Effects of ambient temperature on nitrogen uptake and elimination in humans.

Tissue nitrogen (N2) exchange is primarily dependent on circulation, which may be modified by body thermal status. Thermal effects on uptake and washout of N2 have not been systematically investigated earlier. In the present study of eight subjects, N2 was washed out in thermally neutral ambient conditions (TN; skin temperature (Ts) = 33.69 ± 0.84 degrees C), then washed in during either TN, cool (Ts 30.25 ± 4.15 degrees C) or warm (Ts = 35.81 ± 0.82 degrees C) conditions. It was then washed out during various combinations of those conditions. N2 exchange was monitored during 125 minutes of breathing a normoxic oxygen/argon mixture (Phase I) followed by room air for 125 minutes of N2 reloading (Phase II; no N2 recording) and then 125 minutes N2 washout (Phase III) in order to determine the amount of N2 taken up during Phase II. Cool conditions reduced cardiac output, while warm conditions increased it compared to TN. Among the five Phase I TN recordings in the eight subjects (i.e., 40 control experiments) the N2 yield averaged 857.2 ± 15.3 mL. The reloaded N2 volume in Phase II was significantly smaller during the cool condition (8%, p ≤ 0.05) and significantly larger (22%, p ≤ 0.05) during the warm. The N2 washed out in 125 minutes was significantly less during cold (6%, p ≤ 0.05) and greater during warm conditions (18%, p ≤ 0.05). These observations are consistent with previously reported circulatory changes in cool and warm conditions and effects of thermal status on venous gas bubble dynamics and incidents of decompression sickness.

Factors associated with active commuting among parents-to-be in Karlskrona, Sweden.

AIM: The purpose of the present study is to examine the prevalence of active commuting and factors associated with participation in active commuting in the municipality of Karlskrona, Sweden. Active commuting is defined here as walking or cycling to and from school/work for at least 15 minutes one-way. METHOD: A cross-sectional study was carried out, which included baseline data from parents-to-be. Pregnant females and their partners were invited to participate in the study when they contacted either of the municipality's two antenatal clinics. Data collection ran from March 2008 to February 2009. When completing the questionnaire, the participants were asked to reflect on their situation one month before the female became pregnant. The final sample consisted of 432 participants (response rate 51.9% for females and 85.0% for males). RESULTS: The main mode of commuting was motor vehicle (63.0%), with active commuters forming a minority (8.3%). The main facilitating factor for active commuting was living in an urban as opposed to a rural area. Regular participation in outdoor recreational physical activity was significantly positively associated with active commuting. Being Swedish and being surrounded by a green space environment were significantly negatively associated with active commuting. CONCLUSIONS: This study found that the number of people who are active commuters is modest and other modes of transportation are preferred. Several facilitating and impeding factors associated with active commuting were also found, indicating the importance of applying a broad health-promoting approach to encouraging active commuting.

Negative pressure breathing increases cardiac output and nitrogen elimination in seated subjects.

During denitrogenation for rescue, crew members of an internally pressurized disabled submarine (DISSUB) must sit upright, which may hamper venous return, cardiac output and peripheral circulation. Since negative pressure breathing (NPB) might counteract this problem, denitrogenation was measured in sitting subjects performing NPB. Seven male subjects completed 125-minute nitrogen (N2) washouts breathing either 100% oxygen (O2) or a normoxic gas (21% O2 in argon) in control conditions and intermittent (I: inspirations only) or continuous (C) NPB at -10 or -15 cmH2O. N2 elimination was measured using a closed rebreathing system. INPB (intermittent) (-15cmH2O) and CNPB (continous breathing) (-10 and -15cmH2O) increased cardiac output (CO) 9% during both O2 and normoxic breathing. Systolic and diastolic blood pressures were unaffected by the CO increase, suggesting a peripheral vasodilatation and enhanced tissue perfusion leading to increased N2 elimination. With the CO boost, N2 washout increased 6% breathing O2 at -15 cmH2O CNPB and INPB, while during normoxic breathing there were 6% and 12% increases due to CNBP, -10 and -15 respectively and 6% with -15cmH2O INPB; breathing 100% O2 yielding 5% to 15% less N2 washout than normoxic breathing. Negative pressure breathing during denitrogenation may facilitate decompression in divers and in crew members being rescued from a DISSUB.

