Mariana Alves-Pereira

Respiratory pathology in vibroacoustic disease: 25 years of research

BACKGROUND Respiratory pathology induced by low frequency noise (LFN, < 500 Hz, including infrasound) is not a novel subject given that in the 1960s, within the context of U.S. and U.S.S.R. Space Programs, other authors have already reported its existence. Within the scope of vibroacoustic disease (VAD), a whole-body pathology caused by excessive exposure to LFN, respiratory pathology takes on specific features. Initially, respiratory pathology was not considered a con- sequence of LFN exposure; but today, LFN can be regarded as a major agent of disease that targets the respiratory system. The goal of this report is to put forth what is known to date on the clinical signs of respiratory pathology seen in VAD patients. METHODS Data from the past 25 years of research will be taken together and presented. RESULTS In persons exposed to LFN on the job, respiratory complaints appear af- ter the first 4 years of professional activity. At this stage, they disappear during vacation periods or when the person is removed form his /her workstation for other reasons. With long-term exposure, more serious situations can arise, such as, atypical pleural effusion, respiratory insufficiency, fibrosis and tumours. There is no correlation with smoking habits. In LFN-exposed animal models, morphological changes of the pleura, and loss of the phagocytic ability of pleural mesothelial cells (explaining the atypical pleural effusions). Fibrotic lesions and neo-vascularization were observed along the entire respiratory tract. Fibrosis lesions and neovascularisation were observed through- out the respiratory tract of the animals seen. Pre-malignant lesions, metaplasia e displasia, were also identified. DISCUSSION LFN is an agent of disease and the respiratory tract is one of its preferential targets. The respiratory pathology associated with VAD needs further in-depth studies in order to achieve a greater understanding, and develop methods of pharmaco- logical intervention.

Voice acoustic patterns of patients diagnosed with vibroacoustic disease

BACKGROUND Long-term low frequency noise exposure (LFN) (< or = 500 Hz, including infrasound) may lead to the development of vibroacoustic disease (VAD), a systemic pathology characterized by the abnormal growth of extra-cellular matrices. The respiratory system is a target for LFN. Fibrosis of the respiratory tract epithelia was observed in VAD patients through biopsy, and confirmed in animal models exposed to LFN. Voice acoustic analysis can detect vocal fold variations of mass, tension, muscular and neural activity. Frequency perturbation (jitter), amplitude perturbation (shimmer) and harmonic-to-noise ratio (HNR) are used in the evaluation of the vocal function, and can be indicators of the presence and degree of severity of vocal pathology. Since the respiratory system is the energy source of the phonation process, this raises questions about the effects of VAD on voice production. The purpose of this study was to determine if voice acoustic parameters of VAD patients are different from normative data. METHODS Nine individuals (5 males and 4 females) diagnosed with VAD were recorded performing spoken and sung tasks. The spoken tasks included sustaining vowels and fricatives. The sung tasks consisted of maximum phonational frequency range (MPFR). Voice acoustic parameters ana- lysed were: fundamental frequency (F0), jitter, shimmer, HNR and temporal measures. RESULTS Compared with normative data, both males and females diagnosed with VAD exhibited increased F0, shimmer and HNR. Jitter, MPFR and one temporal measure were reduced. CONCLUSIONS VAD individuals presented voice acoustic parameter differences in spectral, temporal and perturbation measures, which may be indicative of small morphological changes in the phonatory system.

Abnormal respiratory drive in vibroacoustic disease

INTRODUCTION Central nervous system disorders in workers exposed to low frequency noise (LFN, < 500 Hz, including infrasound) were first observed 25 years ago among aircraft technicians. Concurrently, respiratory pathology was identified in these workers, and later reproduced in LFN-exposed animal models. Today vibroacoustic disease (VAD) is defined as the systemic pathology caused by excessive exposure to LFN. The respiratory tract continues to be under heavy scrutiny in both LFN-exposed humans and animal models and has been confirmed as a major target for LFN-induced damage. Given that both the respiratory and central nervous systems were compromised in these workers, it became pertinent to investigate the status of the neurological control of breathing in VAD patients. METHODS The P- 0.1 value, a measure of the suction pressure developed at the mouth 0.1 seconds after the start of inspiration, depends on the respiratory centres and the autonomic nervous system pathway of the neural control of respiratory function. By rebreathing CO2, (6% in air) normal individuals present an average seven-fold increase in P0.1 (CO2) as compared to basal P- 0.1. Twenty-two male VAD patients (ave. age 50.5 +/- 8.5 years, range: 36-66 years) underwent the P0.1(CO2) index respiratory drive tests, as well as standard pulmonary function tests. Seven individuals (ave. age 42.4 +/-14 years, range: 25- 61 years) with reduced LFN exposure served as controls. RESULTS Pulmonary function tests were normal in both VAD patients and controls. The P0.1 (CO2) in- dex was below average value in VAD patients (average: 22.9%) while it presented normal values in the control group (average > 60%). DISCUSSION In the involuntary response to increased PCO2 levels, central chemoreceptors are responsible for 70% of the ventilatory stimulus. In VAD patients, this dysfunction may originate in the brainstem. This is corroborated by the fact that VAD patients register abnormal values for auditory brainstem evoked potentials, and disclose lesions with magnetic resonance imaging. The neurological control of breathing is compromised in VAD patients. The P0.1 (CO2) index may be a useful clinical indicator for VAD diagnosis and follow-up.

