Respiratory Monitoring Systems Research Articles

High-sensitivity QCM humidity sensor based on chitosan/carboxymethylated multiwalled carbon nanotubes composite for non-contact respiratory monitoring

Respiratory humidity is an important indicator that can reflect respiratory disorders and is easily accessible in daily life, thus attracting attention in non-contact home respiratory monitoring systems. In this work, a high-sensitivity quartz crystal microbalance (QCM) humidity sensor based on a chitosan/carboxymethylated multiwalled carbon nanotubes composite coating is developed with a response time of 36 s and a recovery time of 38 s. The humidity variations from 11 to 97 % can be detected while the wet hysteresis is 0.95 % RH. The sensor also exhibits good repeatability and stability. The physicochemical characterizations of the materials reveal the mechanism of the rapid humidity response, i.e., compared to the physically blended CS with MWCNT, the crosslinking CS-MWCNT formed the new intercalation by stronger hydrogen and amide bonding, which leads to the homogeneous coverage of CS on MWCNT, exposing more active sites and facilitating the binding rate of water molecules. Combined with respiration monitoring, the sensor is able to accurately monitor human respiration rate and depth in real time, effectively predicting and differentiating between different types of obstructive sleep apnea syndromes, providing a fast and reliable solution for daily health monitoring.

Comparison of two different respiratory monitoring systems with 4D-CT images for target volume definition in patients undergoing para-aortic nodal irradiation.

Today, respiratory movement can be monitored and recorded with different methods during a simulation on a four-dimensional (4D) computed tomography (CT) device to be used in radiotherapy planning. A synchronized respiratory monitoring system (RPM) with an externally equipped device is one of these methods. Another method is to create 4D images of the patient's breathing phases without the need for extra equipment, with an anatomy-based software program integrated into the CT device. Our aim is to compare the RPM system and the software system (Deviceless) which are two different respiratory monitoring methods used in tracking moving targets during 4D-CT imaging and to assess their clinical usability. Ten patients who underwent paraaortic nodal irradiation were enrolled. The simulation was performed using intravenous contrast material on a 4D-CT device with both respiratory monitoring methods. The right/left kidneys and renal arteries were chosen as references to evaluate abdominal organ movement. It was then manually contoured one by one on both sets of images. The images were compared volumetrically and geometrically after rigid reconstruction. The similarity between the contours was determined by the Dice index. Wilcoxon test was used for statistical comparisons. The motion of the kidneys in all three directions was found to be 0.0 cm in both methods. The shifts in the right/left renal arteries were submillimetric. The Dice index showed a high similarity in both kidney and renal artery contours. In our study, no difference was found between RPM and Deviceless systems used for tracking and detection of moving targets during simulation in 4D-CT. Both methods can be used safely for radiotherapy planning according to the available possibilities in the clinic.

Lead free halide perovskite embedded PVDF based efficient mechanical energy harvester: Self-driven respiratory sensor

Lead-free inorganic perovskites have emerged as a promising material for energy harvesting applications, owing to their superior optoelectronic properties. This enables the insertion of lead-free halide perovskites into polyvinylidene difluoride (PVDF) to feasibly enhance its piezoelectric coefficient. Consequently, piezoelectric nanogenerators based on PVDF composite have evolved as a futuristic, sustainable, and renewable energy alternative due to their flexible, durable, and nontoxic behavior. Herein, we realized a novel composite by incorporating different mass-fractions of pre-synthesized CsCuCl3 particles in the polymer matrix. Notably, the composite containing 4 wt% CsCuCl3 perovskite nucleates an optimum electroactive phase fraction of about ∼93 %. A first-principles investigation is also carried out in order to fully comprehend the interfacial interaction of the PVDF dipole with the CsCuCl3 system. Thereafter, the piezo-sensors are fabricated utilizing the composites, where the 4 wt% CsCuCl3/PVDF- based device delivered optimal output performance owing to its highest electroactive phase. This optimized device, viz., PNG 4 achieves an open-circuit voltage and short-circuit current of ∼73.2 V and ∼5.44 μA, respectively. Besides, the optimized device could operate as a piezo-resistive sensor as well as a pressure sensor. An excellent sensing performance was achieved from the PNG 4 device, where the sensing parameter (∆II0) reached values as high as ∼98.7. The optimized device is efficient in the low-pressure region and exhibits a high sensitivity of 13.8 kPa−1 with notable response ≤26ms and recovery time≤75ms. Furthermore, the device is capable of sensing different bending states with a sensitivity of 0.5/degree, which proves its potential for applications in human health care monitoring regarding self-powered real-time respiratory monitoring systems.

