Characteristics of the nocturnal desaturation waveform pattern of SpO2 in COPD patients: an observational study

Background Nocturnal desaturation is common in patients with chronic obstructive pulmonary disease (COPD) and impacts disease exacerbation and prognosis. In our previous study, we developed a diagnostic algorithm to classify nocturnal desaturation from SpO2 waveform patterns based on data from patients receiving home oxygen therapy. In this study, we aimed to investigate nocturnal desaturation in patients with COPD based on SpO2 waveform patterns and the associations between the waveforms and clinical data. Methods We investigated patients diagnosed with COPD and measured SpO2 and nasal airflow with a type 4 portable long-term recordable pulse oximeter. Then, we classified the SpO2 waveforms with the algorithm and compared the clinical data. Results One hundred fifty-three patients (136 male and 17 female) were analysed. One hundred twenty-eight of the 153 (83.7%) patients had nocturnal desaturation, with an intermittent pattern (70.6%), sustained pattern (13.1%) and periodic pattern (68.0%). Intriguingly, desaturation with an intermittent pattern was associated with the apnoea-hypopnea index obtained with the portable monitor, and desaturation with a sustained pattern was associated with the cumulative percentage of time at a SpO2 below 90%. Conclusions We found that nocturnal desaturation was frequently observed in patients with COPD and could be classified into 3 types of waveform patterns.

A novel wave propagation method for measuring viscoelastic properties of pre-strained materials

Viscoelastic materials are widely used for vibroacoustic solutions due to their ability to mitigate vibration and sound. Wave propagation methods are based on the measurement of the waveform pattern of a transitory pulse in one-dimensional structures. The time evolution of the pattern can be used to deduce the material elasticity and damping characteristics. The most popular propagation methods, namely Hopkinson bar methods, assume no dispersion, i.e. the complex elasticity modulus is not frequency-dependent. This is not significant for resilient materials such as elastomers. More recent approaches have been developed to measure frequency-dependent properties from a pulse propagating in a slender bar. We showed in previous works how to adapt these techniques for shorter samples of materials, representing a real advance, as extrusion is a cumbersome process for many materials. The main concept was to reconstruct the time history of the wave propagating in a composite structure composed of a long incident bar made of a known material and extended by a shorter sample bar. Then the viscoelastic properties of the sample material were determined in the frequency domain within an inverse method held in the time domain. In industry, most isolation solutions using mounts or bushings must support structural weights. This is why it is particularly interesting to know the viscoelastic properties of the material in stressed state. Here, we show how to overcome this challenging issue. The theoretical framework of the computational approach is detailed and the method is experimentally verified.

A case report of a coronary myocardial bridge with impaired full-cycle ratio during dobutamine challenge

Background A myocardial bridge (MB) is a coronary variant in which an epicardial coronary artery tunnels through the myocardial band. Although MBs have been reported to cause ischaemia, physiological assessment of an MB has not been fully established. Case summary We encountered a case with exertional chest pain who underwent coronary angiography showing an MB at the mid-left anterior descending artery with systolic compression. Optical coherence tomography showed an MB defined as a homogeneous intermediate intensity surrounding the epicardial artery. The full-cycle ratio, defined as the lowest ratio of distal coronary pressure (Pd) to aortic pressure (Pa) during the entire cardiac cycle, measured 0.89 at rest and 0.73 with intravenous dobutamine of 20 µg/kg/min with a distinctive waveform pattern (early diastolic Pd drop) during a dobutamine challenge. Metoprolol succinate dosage was increased. The patient has been free from chest pain for 7 months after the discharge. Discussion Optical coherence tomography may contribute to anatomical detections of MBs. Because a systolic compression of the MB and release of the vascular lumen during early diastole leads to an early steep pressure loss, early diastolic Pd drop should be one of the specific haemodynamic characteristics of MBs. On the other hand, in a severe atherosclerotic stenosis, Pd drop is typically observed in late diastole, which could be differentiated from that of MBs. Because full-cycle ratio reflects the whole cardiac cycle including early diastole, this might be more useful than other physiological indices for detection of MB-related ischaemia induced by a dobutamine challenge.

