Objective Noninvasive Measurement of the Volumizing Effect of a Dermal Filler: An In Vivo Study.

BACKGROUND: Information about the volumizing effects of dermal fillers is critical for physicians' understanding of product features and prudent decision-making in clinical practice. It is important for material engineers to develop and optimize new dermal fillers, especially when comparing the physiochemical properties of a new product with those of existing fillers that are used worldwide. OBJECTIVE: This study aimed to establish a reliable, noninvasive method for in vivo quantitative evaluation of the filling effect in order to predict possible effectiveness after filler injection and to evaluate the degradation trend over time. METHODS: A rabbit model of ear injection with dermal fillers was established. Hyaluronic acid (HA) filler was injected into the subcutaneous layer of rabbit ears, resulting in a stable skin bulge. Ultrasonography was used to noninvasively measure the skin bulge for volume calculation; the volume change was analyzed periodically until 38 weeks. Pathological examination, the gold standard, was performed to confirm degradation. RESULTS: The immediate volumizing effect of HA filler injection was macroscopically observed as a local skin bulge. Ultrasound was able to precisely detect the shape of the filler and calculate the length, width, and height of the skin bulge at each time point. The degree of uplift and amount of residual samples in the pathological evaluation were consistent with the results of morphological observation using ultrasound. CONCLUSION: Evaluation of the volume impact of dermal filler through the rabbit ear injection model evaluation enables material science evaluation in the early stage of material development, and has certain clinical reference value. LEVEL OF EVIDENCE I: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Near-Infrared Transillumination for Macroscopic Functional Imaging of Animal Bodies.

The classical transillumination technique has been revitalized through recent advancements in optical technology, enhancing its applicability in the realm of biomedical research. With a new perspective on near-axis scattered light, we have harnessed near-infrared (NIR) light to visualize intricate internal light-absorbing structures within animal bodies. By leveraging the principle of differentiation, we have extended the applicability of the Beer-Lambert law even in cases of scattering-dominant media, such as animal body tissues. This approach facilitates the visualization of dynamic physiological changes occurring within animal bodies, thereby enabling noninvasive, real-time imaging of macroscopic functionality in vivo. An important challenge inherent to transillumination imaging lies in the image blur caused by pronounced light scattering within body tissues. By extracting near-axis scattered components from the predominant diffusely scattered light, we have achieved cross-sectional imaging of animal bodies. Furthermore, we have introduced software-based techniques encompassing deconvolution using the point spread function and the application of deep learning principles to counteract the scattering effect. Finally, transillumination imaging has been elevated from two-dimensional to three-dimensional imaging. The effectiveness and applicability of these proposed techniques have been validated through comprehensive simulations and experiments involving human and animal subjects. As demonstrated through these studies, transillumination imaging coupled with emerging technologies offers a promising avenue for future biomedical applications.

Novel Noninvasive Paraclinical Study Method for Investigation of Liver Diseases.

Based on a prior university patent, the authors developed a novel type of bioimpedance-based test method to noninvasively detect nonalcoholic fatty liver disease (NAFLD). The development of a new potential NAFLD diagnostic procedure may help to understand the underlying mechanisms between NAFLD and severe liver diseases with a painless and easy-to-use paraclinical examination method, including the additional function to detect even the earlier stages of liver disease. The aim of this study is to present new results and the experiences gathered in relation to NAFLD progress during animal model and human clinical trials.

Quantification of Humidity and Salt Detection in Historical Building Materials via Broadband Radar Measurement.

For the investigation of moisture and salt content in historic masonry, destructive drilling samples followed by a gravimetric investigation is still the preferred method. In order to prevent the destructive intrusion into the building substance and to enable a large-area measurement, a nondestructive and easy-to-use measuring principle is needed. Previous systems for moisture measurement usually fail due to a strong dependence on contained salts. In this work, a ground penetrating radar (GPR) system was used to determine the frequency-dependent complex permittivity in the range between 1 and 3 GHz on salt-loaded samples of historical building materials. By choosing this frequency range, it was possible to determine the moisture in the samples independently of the salt content. In addition, it was possible to make a quantitative statement about the salt level. The applied method demonstrates that with ground penetrating radar measurements in the frequency range selected here, a salt-independent moisture determination can be carried out.

