Detection of dynamic lung hyperinflation using cardiopulmonary exercise testing and respiratory function in patients with stable cardiac disease: a multicenter, cross-sectional study.

BACKGROUND: Many patients with heart disease potentially have comorbid chronic obstructive pulmonary disease (COPD); however, there are not enough opportunities for screening, and the qualitative differentiation of shortness of breath (SOB) has not been well established. We investigated the detection rate of SOB based on a visual and qualitative dynamic lung hyperinflation (DLH) detection index during cardiopulmonary exercise testing (CPET) and assessed potential differences in respiratory function between groups. METHODS: We recruited 534 patients with heart disease or patients who underwent simultaneous CPET and spirometry (369 males, 67.0 ± 12.9 years) to scrutinize physical functions. The difference between inspiratory and expiratory tidal volume was calculated (TV E-I) from the breath-by-breath data. Patients were grouped into convex (decreased TV E-I) and non-convex (unchanged or increased TV E-I) groups based on their TV E-I values after the start of exercise. RESULTS: Among the recruited patients, 129 (24.2%) were categorized in the convex group. There was no difference in clinical characteristics between the two groups. The Borg scale scores at the end of the CPET showed no difference. VE/VCO2 slope, its Y-intercept, and minimum VE/VCO2 showed no significant difference between the groups. In the convex group, FEV1.0/FVC was significantly lower compared to that in the non-convex group (69.4 ± 13.1 vs. 75.0 ± 9.0%). Moreover, significant correlations were observed between FEV1.0/FVC and Y-intercept (r=-0.343), as well as between the difference between minimum VE/VCO2 and VE/VCO2 slope (r=-0.478). CONCLUSIONS: The convex group showed decreased respiratory function, suggesting a potential airway obstruction during exercise. A combined assessment of the TV E-I and Y-intercept of the VE/VCO2 slope or the difference between the minimum VE/VCO2 and VE/VCO2 slopes could potentially detect COPD or airway obstruction.

Improved Peak Oxygen Uptake Reduces Cardiac Events After 3 Weeks of Inpatient Cardiac Rehabilitation for Chronic Heart Failure Patients.

Background: The incidence of heart failure (HF) is increasing, and the mortality from HF remains high in an aging society. Cardiac rehabilitation (CR) programs (CRP) increase oxygen uptake (V̇O2) and reduce HF rehospitalization and mortality. Therefore, CR is recommended for every HF patient. However, the number of outpatients undergoing CR remains low, with insufficient attendance at CRP sessions. In this study we evaluated the outcomes of 3 weeks of inpatient CRP (3w In-CRP) for HF patients. Methods and Results: This study enrolled 93 HF patients after acute-phase hospitalization between 2019 and 2022. Patients participated in 30 sessions of 3w In-CRP (30 min aerobic exercise twice daily, 5 days/week). Before and after 3w In-CRP, patients underwent a cardiopulmonary exercise test, and cardiovascular (CV) events (mortality, HF rehospitalization, myocardial infarction, and cerebrovascular disease) after discharge were evaluated. After 3w In-CPR, mean (±SD) peak V̇O2 increased from 11.8±3.2 to 13.7±4.1 mL/min/kg (116.5±22.1%). During the follow-up period (357±292 days after discharge), 20 patients were rehospitalized for HF, 1 had a stroke, and 8 died for any reasons. Proportional hazard and Kaplan-Meier analyses demonstrated that CV events were reduced among patients with a 6.1% improvement in peak V̇O2 than in patients without any improvement in peak V̇O2. Conclusions: 3w In-CRP for HF patients improved peak V̇O2 and reduced CV events in HF patients with a 6.1% improvement in peak V̇O2.

Three Weeks of Inpatient Cardiac Rehabilitation Improves Metabolic Exercise Data Combined With Cardiac and Kidney Indexes Scores for Heart Failure With Reduced Ejection Fraction.