Padrões acústicos da voz em indivíduos com a doença vibroacústica

Background: Long-term low frequency noise exposure (LFN) (≤ 500 Hz, including infrasound) may lead to the development of vibroacoustic disease (VAD), a systemic pathology characterized by the abnormal growth of extra-cellular matrices. The respiratory system is a target for LFN. Fibrosis of the respiratory tract epithelia was observed in VAD patients through biopsy, and confirmed in animal models exposed to LFN. Voice acoustic analysis can detect vocal fold variations of mass, tension, muscular and neural activity. Frequency perturbation (jitter), amplitude perturbation (shimmer) and harmonic-to-noise ratio (HNR) are used in the evaluation of the vocal function, and can be indicators of the presence and degree of severity of vocal pathology. Since the respiratory system is the energy source of the phonation process, this raises questions about the effects of VAD on voice production. The purpose of this study was to determine if voice acoustic parameters of VAD patients are different from normative data. Methods: Nine individuals (5 males and 4 females) diagnosed with VAD were recorded performing spoken and sung tasks. The spoken tasks included sustaining vowels and fricatives. The sung tasks consisted of maximum phonational frequency range (MPFR). Voice acoustic parameters analysed were: fundamental frequency (F0), jitter, shimmer, HNR and temporal measures. Results: Compared with normative data, both males and females diagnosed with VAD exhibited increased F0, shimmer and HNR. Jitter, MPFR and one temporal measure were reduced. Conclusions: VAD individuals presented voice acoustic parameter differences in spectral, temporal and perturbation measures, which may be indicative of small morphological changes in the phonatory system. Rev Port Pneumol 2006; XII (4): 375-382

Respiratory squamous cell carcinomas in vibroacoustic disease

BACKGROUND In 1987, the autopsy of a vibroacoustic disease (VAD) patient disclosed two tumours: a renal cell carcinoma and a malignant glioma in the brain. Since 1987, malignancy in VAD patients has been under close surveillance. To date, in a universe of 945 individuals, there are 46 cases of malignancies, of which 11 are multiple. Of the 11 cases of respiratory tract tumours, all were squamous cell carcinomas (SqCC). This report focuses on the morphological features of these tumours. METHODS Tumour fragments were collected (endoscopic biopsy or surgery) from 11 male VAD patients (ave. age: 58+/-9 years, 3 non-smokers): 2 in glottis and 9 in the lung. In the 3 non-smokers, 2 had lung tumours and 1 had a glottis tumour. All were employed as or retired aircraft technicians, military or commercial pilots. Fragments were fixed either for light and electron microscopy. Immunohistochemistry studies used chromagranine and synaptophysine staining. RESULTS All lung tumours were located in the upper right lobe bronchi and were histologically poorly differentiated SqCC (Figs. 1, 2). The search with neuroendocrine markers was negative. The average age of tumour onset in helicopter pilots was below 50 years old while for the other professional groups it was above 50. Nine patients are deceased. The 2 surviving patients are heavy smokers (> 2 packs/day). Smoking habits had no influence on tumour outcome and progression. DISCUSSION Epidemiological studies indicate that squamous cell carcinomas account for approximately 40% of all lung tumours in men. It seems to be highly relevant that all VAD patient respiratory tract tumours are squamous cell carcinomas. It is not surprising that helicopter pilots are the ones who are affected the earliest because previous studies have shown that helicopter pilots exhibited the highest values for the frequency of sister chromatid exchanges. Generally, epidemiological tumor studies do not take histological tumor type into account, but given the results herein, it would seem of the utmost importance to begin specifiying the exact histological type of tumor in all statistical studies.