Developmental and environmental modulation of fecal thyroid hormone levels in wild Assamese macaques (Macaca assamensis).

Thyroid hormones are key modulators of development, as well as mediators of environmental conditions, by regulating developmental processes and metabolism in primates. Hormone measurement in noninvasively collected samples, that is, feces and urine, is a valuable tool for studying the endocrine function of wildlife, and recent studies have demonstrated the feasibility of measuring thyroid hormones in fecal samples of zoo-housed and wild nonhuman primates. Our study aimed to (i) validate the measurement of immunoreactive fecal total triiodothyronine (IF-T3) in wild Assamese macaques (Macaca assamensis) and (ii) to investigate its developmental changes and its response to environmental changes, including stress responses, in immature individuals. Fecal samples and environmental parameters were collected from individuals of three social groups of wild Assamese macaques living at Phu Khieo Wildlife Sanctuary, Northeastern Thailand. Our study confirmed the methodological feasibility and biological validity of measuring IF-T3 in this population. Specifically, the biological validation demonstrated higher IF-T3 levels in immatures compared to adults, and higher levels in females during late gestation compared to the preconception stage. Our analysis of IF-T3 levels in developing immature macaques revealed a significant increase with age. Furthermore, we found a positive association between IF-T3 and immunoreactive fecal glucocorticoid levels, an indicator of the physiological stress response. Neither minimum temperature nor fruit abundance predicted variation in IF-T3 levels in the immatures. Our findings indicate the possibility for differing effects of climatic factors and food availability on thyroid hormone level changes in immature versus adult animals and in wild compared to experimental conditions. Overall, our study provides the basis for further investigations into the role of thyroid hormones in shaping species-specific traits, growth, and overall primate development.

Validation of Noninvasive Assessment of Pulmonary Gas Exchange in Patients with Chronic Obstructive Pulmonary Disease during Initial Exposure to High Altitude.

Investigation of pulmonary gas exchange efficacy usually requires arterial blood gas analysis (aBGA) to determine arterial partial pressure of oxygen (mPaO2) and compute the Riley alveolar-to-arterial oxygen difference (A-aDO2); that is a demanding and invasive procedure. A noninvasive approach (AGM100), allowing the calculation of PaO2 (cPaO2) derived from pulse oximetry (SpO2), has been developed, but this has not been validated in a large cohort of chronic obstructive pulmonary disease (COPD) patients. Our aim was to conduct a validation study of the AG100 in hypoxemic moderate-to-severe COPD. Concurrent measurements of cPaO2 (AGM100) and mPaO2 (EPOC, portable aBGA device) were performed in 131 moderate-to-severe COPD patients (mean ±SD FEV1: 60 ± 10% of predicted value) and low-altitude residents, becoming hypoxemic (i.e., SpO2 < 94%) during a short stay at 3100 m (Too-Ashu, Kyrgyzstan). Agreements between cPaO2 (AGM100) and mPaO2 (EPOC) and between the O2-deficit (calculated as the difference between end-tidal pressure of O2 and cPaO2 by the AGM100) and Riley A-aDO2 were assessed. Mean bias (±SD) between cPaO2 and mPaO2 was 2.0 ± 4.6 mmHg (95% Confidence Interval (CI): 1.2 to 2.8 mmHg) with 95% limits of agreement (LoA): -7.1 to 11.1 mmHg. In multivariable analysis, larger body mass index (p = 0.046), an increase in SpO2 (p < 0.001), and an increase in PaCO2-PETCO2 difference (p < 0.001) were associated with imprecision (i.e., the discrepancy between cPaO2 and mPaO2). The positive predictive value of cPaO2 to detect severe hypoxemia (i.e., PaO2 ≤ 55 mmHg) was 0.94 (95% CI: 0.87 to 0.98) with a positive likelihood ratio of 3.77 (95% CI: 1.71 to 8.33). The mean bias between O2-deficit and A-aDO2 was 6.2 ± 5.5 mmHg (95% CI: 5.3 to 7.2 mmHg; 95%LoA: -4.5 to 17.0 mmHg). AGM100 provided an accurate estimate of PaO2 in hypoxemic patients with COPD, but the precision for individual values was modest. This device is promising for noninvasive assessment of pulmonary gas exchange efficacy in COPD patients.