A randomized trial of transanal hemorrhoidal dearterialization with anopexy compared with open hemorrhoidectomy in the treatment of hemorrhoids.

BACKGROUND: Doppler guidance in hemorrhoidal surgery has become more frequent during the past decade. The method is mainly studied in nonrandomized trials. Data from randomized controlled trials are lacking. OBJECTIVE: The aim of this study was to compare early and midterm results of transanal hemorrhoidal dearterialization with anopexy to open hemorrhoidectomy. DESIGN, SETTINGS, PATIENTS, AND INTERVENTIONS: Forty patients with grade 2 to 3 hemorrhoids were randomly assigned to transanal hemorrhoidal dearterialization with anopexy (group A, n = 20) or open hemorrhoidectomy (group B, n = 20). A diary was used during the first 2 postoperative weeks. A self-reported symptom questionnaire was answered, and a clinical examination was performed preoperatively, after 2 to 4 months, and after 1 year. MAIN OUTCOME MEASURE: The main outcome measure was postoperative pain. RESULTS: Postoperative peak pain was lower in group A during the first week than in group B (p < 0.05), whereas no difference in overall pain was noted. More patients expressed normal well-being in group A (p = 0.045). Pain, bleeding, and the need for manual reduction of the hemorrhoids were all improved in both groups after 1 year (p < 0.05). Soiling had decreased after both methods at early follow-up. After 1 year, soiling was significantly decreased only after open hemorrhoidectomy. The grade of hemorrhoids was significantly reduced after 1 year for both methods, but there was a trend to more patients with remaining grade 2 hemorrhoids in group A (p = 0.06). LIMITATIONS: There was no blinding, the sample size was small, and follow-up was for only 1 year. The questionnaire was not validated. CONCLUSION: The difference in postoperative pain between transanal hemorrhoidal dearterialization with anopexy and open hemorrhoidectomy may be less than expected based on previous literature.

Effects of different types of respiratory muscle training on exercise performance in runners.

To compare two different types of respiratory muscle training on exercise performance, a protocol was devised consisting of a combination of a 4-week, 12-session resistive respiratory muscle training (RRMT) followed by a 4-week, 12-session voluntary isocapnic hyperpnea training (VIHT) and conducted in experienced runners (4 men, 4 women). Measurements before and 5 days after training included: pulmonary function (spirometry), maximal inspiratory and expiratory mouth pressures, respiratory endurance time, maximal oxygen uptake (V(o2)max), running time to voluntary exhaustion at 80% V(o2)max, blood lactate concentration, and minute ventilation. There were no statistically significant differences in pulmonary functions and V(o2)max post-RRMT and post-VIHT compared to pre-RMT. Following RRMT the inspiratory muscle strength had improved by 23.8 +/- 30% and 18.7 +/- 21.4% at rest and immediately after the running test, respectively. RRMT did not increase the time intense voluntary isocapnic ventilation could be maintained during rest while VIHT increased it (237 +/- 207.8%). The duration of the endurance run was extended 17.7 +/- 6.5% after RRMT and 45.5 +/- 14.3% after VIHT.

Mechanical behaviour and rupture of normal and pathological human ascending aortic wall.

