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Biomedical subjects

N J Zimmerman

Publications and source records attributed to N J Zimmerman.

10 recordsLinked to original sources
PubMed1991

Effects of respirators on performance of physical, psychomotor and cognitive tasks.

Possible work decrements caused by respirator usage were examined. A battery of physical, psychomotor and cognitive tasks was used to investigate the effects of respirator wear on 12 subjects. A repeated measures experimental design was used to study the effects of three types of respirators: a disposable dust mask; an air purifying half-mask; and a full-face airline mask. Performance while wearing a mask was compared to the control condition without a respirator. The results from the physical work task of riding a bicycle ergometer indicated approximately a 10% increase in oxygen consumption when subjects wore half and full-face masks in comparison to when they performed the tasks without a mask. The results indicate that wearing the respirators did not have a significant effect on the performance of cognitive tasks but did affect significantly the performance of psychomotor tasks such as steadiness of work performance and movements requiring accurate control for positioning of objects.

Adult↗
PubMed1989

Giant retinal tears. Surgical techniques and results using perfluorocarbon liquids.

Three low-viscosity perfluorocarbon liquids provided an intraoperative tool during vitrectomy to manage giant retinal tears. These clear fluids have a high specific gravity (1.8 to 1.9) and are immiscible with water. In six eyes, the giant tear was less than 180 degrees; in 11 eyes, it was 180 degrees or greater. In all eyes, the tear was unfolded and the retina was flattened while the patient was supine. The perfluorocarbon liquid was aspirated and replaced by air-perfluorocarbon gas mixtures (16 eyes) or silicone oil (one eye) at the end of the operation. The retina was reattached in 16 eyes (94%), with a minimum follow-up period of 6 months. In five eyes (29%), the retina was reattached without scleral buckling. Residual droplets of perfluorocarbon liquid were observed in four patients. These new materials complement present surgical techniques for managing giant retinal tears.

Air↗
PubMed1989

Perfluorocarbon liquids in the management of traumatic retinal detachments.

Low viscosity perfluorocarbon liquids were used as an intraoperative tool during vitrectomy for retinal detachment (RD) after penetrating ocular trauma. These liquids are immiscible with water and have specific gravities from 1.8 to 1.9. Intraoperatively, the perfluorocarbon liquids flattened the retina in 14 eyes by displacing the subretinal fluid through peripheral breaks. Posterior retinotomy was not required for internal drainage of subretinal fluid. Pooled subretinal fluid was displaced from the macular area in five patients. The perfluorocarbon bubble mechanically stabilized the retina during epiretinal membrane dissection. The perfluorocarbon liquid was removed and replaced perfluorocarbon gas or silicone oil. In 11 patients followed for more than 6 months after the final surgery, eight (73%) eyes were anatomically successful, with six (54.5%) gaining visual acuity of 20/400 or better.

Adolescent↗
PubMed1988

Intraoperative perfluorocarbon liquids in the management of proliferative vitreoretinopathy.

Three low-viscosity perfluorocarbon liquids were used intraoperatively for hydrokinetic manipulation of the retina during vitreous surgery for retinal detachment with advanced proliferative vitreoretinopathy. All 23 patients had massive proliferative vitreoretinopathy (Grade D, Retina Society classification), and 16 (69.6%) had Grade D-3 with a closed-funnel configuration. In 21 eyes the retina could be flattened intraoperatively by perfluorocarbon liquids without requiring posterior retinotomy for internal drainage of subretinal fluid. The temporary mechanical fixation of the retina provided by this tool facilitated the removal of epiretinal membranes and release of traction. Fifteen eyes (65.2%) maintained long-term retinal reattachment with follow-up of six months or more. These liquids are useful adjuncts in the management of retinal detachment with severe proliferative vitreoretinopathy.

Adolescent↗
PubMed1987

Experimental vitreous replacement with perfluorotributylamine.