Noninvasive blood pressure measurement in patients with continuous-flow left ventricular assist devices.

Oscillatory blood pressure (OBP) with a slow cuff-deflation system has been proposed as noninvasive measurement of mean arterial pressure (MAP) in patients with continuous-flow left ventricular assist devices (LVADs). However, the challenge is that the measurement is not obtainable in certain patients. We hypothesized that the combined use of color Doppler imaging during OBP measurement (CDBP) could derive MAP accurately. We conducted a prospective observational study in critically ill patients (30 patients with continuous-flow LVADs and 30 control patients without LVADs). Triplicate OBP and CDBP measurements were performed and invasive blood pressure (IBP) was recorded. The overall success rate of OBP was 63.3% in the LVAD group and 98.9% in the control group. The CDBP was successfully obtained in 100% of all study patients. The CDBP in the LVAD group was closest to the MAP of measured IBP, while that in the control group was closest to the systolic IBP. The mean absolute differences in OBP and CDBP from the closest IBP were similar in both the control and LVAD groups. In nonpulsatile LVAD patients with a pulse pressure IBP < 10 mmHg, the success rate of OBP measurement was only 10.0%, and CDBP showed significantly reduced error in MAP measurement (mean absolute difference: OBP 23.2 ± 8.7 vs CDBP 5.2 ± 3.6 mmHg, p < 0.001). The validity of OBP measurement with a slow cuff-deflation system limited particularly in nonpulsatile LVAD patients. The concurrent use of color Doppler imaging is encouraged for more accurate measurement of MAP in patients with continuous-flow LVADs.

Skin imaging and noninvasive measurements for rosacea / 中华皮肤科杂志

Rosacea is a chronic inflammatory disease. In addition to subjective evaluation, some objective quantifiable indices are needed for the diagnosis and treatment of rosacea. Some skin imaging and noninvasive measurement tools have been applied to clinical practice, and can provide quantitative or semi-quantitative indices to assist the diagnosis and treatment of rosacea. This review summarizes relevant research progress to provide evidence for clinical standardized application.

Optical Measurement of Molar Absorption Coefficient of HbA1c: Comparison of Theoretical and Experimental Results.

Diabetes can cause dangerous complications if not diagnosed in a timely manner. The World Health Organization accepts glycated hemoglobin (HbA1c) as a measure of diagnosing diabetes as it provides significantly more information on the glycemic behavior from a single blood sample than the fasting blood sugar reading. The molar absorption coefficient of HbA1c is needed to quantify the amount of HbA1c present in a blood sample. In this study, we measured the molar absorption coefficient of HbA1c in the range of 450 nm to 700 nm using optical methods experimentally. We observed that the characteristic peaks of the molar absorption coefficient of HbA1c (at 545 nm and 579 nm for level 1, at 544 nm and 577 nm for level 2) are in close agreement with those reported in previous studies. The molar absorption coefficient values were also found to be close to those of earlier reports. The average molar absorption coefficient values of HbA1c were found to be 804,403.5 M−1cm−1 at 545 nm and 703,704.5 M−1cm−1 at 579 nm for level 1 as well as 503,352.4 M−1cm−1 at 544 nm and 476,344.6 M−1cm−1 at 577 nm for level 2. Our experiments focused on calculating the molar absorption coefficients of HbA1c in the visible wavelength region, and the proposed experimental method has an advantage of being able to easily obtain the molar absorption coefficient at any wavelength in the visible wavelength region. The results of this study are expected to help future investigations on noninvasive methods of estimating HbA1c levels.

Validity and success rate of noninvasive mean arterial blood pressure measurements in cf-LVAD patients: A technical review.

