Geometrical aspects of sorted patterned ground in recurrently frozen soil.

A model for sorted patterned ground shows that some types arise from density-driven Rayleigh free convection that occurs during thawing of water-saturated recurrently frozen soils. The regularly spaced convection cells result in an uneven melting of the underlying ice front. Frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front. The implications of the water circulation direction in the cells on the sorting process are considered.

A review of the evidence on the effects and costs of implantable cardioverter defibrillator therapy in different patient groups, and modelling of cost-effectiveness and cost-utility for these groups in a UK context.

OBJECTIVES: To update the systematic review evidence on the effectiveness, health-related quality of life (HRQoL) and cost-effectiveness of implantable cardioverter defibrillators (ICDs); compilation of new data on the service provision in the UK; and on the clinical characteristics, survival, quality of life and costs of ICD patients in the UK, and a new cost-effectiveness model using both international RCT and UK-specific data. DATA SOURCES: Electronic databases searched from November 1999 to March 2003, this was supplemented by a systematic review of research published during 2003-5. Survey data. REVIEW METHODS: Studies were selected and assessed. A survey of ICD centres was carried out. Basic data were obtained from two major implanting centres including 535 patients (approximately 10% of overall UK activity) implanted between 1991 and 2002, and retrieval of fuller data, on patient characteristics, management and resource use, from patient notes for a sample of 426 patients was attempted. A cross-sectional survey collected HRQoL data (using the Nottingham Health Profile, Short Form 36, Hospital Anxiety and Depression questionnaire, EuroQoL 5 Dimensions and disease-specific questions) on a sample of 229 patients. A Markov model combined UK patient data with data from published randomised controlled trials (RCTs) to estimate incremental costs per life-year or quality-adjusted life-year (QALY) gained. RESULTS: None of the economic analyses in the studies found could be directly applied to the UK. The multiple sources of routine data available (including the national ICD database) provide an imperfect picture of the need for and use of ICDs. Implantation rates have been rising to a rate of around 20 per million population. Mean age is increasing and most ICDs are implanted into men aged 45-74 years. There is significant geographical variation. A survey of 41 UK centres provided additional evidence, particularly of variation in level of activity and resourcing. Most detailed data were obtained for 380 patients (89%). The postal survey produced a 73% response rate. Demographic characteristics of these patients were similar to ICD recipients in the UK as a whole and patients included in secondary prevention RCTs. Mean actuarial survival at 1, 3 and 5 years was 92%, 86% and 71%, respectively. Patient age at implantation and functional status significantly affected survival. Levels of most of the HRQoL measures were lower than for a UK general population. There was no evidence of a change with time from implantation. Patients who had suffered ICD shocks had significantly poorer HRQoL. Most patients nevertheless expressed a high level of satisfaction with ICD therapy. Mean initial costs of implantation showed little variation between centres (23,300 pounds versus 22,100 pounds) or between earlier and more recent implants. There appeared to be greater variation between patients presenting along different pathways. Postdischarge costs (tests, medications and follow-up consultations) and costs of additional hospitalisations were also calculated. Using the Markov model it was found that over a 20-year horizon, mean discounted incremental costs were 70,900 pounds (35,000-142,400 pounds). Mean discounted gain was 1.24 years (0.29-2.32) or 0.93 QALYs. Cost-effectiveness was most favourable for men aged over 70 years with a left ventricular ejection fraction (LVEF) below 35%. If the treatment effect were to continue, then the cost per life-year over a lifetime might fall to around 32,000 pounds. Five RCTs of ICDs, a meta-analysis and, a cost-effectiveness analysis of ICDs used in primary prevention, and a meta-analysis of ICDs in patients with non-ischaemic cardiomyopathy have been published recently. These trials provide confirmation of survival benefit of ICDs used in primary prevention in both ischaemic and non-ischaemic cardiomyopathy patients. Costs per QALY ranged from US$34,000 in older trials to controls being both less expensive and more effective (CABG Patch, DINAMIT). More recent trials estimated cost per QALY between $50,300 and $70,200. The inconsistency in evidence for a HRQoL benefit has not been resolved and further work on risk stratification is necessary. CONCLUSIONS: The evidence of short- to medium-term patient benefit from ICDs is strong but cost-effectiveness modelling indicates that the extent of that benefit is probably not sufficient to make the technology cost-effective as used currently in the UK. One reason is the high rates of postimplantation hospitalisation. Better patient targeting and efforts to reduce the need for such hospitalisation may improve cost-effectiveness. Further cost-effectiveness modelling, underpinned by an improved ICD database with reliable long-term follow-up, is required. The absence of a robust measure of the incidence of sudden cardiac death is noted and this may be an area where further organisational changes with improved data collection would help.

