Validating Reference Equations for Impulse Oscillometry in Healthy Mexican Children.

BACKGROUND: The impulse oscillometry system (IOS) measures the impedance (Z) of the respiratory system, but proper interpretation of its results requires adequate reference values. The objectives of this work were: (1) to validate the reference equations for the IOS published previously by our group and (2) to compare the adjustment of new available reference equations for the IOS from different countries in a sample of healthy children. METHODS: Subjects were healthy 4-15-y-old children from the metropolitan area of Mexico City, who performed an IOS test. The functional IOS parameters obtained were compared with the predicted values from 12 reference equations determined in studies of different ethnic groups. The validation methods applied were: analysis of the differences between measured and predicted values for each reference equation; correlation and concordance coefficients; adjustment by Z-score values; percentage of predicted value; and the percentage of patients below the lower limit of normality or above the upper limit of normality. RESULTS: Of the 224 participants, 117 (52.3%) were girls, and the mean age was 8.6 ± 2.3 y. The equations that showed the best adjustment for the different parameters were those from the studies by Nowowiejska et al (2008) and Gochicoa et al (2015). The equations proposed by Frei et al (2005), Hellinckx et al (1998), Kalhoff et al (2011), Klug and Bisgaard (1998), de Assumpção et al (2016), and Dencker et al (2006) overestimated the airway resistance of the children in our sample, whereas the equation of Amra et al (2008) underestimated it. In the analysis of the lower and upper limits of normality, Gochicoa et al equation was the closest, since 5% of subjects were below or above percentiles 5 and 95, respectively. The study found that, in general, all of the equations showed greater error at the extremes of the age distribution. CONCLUSIONS: Because of the robust adjustment of the present study reference equations for the IOS, it can be recommended for both clinical and research purposes in our population. The differential adjustment of other equations underlines the need to obtain local reference values.

Phase angle as a prognostic marker in patients with critical illness.

BACKGROUND: Phase angle (PA) is interpreted as an indicator of cell membrane integrity and a prognostic indicator in some clinical situations. This study aims to evaluate PA as a prognostic marker in critically ill patients admitted to the intensive care unit (ICU) and associate this marker with length of hospital stay, mortality, and clinical scores. METHODS: A cohort study was conducted with 95 patients aged ≥18 years admitted to the ICU, who were assessed in terms of prognostic indexes (Acute Physiology and Chronic Health Evaluation II [APACHE II] and Sequential Organ Failure Assessment [SOFA]), clinical evolution (ICU discharge, death, and length of ICU stay), and PA. RESULTS: Patients were predominantly male (63.1%) and had a mean age of 63.7 ± 14.6 years; length of stay of 4 days (range, 3-9 days); mortality of 15.8%; mean APACHE II and SOFA scores of 17.3 ± 8.2 and 6.1 ± 3.1 points, respectively; and mean PA of 4.91 ± 1.36°. An association was observed between females and PA <5.1° (P = .035), which was the cutoff point determined from the receiver operating characteristic curve. PA was correlated with APACHE II score (r = -0.241; P = .02). This correlation became moderate only when patients without sepsis were considered (r = -0.506; P < .001). CONCLUSIONS: PA seems to be a good prognostic marker for patients without sepsis. The weak correlation between PA and APACHE II score and the lack of association with other clinical outcomes are limitations for interpreting the prognostic value of PA in the entire study sample.

Multi-signal bathroom scale to assess long-term trends in cardiovascular parameters.

This paper describes the circuits and signal processing techniques that convert an electronic bathroom scale intended for bioimpedance analysis (BIA) into a compact system to acquire the electrocardiogram (ECG), the ballistocardiogram (BCG), and the impedance plethysmogram (IPG) using only plantar measurements. The signal processing methods proposed rely on the higher quality of the IPG as compared to the ECG and BCG and they enhance the signal-to-noise ratio (SNR) of these two signals, which otherwise could be too poor in non-controlled environments. The system is suitable for long-term periodic monitoring of cardiovascular function.

Estimation of patient compliance in application of adherent mobile cardiac telemetry device.

In an in home usage outpatient setting, patient compliance is a key factor in determining the adoption and efficacy of treatment for any illness and is paramount for patient dependent medical technologies such as mobile patient monitoring systems. As a leader in the development of these technologies, Corventis has deployed its NUVANT™ Mobile Cardiac Telemetry System to thousands of patients around the world. The NUVANT system includes an externally worn adherent sensing device, the PiiX, whose proper application is critical to the on-patient longevity and thus performance of the NUVANT system. Patient compliance in this context is a universal challenge for such patient-applied adherent devices. Understanding and tracking a problem is key to solving it and the integrated suite of vital sign sensors in the Corventis PiiX offers a unique opportunity for extracting patient application compliance information from the incoming health data. Analysis of data from 5000 randomly selected patients has shown that improper application of the PiiX is a factor in 2.3% of patients. However, no reduction in adherent device longevity or performance was observed. Such information is a valuable feedback metric for product design, instructions for use, packaging of medical technologies, level of customer support and replacement costs.

