develop and analyze a larger database of workers with well-documented exposures to better understand the effect of kurtosis on NIPTS incurred from high level industrial noise exposures. A better understanding of the role of the kurtosis metric may lead to its incorporation into a new generation of more predictive hearing risk assessment for occupational noise exposure.

The Use of the Kurtosis-adjusted Cumulative Noise Exposure Metric in Evaluating the Hearing Loss Risk for Complex Noise

Objective: To test a kurtosis-adjusted cumulative noise exposure (CNE) metric for use in evaluating the risk of hearing loss among workers exposed to industrial noises. Specifically, to evaluate whether the kurtosis-adjusted CNE (1) provides a better association with observed industrial noise-induced hearing loss, and (2) provides a single metric applicable to both complex (non-Gaussian [non-G]) and continuous or steady state (Gaussian [G]) noise exposures for predicting noise-induced hearing loss (dose–response curves). Design: Audiometric and noise exposure data were acquired on a population of screened workers (N = 341) from two steel manufacturing plants located in Zhejiang province and a textile manufacturing plant located in Henan province, China. All the subjects from the two steel manufacturing plants (N = 178) were exposed to complex noise, whereas the subjects from textile manufacturing plant (N = 163) were exposed to a G continuous noise. Each subject was given an otologic examination to determine their pure-tone HTL and had their personal 8-hr equivalent A-weighted noise exposure (LAeq) and full-shift noise kurtosis statistic (which is sensitive to the peaks and temporal characteristics of noise exposures) measured. For each subject, an unadjusted and kurtosis-adjusted CNE index for the years worked was created. Multiple linear regression analysis controlling for age was used to determine the relationship between CNE (unadjusted and kurtosis adjusted) and the mean HTL at 3, 4, and 6 kHz (HTL346) among the complex noise-exposed group. In addition, each subject’s HTLs from 0.5 to 8.0 kHz were age and sex adjusted using Annex A (ISO-1999) to determine whether they had adjusted high-frequency noise-induced hearing loss (AHFNIHL), defined as an adjusted HTL shift of 30 dB or greater at 3.0, 4.0, or 6.0 kHz in either ear. Dose–response curves for AHFNIHL were developed separately for workers exposed to G and non-G noise using both unadjusted and adjusted CNE as the exposure matric. Results: Multiple linear regression analysis among complex exposed workers demonstrated that the correlation between HTL3,4,6 and CNE controlling for age was improved when using the kurtosis-adjusted CNE compared with the unadjusted CNE (R2 = 0.386 versus 0.350) and that noise accounted for a greater proportion of hearing loss. In addition, although dose–response curves for AHFNIHL were distinctly different when using unadjusted CNE, they overlapped when using the kurtosis-adjusted CNE. Conclusions: For the same exposure level, the prevalence of NIHL is greater in workers exposed to complex noise environments than in workers exposed to a continuous noise. Kurtosis adjustment of CNE improved the correlation with NIHL and provided a single metric for dose–response effects across different types of noise. The kurtosis-adjusted CNE may be a reasonable candidate for use in NIHL risk assessment across a wide variety of noise environments.

Radiologic indicators for prediction of difficult laryngoscopy in patients with cervical spondylosis

We identified the most useful variables for prediction of difficult laryngoscopy in patients with cervical spondylosis according to physical indicators and preoperative skeletal X‐ray and soft tissue MRI measurements. We hypothesized that there was a closer association between difficult laryngoscopy and radiologic indicators.

Asymmetric Hearing Loss in Chinese Workers Exposed to Complex Noise.

Objectives: Evaluate the audiometric asymmetry in Chinese industrial workers and investigate the effects of noise exposure, sex, and binaural average thresholds on audiometric asymmetry. Design: Data collected from Chinese industrial workers during a cross-sectional study were reanalyzed. Of the 1388 workers, 266 met the inclusion criteria for this study. Each subject underwent a physical examination and an otologic examination and completed a health-related questionnaire. &khgr;2 and t tests were used to examine the differences between the asymmetric and symmetric hearing loss groups. Results: One hundred thirty-one subjects (49.2%) had a binaural hearing threshold difference of 15 dB or more for at least one frequency, and there was no statistically significant difference between the left and right ears. The asymmetric hearing loss group was not exposed to higher cumulative noise levels (t = 0.522, p = 0.602), and there was no dose–response relation between asymmetry and cumulative noise levels (&khgr;2 = 6.502, p = 0.165). Men were 1.849 times more likely to have asymmetry than women were (95% confidence interval, 1.051 to 3.253). Among the workers with higher high-frequency hearing thresholds, audiometric asymmetry was 1.024 times more prevalent than that among those with lower high-frequency hearing thresholds (95% confidence interval, 1.004 to 1.044). Conclusions: The results indicated that occupational noise exposure contributed minimally to asymmetry, whereas sex and binaural average thresholds significantly affected audiometric asymmetry. There was no evidence that the left ears were worse than the right ears.