BACKGROUND: The life expectancy of patients with a continuous flow left ventricular assist device (cf-LVAD) is increasing. Adequate determination and regulation of mean arterial pressure (MAP) is important to prevent adverse events. Given the low pulsatility characteristics in these patients, standard blood pressure equipment is inadequate to monitor MAP and not recommended. We provide an overview of currently available noninvasive techniques, using an extensive search strategy in three online databases (Pubmed, Scopus and Google Scholar) to find validation studies using invasive intra-arterial blood pressure measurement as a reference. Mean differences with the reference values smaller than 5 ± 8 mm Hg were considered acceptable. OBSERVATIONS: After deduplication, screening, and exclusion of incorrect sources, eleven studies remained with 3139 successful MAP measurements in 386 patients. Four noninvasive techniques, using Doppler, pulse oximetry, finger cuff volume clamp, or slow upper arm cuff deflation, were identified and evaluated for validity and success rate in cf-LVAD patients. Here, a comprehensive technical background of the blood pressure measurement methods is provided in combination with a clinical use comparison. Of the reported noninvasive techniques, slow cuff devices performed most optimally (mean difference 1.3 ± 5.2 mm Hg). CONCLUSIONS: Our results are encouraging and indicate that noninvasive blood pressure monitoring options with acceptable validity and success rate are available. Further technical development and validation is warranted for the growing population of patients on long-term cf-LVAD support.

Effectiveness of VISIA system in evaluating the severity of rosacea.

BACKGROUND: Rosacea is a facial chronic inflammatory skin disease with almost 5.5% prevalence. Although there are various scales of rosacea, they are objective and discordant among different dermatologists. Noninvasive objective measurements such as VISIA system might play essential roles in the diagnosis and evaluation of rosacea. Here, we intended to reveal the effectiveness of VISIA system in rosacea. MATERIALS AND METHODS: A number of 563 participants diagnosed with facial rosacea were enrolled in study. They all received both full-face image-shoot by VISIA system with quantitative analysis software and physician's assessment via five different scales, including investigator global assessment (IGA), clinician erythema assessment (CEA), numerical score, the National Rosacea Society (NRS) grading system and telangiectasis. RESULTS: Absolute score and percentile of red area had significant correlations with IGA and CEA, whereas red area had no significant correlation with numerical score, NRS and telangiectasis. Red area in erythematotelangiectatic rosacea patients demonstrated the highest correlation with IGA and CEA, especially in those aged between 51 and 60. Besides red area, pigmentation parameters in VISIA system (brown spot) also showed significant correlation with IGA and CEA. CONCLUSION: VISIA system might be an effective measurement in the assessment of rosacea severity.

Novel human skin surface antimicrobial peptide quantification method using a skin patch test chamber: A pilot study.

INTRODUCTION: Antimicrobial peptides (AMPs) on the skin surface are related to the innate immunity of the skin in preventing external infection. Skin rinsing and tape stripping (TS) are acceptable methods for analyzing AMPs on the skin surface but have limitations, such as causing skin damage. In this study, we proposed a noninvasive method to measure AMPs on the skin surface with minimal skin damage. METHODS: Using the patch test assay, we aimed to analyze the skin surface human ß-defensin (hBDs) levels without damaging the skin barrier. The concentrations of hBDs on the skin surface were evaluated through the skin patch testing of 13 healthy subjects, and hBD-1 concentrations were compared with those obtained using the TS method in this proof-of-concept study. In addition, changes in skin physiology and concentration of hBDs under 1% sodium lauryl sulfate stimulation were monitored in 14 healthy subjects (8 young and 6 elderly subjects) for 150 h. RESULTS: The correlation between the two methods had a Pearson's coefficient of 0.640, and skin patch analysis led to a relatively less impaired barrier with no significant increase in transepidermal water loss after analysis. Age-specific comparisons suggested that higher skin surface hBD-2 concentrations were present in the young group as compared with the elderly group. Skin surface expression of hBD-2 after skin barrier disruption was also higher in the young group. CONCLUSION: Our findings show that skin patch analysis is a convenient method to analyze hBDs on the skin surface. hBDs are factors of innate immunity that can be used as an index to predict a decreased chemical immune response of skin due to aging.

Magnetic resonance imaging of in vitro urine flow in single and tandem stented ureters subject to extrinsic ureteral obstruction.