A model for analyzing the cost of main clinical events after cardiac transplantation.

Using information from the Papworth Hospital heart transplant service, a model was developed to link the main clinical events after cardiac transplantation to survival and costs. On the basis of the clinical and survival experience of 387 patients treated with triple-drug immunosuppression between 1986 and 1993, together with protocols for patient management, resource use, and costs, a 5-year Markov model with three time periods was used to simulate survival and estimate costs. The model accurately mirrors observed actuarial survival; 1- and 5-year survival rates were 81% and 65%, respectively. An average cost per patient of 26,000 pounds over 5 years (discounted at a rate of 6%) was estimated. The expense of routine care for patients accounts for the majority of the costs; a patient who remains well throughout the 5-year period would incur costs of 23,000 pounds. The sensitivity of the estimates to alternative assumptions is presented, and the way in which the model can be used to compare alternative future scenarios is explored.

Risk factor analysis for the major hazards following heart transplantation--rejection, infection, and coronary occlusive disease.

This study demonstrates the importance of analyzing survival by cause of death in order to achieve a better understanding of the prognostic indicators involved. It further emphasizes the need for analysis of risk factors in both univariate and multivariate models, and the danger of making judgements based on premature analysis of data on follow-up after heart transplantation. Survival following transplantation is characterized by the major hazards of early death due to infection and rejection and late graft loss due to coronary occlusive disease (COD). This study summarizes the first-graft survival experience for 323 transplant patients at Papworth Hospital, and assesses a number of potential risk factors for (1) early mortality, (2) late mortality from COD, and (3) development of COD. The potential risk factors considered for all hazards are donor and recipient age, sex, blood group, and matching of these factors; donor cause of death and recipient immunosuppression; inotropic support; waiting time; preoperative diagnosis and previous cardiac surgery; ischemic time; and extubation time. In addition, for development of, and graft loss from, COD, perioperative rejection and cytomegalovirus infection; hypertension at discharge; and cholesterol, triglycerides, and lipids at two years were assessed as risk factors. Advances in immunosuppression were observed to have increased overall survival rates and decreased mortality from infection, rejection, and COD, as well as decreasing morbidity from COD. Fatal rejection was found to be more likely in female recipients, recipients over 40 years, recipients of grafts from donors over 30 years old, patients who were transplanted for valvular heart disease, and patients who waited less than three months for their transplant. Male recipients of female donor organs were more likely to lose their grafts as a result of COD. Patients older than 50 and hearts from donors older than 40 conferred a high risk of development of and loss from COD. Patients transplanted for ischemic heart disease were more likely to develop COD. High cholesterol, low HDL, high LDL, and high triglycerides at two years after transplant showed some evidence of high risk for the subsequent development of COD, although these relationships are not statistically significant at this stage. Contrary to other recent studies, cytomegalovirus infection was not found to be a risk factor for the development of COD.

Demonstration of a foraging advantage for trichromatic marmosets (Callithrix geoffroyi) dependent on food colour.

It has been suggested that the major advantage of trichromatic over dichromatic colour vision in primates is enhanced detection of red/yellow food items such as fruit against the dappled foliage of the forest. This hypothesis was tested by comparing the foraging ability of dichromatic and trichromatic Geoffroy's marmosets (Callithrix geoffroyi) for orange- and green-coloured cereal balls (Kix) in a naturalized captive setting. Trichromatic marmosets found a significantly greater number of orange, but not green, Kix than dichromatic marmosets when the food items were scattered on the floor of the cage (at a potential detection distance of up to 6 m from the animals). Under these conditions, trichromats but not dichromats found significantly more orange than green Kix, an effect that was also evident when separately examining the data from the end of the trials, when the least conspicuous Kix were left. In contrast, no significant differences among trichromats and dichromats were seen when the Kix were placed in trays among green wood shavings (detection distance < 0.5 m). These results support an advantage for trichromats in detecting orange-coloured food items against foliage, and also suggest that this advantage may be less important at shorter distances. If such a foraging advantage for trichromats is present in the wild it might be sufficient to maintain the colour vision polymorphism seen in the majority of New World monkeys.

