The Si–H stretching–bending overtone polyads of SiHF₃: Assignments, band intensities, internal coordinate force field, and ab initio dipole moment surfaces

Fourier transform overtone spectra of SiHF were recorded in the region of 2500–9000 cm−1 and vibrationally assigned. Experimental intensities were estimated. The 3ʋ1 overtone band at 6753 cm−1 was observed to be more than 10 times weaker than the 4ʋ1 band. A reduced three-dimensional Hamiltonian model in terms of internal coordinates was employed to study the Si–H stretching and bending vibrations including 5ʋ1 and 6ʋ1 which were recently recorded using optoacousticspectroscopy. Potential energy parameters were optimized by fitting to experimental band centers. The Fermi resonance between the Si–H stretching and bending motions was found to be insignificant. Band intensities were computed using ab initio one- and three-dimensional dipole momentsurfaces (DMS) expanded to polynomials in terms of symmetrized internal coordinates. The intensity anomaly of 3ʋ1 is understood as resulting from cancellation of contributions by the linear and quadratic terms in the DMS expansion. The behavior of X–H stretching overtone intensities as excitation increases was also studied in the low and medium energy regions. Whether a rapid or a slow decrease of intensity occurs with increasing excitation depends strongly on the nonlinearity of the DMS. For some molecules, there is an almost complete cancellation of contributions from the lower order terms in the DMS so that the accuracy of the computed overtone intensities is mainly limited by the uncertainty of the higher order expansion coefficients in the DMS

Effect of INTELLiVENT-ASV versus conventional ventilation on ventilation intensity in patients with COVID-19 ARDS—An observational study

Driving pressure (ΔP) and mechanical power (MP) are associated with outcomes in critically ill patients, irrespective of the presence of Acute Respiratory Distress Syndrome (ARDS). INTELLiVENT-ASV, a fully automated ventilatory mode, controls the settings that affect ΔP and MP. This study compared the intensity of ventilation (ΔP and MP) with INTELLiVENT-ASV versus conventional ventilation in a cohort of COVID-19 ARDS patients in two intensive care units in the Netherlands. The coprimary endpoints were ΔP and MP before and after converting from conventional ventilation to INTELLiVENT-ASV. Compared to conventional ventilation, INTELLiVENT-ASV delivered ventilation with a lower ΔP and less MP. With conventional ventilation, ΔP was 13 cmH2O, and MP was 21.5 and 24.8 J/min, whereas with INTELLiVENT-ASV, ΔP was 11 and 10 cmH2O (mean difference –2 cm H2O (95 %CI –2.5 to –1.2 cm H2O), p < 0.001) and MP was 18.8 and 17.5 J/min (mean difference –7.3 J/Min (95% CI –8.8 to –5.8 J/min), p < 0.001). Conversion from conventional ventilation to INTELLiVENT-ASV resulted in a lower intensity of ventilation. These findings may favor the use of INTELLiVENT-ASV in COVID-19 ARDS patients, but future studies remain needed to see if the reduction in the intensity of ventilation translates into clinical benefits