[Disordered cerebral hemodynamics in diabetic patients (based on myelographic data)]. / Narushenie tserebral'noi gemodinamiki u bol'nykh sakharnym diabetom (po dannym mielografii).

Overall seventy-six patients with diabetes mellitus (DM) who ranged from 16 to 65 years old were examined. Of these, 62 subjects were given a diagnosis of insulin-dependent DM, 14 insulin-nondependent DM. Moderate severity course of the illness was documented in 32, severe--in 44 patients. All patients revealed a change in the condition of the cerebrovascular system. This was manifested by predominance of hypertonic type rheograms, increased vasomotor tone with vessels of all calibres, changes in the level of pulse blood filling, signs of varying degree venous hypertension. DM duration, severity, level of compensation were all related to the degree of cerebrovascular disturbances.

[The use of impedance plethysmography in the forensic medical diagnosis of the time of death]. / Ispol'zovanie impedansnoi pletizmografii pri sudebno-meditsinskoi diagnostiki davnosti nastupleniia smerti.

Diagnosis of the time of death (DTD) is a pressing problem of forensic medicine. For defining the criteria of DTD by impedance plethysmography, electric conductivity of tissues was studied in 45 corpses of male subjects aged 18-44 years who died from craniocerebral injuries. Autolytic changes were characterized by a wave-like pattern, with periods of stability replaced by necrobiotic processes. This allows recording residual activity of surviving cells and tissues in a corpse during the early postmortem period. Based on these data, a model of postmortem changes in tissues can be created for DTD.

[The effect of transcerebral electrical impulse exposures on regional hemodynamics after the surgical treatment of uterine myoma]. / Vliianie transtserebral'nykh élektroimpul'snykh vozdeistvii na regionarnuiu gemodinamiku posle khirurgicheskogo lecheniia miomy matki.

After surgical treatment of uterine myoma 28 patients with cardiovascular diseases experienced disturbances of cerebral, upper limb and small pelvis circulation. The course of transcerebral electrotherapy (short bipolar nonsymmetrical impulses with large amplitude of the negative part) relieved the symptoms as a results of better cerebral and upper limb hemodynamics.

[A comparative analysis of the rheographic indices of the pancreatic blood flow in patients who have undergone a subtotal gastric resection and gastrectomy]. / Sravnitel'nyi analiz reograficheskikh pokazatelei pankreaticheskogo krovotoka u bol'nykh, perenesshikh subtotal'nuiu rezektsiiu zheludka i gastréktomiiu.

Overall ninety-two patients with carcinoma of the stomach were studied, 45 of whom had undergone subtotal resection, and 47--gastrectomy. During the first postoperative 10 days a study was made of the pancreatic hemocirculation by contact bipolar rheography. After surgery on the stomach, the pancreas shows phasic changes in bloodflow that include the time of arterial hyperemia, that of insufficiency of arterial blood-filling, and time period of restoration of bloodflow. Fluctuations in pancreatic arterial blood filling in those patients who had survived gastrectomy within the first 48 hours following the operation are more definite than in those having undergone subtotal resection of the stomach.

[A quantitative assessment of the blood supply to the head by indirect rheography]. / Kolichestvennaia otsenka krovosnabzheniia golovy metodom oposredovannoi reografii.

Clinical-experimental basis of the possibility of application of the method of indirect rheography of head (IRH) in wide clinical practice was presented. Estimation of the results reproduction and accuracy of the method was performed too. 40 healthy individuals of both sexes at the age of 18-50 and 102 patients with spinal osteochondrosis, arterial hypertension and neurocirculatory dystonia were examined. It was determined that IRH provided 93% of results reproduction and its precision was 90% and higher in comparison with ultrasound method. It was established that head circulation was 750-1200 ml/min or 12-24% of cardiac output in healthy individuals. The results of the study of head blood circulation in some groups of patients were also discussed.

[The indices of external respiration and oxygen homeostasis in human subjects with different types of blood circulation]. / Pokaznyky zovnishn'oho dykhannia ta kysnevoho homeostaza u liudei z riznymy typamy krovoobihu.

