Tracking tidal volume noninvasively in volunteers using a tightly controlled temperature-based device: A proof of concept paper.

INTRODUCTION: There is a paucity of noninvasive respiratory monitors for patients outside of critical care settings. The Linshom respiratory monitoring device is a novel temperature-based respiratory monitor that measures the respiratory rate as accurately as capnography. OBJECTIVES: Determine whether the amplitude of the Linshom temperature profile was an accurate, surrogate and qualitative metric of the tidal volume (VT ) that tracks VT in healthy volunteers. METHODS: Forty volunteers breathed room air spontaneously through a tight-fitting continuous positive airway pressure mask with a Linshom device mounted in the mask. VT was measured contemporaneously using a standalone Maquet Servo-i ICU ventilator. The amplitudes of the Linshom temperature profiles were paired with the contemporaneous VT measurements using least squares linear regression analysis and the coefficient of variation (R2 ) was determined. RESULTS: Forty volunteers completed the study. The data from 30 of the volunteers were analysed and are presented; data from 10 volunteers were not included due to protocol violations and/or technical issues unrelated to Linshom. The fluctuations in the amplitude of the Linshom temperature profiles mapped closely with the measured VT using least squares linear regression analyses yielding a mean R2 (95% CI) value of 0.87 (0.84-0.90). CONCLUSION: These results support the notion that the Linshom temperature profile is an accurate and reliable surrogate that tracks changes in VT in healthy volunteers. Further studies are warranted in patients in clinical settings to establish the effectiveness of this monitor.

High x-ray resolving power utilizing asymmetric diffraction from a quartz transmission crystal measured in the 6 keV to 22 keV energy range.

A Cauchois-type spectrometer utilizing the (203) lattice planes at an oblique angle of 11.53° to the normal to the surface of a quartz transmission crystal recorded the Kα and Kß spectral lines of six elements from Fe to Ag in the 6-22 keV energy range from a laboratory x-ray source. After deconvolving the natural lifetime widths and the image plate detector broadening from the observed spectral linewidths, the intrinsic crystal resolving power was determined to be 4000 at the lower energies and decreasing to 1000 at the higher energies. Previously, a Si wafer crystal exhibited twice this resolving power when the (331) planes had been used in asymmetric geometry. The investigation of diffraction with this quartz crystal, with a very similar lattice spacing and therefore spectral coverage, was motivated by the larger integrated reflectivity of quartz due to its well-known quasimosaicity upon elastic bending. The measured spectral linewidths were in good agreement with the widths calculated by accounting for various broadening mechanisms, including source size, crystal thickness, crystal height, crystal rocking curve width, geometrical aberrations, and possible spectrometer configuration errors. This is the first, to the best of our knowledge, demonstration of high resolving power achieved by asymmetric diffraction over a wide energy range (6-22 keV) and with detailed comparisons with theoretical broadenings. Based on these results, Cauchois spectrometers employing asymmetric planes of perfect quartz and silicon crystals can be reliably designed and optimized for high-resolution spectroscopy in the >6 keV energy range.

X-ray spectrometer having 12 000 resolving power at 8 keV energy.

An x-ray spectrometer employing a thin (50 µm) silicon transmission crystal was used to record high-resolution Cu Kα spectra from a laboratory x-ray source. The diffraction was from the (331) planes that were at an angle of 13.26° to the crystal surface. The components of the spectral lines resulting from single-vacancy (1s) and double-vacancy (1s and 3d) transitions were observed. After accounting for the natural lifetime widths from reference double-crystal spectra and the spatial resolution of the image plate detector, the intrinsic broadening of the transmission crystal was measured to be as small as 0.67 eV and the resolving power 12 000, the highest resolving power achieved by a compact (0.5 m long) spectrometer employing a single transmission crystal operating in the hard x-ray region. By recording spectra with variable source-to-crystal distances and comparing to the calculated widths from various geometrical broadening mechanisms, the primary contributions to the intrinsic crystal broadening were found to be the source height at small distances and the crystal apertured height at large distances. By reducing these two effects, using a smaller source size and vignetting the crystal height, the intrinsic crystal broadening is then limited by the crystal thickness and the rocking curve width and would be 0.4 eV at 8 keV energy (20 000 resolving power).