OBJECTIVE: To quantify the relative volumetric flows in stent and ureter lumina, as a function of stent size and configuration, in both unobstructed and externally obstructed stented ureters. METHODS: Magnetic resonance imaging was used to measure flow in stented ureters using a phantom kidney model. Volumetric flow in the stent and ureter lumina were determined along the stented ureters, for each of four single stent sizes (4.8F, 6F, 7F, and 8F), and for tandem (6F and 7F) configurations. Measurements were made in the presence of a fully encircling extrinsic ureteral obstruction as well as in benchmark cases with no extrinsic ureteral obstruction. RESULTS: Under no obstruction, the relative contribution of urine flow in single stents is 1-10%, while the relative contributions to flow are ~6 and ~28% for tandem 6F and 7F, respectively. In the presence of an extrinsic ureteral obstruction and single stents, all urine passes within the stent lumen near the extrinsic ureteral obstruction. For tandem 6F and 7F stents under extrinsic ureteral obstruction, relative volumetric flows in the two stent lumina are ~73% and ~81%, respectively, with the remainder passing through the ureter lumen. CONCLUSIONS: Magnetic resonance imaging demonstrates that with no extrinsic ureteral obstruction, minimal urine flow occurs within a stent. Stent lumen flow is significant in the presence of extrinsic ureteral obstruction, in the vicinity of the extrinsic ureteral obstruction. For tandem stents subjected to extrinsic ureteral obstruction, urine flow also occurs in the ureter lumen between the stents, which can reduce the likelihood of kidney failure even in the case of both stent lumina being occluded.

Implementation and Validation of a Novel Noninvasive blood Pressure Measurement Algorithm Based on Oscillometric Method with Obtaining International Hypertension Standards.

Background: One of the most prevalent methods in noninvasive blood pressure (BP) measurement with cuff is oscillometric, which has two different types of deflation, including linear and step deflation. With this approach, in addition to designing a novel algorithm by the step deflation method, a sample of its module was constructed and validated during clinical tests in different hospitals. Method: In this study, by controlling the valve, the pressure would be deflated through optimized steps. By real-time processing on the obtained signal from the pressure sensor, pulses in each step would be extracted. After that, in offline mode, mean arterial pressure is estimated based on curve fitting. Result: A BP simulator, various modules, and an auditory method were used to validate the algorithm and its results. During clinical tests, 80 people (men and women), 11 dialysis patients, and 69 non-dialysis (healthy or with other diseases) in the age range of 17-85 years participated. Conclusion: The obtained results compared with the BP simulator are in the standard range according to the international medical standards of the British Hypertension Society (BHS) and the US Association for the Advancement of Medical Instrumentation (AAMI), which are the global standard of comparison in this field.

An exploratory study of two-dimensional shear-wave elastography in the diagnosis of acute compartment syndrome.

BACKGROUND: Two-dimensional shear-wave elastography (2D-SWE) is an ultrasound elastography technique that uses shear waves to quantitatively measure tissue stiffness and it has recently been developed as a safe, real-time, and noninvasive imaging technique. The purpose of this study was to investigate the value of 2D-SWE in the diagnosis and treatment of acute compartment syndrome (ACS). METHODS: 2D-SWE was used to measure the elasticity values of the main muscles in the superficial compartments of the calf in 212 healthy volunteers, and the difference in the muscle elasticity values between different gender and age groups were analyzed. Nine patients with clinical suspicion of ACS were included in this study and 2D-SWE was used to measure the elasticity values of the muscles on the affected and unaffected sides, and a comparative analysis was performed. RESULTS: The mean elasticity values of the tibialis anterior (TA), peroneus longus (PL), and gastrocnemius medialis (GA) muscles in the relaxed state of the 212 healthy volunteers were 25.4 ± 3.2 kPa, 15.7 ± 1.5 kPa, and 12.1 ± 2.1 kPa, respectively. No statistically significant differences was observed in the elasticity values of the same muscle under the state of relaxation in different gender and age groups (p > 0.05). A statistically significant difference in the elasticity values of the muscle between the affected and unaffected sides in the fasciotomy group (p < 0.05, n = 5) was observed. In contrast, no difference in the elasticity values of the muscle between the affected and unaffected sides in the conservative group (p > 0.05, n = 4) was observed. There was a statistically significant difference in the elasticity values of the muscle on the affected side in the two treatment groups (p < 0.05). CONCLUSIONS: When the ACS occurs, the muscle elasticity of the affected limb increases significantly. 2D-SWE is expected to be a new noninvasive technique for the assessment of ACS and may provide a potential basis for clinical diagnosis and treatment.

