Helium-oxygen mixture does not improve gas exchange in mechanically ventilated children with bronchiolitis.

STATEMENT OF FINDINGS: Varying concentrations of helium-oxygen (heliox) mixtures were evaluated in mechanically ventilated children with bronchiolitis. We hypothesized that, with an increase in the helium:oxygen ratio, and therefore a decrease in gas density, ventilation and oxygenation would improve in children with bronchiolitis. Ten patients, aged 1-9 months, were mechanically ventilated in synchronized intermittent mandatory ventilation (SIMV) mode with the following gas mixtures delivered at 15-min intervals: 50%/50% nitrogen/oxygen, 50%/50% heliox, 60%/40% heliox, 70%/30% heliox, and return to 50%/50% nitrogen/oxygen. The use of different heliox mixtures compared with 50%/50% nitrogen/oxygen in mechanically ventilated children with bronchiolitis did not result in a significant or noticeable decrease in ventilation or oxygenation.

Dynamics of coronary artery curvature obtained from biplane cineangiograms.

A system was developed to track the centerlines (axes) of human coronary arteries during the cardiac cycle from biplane cineangiograms. The system employs a time interpolation technique on one image plane and a smoothing technique on the other to create simultaneous image pairs. The image pairs are then used to reconstruct the three dimensional axes of the vessels during the cardiac cycle. Once the vessel axes are reconstructed, acceleration, velocity and geometric parameters such as curvature can be obtained. In the present work, a sequence of human angiograms is used to obtain the axial and temporal variation of the curvature of a portion of the left anterior descending coronary artery distal to the third diagonal branch during two cardiac cycles. For the case studied, the change in curvature during the cycle ranged from 0.25 to 1.8 cm(-1), depending upon the position of the site.