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Biomedical subjects

J Whittle

Publications and source records attributed to J Whittle.

At least 37 records · Page 2Linked to original sources
PubMed1993

The parallel Lack anaesthetic breathing system.

The parallel Lack system is a new modification of the Mapleson A system comprising separate inspiratory and expiratory tubes. To determine that the function of the system was that anticipated of a Mapleson A, the fresh gas flow requirements to prevent rebreathing during spontaneous ventilation were assessed in three situations: (1) a lung model (2) conscious volunteers and (3) anaesthetised patients. Two sets of criteria to define rebreathing were used; (A) those based on changes in ventilation or end-expired carbon dioxide tension and (B) minimum inspired carbon dioxide tension. Using A, rebreathing occurred at a fresh gas flow to minute ventilation ratio (VF/VE) of 0.75 for the lung model, and 0.73 for conscious volunteers. These results were comparable to those obtained for a Magill attachment. They were also close to the point at which mechanical dead space began to increase in the lung model. Criteria B gave much lower values for the onset of rebreathing. Rebreathing was present by criteria A in five of the six anaesthetised patients at a fresh gas flow of 60 ml.kg-1.min-1 (VF/VF of 0.78). The results confirm that the parallel Lack behaves as a Mapleson A system. The resistance to breathing posed by the parallel Lack was also comparable to the Magill system.

Adult↗
PubMed1993

Mortality after elective total hip arthroplasty in elderly Americans. Age, gender, and indication for surgery predict survival.

Medicare Part A claims records were used to determine the perioperative mortality and cumulative postoperative survival of elderly Americans undergoing total hip arthroplasty (THA) for reasons other than hip fracture. The indication for THA was determined by analysis of the diagnosis codes in the claims records. Perioperative mortality was 0.95% (48/5078) and increased with age, from 0.34% (three of 872) in those 66 years to 69 years of age to 3.75% (nine of 240) among those 85 years of age or older. Perioperative mortality was not related to race, gender, or the indication for which the surgery was performed. Among these elderly patients not operated on for hip fracture, cumulative survival after surgery increased with decreasing age, female gender, and when osteoarthrosis was the indication for surgery. Persons undergoing THA had better survival after surgery than the age-gender-matched general population. Perioperative mortality among elderly Americans undergoing THA in the community is low and similar to that estimated by the 1982 NIH Consensus Conference, which considered primarily data reported from referral centers.

Age Factors↗
PubMed1992

Surgery and compensatory head postures in congenital nystagmus. A longitudinal study.

Null zones and head postures were studied in two patients with idiopathic congenital nystagmus who had been carefully selected from a larger group of patients who had nystagmus with compensatory head postures. Oculomotor and sensory features of the two patients indicated that they would have a reasonable chance of profiting from surgery. Neither patient had a periodic alternating or manifest latent nystagmus or any ocular disease of the fixating eye. Postoperative evaluation of the head posture and the nystagmus behavior of both patients was carried out over a period in excess of 6 years. Neither of the patients readopted a head turn, and visual acuity was found to be equivalent to that prior to surgery when using the null zone. In one of the patients the postoperative null zone was located in the primary position, while in the other the null zone was decreased from an eccentricity of 30 degrees to 15 degrees. These results suggest that the position of the postoperative null zone is not always an accurate predictor of head turn.

Adaptation, Physiological↗
PubMed1992

Results of colectomy in elderly patients with colon cancer, based on Medicare claims data.

Currently available estimates of outcomes following colon resection in elderly patients with colon cancer are based on series collected at academic medical centers. We used Medicare Part A claims and enrollment records of a 5% nationally random sample of elderly Medicare beneficiaries from 1983 to 1985 to estimate how patient age and sex affected perioperative mortality and 1- and 2-year survival rates among elderly patients undergoing a colon resection procedure for colon cancer. Among the 5,586 individuals in our data set, the overall perioperative mortality rate was 5.0%, ranging from 3.3% in beneficiaries 66 to 69 years of age to 9.3% in those 85 years of age and older. Men had a 31% higher perioperative mortality rate than women (5.8% versus 4.4%, p less than 0.05). The overall postoperative survival rates at 1 and 2 years were 72% and 63%, respectively, decreasing with increasing age, but were similar in men and women. This analysis provides age- and sex-specific estimates of outcomes following surgery for elderly patients with colon cancer that are more precise and have more potential for generalization than those that were available previously.

Age Factors↗
PubMed1992

Long-term survival of endothelium following transplantation of corneas stored by organ culture.