The electrocardiographic ‘triangular QRS-ST-T waveform’ pattern: a marker of severe haemodynamic compromise in Takotsubo syndrome—a case report

Background Takotsubo cardiomyopathy is characterized by transient regional systolic dysfunction of the left ventricle, mimicking myocardial infarction. Although systolic left ventricular (LV) function normalizes in most cases, the outcome is not always favourable. Recently, a rare electrocardiogram (ECG) finding, lambda wave ST elevation or ‘triangular QRS-ST-T waveform’, was suggested as a possible marker of poor outcome in Takotsubo patients Case summary After a brief episode of chest pain and shortness of breath, a 67-year-old woman developed cardiogenic shock. Her resting ECG showed widespread ST elevations, which soon evolved into a pattern of triangular QRS-ST-T waveforms in the inferior leads and V3–V6. Emergent coronary angiography was normal. The ejection fraction was 20% with apical ballooning and an LV thrombus. At 1-month follow-up, the patient was asymptomatic and the ECG showed only T-wave inversions. Discussion The triangular QRS-ST-T waveform ECG pattern has recently been introduced as a high-risk marker in the Takotsubo syndrome.

Role of hepatic colour duplex ultrasound in assessment of non alcoholic fatty liver disease-nafld

Background Gray-scale ultrasonography (US) is an initial, easy to use and widely available imaging modality for NAFLD, the presence of fat infiltration in the liver in the absence of excessive alcohol consumption and other causes of liver disease, is the most common cause of fatty liver, with a prevalence as high as 15-25% in many populations. Objective to determine the effect of obesity and NAFLD on the Doppler waveform pattern of the liver vascularity. Methods A case control study, conducted at Ain Shams University in the period between july and December 2018 . In both groups, liver span & subcutaneous fat was measured by ultrasonographic examination. Hepatic vein waveform pattern & portal vein mean flow velocity were assessed & hepatic artery resistance index was measured by duplex Doppler ultrasonography examination. Results Our study included 50 patients , 20 were control & 30 were cases.. The mean age of cases was 45.30 ± 10.15 SD & the mean age of control was 32.70 ± 10.95 SD rendering the mean age of cases & control of high statistical significance (p value=0.000). The Subcutaneous fat showed high significant statistical difference between cases & control groups with mean subcutaneous fat in control =0.75 ± 0.14 SD & mean subcutaneous fat in cases= 1.23 ± 0.42 SD with p –value = 0.000. The liver span showed high significant statistical difference between cases & control groups with mean in control =15.11 ± 0.85 SD & mean liver span in cases= 17.46 ± 1.67SD ( p value = 0.000). Hepatic vein wave pattern was normal in all 20 control (100%). In the 30 cases,the Hepatic vein wave pattern was triphasic in 12 patients (40%) & biphasic or monophasic In 18 patients (60%) with high statistical significance (p-value =0.000). There was negative correlation between the hepatic vein velocity & BMI with ( p value=0.0032). There was no statistically significant difference between cases & control as regards all Doppler indices including the Hepatic artery RI(resistive index), Hepatic artery PSV(peak systolic velocity), Portal vein velocity(maximum & minimum)& hepatic vein velocity (maximum velocity) where the p value was more than 0.05. Conclusion Patients with NAFLD have a high rate of abnormal hepatic vein Doppler waveform patterns ,which can be biphasic or monophasic rather than alterations in hepatic artery resistance index values by duplex Doppler ultrasonography. Also the fatty infiltration of hepatocytes can increase liver span & the subcutaneous fat.

Design of Flying Capacitor Multilevel Inverter for Solar Energy Applications

The continuous rise in electricity demand leads to adoption of renewable energy sources such as sun, wind for power generation. In order to utilize the electric power obtained from renewable solar energy, inverters are required to inject the electricity into the grid. This paper presents single phase flying capacitor multi-level inverter with help of SPWM technique. The comparison of single phase three-level, five-level and seven-level flying capacitor multilevel inverters is carried out with respect to waveform pattern, output current, output voltage, active power and reactive power waveforms. The simulations are conducted in MATLAB/SIMULINK environment.