Heart and lung transplantation for terminal cystic fibrosis. A 4 1/2-year experience.

From among 112 patients with cystic fibrosis who were assessed for heart-lung transplantation, 83 were accepted. Twenty-six died while awaiting heart-lung transplantation and 32 had the operation. The management and the outcome of these 32 patients is reported. Survival, infection, and rejection rates among these patients were compared with those of 61 patients without cystic fibrosis who underwent heart-lung transplantation between 1984 and 1990. The cumulative survival rate was 72.29% +/- 94.91% at 1 year and 55.59% +/- 7.50% at 3 years. The mortality rate was slightly higher in the group with cystic fibrosis during the first year after the operation but it was lower at 3 years. The difference, however, could have been due to chance alone (p = 0.308). The same was true for the prevalence of rejection (up to 6 months: chi 2 = 1.8141, p = 0.17), and infection (up to 6 months: chi 2 = 2.20, p = 0.14), between the two groups. It is concluded that cystic fibrosis does not constitute an additional risk in terms of survival and morbidity after heart-lung transplantation.

Heart transplantation in patients over 54 years of age with triple-drug therapy immunosuppression.

Between April 1, 1986, and December 31, 1989, 206 patients received orthotopic heart transplants with triple-drug therapy immunosuppression (cyclosporine, azathioprine, prednisone). Forty-six patients were aged 55 years or more at the time of transplantation and 160 patients were less than 55 years of age; these two groups were compared. Selection criteria and treatment regimen were the same in both groups. In our experience, although both groups had good postoperative survival, older patients had higher mortality rates early after transplantation, particularly from rejection and infection. Patients over 55 years of age had similar nonfatal rejection rates and were no more likely to have infectious episodes than younger patients. As demand for heart transplantation increases and waiting lists lengthen, the age of potential recipients should be an important factor in deciding how to allocate scarce donated organs, although age should not be exclusive.

Prognosis of patients with cystic fibrosis awaiting heart and lung transplantation.

Heart-lung transplantation is a successful treatment for patients with cystic fibrosis and chronic respiratory failure. Patients are assessed for surgery when life expectancy is deemed short. This study assesses the ability of measurements of pulmonary function, blood gas levels, and nutritional status to predict survival of patients awaiting heart-lung transplantation and to assess the effect of heart-lung transplantation on survival. Sixty-seven patients with cystic fibrosis were accepted for heart-lung transplantation from 1985 through 1990. Each patient underwent tests of pulmonary function, exercise tolerance, blood-gas levels, and nutritional status. Cox regression was used to analyze the prognostic value of these data. Of the 67 patients accepted for heart-lung transplantation, organs became available for 30; 24 patients died waiting, and 13 patients were on the list December 31, 1990. Eight patients died after transplantation. Patients with above-average forced expiratory volume in 1 second (FEV1) (median, 17% predicted) at assessment were half as likely to die waiting (relative risk, 0.47; 95% confidence interval, 0.23 to 0.97) as patients with below-average FEV1. The relative risk of death for patients on the waiting list was 1.44 (95% confidence interval, 1.17 to 1.77) for each increment in PCO2 of 1 kPa. No effect of nutritional status on waiting list death was found, but seven of eight patients who died after heart-lung transplantation were below 80% predicted weight for height. Using a time-dependent analysis, heart-lung transplantation almost halved the risk of death (relative risk, 0.57; 95% confidence interval, 0.22 to 1.48). Postoperative actuarial survival was 79% (95% confidence interval, 63% to 95%).(ABSTRACT TRUNCATED AT 250 WORDS)

A model for analyzing the cost of the main clinical events after lung transplantation.

