Human forced expiratory noise. Origin, apparatus and possible diagnostic applications.

Forced expiratory (FE) noise is a powerful bioacoustic signal containing information on human lung biomechanics. FE noise is attributed to a broadband part and narrowband components-forced expiratory wheezes (FEWs). FE respiratory noise is composed by acoustic and hydrodynamic mechanisms. An origin of the most powerful mid-frequency FEWs (400-600 Hz) is associated with the 0th-3rd levels of bronchial tree in terms of Weibel [(2009). Swiss Med. Wkly. 139(27-28), 375-386], whereas high-frequency FEWs (above 600 Hz) are attributed to the 2nd-6th levels of bronchial tree. The laboratory prototype of the apparatus is developed, which includes the electret microphone sensor with stethoscope head, a laptop with external sound card, and specially developed software. An analysis of signals by the new method, including FE time in the range from 200 to 2000 Hz and band-pass durations and energies in the 200-Hz bands evaluation, is applied instead of FEWs direct measures. It is demonstrated experimentally that developed FE acoustic parameters correspond to basic indices of lung function evaluated by spirometry and body plethysmography and may be even more sensitive to some respiratory deviations. According to preliminary experimental results, the developed technique may be considered as a promising instrument for acoustic monitoring human lung function in extreme conditions, including diving and space flights. The developed technique eliminates the contact of the sensor with the human oral cavity, which is characteristic for spirometry and body plethysmography. It reduces the risk of respiratory cross-contamination, especially during outpatient and field examinations, and may be especially relevant in the context of the COVID-19 pandemic.

An attempt at hydroacoustic localization of an open-circuit scuba diver.

Passive acoustic monitoring of scuba divers is a promising way to ensure the safety of recreational divers and prevent waterside intrusion by terrorists. It is shown experimentally that the low-frequency underwater respiratory-associated noise of an open-circuit scuba diver can be used successfully to monitor the respiratory rate at distances of up to 100 m. Respiratory-associated noise in the frequency band of 30-1200 Hz provides the possibility of localizing an open-circuit scuba diver in a noisy shallow-water area by using two pairs of hydrophones at distances of up to 220 m and with a predominant discrepancy of no more than 10 m in comparison with Global Positioning System data.

A Technique of Forced Expiratory Noise Time Evaluation Provides Distinguishing Human Pulmonary Ventilation Dynamics During Long-Term Head-Down and Head-Up Tilt Bed Rest Tests Simulating Micro and Lunar Gravity.

Estimating the effect of microgravity/hypogravity on pulmonary ventilation function remains topical. Recently developed acoustic techniques based on the evaluation of the forced expiratory noise time (FETa) were hypothesized to be a promising tool for this aim. The aim of the protocol is to study the effect of two different modalities of bed rest space simulations (microgravity and lunar gravity) on FETa and spirometric indices. The FETa in the frequency band of 200-2000 Hz, recorded above human trachea, was evaluated. The 21st-day exposure to 6 degree head-down tilt (HDT) bed rest, simulating microgravity, and 9.6 degree head-up tilt (HUT) bed rest with head-zero tilt (HZT) rest intervals (HUT + HZT), simulating lunar gravity, in statistically identical subgroups of five and six healthy male volunteers, was studied. In the course of HDT bed rest, a significant elongation of FETa was found in relation to background measurements in "sitting" position (p = 0.016). The effect corresponded to a significant decrease of basic spirometric indices (p < 0.02). Moreover, FETa provided reliable discrimination of HDT and HUT + HZT bed rest tests (p = 0.018), while spirometric indices did not (p > 0.05). Based on previously found correlations (Korenbaum and Pochekutova, 2008; Malaeva et al., 2017), a FETa elongation in response to HDT bed rest was attributed to an increase of aerodynamic resistance of the respiratory tract. The technique seems promising to monitor human pulmonary ventilation dynamics in long-term space missions; however, new studies are welcome to verify it in real spaceflight.

Diagnosis of hidden bronchial obstruction using computer-assessed tracheal forced expiratory noise time.

