An improved video-based computer tracking system for soft biomaterials testing

We present an improved video-based computer system for on-line tracking of small markers moving in a plane. The system consists of a CCD camera, a video monitor, a dedicated 80386/20 microcomputer, a video frame grabber, and custom software. Up to four markers can be tracked at the 30-Hz video frame rate using a two-step, correlation-based search procedure. We discuss the requisite hardware and software requirements and illustrate how this tracking system can be used to collect strain data during biaxial stretching tests on planar soft tissues. Operating at 30 Hz, this system is an improvement over those previously reported, which are either slower or yield less information.

N-nitrosodimethylamine in domestic beer in China

Samples of domestic (Chinese) beer were analysed for N-nitrosamines using gas chromatography--high resolution mass spectrometry with a peak-matching technique. Of 26 samples tested, 20 (77%) were found to be contaminated with N-nitrosodimethylamine (NDMA)L. The mean content of these samples was 2.7 micrograms/litre, without correction for recovery of NDMA from beer (74% with a coefficient of variance of 18%). The remaining six samples contained less than 0.5 micrograms/litre, the lower limit of detection.

Determinants and clinical significance of jugular venous valve competence

We studied the function of right internal jugular vein valves during cardiac catheterization in 32 patients and external jugular vein valves in vitro from 13 dogs. Patients with normal central venous pressure had competent valves during cough-induced transvalvular pressure gradients of 52.4 +/- 8.6 mm Hg. Ten of 15 patients with elevated central venous pressure had either incompetent or absent internal jugular valves, the latter occurring only in patients with long-standing, severe tricuspid regurgitation. During coughing, competent valves were also demonstrated in the left internal jugular and in the right and left subclavian veins. The excised canine valves were competent at a static transvalvular pressure of 81.8 +/- 3.7 mm Hg. Five of six excised valves remained competent during pulsatile transvalvular pressure of 64.8 +/- 1.9 mm Hg. Thus, thoracic inlet venous valves are usually competent during sudden increases in intrathoracic pressure. These valves may play an important role in establishing the extrathoracic arteriovenous pressure gradient necessary for forward blood flow during cardiopulmonary resuscitation and other states with high intrathoracic pressure.

Reduced inspiratory effort during intermittent mandatory ventilation with PEEP

The use of intermittent mandatory ventilation (IMV) and positive and expiratory pressure (PEEP) may demand the patient mount an inspiratory pressure equivalent to the pressure level of the PEEP for spontaneous breathing. During respiratory failure, ineffective inspiratory muscles may be unable to consistently meet such demands, especially if high levels of PEEP are used. A technique which reduces the required inspiratory effort was devised for use in patients being treated with IMV and PEEP. Using this technique, isovolume inspiratory time was dramatically reduced and less inspiratory effort was required. This maneuver may assist spontaneous breathing in patients with respiratory failure on high levels of PEEP.