High-speed low-noise optical respiratory monitoring for spot scanning proton therapy

PurposeTo investigate a novel optical markerless respiratory sensor for surface guided spot scanning proton therapy and to measure its main technical characteristics. MethodsThe main characteristics of the respiratory sensor including sensitivity, linearity, noise, signal-to-noise, and time delay were measured using a dynamic phantom and electrical measuring equipment on a laboratory stand. The respiratory signals of free breathing and deep-inspiration breath-hold patterns were acquired for various distances with a volunteer. A comparative analysis of this sensor with existing commercially available and experimental respiratory monitoring systems was carried out based on several criteria including principle of operation, patient contact, application to proton therapy, distance range, accuracy (noise, signal-to-noise ratio), and time delay (sampling rate). ResultsThe sensor provides optical respiratory monitoring of the chest surface over a distance range of 0.4–1.2 m with the RMS noise of 0.03–0.60 mm, SNR of 40–15 dB (for motion with peak-to-peak of 10 mm), and time delay of 1.2 ± 0.2 ms. ConclusionsThe investigated optical respiratory sensor was found to be appropriate to use in surface guided spot scanning proton therapy. This sensor combined with a fast respiratory signal processing algorithm may provide accurate beam control and a fast response in patients’ irregular breathing movements. A careful study of correlation between the respiratory signal and 4DCT data of tumor position will be required before clinical implementation.

Carbon nanodot-based humidity sensor for self-powered respiratory monitoring

Developing low-cost, portable, and high-performance humidity sensors for respiratory monitoring has received considerable attention in recent years. Herein, humidity sensors have been fabricated based on carbon nanodots (CDs), which exhibit high sensitivity (5318%) at 94% relative humidity (RH) and excellent long-time stability under the RH range of 11% to 94%. The high sensitivity can be attributed to the adsorption of the water molecules by the massive hydrophilic functional groups on the surface of CDs. By introducing a breath-driven triboelectric nanogenerator (TENG), the self-powered humidity sensor is developed for the first time, exhibiting a wide sensing range (11–94% RH) and excellent stability. The maximum output voltage of the TENG is up to 200 V and the maximum short-circuit current is about 9.2 μA. Furthermore, the self-powered humidity sensor further demonstrates the potential ability for real-time respiration monitoring, which can detect different breathing statuses. This work provides a convenient and low-cost strategy for constructing sensitive CDs-based humidity sensors, and prospects their applications in respiratory monitoring systems.

Helical Fiber Strain Sensors Based on Triboelectric Nanogenerators for Self-Powered Human Respiratory Monitoring.

Respiration is a major vital sign, which can be used for early illness diagnosis and physiological monitoring. Wearable respiratory sensors present an exciting opportunity to monitor human respiratory behaviors in a real-time, noninvasive, and comfortable way. Among them, fiber-shaped triboelectric nanogenerators (FS-TENGs) are attractive for their comfort and high degree of freedom. However, the single-electrode FS-TENGs cannot respond to their own tensile strains, and the coaxial double-electrode FS-TENGs show low sensitivity to strain due to structural limitations. Here, a type of helical fiber strain sensor (HFSS) is developed, which can respond to tiny tensile strains. In addition, a smart wearable real-time respiratory monitoring system is developed based on the HFSSs, which can measure some key breathing parameters for disease prevention and medical diagnosis. An intelligent alarm can automatically call a preset mobile phone for help in response to respiratory behavior changes. This work provides an effective helical structure for fabricating highly sensitive strain sensors based on FS-TENGs and develops wearable self-powered real-time respiratory monitoring systems.

QRS Morphology-Based EDR Signal—Factors Determining its Properties

Respiration-induced signals contain a clinically significant information. It could be obtained utilizing both direct and indirect methods. ECG-Derived Respiration (EDR) method is the latter one. However, in this case, two approaches could be distinguished. First one is based on determining changes in the morphology of QRS complexes while the second one is based on the Respiratory Sinus Arrhythmia (RSA) mechanism. The former approach is discussed in the paper. The basic properties of QRS morphology-based EDR signal were evaluated by means of simulations performed using a developed FEM model and appropriate experiments. In effect, basing on changes of the leads’ voltages induced by a heart translation or rotation, or by both mechanisms undergoing simultaneously, the sensitivity-like surfaces and the synthetic EDR signals were obtained. A very good agreement of the experimental and simulation results was achieved. The QRS morphology-based signal’s properties strongly depend on geometrical relation of the used lead to dominating direction of the heart translation, its rotation, and on personal relation between these two mechanisms. The conclusions presented should be taken into account especially when developing or using QRS morphology-based approach in respiratory monitoring systems.