Background: Heart failure with reduced ejection fraction (HFrEF) has a high mortality rate, and cardiac rehabilitation programs (CRP) reduce HFrEF rehospitalization and mortality rates. Some countries attempt 3 weeks of inpatient CRP (3w In-CRP) for cardiac diseases. However, whether 3w In-CRP reduces the prognostic parameter of the Metabolic Exercise data combined with Cardiac and Kidney Indexes (MECKI) score is unknown. Therefore, we investigated whether 3w In-CRP improves MECKI scores in patients with HFrEF. Methods and Results: This study enrolled 53 patients with HFrEF who participated in 30 inpatient CRP sessions, consisting of 30 min of aerobic exercise twice daily, 5 days a week for 3 weeks, between 2019 and 2022. Cardiopulmonary exercise tests and transthoracic echocardiography were performed, and blood samples were collected, before and after 3w In-CRP. MECKI scores and cardiovascular (CV) events (heart failure rehospitalization or death) were evaluated. The MECKI score improved from a median 23.34% (interquartile range [IQR] 10.21-53.14%) before 3w In-CRP to 18.66% (IQR 6.54-39.94%; P<0.01) after 3w In-CRP because of improved left ventricular ejection fraction and percentage peak oxygen uptake. Patients' improved MECKI scores corresponded with reduced CV events. However, patients who experienced CV events did not have improved MECKI scores. Conclusions: In this study, 3w In-CRP improved MECKI scores and reduced CV events for patients with HFrEF. However, patients whose MECKI scores did not improve despite 3w In-CRP require careful heart failure management.

High-Isolation SAW Duplexer With On-Chip SAW Compensation Circuit Optimized for Isolated Multiple Frequency Bands.

This article describes the simulation analysis and experimental verification of a new type of high-isolation surface-acoustic wave (SAW) duplexer by using an SAW on-chip compensation circuit designed to cancel the leakage signal of the main SAW duplexer at multiple frequency bands. First, an analysis of amplitude and phase change of the SAW duplexer consists of a ladder-type transmitter (Tx) filter, and the double-mode SAW (DMS) receiver (Rx) filter is applied to clarify the cancellation conditions. Then, the feasibility of the SAW compensation circuit using a three-interdigital transducer (IDT) DMS resonator specially designed to satisfy the cancellation conditions is studied in circuit simulation based on the coupling-of-mode (COM) theory. Finally, we analyzed this concept in detail for a long-term-evolution (LTE) Band-I SAW duplexer for Tx and Rx band isolation in both a circuit simulation and experiment. Results showed that around 10-dB improvement of isolation in both the Tx and Rx bands was obtained without sacrificing other properties (e.g., insertion loss and attenuation) and that it agrees well with the result obtained by simulation analysis. These results are expected to be useful for now, considering that future mobile systems demand higher Rx sensitivity in multiple frequency bands.

Highly piezoelectric MgZr co-doped aluminum nitride-based vibrational energy harvesters.

The first MgZr co-doped AlN-based vibrational energy harvester (VEH) is presented. (MgZr)AlN, which is a new class of doped AlN, provides high piezoelectricity and cost advantage. Using 13%-(MgZr)-doped AlN for micromachined VEHs, maximum output power of 1.3 µW was achieved with a Q-factor of 400 when resonant frequency, vibration acceleration, load resistance were 792 Hz, 8 m/s(2), and 1.1 MΩ, respectively. Normalized power density was 8.1 kW·g(-2)·m(-3). This was one of the highest values among the currently available piezoelectric VEHs.

Highly piezoelectric co-doped AlN thin films for wideband FBAR applications.

