Application of structured light technology for non-contact assessment of respiratory system parameters and activity in humans

Frequency of mechanical ventilation and respiratory activity after double lung transplantation

Human respiratory activity parameters are important indicators of vital signs. Most respiratory activity detection methods are naïve abd simple and use invasive detection technology. Non-invasive breathing detection methods are the solution to these limitations. In this research, we propose a non-invasive breathing activity detection method based on C-band sensing. Traditional non-invasive detection methods require special hardware facilities that cannot be used in ordinary environments. Based on this, a multi-input, multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system based on 802.11n protocol is proposed in this paper. Our system improves the traditional data processing method and has stronger robustness and lower bit relative error. The system detects the respiratory activity of different body postures, captures and analyses the information, and determines the influence of different body postures on human respiratory activity.

Changes in inspired volume and inspiratory flow rate alter the activity of vagal receptors in animals and this, in turn, causes reflex changes in respiratory neural activity (Bartoli et al., 1975). However, little is known about the effects of such changes on respiratory activity in humans. The present study, in normal subjects, examined the effects of mechanically controlled changes in inspired volume and inspiratory flow rate on the level and pattern of respiratory motor output.

The respiratory and circulatory activities of patients who underwent carotid body resection (CBR) more than two decades ago were reviewed. No significant ventilatory response to continuous hypoxia was observed. However, in response to stimulation of peripheral chemoreceptors, transient hyperventilation occurred before hypoxemic blood arrived at the central nervous system (single-breath test), which indicated the presence of weak peripheral chemosensitivity. Because of this slight residual peripheral chemosensitivity, which was found shortly after the operation and apparently remained more or less unchanged for greater than 20 years, peripheral chemoreceptor activity, which has been reported in other animal species, does not seem to have returned. Delayed hypoxic hyperventilation reported in dogs and cats with CBR was not observed. Hypoxia significantly depressed the ventilatory response to CO2, but the delayed ventilatory depression with time that has been demonstrated in normal subjects did not occur. In our circulatory studies, hypoxia augmented the heart rate and slightly depressed the stroke volume and total peripheral resistance in the systemic circulation but induced no appreciable changes in arterial blood pressure or cardiac output. We used these results to partition the relative contributions to the overall circulatory response of carotid body stimulation, pulmonary inflation, and other modifying influences. From these calculations, it was inferred that the carotid body reflex plays a dominant role in vascular activities whereas the pulmonary inflation reflex dominates in cardiac activities in humans.

Breathing exercises are widely used to enhance respiratory function and athletic performance. This study aimed to assess the efficacy of a modified exercise regimen on respiratory parameters and its effect on the performance of young swimmers in competition. Thirty-one swimmers aged 16–17 from various clubs in Latvia were selected, comprising an experimental group (n = 15, height: 174.36 ± 7.85 cm, weight: 65.80 ± 9.35 kg, body mass index: 21.60 ± 1.54) and a control group (n = 16, height: 180.78 ± 7.05 cm, weight: 69.90 ± 6.49 kg, body mass index: 21.40 ± 1.56). With an average of eight years of experience, participants trained for approximately 43–45 weeks annually (pool and gym sessions), with an average training duration of 20 ± 2 hours per week. Measurements were conducted on days one and 30, involving spirometry and swimming performance assessment based on the best results in the freestyle 100-meter distance. The experiment consisted of a modified breathing exercise performed thrice weekly for four weeks. Significant improvements were observed in the experimental group compared to the control group in forced vital capacity (p = 0.02), peak inspiratory flow (p = 0.001), and performance (p = 0.001), with p-values < 0.05. However, no significant changes were noted in peak expiratory flow (p = 0.46 > 0.05). The findings indicate that modified breathing exercises effectively enhance respiratory parameters and performance in competitive swimmers.

The types of human activities occupants are engaged in within indoor spaces significantly contribute to the spread of airborne diseases through emitting aerosol particles. Today, ubiquitous computing technologies can inform users of common atmosphere pollutants for indoor air quality. However, they remain uninformed of the rate of aerosol generated directly from human respiratory activities, a fundamental parameter impacting the risk of airborne transmission. In this paper, we present AeroSense, a novel privacy-preserving approach using audio sensing to accurately predict the rate of aerosol generated from detecting the kinds of human respiratory activities and determining the loudness of these activities. Our system adopts a privacy-first as a key design choice; thus, it only extracts audio features that cannot be reconstructed into human audible signals using two omnidirectional microphone arrays. We employ a combination of binary classifiers using the Random Forest algorithm to detect simultaneous occurrences of activities with an average recall of 85%. It determines the level of all detected activities by estimating the distance between the microphone and the activity source. This level estimation technique yields an average of 7.74% error. Additionally, we developed a lightweight mask detection classifier to detect mask-wearing, which yields a recall score of 75%. These intermediary outputs are critical predictors needed for AeroSense to estimate the amounts of aerosol generated from an active human source. Our model to predict aerosol is a Random Forest regression model, which yields 2.34 MSE and 0.73 r2 value. We demonstrate the accuracy of AeroSense by validating our results in a cleanroom setup and using advanced microbiological technology. We present results on the efficacy of AeroSense in natural settings through controlled and in-the-wild experiments. The ability to estimate aerosol emissions from detected human activities is part of a more extensive indoor air system integration, which can capture the rate of aerosol dissipation and inform users of airborne transmission risks in real time.