Development of MEMS accelerometer based real time data acquisition prototype for COVID-19 patient breath monitoring and assessment

In late 2019, coronavirus-2, a dangerous human pathogen that causes the disease coronavirus disease 2019, arose as a severe human pathogen (COVID-19). Acute respiratory failure, which is similar to acute respiratory distress syndrome, is the most frequent clinical presentation of extreme COVID-19. COVID-19 includes diseases of the airway, lung parenchymal, pulmonary vascular, and respiratory neuromuscular systems. This essay summarises what is learned about the impact of coronavirus-2 infection on various areas of the respiratory system, provides insights into the basic pathology of respiratory disease, and highlights current and prospective translational and clinical research. This paper discusses economic and reliable respiratory monitoring systems using prototype popular embedded controller and built-in smartphone MEMS accelerometer. The hardware is tested and implemented on healthy, and Covid-19 affected persons for respiratory data, and Correlation has been made among them. One class SVM(Support Vector Machine) learning algorithm further processes the data collected from the sensor. The project primarily aims to detect anomalies in the respiratory data set to assess the rate of respiration by matching the data sets of a healthy individual and a COVID infected person.

61 Comparative study of the two respiratory monitoring systems for 4D-Computed Tomography

61 Comparative study of the two respiratory monitoring systems for 4D-Computed Tomography

Investigation of Internal Target Volumes Using Device and Deviceless Four‑dimensional Respiratory Monitoring Systems for Moving Targets in Four‑dimensional Computed Tomography Acquisition

Investigation of Internal Target Volumes Using Device and Deviceless Four‑dimensional Respiratory Monitoring Systems for Moving Targets in Four‑dimensional Computed Tomography Acquisition

Investigation of Internal Target Volumes Using Device and Deviceless Four-dimensional Respiratory Monitoring Systems for Moving Targets in Four-dimensional Computed Tomography Acquisition.

Aims and Objectives:The influence of target motion on the reconstructed internal target volume (ITV) for device-based (DB) external surrogate system and Smart deviceless (DL) 4-dimensional (4D) system were compared in a controlled phantom experiment. The volumetric changes in reconstructed ITVs from the average intensity projection (AveIP) images using DB method (Anzai Respiratory Gating System, ANZAI MEDICAL CO., LTD, Japan) and DL method (Smart deviceless 4D system by GE Medical Systems (Chicago, USA)) with the theoretical true volume (ITVth) for moving target with the increasing target motion in anterior-posterior (A-P), lateral (left-right [L-R]) and inferior-superior (S-I) directions were assessed.Materials and Methods:4D computed tomography (4DCT) of CIRS dynamic phantom (Computerized Imaging Reference Systems Inc., Norfolk, VA, USA) with 2.5 cm diameter spherical target of volume 8.2 cc programmed to move in a cos4(x) motion pattern placed in the lung volume were acquired for various target motion pattern using DB and DL method of gating. AveIP images of 10 phase binned image sets were generated and ITVs were delineated.Results:The maximum absolute percent differences between ITVave and ITVth for DL and DB methods were 15.91% and 4.94 % respectively for target motion of 5 mm in AP with 15 mm S-I direction. When the S-I motion was decreased to 10 mm, the observed % difference of the ITVs were also decreased to 12.5% and 0.3% for DL and DB method. When the lateral [L-R] motion was varied from 0 mm to 5 mm for S-I motion of 5 mm to 15 mm, the differences in the ITVs were significant (P = 0.004) with the maximum absolute percent difference of 18.61% and 4.94 % for DL and DB gating. With the simultaneous motion of the target in all the 3 directions, the difference in the reconstructed ITVs were statistically significant for DL method (P = 0.0002) and insignificant for DB method (P = 0.06) with an average increase of 10% in ITVDL against 2% in the ITVDB. The difference in ITVDL was significant for the target motion above 3 mm in A-P and L-R directions for S-I movement of above 10 mm (P = 0.0002). However, for low excursions of the target movement, no significant difference in the ITVs were observed (P > 0.06). In general, ITVDBs were closer to the ITVth (within 7.8%) than ITVDL (18.61%).Conclusion:The results showed that the DL method is an effective way of image sorting in 4D acquisition for smaller target excursion. When the target motion exceeds 3 mm in A-P and L-R directions with S-I more than 10 mm, DB method is the choice due to its accuracy in reproducing the absolute target volume.