Perfluorotributylamine, a liquid fluorochemical used in artificial blood substitution, was evaluated for potential application as a vitreous substitute having heavier density than saline. It was injected into the vitreous of 38 rabbit eyes after mechanical vitrectomy or gas compression of the vitreous with perfluoropropane. The eyes were observed for periods of up to five months. Clinically the liquid occupied the lower vitreous space but gradually dispersed into smaller fluorochemical droplets. In the upper vitreous clusters of cells appeared within three to four weeks which precipitated on the posterior lens surface and in the cortical vitreous. In eyes with experimental retinal detachment perfluorotributylamine had physical properties which provided mechanical retinal tamponade. Its interfacial tension prevented passage through iatrogenic retinal breaks. Histopathologic findings showed irregularly shaped defects in the outer segment disks as early as two days after vitreous replacement. These changes appeared to reverse if perfluorotributylamine was removed after two days. The cellular response in the vitreous consisted primarily of monocyte-derived macrophages capable of ingesting fluorochemical (foam cells).

Animals↗
PubMed1987

Comparison of two biological aerosol sampling methods.

Two biological aerosol samplers, the Andersen two-stage microbial impactor and the May three-stage glass impinger, were examined to determine the benefits and effectiveness of the May sampler compared with the Andersen sampler, one of the most widely accepted samplers. Side-by-side samples were collected during simulated wastewater spray irrigation dispersion studies. Escherichia coli colony counts and air concentrations were statistically treated to determine the dependability of the May results with respect to the Andersen results. After data pairs containing potentially overloaded Andersen counts were eliminated, a linear regression of the remaining data was performed. It indicates that although the May sampler reports 82% of the Andersen sampler value, the correlation between the two samplers is good with an r2 value of 0.84. This comparison indicates that although there are differences between the two samplers, they do give comparable results and that when both are used in a sampling program, they tend to complement each other.

Air Microbiology↗
PubMed1984

The critical orifice revisited: a novel low pressure drop critical orifice.

The ability to maintain a constant air flow rate under varying load conditions is of basic importance in air sampling. Critical orifice flow devices are often used to accomplish this. A major disadvantage of most critical orifice designs is that a pressure drop in excess of 350 mm Hg (14 in. Hg) is required to ensure stable flow. It is possible, however, to design a flow restricting device which will function as a critical orifice at pressure drops significantly less than those required for conventional designs. Presented here is an inexpensive and convenient method for controlling flow in the range of 20-90 L/min. Pressure drop versus flow rate data demonstrate that a vacuum of 150 mm Hg (6 in. Hg) or less is required to reach critical flow conditions using this design. Thus the convenience of unattended constant flow rate control with a substantial reduction in vacuum pump capacity and cost is achieved.

Air↗
PubMed1976

The contribution of anticoagulants to platelet dysfunction with extracorporeal circulation.

This investigations evaluates the effects of anticoagulants on platelet function. Fresh human blood from 40 nonmedicated volunteers was anticoagulated with 4.3 units per milliliter heparin and/or acid-citrate-dextrose (ACD) solution 1:9. Retention of platelets from whole blood on glass beads was performed by the method of Bowie. Platelet retention of heparinized blood averaged 88.1 +/- S.E. 1.5 per cent; ACD platelets averaged 24.6 +/- S.E. 2.8 per cent. Platelet retention with citrate-phosphate-dextrose (CPD) and ethylenediaminetetraacetic acid (EDTA) yielded 26.0 +/- S.E. 3.9 per cent and 19.1 +/- S.E. 7.5 respectively. The addition of ACD to heparinized blood decreased platelet retention (19.7 +/- S.E. 3.1 per cent). The addition of heparin to ACD or CPD blood did not alter the original decreased retention. Calcium added, even in excess, to blood containing heparin and ACD did not reverse the depressed retention (29.3 +/- S.E. 4.6 per cent). The substitution of CPD gave similar results. With mixtures of separately collected ACD and heparininzed blood, depression of platelet retention was directly proportional to the amount of ACD blood present. Altering the pH of the ACD blood did not affect its depressed retention of platelets. Neutralizing heparinized blood 50 per cent with protamine or Polybrene also significantly depressed platelet retention 34.6 +/- S.E. 5.8 per cent and 35.5 +/- S.E. 4.0 per cent, respectively. Neither protamine nor Polybrene had any effect upon ACD blood. These data indicate that anticoagulants may play a significant role in the depressed platelt function observed during and following extracorporeal circulation.

Anticoagulants↗