An On-Demand Oxygen Flow Meter for Enhanced Patient Comfort and Reduced Oxygen Cost in Hospitals.

Background: Hypoxemia is currently treated in hospital wards with oxygen, released continuously by "conventional" flow meters. A new type of hybrid flow meter allows to switch between on-demand and continuous mode. The aim of this observational study was to assess whether this new device reduces oxygen expenditure, is well accepted in a hospital setting and improves patient comfort during oxygen therapy. Methods: Oxygen was administered in hypoxemic patients with conventional or hybrid flow meters to maintain an oxygen saturation of ≥ 92% over a 12-week period. Every two weeks conventional and hybrid flow meters were switched. The overall oxygen delivery to the ward was continuously measured with a data logging device installed in the main oxygen pipeline and corrected for multiple confounding factors. Humidity measurements, for which a sensor placed in front of one of the nostrils, and patient questionnaires, were used to assess patient comfort during continuous and on-demand flow. Results: Overall oxygen delivery decreased by 39% when switching from continuous flow to on-demand therapy after correction for confounding factors. Continuous flows significantly decreased relative humidity more than equivalent on-demand settings and the latter tended to increase comfort. Conclusions: Hybrid flow meters cause a significant reduction in oxygen delivery in a hospital ward, which may lead to financial savings. Using the on-demand technology also lowers the dryness of the upper airways (and may increase patient comfort), while maintaining an adequate oxygenation.

Test-retest reliability of skeletal muscle oxygenation measurement using near-infrared spectroscopy during exercise in patients with sport-related iliac artery flow limitation.

The ankle-brachial index is an accurate tool for detecting claudication in atherosclerotic patients. However, this technique fails to identify subtle flow limitations of the iliac arteries (FLIA) in endurance athletes. Near-infrared spectroscopy (NIRS) is a noninvasive technique that measures skeletal muscle tissue oxygenation status. The aim of the present study is to examine the absolute and relative test-retest reliability of NIRS and evaluate its potential as a diagnostic tool in FLIA. NIRS-derived exercise variables were analyzed during exercise and recovery in FLIA 17 patients and 19 healthy controls. The relative reliability of absolute variables (such as the maximal value) were slight to yet predominantly substantial (intraclass correlation coefficient [ICC], ICC range: 0.06-0.76) with good to excellent absolute reliability (absolute limits of agreement [ALoA], ALoA range: 0.8 ± 10.2 to 0.7 ± 13.1; coefficient of variation [CV], CV range: 5%-11%). Absolute values encompassing signal amplitudes showed moderate to almost perfect relative reliability (ICC range: 0.51-0.89) and poor to good absolute reliability (ALoA range: -1.3 ± 7.0 to -2.5 ± 15.7; CV range: 15%-32%). Kinetic variables showed moderate to almost perfect relative reliability for most recovery kinetics variables (ICC range: 0.54-0.86) with fair to good absolute reliability (ALoA range: 0.4 ± 12.2 to 3.9 ± 37.9; CV range: 18%-27%). Particularly, kinetic variables showed significant differences between patients and healthy subjects. NIRS is found to be a reliable method for examining muscle tissue oxygenation variables. Given the significant differences in especially recovery kinetics between normal subjects and patients, NIRS may contribute to diagnosing FLIA in endurance athletes.

Pedal power measurement as a diagnostic tool for functional vascular problems.

BACKGROUND: Cyclists with flow limitations in the iliac arteries complain of pain and loss of power. To investigate whether pedal power measurement has added value in diagnosing the underlying cause of flow limitations in the iliac arteries, we explored the sensitivity and specificity of various pedal power measurement variables. Moreover, it was assessed what the added value of pedal power measurement is compared to diagnosis based on the conventional ankle-brachial blood pressure index. METHODS: 25 healthy participants and 45 patients with unilateral arterial flow limitations were recruited. Participants received Echo-Doppler examination to determine the condition of the iliac arteries. Subsequently, participants performed a maximal cycle ergometer test. During the cycling test the exerted left and right pedal power was measured. From these measurements several variables were derived to diagnose arterial flow limitations. A receiver operating characteristics curve based on a predicted cross-validated model was used to select the variable with the highest predictive value and its cut-off value. FINDINGS: The mean power difference between both legs relative to the exerted power at 95% of the maximal power showed the best predictive value with a sensitivity of 0.76 and a specificity of 0.88. Combining the pedal power measurement and ankle-brachial blood pressure index resulted in a sensitivity of 0.91 and a specificity of 0.88. INTERPRETATION: Pedal power measurement improves sensitivity of diagnosis of iliac artery flow limitations, without increasing the burden of clinical investigation to the patients.

The influence of adipose tissue on spatially resolved near-infrared spectroscopy derived skeletal muscle oxygenation: the extent of the problem.

OBJECTIVE: Near-infrared spectroscopy (NIRS) measurements of tissue oxygen saturation (StO2) are useful for the assessment of skeletal muscle perfusion and function during exercise, however, they are influenced by overlying skin and adipose tissue. This study explored the extent and nature of the influence of adipose tissue thickness (ATT) on StO2. APPROACH: NIR spatially resolved spectroscopy (SRS) derived oxygenation was measured on vastus lateralis in 56 patients with chronic heart failure (CHF) and 20 healthy control (HC) subjects during rest and moderate intensity exercise with simultaneous assessment of oxygen uptake kinetics (τ [Formula: see text]). In vitro measurements were performed on a flow cell with a blood mixture with full oxygen saturation (100%), which was gradually decreased to 0% by adding sodium metabisulfite. Experiments were repeated with 2 mm increments of porcine fat layer between the NIRS device and flow cell up to 14 mm. MAIN RESULTS: Lower ATT, higher τ [Formula: see text], and CHF were independently associated with lower in vivo StO2 in multiple regression analysis, whereas age and gender showed no independent relationship. With greater ATT, in vitro StO2 was reduced from 100% to 74% for fully oxygenated blood and increased from 0% to 68% for deoxygenated blood. SIGNIFICANCE: This study shows that ATT independently confounds NIR-SRS derived StO2 by overestimating actual skeletal muscle oxygenation and by decreasing its sensitivity for deoxygenation. Because physiological properties (e.g. presence of disease and slowing of τ [Formula: see text]) also influence NIR-SRS, a correction based on optical properties is needed to interpret calculated values as absolute StO2.

Flexible active-matrix displays and shift registers based on solution-processed organic transistors.

At present, flexible displays are an important focus of research. Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate. Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-microm-thick polyimide substrates. The displays can be bent to a radius of 1 cm without significant loss in performance. Using the same process flow we prepared row shift registers. With 1,888 transistors, these are the largest organic integrated circuits reported to date. More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed. This work therefore represents a major step towards 'system-on-plastic'.