Use Preferences for Continuous Cardiac and Respiratory Monitoring Systems in Hospitals: A Survey of Patients and Family Caregivers

The overarching objective of this research is to reduce the burden of 'alert fatigue' on patients and family caregivers who stay overnight in hospitals on units that provide continuous monitoring of cardiac and respiratory systems. When a patient develops respiratory compromise on the medical-surgical units of the hospital, the mortality rate is 29 times higher. Alarms require nurses to quickly respond, even when it is likely a false alarm. An anonymous survey was distributed to patients and family caregivers with 72 responses. Alarm sounds were judged most helpful to detect a high heart rate or unusual rhythm, and less helpful to detect a patient exiting from bed. The expectation was for an immediate response to an alarm, and that it would be annoying to have an alarm go off for hours. There was strong agreement with wanting alarm sounds to go to the nurse, but not be heard in the hospital room by patients or caregivers. Implications of these findings are discussed.

Comparison of Two Different Respiratory Monitoring Systems Using External Surrogates for Respiratory-Guided Radiation Therapy

Comparison of Two Different Respiratory Monitoring Systems Using External Surrogates for Respiratory-Guided Radiation Therapy

Impact of two ionic liquids, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium methylphosphonate, on Saccharomyces cerevisiae: metabolic, physiologic, and morphological investigations.

BackgroundIonic liquids (ILs) are considered as suitable candidates for lignocellulosic biomass pretreatment prior enzymatic saccharification and, obviously, for second-generation bioethanol production. However, several reports showed toxic or inhibitory effects of residual ILs on microorganisms, plants, and animal cells which could affect a subsequent enzymatic saccharification and fermentation process.ResultsIn this context, the impact of two hydrophilic imidazolium-based ILs already used in lignocellulosic biomass pretreatment was investigated: 1-ethyl-3-methylimidazolium acetate [Emim][OAc] and 1-ethyl-3-methylimidazolium methylphosphonate [Emim][MeO(H)PO2]. Their effects were assessed on the model yeast for ethanolic fermentation, Saccharomyces cerevisiae, grown in a culture medium containing glucose as carbon source and various IL concentrations. Classical fermentation parameters were followed: growth, glucose consumption and ethanol production, and two original factors: the respiratory status with the oxygen transfer rate (OTR) and carbon dioxide transfer rate (CTR) of yeasts which were monitored online by respiratory activity monitoring systems (RAMOS). In addition, yeast morphology was characterized by environmental scanning electron microscope (ESEM).The addition of ILs to the growth medium inhibited the OTR and switched the metabolism from respiration (conversion of glucose into biomass) to fermentation (conversion of glucose to ethanol). This behavior could be observed at low IL concentrations (≤5% IL) while above there is no significant growth or ethanol production. The presence of IL in the growth medium also induced changes of yeast morphology, which exhibited wrinkled, softened, and holed shapes. Both ILs showed the same effects, but [Emim][MeO(H)PO2] was more biocompatible than [Emim][OAc] and could be better tolerated by S. cerevisiae.ConclusionsThese two imidazolium-derived ILs were appropriate candidates for useful pretreatment of lignocellulosic biomass in the context of second-generation bioethanol production. This fundamental study provides additional information about the toxic effects of ILs. Indeed, the investigations highlighted the better tolerance by S. cerevisiae of [Emim][MeO(H)PO2] than [Emim][OAc].

Integrated Circuits and Electrode Interfaces for Noninvasive Physiological Monitoring

This paper presents an overview of the fundamentals and state of the-art in noninvasive physiological monitoring instrumentation with a focus on electrode and optrode interfaces to the body, and micropower-integrated circuit design for unobtrusive wearable applications. Since the electrode/optrode-body interface is a performance limiting factor in noninvasive monitoring systems, practical interface configurations are offered for biopotential acquisition, electrode-tissue impedance measurement, and optical biosignal sensing. A systematic approach to instrumentation amplifier (IA) design using CMOS transistors operating in weak inversion is shown to offer high energy and noise efficiency. Practical methodologies to obviate 1/f noise, counteract electrode offset drift, improve common-mode rejection ratio, and obtain subhertz high-pass cutoff are illustrated with a survey of the state-of-the-art IAs. Furthermore, fundamental principles and state-of-the-art technologies for electrode-tissue impedance measurement, photoplethysmography, functional near-infrared spectroscopy, and signal coding and quantization are reviewed, with additional guidelines for overall power management including wireless transmission. Examples are presented of practical dry-contact and noncontact cardiac, respiratory, muscle and brain monitoring systems, and their clinical applications.

