Diffusion of water vapor in binary and ternary gas mixtures at increased pressures.

Diffusion of water vapor was measured at 25 degrees C in the binary systems water vapor-He and water vapor-N2 at approximately 1, 4 10, 20 and 50 atm. Diffusion was also measured in the ternary system water vapor-He-O2 in both 2%O2-98%He, and at 1 and 20 atm. At 1 atm, comparison of binary diffusion coefficients (delta) shows that water vapor diffuses 3.3 times more readily in He than in N2. Values of delta at elevated pressures were reduced in proportion to 1/p, the absolute pressure, in qualitative agreement with Chapman-Enskog theory. However, the reduction in Delta was less than predicted at pressure above 4 atm in water vapor-N2 and above 20 atm in water vapor-He. The deviations from theory are more pronounced in N2 than in He, and become larger at higher pressures. When 26% O2 is present in the ternary system water vapor-He-O2, diffusion of water vapor is reduced to about 60% of its rate in pure He. In contrast, 2% O2 in He has little effect on diffusion of water vapor.

Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. VII: Auditory, visual, and gustatory sensations.

Five divers were tested for alterations in auditory, visual, and gustatory functioning during a 17-day saturation exposure to He-O2 at 18.6 ATA. No evidence of permanent hearing loss was disclosed. Critical flicker fusion was not affected, but peripheral visual thresholds were significantly increased during the first two weeks at 18.6 ATA; this was interpreted to be evidence of severe psychological and physiological stress. Foveal vision was unaffected across testings. Magnitude estimation techniques disclosed changes in taste sensitivity, with sweet sensitivity increasing over time and sour sensitivity declining over the course of the dive. Subjects were more sensitive to bitter stimuli at maximum pressure than at sea level, and less sensitive to salt at maximum pressure. The results indicate that appreciable alterations in sensory functioning can occur during saturation exposures, although the sense modalities were differentially affected by such environmental stressors as pressure, psycho-social stress, fatigue, and perceptual deprivation.

Ocular lubricants and corneal injury during anesthesia.

Seventy-six patients undergoing general endotracheal anesthesia were studied prospectively to determine whether simply taping the eyelids closed during the surgical procedure as opposed to taping the lids after instilling a bland lubricating ointment had any different effect on corneal or conjunctival epithelium. No significant difference was found.

Argon laser trabeculoplasty in black and white patients with primary open-angle glaucoma.

The effect of argon laser trabeculoplasty (ALT) on lowering intraocular pressure (IOP) was studied retrospectively in 68 black patients and 42 white patients with uncontrolled primary open-angle glaucoma on maximally tolerated medical therapy. Patients with the diagnosis of pigmentary or pseudoexfoliation glaucoma and those having previous intraocular or laser surgery were excluded. While the mean age of the black patients (66.9 years) was lower than the white patients (72.2 years), the prelaser IOP was similar between the two groups: 26.2 mmHg for the black patients and 25.5 mmHg for the white patients. The mean IOP one year (18.4 mmHg for black patients and 18.4 mmHg for white patients) and two years (19.5 mmHg and 20.3 mmHg, respectively) after ALT was the same between the two groups of patients. A similar percentage of black (85%) and white (83%) patients showed more than a 15% decrease in IOP from their prelaser values one year after treatment. The IOP lowering effect of ALT decreased during the second post-operative year; but the diminished response was identical in patients of both races, with 71% of patients of both groups still showing greater than 15% reduction from their pre-laser IOP. We conclude that ALT is equally effective in lowering IOP for black and white patients with medically uncontrolled primary open-angle glaucoma.