Reply to “Use of radiologic indicators to predict difficult laryngoscopy in patients with cervical spondylosis”

Sir: We thank professor F. S. Xuefor the comments on our article. Regarding the first point, operator experience had an important impact on the results of the study. We could not agree with it more. In view of this, during the study, the operation and laryngeal classification was determined during Macintosh laryngoscopy by the same senior anesthesiologist who had worked for more than 5 years. We have clarified this in the method section. Also, the laryngeal classification (Macintosh 3-4 blade) used in our study was defined according to the method of Cormack and Lehane, in which the initial view should be performed without the application of external laryngeal pressure. We admitted that external laryngeal pressure was widely used in clinical practice during laryngoscopy with Macintosh laryngoscope. However, any external pressure on the neck might have a potentially detrimental effect on the cervical disease. Besides, it was difficult to quantify the impact of strength of external pressure on laryngoscopy. In order to achieve the consistency of the study result, we did not give external laryngeal pressure for all study objectives. Secondly, the ideal indicator for prediction of difficult laryngoscopy would need to have perfect sensitivity and specificity. Sensitivity and specificity are dependent on each other: the increase in one of them usually results in a decrease in the other. We admit that Youden index is not a perfect evaluation index. If we choose the maximum value of Youden index, indicators will have different sensitivity and specificity. In order to facilitate the comparison of the five indicators, we try to have similar specificity and find the optimal sensitivity. Considering the practical application and clinical safety, we pay more attention to sensitivity, which helps to screen out potentially difficult laryngoscopy. According to the ROC curve, the optimal sensitivity and specificity values for distance from the highest point of the hyoid bone to the mandibular body (X4) were in the range of 19.25 to 22.3 mm, and are shown in Table 1. To facilitate clinical application, a cutoff value equal to 20 mm was chosen. Thirdly, no single factor can reliably predict difficult laryngoscopy and combinations of individual indictor or risk factors would add some incremental diagnostic value compared to that of each test alone. However, the clinical value of the combined screening tests for predicting difficult laryngoscopy remains limited if the individual indictor had only poor to moderate discriminative power when used alone. In this study, we found three independent risk factors, of which the accuracy of modified Mallampati test score is low (AUC=0.620). Even though we give a combination of several risk factors, the accuracy of evaluation is not high enough. This study aims to find out the most accurate radiologic indicator for difficult laryngoscopy in patients with cervical spondylosis. Multi-parameter evaluation should combine the best index of radiologic indicators and physical features, which can improve the accuracy of prediction. We hope to establish a new difficult airway assessment system by combining multiple tests with high discriminative power when used alone and the related research is in progress. We hope above explanation could clarify the findings of our study.

A cross-sectional study in a tertiary care hospital in China: noise or silence in the operating room

Objectives This study aims to provide a comprehensive description of noise levels in operating rooms (ORs) in a tertiary care hospital in China. Additionally, the study aims to examine the deviation in noise levels from international and internal standards as well as the differences in noise levels by category of surgery and day of the week. Methods We monitored noise levels in 23 ORs in a tertiary care hospital in China between August 2015 and March 2016. Dosimeters were used to determine noise levels. The noise data collected in the dosimeter were downloaded to an IBM computer for subsequent analysis. One-way analysis of variance and Student’s t-test were used to examine the differences in noise levels. Results The noise level in the ORs ranged between 59.2 and 72.3 dB(A), with 100% of the measurements exceeding the recommended hospital noise standards. There was substantial similarity in noise levels from Monday to Friday (F=1.404, p=0.234), with a range between 63.7 and 64.5 dB(A). The difference in noise levels by category of surgery was significant (F=3.381, p<0.001). The results of the post hoc analysis suggested that ophthalmic surgery had significantly higher noise levels than otolaryngological surgery or general surgery. Conclusions Ophthalmic surgery had significantly higher noise levels than otolaryngological or general surgeries. High noise levels were identified in all evaluated ORs during weekdays, and these levels consistently exceeded the currently accepted standards. These findings warrant further investigation to determine the harmful effects of noise on both patients and staff in ORs.