Linshom respiratory monitoring device: a novel temperature-based respiratory monitor.

PURPOSE: We sought to develop a temperature-based respiratory instrument to measure respiration noninvasively outside critical care settings. METHOD: Respiratory temperature profiles were recorded using a temperature-based noninvasive instrument comprised of three rapid responding medical-grade thermistors-two in close proximity to the mouth/nose (sensors) and one remote to the airway (reference). The effect of the gas flow rate on the amplitude of the tracings was determined. The temperature-based instrument, the Linshom Respiratory Monitoring Device (LRMD) was mounted to a face mask and positioned on a mannequin face. Respiratory rates of 5-40 breaths·min(-1) were then delivered to the mannequin face in random order using artificial bellows (IngMar Lung Model). Data from the sensors were collected and compared with the bellows rates using least squares linear regression and coefficient of determination. The investigators breathed at fixed rates of 0-60 breaths·min(-1) in synchrony with a metronome as their respiratory temperature profiles were recorded from sensors mounted to either a face mask or nasal prongs. The recordings were compared with a contemporaneously recorded sidestream capnogram from a CARESCAPE GEB450 Monitor. The extracted respiratory rates from the LRMD tracings and capnograms were compared using linear regression with a coefficient of determination and a Bland-Altman plot. RESULTS: The amplitude of the sensor tracings was independent of the oxygen flow rate. Respiratory rates from the new temperature-based sensor were synchronous and correlated identically with both the artificial bellows (r(2) = 0.9997) and the capnometer mounted to both the face mask and nasal prongs (r(2) = 0.99; bias = -0.17; 95% confidence interval, -2.15 to 1.8). CONCLUSIONS: Respiratory rates using the LRMD, a novel temperature-based respiratory instrument, were consistent with those using capnometry.

RéSUMé: OBJECTIF: Nous avons tenté de mettre au point un instrument respiratoire se fondant sur la température afin de mesurer la respiration de façon non invasive en dehors des unités de soins critiques. MéTHODE: Les profils de température respiratoire ont été enregistrés à l'aide d'un instrument non invasif se fondant sur la température et composé de trois thermistances de qualité médicale à réponse rapide ­ deux à proximité de la bouche et du nez (capteurs) et un troisième à l'écart des voies aériennes (référence). L'effet du débit gazeux sur l'amplitude des tracés a été déterminé. L'instrument fondé sur la température, nommément le dispositif de monitorage respiratoire Linshom (LRMD), a été fixé à un masque facial et positionné sur le visage d'un mannequin. Des fréquences respiratoires de 5-40 respirations·min−1 ont ensuite été livrées au visage du mannequin dans un ordre aléatoire à l'aide de soufflets artificiels (modèle de poumon IngMar). Les données des capteurs ont été colligées et comparées aux fréquences des soufflets à l'aide d'une méthode de régression linéaire des moindres carrés et d'un coefficient de détermination. Les chercheurs ont respiré à des fréquences fixes de 0-60 respirations·min−1 en synchronie avec un métronome pendant que leurs profils de température respiratoire étaient enregistrés par des capteurs fixés à un masque facial ou à des canules nasales. Les enregistrements ont été comparés à un tracé de capnogramme latéral enregistré simultanément par un moniteur CARESCAPE GEB450. Les fréquences respiratoires extraites des tracés du LRMD et des capnogrammes ont été comparées à l'aide d'une méthode de régression linéaire avec un coefficient de détermination et un graphique de Bland-Altman. RéSULTATS: L'amplitude des tracés des capteurs était indépendante du débit d'oxygène. Les fréquences respiratoires du nouveau capteur basé sur la température étaient synchrones et identiquement corrélées aux soufflets artificiels (r2 = 0,9997) et au capnomètre fixé au masque facial et aux canules nasales (r2 = 0,99; biais = −0,17; intervalle de confiance 95 %, −2,15 à 1,8). CONCLUSION: Les fréquences respiratoires mesurées à l'aide du LRMD, un nouvel instrument respiratoire fondé sur la température, étaient cohérentes à celles mesurées par capnométrie.

Tunable hard X-ray spectrometer utilizing asymmetric planes of a quartz transmission crystal.