This study reports corneal graft survival, endothelial cell changes, and visual outcome in 20 patients who received some of the first corneas stored by organ culture in the Corneal Transplant Service Eye Bank in Bristol. Mean donor age was 48 years (SD 15, n = 20) and corneas were stored for an average of 21 days (SD 7, n = 20). Preoperative endothelial cell density was 2334 cells/mm2 (SD 235, n = 18) and this fell by 8% (SD 12) to 2158 cells/mm2 (SD 372) within the first 2 months following transplantation. In 13 patients, endothelial cell density thereafter declined exponentially with a half-life of 41 months (SD 17, n = 12; one patient excluded as an outlier). Corneas that suffered rejection episodes showed the highest rates of loss of endothelial cells. Endothelial cell loss 4 years after transplantation was 46% (SD 16, n = 12), which was similar to the postoperative decline in cell density reported for corneas stored for far shorter periods in McCarey-Kaufman medium at 4 degrees C.

Adult↗
PubMed1991

The nature of head postures in congenital nystagmus.

We investigated the factors that determine the nature and extent of abnormal head postures in patients with congenital nystagmus. The head positions and eye movements of 16 patients were monitored while they adopted a variety of gaze positions. Five patients displayed a single head posture and four displayed multiple head postures. Six of the nine head postures matched the minimum intensity zone. The extent of the head posture was also found to be dictated by the velocity distribution of the slow phase, the nystagmus beat direction, and the neutral zone. Our results suggest that the surgical management of a head posture should not always be based only on the relocation of the minimum intensity zone to the primary gaze position.

Adolescent↗
PubMed1991

Accuracy of Medicare claims data for estimation of cancer incidence and resection rates among elderly Americans.

To explore the reliability of Medicare Part A claims data for clinical and health services research related to the care of patients with cancer, the authors compared estimates of the incidence of and resection rates for cancer of the breast, colon, and lung derived from analysis of Medicare Part A data versus data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program. Incidence rates of breast, colon, and lung cancer estimated from Medicare Part A data were within 6% of estimates derived from SEER data. Resection rates estimated from Medicare Part A data, in contrast, were 12% to 27% lower than resection rates based on SEER data. This discrepancy is not explained by variations in practice between regions participating in versus those not participating in the SEER registries but may be due to undercoding of surgical procedures in Medicare Part A data. This analysis suggests that Medicare data can provide useful insights into the care of patients with cancer, but research regarding inpatient procedures employed in management of cancer should be based on analysis of Medicare Parts A and B data combined.

Abstracting and Indexing↗
PubMed1991

Use of Medicare claims data to evaluate outcomes in elderly patients undergoing lung resection for lung cancer.

OBJECTIVE: To estimate, using Medicare claims data, the outcomes in elderly Americans undergoing lung resection for lung cancer. DESIGN: We used discharge diagnosis and procedure codes in 1983 to 1985 Medicare hospital (part A) claims records to identify patients who underwent lung resection for lung cancer; we assessed perioperative, one-year, and two-year survival using Medicare enrollment file data. PATIENTS: From a nationally random sample of 1,138,000 Medicare beneficiaries over 65 years of age, we identified 1,290 individuals who fulfilled our definition for lung resection for lung cancer. MEASUREMENTS AND MAIN RESULTS: Overall perioperative (30-day) mortality was 7.4 percent. Postoperative survival at one and two years was 69 percent and 54 percent, respectively. Male sex, older age, and pneumonectomy, as opposed to a lesser procedure, were associated with reduced perioperative and one-year and two-year survival. The adverse effect of advanced age on one-year and two-year survival following lung resection was not explained by the lower life expectancy of older individuals. CONCLUSIONS: Medicare claims data can be used to estimate likely outcomes for elderly patients undergoing surgery for lung cancer. Expected outcomes vary with the patient's age, sex, and the type of surgical procedure performed.

Aged↗
PubMed1990

Development of clinical and economic prognoses from Medicare claims data.

Using a 5% nationally random sample of Medicare beneficiaries, we calculated the probability of dying, the probability of being readmitted, and the mean level of inpatient hospital expenditures within various time periods following discharge for those beneficiaries who were discharged alive from an acute-care hospital during 1983. We then examined the 674 most common principal discharge diagnoses and found significant variations by diagnosis code for all three outcomes. We believe that analyses of claims data by diagnosis code can provide useful information to clinicians and their patients regarding the clinical and economic prognosis of specific diseases, help managed-care programs identify patients likely to incur substantial costs over a several-year period, and inform insurers regarding the expected level of resources that will be used following discharge for patients with specific diseases.

Health Expenditures↗
PubMed1990

Impact of claims data research on clinical practice.