Metabolic Disorders Combined with Noninvasive Tests to Screen Advanced Fibrosis in Nonalcoholic Fatty Liver Disease.

BACKGROUND AND AIMS: Nonalcoholic fatty liver disease (NAFLD) is associated with metabolic disorders. This study aimed to explore the role of metabolic disorders in screening advanced fibrosis in NAFLD patients. METHODS: A total of 246 histologically-proven NAFLD patients were enrolled across 14 centers. We compared the severity of fibrosis in patients with different components of metabolic disorders. Based on standard noninvasive tests and metabolic disorders, we developed new algorithms to identify advanced fibrosis. RESULTS: Metabolic syndrome (MetS) was frequent in NAFLD patients (133/246, 54%). Patients with MetS had a higher proportion of significant fibrosis (p=0.014) and higher LSM values (9.2 kPa, vs. 7.4 kPa, p=0.002) than those without MetS. Patients with more metabolic disorders had higher fibrosis stages (p=0.017). Reduced high-density lipoprotein cholesterol (odds ratio [OR]: 2.241, 95% confidence interval [CI]: 1.004-5.002, p=0.049) and raised fasting glucose (OR: 4.500, 95% CI: 2.083-9.725, p<0.001) were significantly associated with advanced fibrosis. Using these two metabolic disorders as a screening tool, a sensitivity, specificity and accuracy of 92%, 81% and 83% was achieved, respectively. With the new algorithms combining metabolic disorders with noninvasive measurements, the number of patients requiring liver biopsy was reduced, especially in combination with the Fibrosis-4 score and metabolic disorders (36% to 17%, p<0.001). In addition, this stepwise algorithm could achieve a high accuracy (85%) and high negative predictive value (93%). CONCLUSIONS: Metabolic disorders should be taken into consideration in the diagnosis of advanced fibrosis. With further validation and investigation, new algorithms could be recommended in primary care units to spare patients from unnecessary referral and liver biopsies.

Noninvasive Flow Monitoring in Simple Flow Phantom Using Resistive Strain Sensors.

In this paper, we introduce a monitoring method for flow expansion and contraction in a simple flow phantom based on electrical resistance changes in an epidermal strain sensor attached to the phantom. The flow phantom was fabricated to have a nonflat surface and small modulus that are analogous to human skin. The epidermal sensors made of polydopamine and polyvinyl alcohol show sufficient linearity (R = 0.9969), reproducibility, and self-adhesion properties, as well as high sensitivity to small modulus measurements (<1% tensile strain). Pulsatile flow monitoring experiments were performed by placing the epidermal sensor on the flow phantom and measuring the relative changes in resistance by the heartbeat. Experiments were conducted for three types of vessel diameters (1.5, 2, and 3 mm). In each of the experiments, the vessels were divided into Top, Middle, and Bottom positions. Experiments for each position show that the relative changes in resistance increase proportionally with the diameter of the vessel. The vessels located close to the epidermal layer have greater relative electrical changes. The results were analyzed using the Bernoulli equation and hoop stress formula. This study demonstrates the feasibility of a noninvasive flow monitoring method using a novel resistive strain sensor.

Novel Computerized Method for Automated Determination of Ventilatory Threshold and Respiratory Compensation Point.