BACKGROUND: The aim of this project was to model clinically important events experienced by lung transplant patients (from the day after transplant to 5 years or death) and costs associated with these events, and to assess the economic impact of different immunosuppression therapies. METHODS: The population comprised 356 lung transplant patients (223 heart-lung, 102 single lung and 31 double lung) transplanted between April 1984 and December 1997. All patients received a cyclosporine-based triple-immunosuppression protocol. We designed a Markov model that included 3 time periods (0 to 6, 7 to 12, and 13 to 60 months), 5 clinical states (well, acute rejection, cytomegalovirus infection, non-cytomegalovirus infection and bronchiolitis obliterans syndrome), and death. For the well state, cost elements were immunosuppression, prophylaxis, and routine clinic visits. For all other states, cost elements were diagnosis, treatment, and bed days/visits. We excluded costs of the procedure. RESULTS: The monthly costs associated with the well state decreased over time, from pound sterlings 1,778 ($2,658) in the first 6 months to pound sterlings 503 ($752) in months 7 to 12 and pound sterlings 350 ($523) after the first 12 months. The cost per event of the acute states remained reasonably constant over the 3 periods: pound sterlings 1,850 ($2,766) for rejection, pound sterlings 3,380 ($5,053) for cytomegalovirus, and pound sterlings 2,790 ($4,171) for other infections. The average cost per patient, discounted at 6%, over 5 years was pound sterlings 35,429 ($52,966) (95% range, pound1,435 [$2,145] to pound67,079 [$100,283]). This estimate is most sensitive to changes in immunosuppression. Substituting tacrolimus for cyclosporine increased 5-year costs by 5%; substituting mycophenolate mofetil for azathioprine increased 5-year costs by 26%. CONCLUSIONS: This model is valuable in estimating the effect of new immunosuppression agents on the costs of follow-up care.

Measurement of health-related quality of life before and after heart-lung transplantation.

BACKGROUND: The measurement of the quality of the outcome of treatment as viewed by patients is becoming increasingly recognized as an important aspect of decision making in all health services. This major study, which set out to measure the health-related quality of life outcomes of heart and lung transplantation, developed from the experience gained in the United Kingdom and United States studies of the cost and benefits of heart transplantation in the 1980s. METHODS: The design was prospective with a cohort of patients completing a variety of generic and specific health-related quality of life questionnaires at intervals before and after heart and lung transplantation. The sample size was not prescribed; one of the aims of the project was to test the feasibility of introducing routine monitoring of health-related quality of life outcomes as an integral part of a developing transplant service. RESULTS: Before the operation, there was evidence of deterioration over time in all dimensions of the Nottingham Health Profile. In comparing Profile scores at less than 3 months before with those at 3 to 6 months after transplantation, statistically significant improvements were evident (p < 0.001). Mean scores at intervals up to 2 years after transplantation showed little change over time and compared well with those from a general population sample. Hospital Anxiety and Depression Scale scores were reduced significantly (p < 0.01) by 1 year after heart and lung transplantation. In the pretransplantation period, at least 90% of 101 patients had some level of restriction in home and leisure activities, reducing to between 2% and 24% at 1 year after transplantation. Similarly, 79 patients (78%) had chest pain, and 101 (100%) were breathless before transplantation, reducing to 54% and 39%, respectively, at 1 year after surgery; by which time, for 8 of 10 patients, the problem was occasional. CONCLUSIONS: Highly significant improvements were observed in the physical, social, and emotional dimensions of health-related quality of life of patients after heart-lung transplantation. The advantages and feasibility of combining generic and condition-specific questionnaires are shown together with the need to develop new measures with greater sensitivity to the smaller peaks and troughs of recovery.

Heart-lung transplantation for end-stage respiratory disease in patients with cystic fibrosis at Papworth Hospital.

