Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients

Background: Monitoring of cardiac output and blood pressure are standard procedures in critical care medicine. Traditionally, invasive techniques like pulmonary artery catheter (PAC) and arterial catheters are widely used. Invasiveness bears many risks of deleterious complications. Therefore, a noninvasive reliable cardiac output (CO) and blood pressure monitoring system could improve the safety of cardiac monitoring. The aim of the present study was to compare a noninvasive versus a standard invasive cardiovascular monitoring system. Methods: Nexfin HD is a continuous noninvasive blood pressure and cardiac output monitor system and is based on the development of the pulsatile unloading of the finger arterial walls using an inflatable finger cuff. During continuous BP measurement CO is calculated. We included 10 patients with standard invasive cardiac monitoring system (pulmonary artery catheter and arterial catheter) comparing invasively obtained data to the data collected noninvasively using the Nexfin HD. Results: Correlation between mean arterial pressure measured with the standard arterial monitoring system and the Nexfin HD was r2 = 0.67 with a bias of -2 mmHg and two standard deviations of ± 16 mmHg. Correlation between CO derived from PAC and the Nexfin HD was r2 = 0.83 with a bias of 0.23 l/min and two standard deviations of ± 2.1 l/min; the percentage error was 29%. Conclusion: Although the noninvasive CO measurement appears promising, the noninvasive blood pressure assessment is clearly less reliable than the invasively measured blood pressure. Therefore, according to the present data application of the Nexfin HD monitoring system in the ICU cannot be recommended generally. Whether such a tool might be reliable in certain critically ill patients remains to be determined

Search for Sterile Neutrinos in MINOS and MINOS+ Using a Two-Detector Fit.

A search for mixing between active neutrinos and light sterile neutrinos has been performed by looking for muon neutrino disappearance in two detectors at baselines of 1.04 and 735 km, using a combined MINOS and MINOS+ exposure of 16.36×10^{20} protons on target. A simultaneous fit to the charged-current muon neutrino and neutral-current neutrino energy spectra in the two detectors yields no evidence for sterile neutrino mixing using a 3+1 model. The most stringent limit to date is set on the mixing parameter sin^{2}θ_{24} for most values of the sterile neutrino mass splitting Δm_{41}^{2}>10^{-4}  eV^{2}

Search for Sterile Neutrinos in MINOS and MINOS plus Using a Two-Detector Fit

A search for mixing between active neutrinos and light sterile neutrinos has been performed by looking for muon neutrino disappearance in two detectors at baselines of 1.04 and 735 km, using a combined MINOS and MINOS+ exposure of 16.36 × 10 20 protons on target. A simultaneous fit to the charged-current muon neutrino and neutral-current neutrino energy spectra in the two detectors yields no evidence for sterile neutrino mixing using a 3 + 1 model. The most stringent limit to date is set on the mixing parameter sin 2 θ 24 for most values of the sterile neutrino mass splitting Δ m 2 41 > 10 − 4     eV 2

Discrimination of healthy and glaucomatous eyes based on the ocular pulse amplitude: A diagnostic case-control study

By measuring the ocular pulse amplitude (OPA), the dynamic contour tonometer (DCT) assesses intraocular pressure (IOP). Hypothesizing that OPA is characteristic for the IOP when considered with the systemic arterial blood pressure, we assumed the ratio of ocular and arterial pulsation amplitudes is larger in glaucoma patients. Bi-ocular DCT-OPA assessment was synchronized with arterial pulsations using Finapres® technology, thereby enabling blood pressure determination for each corresponding IOP value every 0.01 s for 12 s. Based on measurements and calculations in 10 healthy subjects and 11 glaucoma patients, we conclude that the ratio of the OPA and blood pressure variances is a strong glaucoma diagnostic indicator, thereby justifying further investigation

Reliability of a new 4th generation FloTrac algorithm to track cardiac output changes in patients receiving phenylephrine

Phenylephrine is often used to treat intra-operative hypotension. Previous studies have shown that the FloTrac cardiac monitor may overestimate cardiac output (CO) changes following phenylephrine administration. A new algorithm (4(th) generation) has been developed to improve performance in this setting. We performed a prospective observational study to assess the effects of phenylephrine administration on CO values measured by the 3(rd) and 4(th) generation FloTrac algorithms. 54 patients were enrolled in this study. We used the Nexfin, a pulse contour method shown to be insensitive to vasopressor administration, as the reference method. Radial arterial pressures were recorded continuously in patients undergoing surgery. Phenylephrine administration times were documented. Arterial pressure recordings were subsequently analyzed offline using three different pulse contour analysis algorithms: FloTrac 3(rd) generation (G3), FloTrac 4(th) generation (G4), and Nexfin (nf). One minute of hemodynamic measurements was analyzed immediately before phenylephrine administration and then repeated when the mean arterial pressure peaked. A total of 157 (4.6 ± 3.2 per patient, range 1–15) paired sets of hemodynamic recordings were analyzed. Phenylephrine induced a significant increase in stroke volume (SV) and CO with the FloTrac G3, but not with FloTrac G4 or Nexfin algorithms. Agreement between FloTrac G3 and Nexfin was: 0.23±1.19 l/min and concordance was 51.1%. In contrast, agreement between FloTrac G4 and Nexfin was: 0.19±0.86 l/min and concordance was 87.2%. In conclusion, the pulse contour method of measuring CO, as implemented in FloTrac 4th generation algorithm, has significantly improved its ability to track the changes in CO induced by phenylephrine

Feasibility of noninvasive continuous finger arterial blood pressure measurements in very young children, aged 0-4 years

Our goal was to study the feasibility of continuous noninvasive finger blood pressure (BP) monitoring in very young children, aged 0-4 y. To achieve this, we dedigned a set of smallsized finger cuffs based on the assessment of finger circumference. Finger arterial BP measured by a volume clamp device (Finapress technology) was compared with simultaneously measured intra-arterial BP in 15 very young children (median age, 5 mo; range, 0-48), admitted to the intensive care unit for vital monitoring. The finger cuff-derived BP waveforms showed good resemblance with the invasive arterial waveforms (mean root-mean-square error, 3 mm Hg). The correlation coefficient between both methods was 0.79 ± 0.19 systolic and 0.74 ± 0.24 diastolic. The correlation coefficient of beat-to-beat changes between both methods was 0.82 ± 0.18 and 0.75 ± 0.21, respectively. Three measurements were related to measurement errors (loose cuff application; wrong set-point). Excluding these erroneous measurements resulted in clinically acceptable measurement bias (-3.8 mm Hg) and 95% limits of agreement (-10.4 to + 2.8 mm Hg) of mean BP values. We conclude that continuous finger BP measurement is feasable in very young children. However, cuff application is critical, and the current set-point algorithm needs to be revised in very young children. (Pediatr Res 63: 691-696, 2008