The cardiac output and other parameters of central hemodynamics in human were evaluated by means of tetrapolar rheography. Three types of circulation (hypo-, eu- and hyperkinetic) were picked out according to value of their cardiac index. Quantity of persons in groups of hypo-, eu- and hyperkinetics was as 25:35:40, 85 healthy people of both sex 18-27 years old were examined. There is no statistically significant difference in values of respiration rate, the tidal volume, a minute volume, the oxygen consumption, the concentration of O2 and CO2 in the alveolar air between groups with different types of circulation. The respiration rate, the tidal volume, a minute volume and the oxygen consumption have been studied spirographically. The concentration of O2 and CO2 in the alveolar air have been studied by means of mass-spectrometry. Comparison of the CO defined by means of impedance cardiography (COic) and the CO calculated by oxygen consumption data (COox) demonstrated that COox in group of the hypokinetics is more than COic, the eukinetics have them almost equal, and the hyperkinetics have COic which is more than COox. There is positive correlation between the COic/COox ratio and CI (r = 0.85, P < 0.01). In spite of almost equal oxygen consumption in all groups of human, hypokinetics use less blood volume for providing their body by oxygen.

[Comparative rheoencephalographic and convective radiation encephalic thermometric studies]. / Sravnitel'nye reoéntsefalograficheskie i radiatsionno-konvektsionnye éntsefaloteplometricheskie issledovaniia.

It is for the first time that thermoassimetry of heart flows of brain right and left hemispheres presenting as predominance of radiative-convective heat radiation from the left has been revealed, the thermoassimetry gradient being rostral-caudal. Disclosed in cerebral hemispheres was complimentarity of energetic processes: the right hemisphere secures the background energy state, the left one functions in ensuring the discrete adaptive thermoenergy reactions. The thermoassimetry revealed may be the basis of other functional asymmetries of the brain. There was no parallelism between the studied parameters of circulation and heat flow.

[The RA6-02 rheoanalyzer for studying systemic hemodynamics by the methods of tetrapolar and focusing rheography]. / Reoanalizator RA6-02 dlia issledovaniia sistemnoi gemodinamiki metodami tetrapoliarnoi i fokusiruiushchei reografii.

The paper analyzes automatic rheographic (impedance) equipment, shows the prospects for using rheography to study systemic hemodynamics, as well as describes the potentialities of a new universal rheoanalyzer by employing tetrapolar and focusing rheography. The device uses an algorithm of automatic recording and processing rheosignals, which has been developed on 20-year worldwide experience in applying rheography. Specific volumetric and velocity parameters, as well as total amplitude-time parameters of rheosignals and their ratios, which virtually satisfy all users are identified in the procedures for examining hemodynamics in the heart, extremity, head, liver and lung.

Reduction of motion artifacts using a two-frequency impedance plethysmograph and adaptive filtering.

We measured transthoracic impedance in nine presumed healthy adult subjects with a two-frequency plethysmograph at 57 kHz and 185 kHz. The measurement protocol included periods of normal breathing without motion and periods of motion without breathing. We analyzed the cross-correlation and the ratio between the signals at both frequencies for all the different maneuvers. The correlation coefficient was between 0.97 and 1 for breathing, the minimal cross-correlation (0.81) was for simulated obstructive apnea. We found that the amplitude ratio between the two-frequency signals was different for normal breathing and for motion. Based on these results, we designed and tested an adaptive filter to increase the signal-to-artifact ratio (SAR). The increase in SAR (mean +/- standard deviation) compared with the signal at 57 kHz was: 183% +/- 117% for arm movement, 133% +/- 93% for leg movement, and 34% +/- 62% for simulated obstructive apnea.

[The cerebral blood flow in smokers]. / Sostoianie mozgovogo krovotoka u kuril'shchikov.

Effect of smoking on cerebral blood flow was studied with the aid of rheography in 60 young smokers and 30 nonsmokers (control group). Tobacco smoking was found to results in rising the tone of cerebral arteries of large and medium calibres, the pulse organ filling being on the decrease. The tone of small arterial vessels and venous network decreases. The effect of the inhaled tobacco smoke on cerebral blood flow is particularly pronounced in prolonged and continuous users of tobacco.

[Reactive hyperemia in vibration-induced disease]. / Vyvchennia reaktyvnoï hiperemiï pry vibratsiinii khvorobi.

The study of a blood flow in the forearm of patients with vibration disease has shown its significant lowering accompanied by an increase in vascular resistance in this region. Reactive hyperemia in the forearm vessels of these patients was diminished significantly, which shows decrease in the vasodilatation reserve induced by disturbances in functional activity of the endothelium. These disturbances are probably manifested in decrease of production of vasodilatation factors. Reactive hyperemia may be used to determine the endothelium dysfunctions caused by action of different pathogenic factors.