Between October 1985 and July 1992 we performed heart-lung transplantation in 42 patients with end-stage respiratory disease caused by cystic fibrosis. Twenty-eight of these patients are alive at 3 months to 7 years after heart-lung transplantation. Actuarial survival at 1 year and 3 years after transplantation was 78% and 65%, respectively, in this group, which compares favorably with 77% and 60%, respectively, in patients without cystic fibrosis undergoing heart-lung transplantation. Similarly no significant difference was found in the incidence of postoperative infections between patients with cystic fibrosis and patients without cystic fibrosis undergoing heart-lung transplantation. Quality of life indexes analyzed by the Nottingham Health Profile reveal significant improvements for patients surviving longer than 3 months from surgery. Long-term survival is determined by the development of obliterative bronchiolitis, which has occurred in 11 patients, six of whom have died. Early postoperative survival appears to be compromised by poor preoperative nutritional status. The study provides evidence that patients with end-stage respiratory disease caused by cystic fibrosis gain a survival advantage and improvement in quality of life after heart-lung transplantation when compared with patients who do not receive this form of therapy.

Influence of recipient and donor gender on outcome after heart transplantation.

To investigate the effect of recipient and donor genders on the outcome after heart transplantation, a retrospective survey was undertaken of 356 patients (366 transplants: 316 males, 40 females) undergoing transplantation between January 1979 and December 31, 1989, at Papworth Hospital. Ninety-three organs came from female donors; 263 organs came from males. Twelve females (30%; 95% confidence interval 16% to 44%) and 51 males (16%; 95% confidence interval 12% to 20%) died in the early postoperative period (within 90 days of operation). To date, two females (5%) and 51 males (16%) have died in the late postoperative period. Comparison between recipient genders showed no statistically significant difference in early mortality rates from any cause or in actuarial survival overall, although fatal acute rejection was significantly more common in female recipients (7 of 40 female recipients versus 19 of 316 male recipients). The higher incidence of fatal rejection among female recipients was related to the higher proportion of female donors in this group, because recipients of female donor grafts had significantly higher mortality rates, particularly in the early postoperative period and as a result of acute rejection, than did recipients of organs from male donors. Death from rejection after the first 3 months and death from infection were not gender-related. Recipients of grafts from female donors did not suffer significantly more early morbidity, such as rejection and infection, or late morbidity in the form of coronary artery disease. Acute rejection episodes were more common in female recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective study of health related quality of life before and after coronary artery bypass grafting: outcome at five years.

OBJECTIVE: To determine the long term health related quality of life of coronary artery bypass graft patients, to look at changes between one and five years after surgery, and to examine the ability of preoperative variables to predict longer term outcome. DESIGN: Nottingham health profile (NHP) was used to assess patients at five years compared to results obtained at one year. PATIENTS: 100 male patients aged < 60 years at time of surgery; 77 had three vessel disease and 84 received three or more saphenous vein grafts. RESULTS: In comparing the five year results with those at one year, lower mean scores, indicating slight improvements, were seen in the NHP dimensions of pain, sleep, social isolation, and emotional reactions, whereas signs of deterioration were noted in the physical mobility and energy scores. Chest pain was experienced by 34 of 84 patients at five years compared with 17 of 89 patients at one year. The proportion of patients who were unrestricted in their activities ranged from 61-70% at five years compared with 82-88% at one year. Absence of dyspnoea before surgery, indicating relatively good left ventricular function, was a predictor of good outcome at both one and five years. CONCLUSIONS: Evidence of deterioration in physical function is compatible with expected decline in graft patency; specific rather than generic measures were most sensitive to this change.

A UK trial-based cost--utility analysis of transmyocardial laser revascularization compared to continued medical therapy for treatment of refractory angina pectoris.