A Cauchois type hard x-ray spectrometer was developed that utilizes the (301) diffraction planes at an asymmetric angle of 23.51° to the normal to the surface of a cylindrically curved quartz transmission crystal. The energy coverage is tunable by rotating the crystal and the detector arm, and spectra were recorded in the 8 keV to 20 keV range with greater than 2000 resolving power. The high resolution results from low aberrations enabled by the nearly perpendicular angle of the diffracted rays with the back surface of the crystal. By using other asymmetric planes of the same crystal and rotating to selected angles, the spectrometer can operate with high resolution up to 50 keV.

Transmission crystal x-ray spectrometer covering the 6 keV-18 keV energy range with E∕ΔE = 1800 instrumental resolving power.

A high-resolution x-ray spectrometer utilizing a thin quartz transmission crystal and covering the 6 keV-18 keV energy range has been developed and tested. The spectrometer consists of a cylindrically bent crystal in a vacuum housing. The crystal position and the range of Bragg angles that are incident on the crystal can be adjusted to record an ≈4 keV wide spectrum in the 6 keV-18 keV range. The spectrometer is of the Cauchois type and has a compact linear geometry that is convenient for deployment at laser-produced plasma, EBIT, and other x-ray sources. Test spectra of the W L and Mo K lines from laboratory sources have linewidths as small as 11 eV, approaching the natural widths, and instrumental resolving power as high as 1800. Techniques for enhancing the energy resolution are experimentally demonstrated.

Efficiency calibrations of cylindrically bent transmission crystals in the 20 to 80 keV x-ray energy range.

Two quartz (10-11) crystals were cylindrically bent to a 25.4 cm radius of curvature and were mounted in identical Cauchois-type transmission spectrometers, and the crystal diffraction efficiencies were measured to 5% absolute accuracy using narrow bandwidth x-ray source fluences in the 20 to 80 keV energy range. The measured integrated reflectivity values were compared to calculations performed using a computational model that accounts for the diffraction geometry of the bent transmission crystal. These crystal calibrations enable the accurate measurement of absolute hard x-ray emission levels from laser-produced plasmas and other laboratory sources.

High-resolution imaging spectrometer for recording absolutely calibrated far ultraviolet spectra from laser-produced plasmas.

An imaging spectrometer was designed and fabricated for recording far ultraviolet spectra from laser-produced plasmas with wavelengths as short as 155 nm. The spectrometer implements a Cassegrain telescope and two gratings in a tandem Wadsworth optical configuration that provides diffraction limited resolution. Spectral images were recorded from plasmas produced by the irradiation of various target materials by intense KrF laser radiation with 248 nm wavelength. Two pairs of high-resolution gratings can be selected for the coverage of two wavebands, one grating pair with 1800 grooves/mm and covering approximately 155-175 nm and another grating pair with 1200 grooves/mm covering 230-260 nm. The latter waveband includes the 248 nm KrF laser wavelength, and the former waveband includes the wavelength of the two-plasmon decay instability at 23 the KrF laser wavelength (165 nm). The detection media consist of a complementary metal oxide semiconductor imager, photostimulable phosphor image plates, and a linear array of 1 mm(2) square silicon photodiodes with 0.4 ns rise time. The telescope mirrors, spectrometer gratings, and 1 mm(2) photodiode were calibrated using synchrotron radiation, and this enables the measurement of the absolute emission from the laser-produced plasmas with temporal, spatial, and spectral resolutions. The spectrometer is capable of measuring absolute spectral emissions at 165 nm wavelength as small as 5x10(-7) J/nm from a plasma source area of 0.37 mm(2) and with 0.4 ns time resolution.

Measurement of wavelengths with phosphor storage image plates on a grazing incidence spectrograph.

We recorded the spectra emitted by a Ne/Mg Penning discharge and by sliding spark discharges of Y and Mo in the 150-450 A range with phosphor storage image plates on a 10.7 m grazing incidence spectrograph. To obtain better conformance of the image plates to the focal surface of the concave grating, the plates were mounted on the curved surface with a backing of flexible steel plates. The exposed plates were read by a rotary drum scanner. With these techniques we achieved a wavelength accuracy of approximately 0.003 A. This is comparable to what is normally obtained with photographic plates on this instrument.