We report piezoelectric materials composed of charge-compensated co-doped (Mg, ß)(x)Al(1-x)N (ß = Zr or Hf) thin films. The effect of the dopant element into AlN on the crystal structure, and piezoelectric properties of co-doped AlN was determined on the basis of a first-principles calculation, and the theoretical piezoelectric properties were confirmed by experimentally depositing thin films of magnesium (Mg) and zirconium (Zr) co-doped AlN (Mg-Zr-doped AlN). The Mg-Zrdoped AlN thin films were prepared on Si (100) substrates by using a triple-radio-frequency magnetron reactive co-sputtering system. The crystal structures and piezoelectric coefficients (d33) were investigated as a function of the concentrations, which were measured by X-ray diffraction and a piezometer. The results show that the d33 of Mg-Zr-doped AlN at total Mg and Zr concentrations (both expressed as ß) of 0.35 was 280% larger than that of pure AlN. The experimentally measured parameter of the crystal structure and d33 of Mg-Zr-doped AlN (plotted as functions of total Mg and Zr concentrations) were in very close agreement with the corresponding values obtained by the first-principle calculations. Thin film bulk acoustic wave resonators (FBAR) employing (Mg,Zr)0.13Al0.87N and (Mg, Hf)0.13 Al0.87N as a piezoelectric thin film were fabricated, and their resonant characteristics were evaluated. The measured electromechanical coupling coefficient increased from 7.1% for pure AlN to 8.5% for Mg-Zr-doped AlN and 10.0% for Mg- Hf-doped AlN. These results indicate that co-doped (Mg, ß)(x)Al(1-x)N (ß = Zr or Hf) films have potential as piezoelectric thin films for wideband RF applications.

Correlation between propagation loss and silicon dioxide film properties for surface acoustic wave devices.

The correlation between the propagation loss and SiO2 film properties has been studied for temperature-compensated SAW devices using the SiO2/LiNbO3 structure. The SAW devices were prepared under different deposition temperatures for SiO2 film. Although they possessed excellent temperature coefficient of elasticity characteristics, devices prepared at lower temperature showed lower Q-factors. The SiO2 films were also deposited on a Si substrate under the same deposition conditions used for the SAW device preparation. Optical characterization was performed with Fourier transform infrared spectroscopy (FT-IR), spectrometer measurement, and Raman spectroscopy. IR absorbance spectra were almost same in the FT-IR measurement. However, optical attenuation in the UV region decreased with the deposition temperature in the spectrometer measurement. The optical attenuation is caused by the increase of the extinction coefficient in the SiO2 layer, and its optical wavelength dependence indicated that observed excess attenuation is caused by Rayleigh scattering. The Raman scattering also decreased with the deposition temperature in the Raman spectroscopy. The scattering is caused by the distortion of the SiO2 network. These results indicate that the Rayleigh scattering caused by the distortion of the SiO2 network is the main contributor to the excess SAW propagation loss in this case.

A thin-film bulk acoustic resonator and filter with optimal edge shapes for mass production.

The manufacturing conditions of a thin-film bulk acoustic resonator (FBAR) filter were investigated to obtain a high Q factor which is stable for mass production. The FBAR consist of patterned electrodes and piezoelectric films. In this study, the influence of edge shape of the films on the anti-resonance characteristics was investigated using a numerical method. Optimized shape was applied to a 2.5-GHz band resonator and filter. As a result, significant improvement of the Q factor and the insertion loss was confirmed.

Use of fluorine-doped silicon oxide for temperature compensation of radio frequency surface acoustic wave devices.

This paper investigates acoustic properties, including the temperature coefficient of elasticity (TCE), of fluorine-doped silicon oxide (SiOF) films and proposes the application of the films to the temperature compensation of RF SAW devices. From Fourier transform infrared spectroscopy (FT-IR), SiOF films were expected to possess good TCE properties. We fabricated a series of SAW devices using the SiOF-overlay/Cu-grating/LiNbO(3)-substrate structure, and evaluated their performance. The experiments showed that the temperature coefficient of frequency (TCF) increases with the fluorine content r, as we expected from the FT-IR measurement. This means that the Si-O-Si atomic structure measurable by the FT-IR governs the TCE behavior of SiO(2)-based films even when the dopant is added. In comparison with pure SiO(2) with the film thickness h of 0.3 wavelengths (λ), TCF was improved by 7.7 ppm/°C without deterioration of the effective electromechanical coupling factor K2 when r = 3.8 atomic % and h = 0.28λ. Fluorine inclusion did not obviously influence the resonators' Q factors when r < 8.8 atomic %.

