An investigation of cardiovascular reflexes during a trimix saturation dive to 450 msw (GUSI 17).

The study examines the hypothesis that the carotid sinus heart rate baroreflex responses are changed in human subjects on exposure to 450 msw. Baroreceptor reflex changes in heart rate (expressed as ms/mmHg applied pressure) were evoked by application of negative or positive pressure to a cuff surrounding the neck. At 450 msw using trimix, the mean resting heart rate of divers slowed significantly from 64 +/- 1.3 beats/min at surface to 55 +/- 1.4 beats/min at 450 msw, respiratory rate decreased from 15 +/- 1.4 at surface to 11 +/- 2 at 450 msw, and sinus arrhythmia increased. There was no change in arterial blood pressure. Baroreceptor reflex sensitivity to an increased carotid sinus transmural pressure was reduced from 5.6 +/- 2.9 (mean +/- SEM) at surface to 2.4 +/- 0.8 ms.mmHg-1 at 450 msw; sensitivity to decreased carotid sinus transmural pressure increased from 2.2 +/- 0.4 ms.mmHg-1 at surface to 5.1 +/- 0.2 ms.mmHg-1 at 450 msw. A progressive shortening of cardiac interval during breath hold in expiration was also noted. When this shortening of interval was incorporated into the analysis of baroreceptor reflex sensitivity, no significant change in sensitivity was observed but the overall baroreflex stimulus-response relationship shifted downward.

The association of multiple colonic adenomatous polyps with cancer of the colon.

We reviewed our colonoscopy data for the past 10 yr for patients with five or more polyps to determine the association of multiple adenomatous polyps and colon cancer. During that period, 3,834 patients underwent colonoscopy. Fifty-two patients with five or more polyps at the initial colonoscopy were found. In 25 patients (group I) there were at least five synchronous adenomas, and in 27 patients (group II) a combination of adenomas and hyperplastic polyps totaling five or more. The number of polyps ranged from five to 30 (median, six). There was no significant difference in the location of polyps between groups I and II. Eight of 52 patients (15%) were found to have colon cancer at the initial colonoscopy. In group I, there were six cancers (24%), five of which were in the cecum. Two of 27 patients (7%) in group II had cancer, one of which was located in the cecum. Patients with five or more adenomas at the index colonoscopy are at high risk of having colon cancer that is particularly prone to arise from the right side of the colon.