Introduction: The ventilatory threshold (named as VT1) and the respiratory compensation point (named as VT2) describe prominent changes of metabolic demand and exercise intensity domains during an incremental exercise test. Methods: A novel computerized method based on the optimization method was developed for automatically determining VT1 and VT2 from expired air during a progressive maximal exercise test. A total of 109 peak cycle tests were performed by members of the US astronaut corps (74 males and 35 females). We compared the automatically determined VT1 and VT2 values against the visual subjective and independent analyses of three trained evaluators. We also characterized VT1 and VT2 and the respective absolute and relative work rates and distinguished differences between sexes. Results: The automated compared to the visual subjective values were analyzed for differences with t test, for agreement with Bland-Altman plots, and for equivalence with a two one-sided test approach. The results showed that the automated and visual subjective methods were statistically equivalent, and the proposed approach reliably determined VT1 and VT2 values. Females had lower absolute O2 uptake, work rate, and ventilation, and relative O2 uptake at VT1 and VT2 compared to men (p ≤ 0.04). VT1 and VT2 occurred at a greater relative percentage of their peak VO2 for females (67 and 88%) compared to males (55 and 74%; main effect for sex: p < 0.001). Overall, VT1 occurred at 58% of peak VO2, and VT2 occurred at 79% of peak VO2 (p < 0.0001). Conclusion: Improvements in determining of VT1 and VT2 by automated analysis are time efficient, valid, and comparable to subjective visual analysis and may provide valuable information in research and clinical practice as well as identifying exercise intensity domains of crewmembers in space.

Noninvasive measurement of arterial blood pressure in patients with continuous-flow left ventricular assist devices: a systematic review.

Accurate mean blood pressure determination is essential to prevent adverse events in patients with continuous-flow left ventricular assist devices (CFLVAD). We sought to evaluate the accuracy of noninvasive methods of blood pressure measurement compared with invasive intra-arterial recordings in patients with CFLVAD. Systematic electronic search was performed on four online databases (PubMed, Scopus, Embase, and Web of Knowledge) for the terms "Blood Pressure" AND ("Heart-Assist Devices" OR "Left ventricular Assist Devices"). Only studies that compared an intra-arterial and noninvasive blood pressure measurement were included. Electronic search of scientific literature identified 5968 articles. After deduplication, screening of titles and abstracts, full-text review, and excluding incorrect populations and comparator, a total of 12 studies with 502 participants were included, of those 402 participants who had intra-arterial blood pressure measurement. Doppler mean arterial blood pressure showed a very high correlation with mean intra-arterial blood pressure (r = 0.97, r = 0.87) in low pulsatility situations. When the pulsatility was not evaluated, the correlation was high moderate (r = 0.63, r = 0.741). In low pulsatility situations, the correlation was moderate to high moderate (r = 0.42 to r = 0.65). Oscillometer automatic blood pressure cuff showed a moderate to very high correlation with intra-arterial mean arterial blood pressure (r = 0.42, r = 0.86) but also could be low in the context of low pulsatility associated with inconsistent success in noninvasive measurement (r = 0.25). Studies correlating intra-arterial with noninvasive techniques were performed in the context of routine clinical care using fluid-filled catheters. The degree of correlation between both methods is at least moderate.

Measuring the efficiency of pulmonary gas exchange using expired gas instead of arterial blood: comparing the "ideal" Po2 of Riley with end-tidal Po2.

When using a new noninvasive method for measuring the efficiency of pulmonary gas exchange, a key measurement is the oxygen deficit, defined as the difference between the end-tidal alveolar Po2 and the calculated arterial Po2. The end-tidal Po2 is measured using a rapid gas analyzer, and the arterial Po2 is derived from pulse oximetry after allowing for the effect of the Pco2 on the oxygen affinity of hemoglobin. In the present report we show that the values of end-tidal Po2 and Pco2 are highly reproducible, providing a solid foundation for the measurement of the oxygen deficit. We compare the oxygen deficit with the classical ideal alveolar-arterial Po2 difference (A-aDO2) as originally proposed by Riley, and now extensively used in clinical practice. This assumes Riley's criteria for ideal alveolar gas, namely no ventilation-perfusion inequality, the same Pco2 as arterial blood, and the same respiratory exchange ratio as the whole lung. It transpires that, in normal subjects, the end-tidal Po2 is essentially the same as the ideal value. This conclusion is consistent with the very small oxygen deficit that we have reported in young normal subjects, the significantly higher values seen in older normal subjects, and the much larger values in patients with lung disease. We conclude that this noninvasive measurement of the efficiency of pulmonary exchange is identical in many respects to that based on the ideal alveolar Po2, but that it is easier to obtain.