Biomedical subjects

James D Johnston

Publications and source records attributed to James D Johnston.

4 recordsLinked to original sources

PubMed2004

Primary angioplasty in acute myocardial infarction at hospitals with no surgery on-site (the PAMI-No SOS study) versus transfer to surgical centers for primary angioplasty.

OBJECTIVES: To investigate primary angioplasty (PA) for high-risk acute myocardial infarction (AMI) at hospitals with no cardiac surgery on-site (No SOS), we hypothesized that a nonrandomized registry of such patients treated with PA would show clinical outcomes similar to those of a group randomized to transfer for PA, and that reperfusion would occur faster. BACKGROUND: Primary angioplasty provides outcomes superior to fibrinolytic therapy in AMI, but its use in community hospitals with No SOS has been limited. METHODS: Fibrinolytic-eligible patients with high-risk AMI prospectively consented if they had one or more high-risk characteristic. Nineteen hospitals with No SOS prospectively enrolled 500 patients for PA on-site. Seventy-one similar Air Primary Angioplasty in Myocardial Infarction trial patients were randomized to transfer for PA. RESULTS: Primary angioplasty was performed in 88% of patients. Patients transferred for PA had a longer mean time to treatment (187 vs. 120 min; p < 0.0001). Thrombolysis In Myocardial Infarction (TIMI) flow grade 3 was achieved in 96% for on-site PA, 86% in the transfer group (p = 0.004). The combined primary end point of 30-day mortality, re-infarction, and disabling stroke occurred in 27 (5%) on-site PA patients and 6 (8.5%) transfer patients (p = 0.27). Unadjusted one-year mortality was improved in on-site PA patients compared with those transferred (6% vs. 13%, p = 0.043), but after adjustment for differences in baseline variables, this difference was not significant. CONCLUSIONS: On-site PA and transfer groups had similar 30-day outcomes and more rapid reperfusion for on-site PA. Primary angioplasty in high-risk AMI patients at hospitals with No SOS is safe, effective, and faster than PA after transfer to a surgical facility.

Angioplasty, Balloon, Coronary↗

PubMed2004

Mechanical properties of the scapholunate ligament correlate with bone mineral density measurements of the hand.

The mechanical properties of the scapholunate ligament have been previously examined in small sample sizes, with ultimate load and occasionally stiffness reported. The present study examined 16 scapholunate ligaments in uniaxial extension at two rates and determined stiffness, ultimate load, and stress relaxation properties. Mean stiffness values of 66.4+/-28.6 N/mm at an elongation rate of 50 mm/min and 94.5+/-44.4 N/mm at an elongation rate of 100 mm/min were found. Relaxation behavior, determined by the percent load remaining after 100 s, was found to be 68.1+/-12%. Mean ligament ultimate loads were 357+/-110 N (n = 8). In eight specimens, failure occurred in bone. Positive correlations were observed between bone mineral density of the hand and ligament stiffness, ligament ultimate load, and bone ultimate load. No correlation was observed between bone mineral density and ligament load relaxation behavior. The results provide a comprehensive understanding of scapholunate ligament biomechanics and demonstrate a relationship between bone and ligament properties.

Absorptiometry, Photon↗

PubMed2003

Computer simulation: how can it help the surgeon optimize implant position?

Component placement critically affects the performance and longevity of total hip replacements (THRs). Because of limitations of observation and anatomic orientation imposed by the operative site, selection of the correct size, and position of the acetabular and femoral components is best done through preoperative planning. Currently, this is done by comparing two-dimensional templates of prosthetic components with clinical radiographs; however, this method has the inherent limitation that AP and lateral radiographs each provide one projection of the pelvis and the femur. Computer technology makes it possible to observe implantation of the femoral and acetabular components in three dimensions. This approach allows surgeons to template with superior accuracy, while providing an intimate view of the fit of the components in the implantation site. Additionally, computer routines can predict the functional outcome of a preoperative plan before its implementation. Restoration of leg length, center of rotation, ROM of the joint during various activities, and points of bony and prosthetic impingement can be analyzed preoperatively by the surgeon. This is a valuable tool for surgical navigation and surgeon training. With emerging technologic advances in surgical technique, computer-based preoperative planning tools should prove all the more essential to reliable component placement.

Arthroplasty, Replacement, Hip↗

PubMed2002

Thermal loading as a causal factor in exceeding the 0.1 PPM laboratory fume hood control level.

Tracer gas testing per ANSI/ASHRAE 110-1995 Method of Testing Performance of Laboratory Fume Hoods was used to investigate the role of thermal loading in exceeding laboratory fume hood control levels. Three types of typical laboratory burners (blast, Meeker, and economy) were used to provide a thermal challenge. Heat outputs of between 0 and 61,610 Btu/hr were based on fuel heat capacity (for liquid propane gas) and fuel gas flow rates. Breathing zone concentrations were measured with a MIRAN 1B2 infrared gas analyzer. Also, for each test, the difference between the room and duct temperatures (delta temperature) was measured. Results indicated a linear relationship between heat loads and tracer gas breathing zone concentrations for both Btu/hr and delta temperature. Control levels of 0.1 ppm were exceeded at less than 12,000 Btu/hr. Also, control levels were exceeded at a lower heat load when the tracer gas generation rate was increased. These results indicate that thermal loads in laboratory fume hoods increase the risk of exceeding laboratory fume hood control levels. Some compensatory measures relative to hood configuration and flow rates are recommended for laboratory operations involving heat sources.

Air Pollution, Indoor↗