OBJECTIVE: Transmyocardial laser revascularization (TMLR) is used to treat patients with refractory angina considered unsuitable for conventional forms of revascularization. Using patient specific data from a single centre UK randomised-controlled trial, we aimed to determine whether, from a UK National Health Service (NHS) perspective, TMLR plus standard medical management is cost-effective when compared with standard medical management alone. METHODS: One hundred and eighty-eight patients assessed as having refractory angina, and not suitable for conventional forms of revascularization were randomized to receive TMLR and medical management (94) or medical management alone (94). Costs to the UK NHS of TMLR (where appropriate), and all secondary sector health care contacts and cardiac-related medication in the 12 months following randomization, were collected. Patient utility as measured using the EuroQol EQ-5D questionnaire was combined with 12-month survival data to generate quality adjusted life years (QALYs). RESULTS: The mean cost per patient over the year from hospitalization for TMLR was 11,470 pounds sterling and for medical management alone was 2586 pounds sterling, giving a cost difference of 8901 pounds sterling (95% confidence interval (CI) 7502 pounds sterling--10,008 pounds sterling: P < 0.0001). The mean QALY difference, in favour of TMLR was 0.039 (95% CI -0.033 to 0.113: P = 0.268). This gives an incremental cost per QALY of over 228,000 pounds sterling. Analysis of stochastic uncertainty and of sensitivity to gross changes in key parameters consistently produces very high costs per QALY. CONCLUSIONS: The policy implications are clear: for such patients TMLR is an inefficient use of UK health service resources. This conclusion would not be changed by considerable improvements in effectiveness or reductions in cost.

General practitioners' knowledge about patients and use of medical records in out of hours calls.

The medical record is an established adjunct to good care and this paper describes the extent to which general practitioners use patients' records in out of hours calls and how their previous knowledge of their patients affects the decision to visit. Seven general practitioners from three group practices in Cambridge and Newmarket each operating a separate out of hours rota recorded details of out of hours telephone calls. Of 368 calls recorded, 293 (80%) resulted in a visit. In 51% of calls the patient was known to the doctor but the doctors were just as likely to visit patients they knew as those unknown to them. In 41% of the calls the doctors were able to recall a degree of clinically relevant information about the patient. In 47 of the calls (13%) recalled information concerning the patient was an influence in the decision whether to visit. The patient's record was collected before the visit in 30% of visits to the elderly compared with 17% for all age groups. The most often quoted reasons for not collecting the medical record were that it was likely to be unhelpful and/or it was geographically inconvenient. Although doctors who collected the record found it useful in 84% of cases, obtaining the record either before or after the visit rarely changed the management of the patient. On the occasions when it did affect management it was of importance both clinically and medico-legally.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal and metabolic responses of high and low fat women to cold water immersion.

BACKGROUND: At rest during cold exposure, the amount of body fat plays an important role in the maintenance of core temperature. High fat (HF) individuals would therefore have an advantage as compared with their low fat (LF) counterparts. Since females usually have a higher amount of body fat than males they are expected to maintain core temperature at a lower energy cost. METHODS: The purpose of the present investigation was to dichotomize female subjects by percent fat (LF = 20.5 +/- 2%, n = 6 vs. HF = 30 +/- 3%, n = 6) to elucidate the thermal and metabolic responses during acute exposure to 17 degrees C water for 120 min. The following variables were measured: rectal temperature (Tre; degrees C), mean skin temperature (Tsk; degrees C), oxygen consumption (VO2; ml x kg(-1) x min(-1)), and tissue insulation (I; degrees C x m2 x W(-1)). The experiment-wise error rate was set a priori at p = 0.05. RESULTS: Unexpectedly, only one of the variables demonstrated a main effect for fat (p < 0.05). Tre demonstrated a significant (p < 0.05) group by time interaction. However, Tsk and I demonstrated a main effect for time (p < 0.05). While VO2 demonstrated an increase across time, these changes were non-significant (p > 0.05). It appears that the HF group demonstrated a similar thermal (I and Tsk) and metabolic (VO2) response as compared with the LF counterparts. However, the LF groups maintained a lower Tre as compared with the HF subjects. Perhaps leaner subjects or colder water temperatures would elucidate the value of body fat in females, and demonstrate a differential response with respect to females varying in percent body fat.

The influence of ethnicity on thermosensitivity during cold water immersion.

