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

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 innovative technology of an athlete’s organism functional reserves increase based on bioacoustical stimulation of the respiratory system

In order to increase an athlete’s organism functional reserves we created the innovative technology based on low-frequency vibrations influence on respiratory system. First we measured acoustic impedance of an athlete’s organism for three phases of respiration at polyharmonic acoustic signal within the range of frequency from 3 Hz to 51 Hz. After that during 2 weeks we organized six sessions of bioacoustical stimulation among the group of 20 athletes, divided into subgroups with an effective (130 dB) and placebo (60 dB) effect. It was stated that six-fold effect of a scanning tonal signal with the level of sound pressure 130 dB within the range 22-36 Hz led to resonance frequency of respiratory system increase, respiratory system sound vibrations imbibitio coefficient decrease and its resistance to sound wave increase because of reserve alveoli opening and the increase of area of cross section of alveolar ways and respiratory bronchial tubes.

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.