Correlation between temperature coefficient of elasticity and fourier transform infrared spectra of silicon dioxide films for surface acoustic wave devices.

We investigated the correlation between the temperature coefficient of elasticity (TCE) and Fourier transform infrared (FT-IR) absorption spectra of SiO(2) for SAW devices. The measurement indicated that the TCE is strongly correlated with peak frequencies; that is, with the fractional change of the Si-O-Si bond angle with temperature.

A circuit model for nonlinear simulation of radio-frequency filters using bulk acoustic wave resonators.

This paper describes a circuit model for the analysis of nonlinearity in the filters based on radiofrequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments.

Ultra-steep cut-off double mode SAW filter and its application to a PCS duplexer.

This paper describes the double mode surface acoustic wave (DMS) filter design techniques for achieving the ultra-steep cut-off characteristics and low insertion loss required for the Rx filter in the personal communications services (PCS) duplexer. Simulations demonstrate that the optimal combination of the additional common ground inductance Lg and the coupling capacitance Cc between the input and output terminals of the DMS filters drastically enhances the skirt steepness and attenuation for the lower frequency side of the passband. Based on this result, we propose a novel DMS filter structure that utilizes the parasitic reactance generated in bonding wires and interdigital transducer (IDT) busbars as Lg and Ce, respectively. Because the proposed structure does not need any additional reactance component, the filter size can be small. Moreover, we propose a compact multiple-connection configuration for low insertion loss. Applying these technologies to the Rx filter, we successfully develop a PCS SAW duplexer.

Analysis and suppression of side radiation in leaky SAW resonators.

This paper discusses side acoustic radiation in leaky surface acoustic wave (LSAW) resonators on rotated Y-cut lithium tantalite substrates. The mechanism behind side radiation, which causes a large insertion loss, is analyzed by using the scalar potential theory. This analysis reveals that side radiation occurs when the guiding condition is not satisfied, and the LSAW most strongly radiates at the frequency in which the LSAW velocities in the grating and busbar regions approximately correspond to each other. Based on these results, we propose a "narrow finger structure," which satisfies the guiding condition and drastically suppresses the side radiation. Experiments show that the resonance Q of the proposed structure drastically improves to over 1000 by suppressing the side radiation, which is three times higher than for a conventional structure. Applying the proposed resonators to the ladder-type SAW filters, ultra-low-loss and steep cut-off characteristics are achieved in the range of 800 MHz and 1.9 GHz.

Suppression of reflection coefficients of surface acoustic wave filters using quadrature hybrids.

This paper proposes a simple technique to suppress the reflection coefficients S11 and S22 of surface acoustic wave (SAW) filters. Two identical SAW filters are sandwiched in between two quadrature hybrids, where their two ports are used as input and output, and others are terminated by matched loads. First, it is shown by simulation that both [S11] and [S22] are suppressed to be less than -20 dB without deteriorating the transmission characteristics. Next, two hybrids using microstrip lines were fabricated, and two RF SAW filters for GSM850 were sandwiched in between them. The result showed that the maximum [S11] within the passband was improved from -12.5 dB to -21.7 dB, i.e., 9.2 dB suppression of [S11] was achieved by sacrificing only the insertion loss of less than 0.6 dB. We also attempted to replace the microstrip lines with lumped elements. In this case, the maximum [S11] within the passband was improved more than 7.5 dB with the increased insertion loss of less than 1.5 dB. Finally, simple discussion is given on the inclusion of the transformer function in the quadrature hybrid.