PURPOSE: This investigation evaluated the influence of ethnicity, Caucasian (CAU) vs. African American (AA), on thermosensitivity and metabolic heat production (HP) during cold water immersion (20 degrees C) in 15 CAU (22.7 +/- 2.7 yr) vs. 7 AA (21.7 +/- 2.7 yr) males. METHODS: Following a 20-min baseline period (BASE), subjects were immersed in 20 degrees C water until esophageal temperature (Tes) reached 36.5 degrees C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. Arm and thigh cuffs were then inflated to 180 and 220 mm Hg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope of the relationship between the decrease in Tes and the increase in HP was used to define thermosensitivity (beta). RESULTS: ANOVA revealed no significant difference in thermosensitivity between CAU and AA (CAU = 3.56 +/- 1.54 vs. AA = 2.43 +/- 1.58 W.kg(-1). degrees C(-1)). No significant differences (p > 0.05) were found for Tsk (CAU = 24.2 +/- 1.1 vs. AA = 25.1 +/- 1.1 degrees C) or HP (p > 0.05; CAU = 2.5 +/- 0.8 vs. AA = 36.5 +/- 1.8 W.kg(-1)). However, a significant (p < 0.05) main effect for ethnicity for Tes was observed (CAU = 36.7 +/- 1.8 vs. AA = 36.5 +/- 1.8 degrees C). CONCLUSION: These data suggest, despite a differential response in Tes between AA and CAU groups, the beta of HP during cold water immersion is similar between CAU and AA. Therefore, these data demonstrate that when faced with a cold challenge, there is a similar response in HP between CAU and AA that is accompanied by a differential response in Tes.

The influence of gender and menstrual phase on thermosensitivity during cold water immersion.

BACKGROUND: This investigation evaluated the influence of gender and phase of menstrual cycle [follicular (FOL: days 2-6) and luteal (LUT: days 19-24) phases] on thermosensitivity and metabolic heat production (HP) during cold water immersion (20 degrees C) in 10 females (22.4 +/- 2.8 yr) and 16 males (22.4 +/- 2.9 yr). METHODS: Following a 20-min baseline period (BASE), subjects were immersed until esophageal temperature (Tes) reached 36.5 degrees C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. An arm and thigh cuff were then inflated to 180 and 220 mmHg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope (beta) of the relationship between the decrease in Tes and the increase in HP was used to quantify thermosensitivity. RESULTS: ANOVA revealed no significant difference in thermosensitivity between phases of the menstrual cycle or between men and women (FOL = -2.76, LUT = -3.05, Males = -3.24 W x kg(-1) x degrees C(-1)). A significant (p < 0.05) main effect for gender for HP, and a significant (p < 0.05) main effect for menstrual phase for mean skin temperature (Tsk) were observed. CONCLUSIONS: These data suggest, despite gender differences in HP, that the thermosensitivity of HP during cold water immersion is similar between males and females and is not influenced by menstrual cycle phase. Therefore, these data indicate that when faced with a cold challenge, women respond similarly to men in both phases of their menstrual cycle.

Thermal and metabolic responses of women with high fat versus low fat body composition during exposure to 5 and 27 degrees C for 120 min.

BACKGROUND: Men with high fat body composition maintain higher core temperatures, and lower aerobic metabolic rates than their low fat counterparts thus, verifying the insulatory benefit of body fat. Females, on average have more body fat and less muscle mass than males, and may maintain rectal temperature (Tre) at a lower energy cost. METHODS: The present investigation dichotomized female subjects by percent fat (low fat; n = 3, LF = 19.2+/-3% vs. high fat; n = 4 HF: 29.9+/-3%) to elucidate the thermal and metabolic responses during acute exposure to 5 and 27 degrees C air for 120 min. An ANOVA was used to examine the following: Tre (degrees C), mean skin temperature (Tsk; degrees C), oxygen consumption (VO2; ml x kg(-1) x min(-1)) and tissue insulation (I; degrees C x m2 x W(-1)). For Tre, a significant fat x time interaction (p < 0.05) was demonstrated at both 5 and 27 degrees C, whereby Tre tended to be lower in the LF group than the HF group. VO2 at 5 degrees C demonstrated a main effect for time only. For I, a main effect for time was noted at 5 degrees C. Also for I, a trend (p = 0.06) toward a main effect of fat during exposure to 5 degrees C was noted while at 27 degrees C a main effect (p < 0.05) was demonstrated. RESULTS: From this data it appears that under these conditions, the HF group demonstrated higher Tre and I values than their LF counterparts that was not accompanied with a differential response with respect to aerobic metabolic rate. Thus, the impact of body composition on energy expenditure to maintain Tre differs between LF and HF males and females.