Despite their potential utility, clinicians are skeptical about claims data as a substrate for clinical research. Clinician's concerns are centered on two issues-the quality of the data and the fairness of comparisons that are made. To increase the impact of claims data research on clinical practice, several strategies should be pursued.

Humans↗
PubMed1990

Setting payment rates for capitated systems: a comparison of various alternatives.

Numerous proposals have been suggested to revise the current adjusted annual per capita cost (AAPCC) method for paying HMOs in the Medicare program. Several evaluations of the various alternatives conclude that including a prior utilization variable is the most promising alternative. In this paper, using statistical and other criteria, we compare the current AAPCC method with three different prior utilization models. The results suggest that all three prior utilization models can predict expenditures for either individuals or a group--drawn from a cross section and a risk selected sample of aged Medicare beneficiaries--more accurately than the AAPCC method. Of the three prior utilization measures, Payment Amount for Capitated Systems (PACS) predicts actual expenditures most accurately.

Capitation Fee↗
PubMed1989

The dynamic nature of ethnic identity among Greek-Australian adolescents.

The dynamic nature of ethnic identity was explored by exposing Greek-Australian adolescents to one of three experimental conditions: positive (highlighting the advantages of their ethnic group membership), negative (the disadvantages), or a neutral control condition. Sensitizing respondents to their ethnic group membership resulted in an increase in the salience of Greek identity. Multi-dimensional scaling yielded two dimensions that best represented the interrelationships among items describing ethnic reference groups: an ethnicity dimension and a multi-cultural-segregated dimension. There was no discrimination among the three groups on the latter, but the two experimental groups differentiated between the Australian and Greek items significantly more than did the controls. Respondents in the negative condition had significantly less positive attitudes to their ethnic origins than the other two groups.

Acculturation↗
PubMed1989

Retinal fixation behavior in human albinos.

The retinal fixation behavior of 17 albinos was examined whilst they fixated a stationary target. An optical system was arranged so that the motion of the target on the retina, due to the nystagmus, could be video-recorded. Eye movements were monitored simultaneously. Eight of the 17 subjects were judged to use consistently a retinal location compatible with the anatomical position of the fovea. The implications of this for subjects with foveal hypoplasia are discussed.

Adolescent↗
PubMed1982

Short- and long-term responses to diltiazem in patients with variant angina.

Short- and long-term effects of diltiazem on angina frequency were studied in 12 patients with variant angina (pain at rest with S-T elevation). Each patient first entered a double-blind short-term trial. Either diltiazem, in two dosage schedules (120 and 240 mg/day), or placebo was administered in a randomized double-blind program over 10 weeks. Significant decreases in frequency of angina were observed when diltiazem treatment periods were compared with placebo periods. Six patients were asymptomatic, one had 50 percent or greater decrease, and two had a smaller decrease in angina frequency. Two patients showed no important improvement during short-term diltiazem therapy. One patient experienced ventricular fibrillation in the placebo period and was advanced to treatment with open label diltiazem before responses could be ascertained in the double-blind trial. All other patients were then advanced to open label diltiazem therapy and followed up for an average of 16 months (range 8 to 23). Responses during the short-term trial accurately predicted responses during long-term therapy. Of the six patients who were asymptomatic during short-term therapy, five remained asymptomatic and one had rare episodes of angina. One other patient continued to have a good response (50 percent or greater decrease in angina frequency) and two other patients had a partial response. The two patients who did not respond during short-term therapy did not respond during long-term therapy.

Adult↗
PubMed1981

Effect of diltiazem in patients with variant angina: a randomized double-blind trial.

Effects of diltiazem of frequency of angina and nitroglycerin (NTG) consumption were studied in 12 patients with variant angina (rest pain with ST elevation). Either diltiazem in two dosage schedules (120 mg/day and 240 mg/day), or placebo was administered in a randomized double-blind program over 10 weeks. Significant decreases in angina frequency and TNG consumption were observed when diltiazem treatment periods were compared to placebo periods. Furthermore, when placebo periods following diltiazem were compared to placebo periods following placebo, significant "carry-over" effect with respect to reduced angina frequency was observed. No patient had an increase in angina frequency or TNG consumption on diltiazem compared to placebo. No "rebound effects" or changes in blood pressure or heart rate were observed. One patient complained of dry mouth on diltiazem. These findings, although in a limited number of patients, suggest that diltiazem is effective in decreasing angina frequency and TNG consumption in patients with variant angina. These encouraging results warrant evaluation of diltiazem in a larger patient population over a longer time period.

Adult↗