BACKGROUND AND OBJECTIVE: Increased forced expiratory time was first recognized as a marker of obstruction half a century ago. However, the reported diagnostic capabilities of both auscultated forced expiratory time (FET(as)) and spirometric forced expiratory time are contradictory. Computer analysis of respiratory noises provides a precise estimation of acoustic forced expiratory noise time (FET(a)) being the object-measured analogue of FET(as). The aim of this study was to analyse FET(a) diagnostic capabilities in patients with asthma based on the hypothesis that FET(a) could reveal hidden bronchial obstruction. METHODS: A group of asthma patients involved 149 males aged 16-25 years. In this group, 71 subjects had spirometry features of bronchial obstruction, meanwhile, the remaining 78 had normal spirometry. A control group involved 77 healthy subjects. Spirometry and forced expiratory tracheal noise recording were sequentially measured for each participant. FET(a) values were estimated by means of a developed computer procedure, including bandpass filtration (200-2000 Hz), waveform envelope calculation with accumulation period of 0.01 s, automated measurement of FET(a) at 0.5% level from the peak amplitude. RESULTS: Specificity, sensitivity and area under Receiver Operating Characteristic curve of FET(a) and its ratios to squared chest circumference, height, weight were indistinguishable with baseline spirometry index FEV1 /forced vital capacity. Meanwhile, acoustic features of obstruction were revealed in 41%-49% of subgroup of patients with asthma but normal spirometry. CONCLUSIONS: FET(a) of tracheal noise and its ratio to anthropometric parameters seem to be sensitive and specific tests of hidden bronchial obstruction in young male asthma patients.

Flow noise of an underwater vector sensor embedded in a flexible towed array.

The objective of this work is to simulate the flow noise of a vector sensor embedded in a flexible towed array. The mathematical model developed, based on long-wavelength analysis of the inner space of a cylindrical multipole source, predicts the reduction of the flow noise of a vector sensor embedded in an underwater flexible towed array by means of intensimetric processing (cross-spectral density calculation of oscillatory velocity and sound-pressure-sensor responses). It is found experimentally that intensimetric processing results in flow noise reduction by 12-25 dB at mean levels and by 10-30 dB in fluctuations compared to a squared oscillatory velocity channel. The effect of flow noise suppression in the intensimetry channel relative to a squared sound pressure channel is observed, but only for frequencies above the threshold. These suppression values are 10-15 dB at mean noise levels and 3-6 dB in fluctuations. At towing velocities of 1.5-3 ms(-1) and an accumulation time of 98.3 s, the threshold frequency in fluctuations is between 30 and 45 Hz.

Regression simulation of the dependence of forced expiratory tracheal noises duration on human respiratory system biomechanical parameters.

BACKGROUND: Estimating the duration of forced exhalation tracheal noises shows promise for recognizing bronchial obstruction. OBJECTIVE: Experimental simulation of an influence of biomechanical parameters on the duration of normal forced exhalation tracheal noises. METHOD AND MATERIALS: Thirty-two healthy non-smoking men aged 16-22 years were examined. The duration of noises, the parameters of computer spirometry, and the maximum static expiratory pressure are recorded. These data were analyzed by means of multiple linear regression simulation for logarithms of the elements of the proportionality relation obtained with the use of a one-component biomechanical model of forced exhalation and a linearized approximation of flow-volume curve. RESULTS: Dependence between duration of the forced expiratory noises recorded on human trachea and the product of forced volume capacity (in power of 1.05 +/- 0.27), maximum static expiratory pressure (in power of 0.46 +/- 0.23), equivalent expiratory resistance in the stage of functional expiratory stenosis (in power of 0.72 +/- 0.15 in healthy is an estimate of the equivalent expiratory resistance of human bronchial tree in the functional expiratory stenosis phase, whereas in patients with bronchial obstruction it is supposed to take into account an excess of noise generation time compared with the time predicted from normal individual value of this resistance.

Absorption spectra of electronic-homoeopathic copies of homoeopathic nosodes and placebo have essential differences.

BACKGROUND: Electronic-homoeopathic copies (EHC), i.e. preparations made by 'imprinting' the parent substance onto water (or other carriers) with the help of M. Rae devices, have gained certain acceptance in some fields of alternative medicine as homoeopathic nosodes. OBJECTIVE: To verify the electronic-homoeopathic copying effect with the use of absorption spectroscopy. MATERIALS AND METHODS: In a double-blind randomized procedure 7 homoeopathic nosodes and a blank placebo were 'imprinted' onto ampoules with saline solution by means of a 'simulator' apparatus by Metabolics Ltd (Wiltshire, UK). There were 63 ampoules of the EHC (9 of each nosode) and 27 ampoules of the placebo (3 groups). The absorption spectra of the preparations were determined by a UV-2101 PC (Shimadzu, Kyoto, Japan) double-beam spectrometer in the wave band 800-600 nm at an interval of 0.5 nm. The values of optical density - log (1/transmission coefficient) - were written. RESULTS: The absorption spectra of 3 EHC of the 7 homoeopathic nosodes investigated showed regions marked by statistically significant differences (p < 0.05 for 2 adjacent wavelengths) in the band of 800-700 nm in 2 (as a minimum) out of 3 independent placebo groups. When compared in independent groups of placebo, the spectral regions - for which the significant differences between the EHC and the placebo were evident - are close to each other (in the range of 0.5-7.0 nm). CONCLUSION: The result obtained supports the existence of an electronic-homoeopathic copying effect.