Respiratory monitoring with an acceleration sensor

Respiratory gating radiotherapy is used to irradiate a local area and to reduce normal tissue toxicity. There are certain methods for the detection of tumor motions, for example, using internal markers or an external respiration signal. However, because some of these respiratory monitoring systems require special or expensive equipment, respiratory monitoring can usually be performed only in limited facilities. In this study, the feasibility of using an acceleration sensor for respiratory monitoring was evaluated. The respiratory motion was represented by means of a platform and measured five times with the iPod touch® at 3, 4 and 5 s periods of five breathing cycles. For these three periods of the reference waveform, the absolute means ± standard deviation (SD) of displacement were 0.45 ± 0.34 mm, 0.33 ± 0.24 mm and 0.31 ± 0.23 mm, respectively. On the other hand, the corresponding absolute means ± SD for the periods were 0.04 ± 0.09 s, 0.04 ± 0.02 s and 0.06 ± 0.04 s. The accuracy of respiratory monitoring using the acceleration sensor was satisfactory in terms of the absolute means ± SD. Using the iPod touch® for respiratory monitoring does not need special equipment and makes respiratory monitoring easier. For these reasons, this system is a viable alternative to other respiratory monitoring systems.

A comparison of the respiratory signals acquired by different respiratory monitoring systems used in respiratory gated radiotherapy

Respiratory monitoring systems are used to detect the respiratory phase of patients during the planning and administration of respiratory gated radiotherapy by using four-dimensional computed tomography (4DCT) or 4D positron-emission tomography/CT (4DPET/CT) and the linear accelerator (linac), respectively. Generally, identical respiratory monitoring systems are used for 4DCT, 4DPET/CT, and linac. However, different systems are sometimes used in combination because the accessibility of the respiratory monitoring systems may differ by manufacturer. The combined use of different respiratory monitoring systems in phase-based gating is of concern because the differences in the timing of tags (end-respiration signals algorithmically determined by the respiratory monitoring system), defined by the two systems, may result in phase differences, The purpose of this study is to estimate this difference and evaluate its effect on 4DCT data. Ten patients (seven men and three women) with a median age of 75 yr (range: 57-84 yr) were treated by gated stereotactic body radiation therapy between April and December 2009. Two types of respiratory monitoring systems--RPM (Varian Medical Systems) and AZ-733V (Anzai MEDICAL)--were placed on the abdominal surface of the patients, and the respiratory signals were acquired by both systems. The relationship between the amplitude peak and the tag obtained by each respiratory system was analyzed for each patient. Further, the 4DCT images were reconstructed by using the signals obtained from both the RPM and the AZ-733V systems, and the tumor volumes and the tumor centroid positions in the craniocaudal plane were analyzed for each patient. The correlation factor between the respiratory signals from the RPM system and AZ-733V system was 0.990 (range: 0.940-0.994). The amplitude peak of the RPM system corresponded well with that of the AZ-733V system. The median +/- standard deviation of the phase difference for all the patients ranged from -4.3 +/- 7.1% to 3.5 +/- 2.2%. In the case of some patients, differences were noted between the two systems in the estimation of the tumor centroid position and tumor shape. The estimation of the position of the tumor centroid and tumor shape may vary with the use of different respiratory monitoring systems. This implies that it is preferable to use the same respiratory monitoring system with 4DCT, 4DPET-CT, and linac.

MIMO Radar System for Respiratory Monitoring Using Tx and Rx Modulation with M-Sequence Codes

The importance of respiratory monitoring systems during sleep have increased due to early diagnosis of sleep apnea syndrome (SAS) in the home. This paper presents a simple respiratory monitoring system suitable for home use having 3D ranging of targets. The range resolution and azimuth resolution are obtained by a stepped frequency transmitting signal and MIMO arrays with preferred pair M-sequence codes doubly modulating in transmission and reception, respectively. Due to the use of these codes, Gold sequence codes corresponding to all the antenna combinations are equivalently modulated in receiver. The signal to interchannel interference ratio of the reconstructed image is evaluated by numerical simulations. The results of experiments on a developed prototype 3D-MIMO radar system show that this system can extract only the motion of respiration of a human subject 2m apart from a metallic rotatable reflector. Moreover, it is found that this system can successfully measure the respiration information of sleeping human subjects for 96.6 percent of the whole measurement time except for instances of large posture change.