Wearable devices are extensively used for monitoring physiological parameters both in clinical settings and in sports science. Among others, respiratory rate is mostly neglected but is a valid index to assess athletes' performance. The purpose of this work was to test a wearable device composed of two elastic bands embedding conductive textiles during a running session of approximately 9.5 km. The test has been carried out by a young healthy volunteer who worn two bands on the rib cage (one on the upper thorax and one on the umbilicus). The frequency-domain analysis allowed estimating both respiratory parameters (i.e., the average respiratory rate, $\overline{f_{R}})$ and running related parameters (i.e., estimated running distance and average running pace). The wearable system was able to perform a good estimation of both respiratory and gait parameters allowing a better understanding of the relationship between the fatigue and the respiratory activity, enabling a more accurate running performance evaluation.

Role of A5 noradrenergic neurons in the chemoreflex control of respiratory and sympathetic activities in unanesthetized conditions

This study analyzed the direct short-term effect of vagus nerve stimulation (VNS) on respiratory sinus arrhythmia (RSA) in children with pharmacoresistant epilepsy. RSA magnitude is calculated as the ratio between maximum and minimum heart rate for each respiratory cycle-before, during, and after the actual VNS period. In 10 children, changes in RSA magnitude were evaluated on polysomnographic recordings, including electrocardiography (ECG), electroencephalography (EEG), thoracoabdominal distension, nasal airflow, and VNS artifacts. Measurements during stimulation were compared with those at baseline, immediately preceding the VNS periods and individually for each patient. During VNS, respiratory frequency increased and respiratory amplitude decreased with a variable effect on cardiac activity. The coupling between heart rate and respiratory rate was disturbed and RSA magnitude decreased significantly in 6 of 10 children during VNS. These changes in RSA magnitude varied from one child to another. The observed changes for respiratory and cardiac activity were concomitant with changes in RSA but were not correlated. Together with disorders of respiration, cardiac activity, and oxygen saturation (SaO(2)) described previously. VNS also modifies synchronization between cardiac and respiratory activity, resulting in poor optimization of oxygen delivery to tissues that can be regarded as an additive side effect, which should be considered in patients with already altered brain function. This interaction between the effects of VNS and potential autonomic nervous system (ANS) dysfunction already reported in epileptic patients should be considered to be potentially life-threatening. In addition, evaluation of changes in respiratory parameters can also provide reliable markers for further evaluation of the effectiveness of VNS.

Central control of breathing in mammals: neuronal circuitry, membrane properties, and neurotransmitters

Computer-controlled research ventilators for small animals (SAV) are often used to assess the respiratory mechanics’ parameters such as resistance and elastance of the respiratory system in animal models of disease. In commercially available SAVs, it is common to obtain such parameters with the forced oscillation of a given volume of air into respiratory system with a quasi-sinusoidal pattern in a closed pneumatic circuit (i.e. both the injection and the removal of gas during the piston movement). We hypothesized that obtaining the respiratory mechanical parameters with the linear single-compartment model (LSCM) during the forced inspiration and forced expiration (when calculated together) is not sufficient to explain the physiology of the respiratory system exposed to high doses of bronchial agonist. In order to verify this, male Wistar rats (n = 5) were anesthetized, orotracheally intubated, mechanically ventilated at 90bpm (or 1.5Hz) with a tidal volume of 10mL/kg, and a positive end-expiratory pressure (PEEP) was set at 3cmH2O. The ventilation was performed in a commercial mechanical ventilator (flexiVent, SCIREQ Inc., Canada) and the animals were infused with a saline solution (PBS), followed by 3 increasing doses (3, 30 and 300mg/mL) of the bronchial agonist methacholine (MCh). Respiratory parameters were calculated by the LSCM. Pressure and volume data, calibrated and corrected by a proprietary software, were analyzed using a computational routine. The full quasi-sinusoidal signal data was compared to inlet and outlet of air from the lungs separately. The data obtained showed that the difference among the three signals (i.e. whole signal, imposed-inspiration, and imposed-expiration) is pronounced at the higher dose (MCh 300mg/mL). Data from imposed-inspiration alone seem to better reflect the respiratory mechanics when a large dose of bronchial agonist is used.