Nanospheres for DNA separation chips.

We report here a technology to carry out separations of a wide range of DNA fragments with high speed and high resolution. The approach uses a nanoparticle medium, core-shell type nanospheres, in conjunction with a pressurization technique during microchip electrophoresis. DNA fragments up to 15 kilobase pairs (kbp) were successfully analyzed within 100 s without observing any saturation in migration rates. DNA fragments migrate in the medium while maintaining their characteristic molecular structure. To guarantee effective DNA loading and electrofocusing in the nanosphere solution, we developed a double pressurization technique. Optimal pressure conditions and concentrations of packed nanospheres are critical to achieve improved DNA separations.

Separation of long DNA molecules by quartz nanopillar chips under a direct current electric field.

We have established the nanofabrication technique for constructing nanopillars with high aspect ratio (100-500 nm diameter and 500-5000 nm tall) inside a microchannel on a quartz chip. The size of pillars and the spacing between pillars are designed as a DNA sieving matrix for optimal analysis of large DNA fragments over a few kilobase pairs (kbp). A chip with nanopillar channel and simple cross injector was developed based on the optimal design and applied to the separation of DNA fragments (1-38 kbp) and large DNA fragments (lambda DNA, 48.5 kbp; T4 DNA, 165.6 kbp) that are difficult to separate on conventional gel electrophoresis and capillary electrophoresis without a pulsed-field technique. DNA fragments ranging from 1 to 38 kbp were separated as clear bands, and furthermore, the mixture of lambda DNA and T4 DNA was successfully separated by a 380-microm-long nanopillar channel within only 10 s even under a direct current (dc) electric field. Theoretical plate number N of the channel (380-1450 microm long) was 1000-3000 (0.7 x 10(6)-2.1 x 10(6) plates/m). A single DNA molecule observation during electrophoresis in a nanopillar channel revealed that the optimal nanopillars induced T4 DNA to form a narrow U-shaped conformation during electrophoresis whereas lambda DNA kept a rather spherical conformation. We demonstrated that, even under a dc electric field, the optimal nanopillar dimensions depend on a gyration radius of DNA molecule that made it possible to separate large DNA fragments in a short time.

Investigation of the possibility of geometrical electrophoresis.

We investigate the possibility of geometrical electrophoresis, which is based on nanofabrication techniques. (GEE) utilizes geometrical effects during electrophoresis, which are generated by physical interactions between walls and a macromolecule confined in spaces smaller than the Flory radius. When a polymer is injected into a small space, confinement energy is usually required. However, the confinement energy form depends on the geometry of the space. In the case of electrophoresis, the electric field itself changes depending on the geometry. Using a nanofabricated quartz chip with a curved channel, we investigated electrophoretic behavior of high molecular weight DNA based on the curvature effect.

Molecular stretching of long DNA in agarose gel using alternating current electric fields.

We demonstrate a novel method for stretching a long DNA molecule in agarose gel with alternating current (AC) electric fields. The molecular motion of a long DNA (T4 DNA; 165.6 kb) in agarose gel was studied using fluorescence microscopy. The effects of a wide range of field frequencies, field strengths, and gel concentrations were investigated. Stretching was only observed in the AC field when a frequency of approximately 10 Hz was used. The maximal length of the stretched DNA had the longest value when a field strength of 200 to 400 V/cm was used. Stretching was not sensitive to a range of agarose gel concentrations from 0.5 to 3%. Together, these experiments indicate that the optimal conditions for stretching long DNA in an AC electric field are a frequency of 10 Hz with a field strength of 200 V/cm and a gel concentration of 1% agarose. Using these conditions, we were able to successfully stretch Saccharomyces cerevisiae chromosomal DNA molecules (225-2,200 kb). These results may aid in the development of a novel method to stretch much longer DNA, such as human chromosomal DNA, and may contribute to the analysis of a single chromosomal DNA from a single cell.