Effects of volume and frequency of mechanical ventilation on respiratory activity in humans

BackgroundThe cardiorespiratory effect in mental illnesses has recently received much attention. However, the cardiovascular and pulmonary effects of mood disorders have not been clearly demonstrated.AimsThis study aims to compare individuals with mood disorders and healthy people in terms of exercise capacity, functionality, respiratory muscle strength, pulmonary function, dyspnoea and physical activity level.MethodThis cross-sectional study involved 30 patients with mood disorders and 35 age- and gender-matched healthy individuals. Exercise capacity (6-Minute Walk Test (6MWT), 3-Minute Step Test (3MST)), functionality (vertical jump test, functional reach test), respiratory parameters (respiratory muscle strength, pulmonary function test), dyspnoea (Modified Medical Research Council Dyspnoea Scale) and physical activity level (Short-Form International Physical Activity Questionnaire (IPAQ)) were evaluated.Results6MWT results (P < 0.001) and functional test scores (vertical jump test, P = 0.006; functional reach test, P < 0.001) were significantly lower, and heart rate recovery after 3MST (P < 0.001) was higher in mood disorder patients. Although patients' respiratory parameters were lower than healthy individuals, only measured and predicted respiratory muscle strength (P < 0.001), peak expiratory flow rate litres (P < 0.001), forced vital capacity predicted (P = 0.010) and forced expiratory volume in 1 s predicted (P = 0.002) values were statistically significantly different. Dyspnoea with activities was higher in patients (P < 0.001). Patients spent more time sitting (IPAQ, P < 0.001), but overall physical activity levels were similar between the two groups (P > 0.05).ConclusionsPatients with mood disorders had decreased exercise capacity and pulmonary function, lower functionality scores and respiratory muscle strength, and increased dyspnoea. Exercise-based rehabilitation protocols are recommended for the management of risk factors affecting the mood disorder patients' cardiorespiratory status.

The objective of this study was to investigate the influence of different backpack weights on trunk kinematics and respiratory parameters during walking in 10-year-old children. Fifteen boys with a mean age of 10.31 (0.26) years were selected from a primary school to participate in four walking trials on a treadmill: one with a backpack of 0% of body mass, and three whilst carrying backpacks that weighed 10%, 15%, and 20% of the child's body mass. The walking speed was set at 1.1 m s(-1) for 20 min duration. The walking movement was recorded on video and analysed in two dimensions. The breathing frequency, tidal volume, and respiratory muscles activity were measured with a cardiopulmonary system (Oxycon Champion, Jaeger) and a respiratory inductance plethysmograph (TR-601T, Nihon Kohden, Japan). A repeated ANOVA and Pearson correlation analysis were used to examine any significant differences in the measured parameters when comparing the different loads. The results showed a significant positive linear relationship between load weight, trunk inclination angle, and breathing frequency ( P<0.01). Walking for 20 min, carrying a load that weighed 20% of body mass induced a significantly increased trunk inclination angle. A significant increase in ventilation during walking with a backpack of 15% and 20% of bodymass was associated with a more rapid breathing frequency. Walking with a backpack of 10% body mass did not significantly change trunk posture or respiratory parameters. However, the results suggested that walking with a backpack of greater than 10% body mass induced significant changes in trunk posture and respiratory parameters in 10-year-old children.

BackgroundDysfunction of human respiratory and electro-cardiac activities could affect the ability of the heart to pump blood and the lungs to inhale oxygen. Thus, a device could simultaneously measure electro-cardiac signal and respiratory pressure could provide vital signs for predicting early warning of cardio-pulmonary function-related chronic diseases such as cardiovascular disease, and respiratory system disease.ResultsIn this study, a flexible device integrated with piezo-resistive sensing element and voltage-sensing element was developed to simultaneously measure human respiration and electro-cardiac signal (including respiratory pressure, respiration frequency, and respiration rhythm; electro-cardio frequency, electro-cardio amplitude, and electro-cardio rhythm). When applied to the measurement of respiratory pressure, the piezo-resistive performance of the device was enhanced by nano-copper modification, which detection limitation of pressure can reduce to 100 Pa and the sensitivity of pressure can achieve to 0.053 ± 0.00079 kPa−1. In addition, the signal-to-noise ratio during bio-electrical measurement was increased to 10.7 ± 1.4, five times better than that of the non-modified device.ConclusionThis paper presents a flexible device for the simultaneous detection of human respiration and cardiac electrical activity. To avoid interference between the two signals, the layout of the electrode and the strain sensor was optimized by FEA simulation analysis. To improve the piezo-resistive sensitivity and bio-electric capturing capability of the device, a feather-shaped nano-copper was modified onto the surface of carbon fiber. The operation simplicity, compact size, and portability of the device open up new possibilities for multi-parameter monitoring.