The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship with age and pathologies. Fresh ascending aortic specimens harvested from 23 healthy donors, 12 patients with bicuspid aortic valve (BAV) and 14 with aneurysm were tensile-tested in vitro under physiological conditions. Tensile strength, stretch at failure and elbow stress were measured. The obtained results showed that age causes a major reduction in the mechanical parameters of healthy ascending aortic tissue, and that no significant differences are found between the mechanical strength of aneurysmal or BAV aortic specimens and the corresponding age-matched control group. The physiological level of the stress in the circumferential direction was also computed to assess the physiological operation range of healthy and diseased ascending aortas. The mean physiological wall stress acting on pathologic aortas was found to be far from rupture, with factors of safety (defined as the ratio of tensile strength to the mean wall stress) larger than six. In contrast, the physiological operation of pathologic vessels lays in the stiff part of the response curve, losing part of its function of damping the pressure waves from the heart.

Psychological implications of living with familial adenomatous polyposis.

BACKGROUND AND STUDY AIMS: Psychosocial implications of living with FAP remain largely unexplored. This article reviews available literature on three topics: 1) Implications of living with FAP 2) genetic testing and reproductive decision-making and 3) family communication. PATIENTS AND METHODS: Papers published until 2009 about psychosocial and behavioral issues in FAP were identified. RESULTS: Psychometric data indicate that FAP patients and at-risk relatives as a group do not exhibit clinical symptoms of mental health problems after clinical or genetic diagnosis. However, some subgroups revealed to be more vulnerable to distress. Also, concerns related to the disease and its consequences were reported. While interest in prenatal diagnosis or preimplantation genetic diagnosis seems to be high it is important to study actual uptake because this may reveal to be much lower. Family members are an important source of information and the few available data suggest that family communication is problematic. The findings described have several shortcomings. They were obtained from only a few studies often conducted using specific or mixed study groups, originating from the 90ties and mostly cross-sectional in nature. CONCLUSIONS: For clinical practice, it is important to have more research data on how FAP patients at different ages cope with the disease, on the impact of genetic testing on reproductive decision-making and on family communication. Results reported here need to be confirmed by additional research and new themes need to be explored.

Nitrogen washout during a fatty meal while breathing nitrogen-free gas at sea level.

INTRODUCTION: The reasons for wide variability in the incidence of decompression sickness (DCS) are not well known, but diet may play a role. The hypothesis of the present study was that raising plasma triglycerides via a high-fat meal would increase the rate of nitrogen washout and, therefore, might be a useful adjunct when denitrogenation is used to reduce the likelihood of DCS in diving and exposure to altitude. METHODS: Nitrogen elimination was measured for 125 min in 10 subjects by gas chromatography while they breathed a normoxic argon-oxygen mixture at sea level. Measurements were performed on separate days after high-fat and control, low-fat meals. RESULTS: The high-fat meal increased blood triglycerides by 236 +/- 86% while there was no significant change after the control meal. Despite causing a significant increase in cardiac output (21.6 +/- 13.8%), there was no difference in nitrogen elimination after high-fat (817.4 +/- 233.1 ml) vs. control (828.3 +/- 180.5 ml). DISCUSSION: These data suggest that raising blood triglycerides via a high-fat meal does not affect the rate of whole-body nitrogen elimination. The lack of effect of the increase in cardiac output may be due to an increased blood flow to the gastrointestinal tract being negated by decreased blood flow in other vascular beds.

Mechanical properties of human coronary arteries.

The lack of reliable mechanical data on coronary arteries and, more specifically, on their wall strength hampers the application of numerical models and simulations to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. Studies of the mechanical properties of coronary arteries have been carried out almost exclusively on animals. Only a few studies have tried to characterize the in vivo behavior of human coronaries through tests under physiological conditions. In this work, the mechanical properties of human coronary arteries have been characterized. Whole samples from human right (RC) and left anterior descending (LAD) coronary arteries aged between 23 and 83 years have been studied by means of in-vitro tensile testing up to failure.

Extending submarine crew survival by reducing CO2 production with quickly reversible sedation.

INTRODUCTION: CO2 accumulation may limit crew survival in a disabled submarine. Reversible sedation using diazepam and flumazenil was proposed to reduce CO2 production. METHODS: Two groups of three resting subjects were studied during a 48-h placebo phase with diazepam and flumazenil placebos, followed by a 48-h drug phase with oral diazepam to induce sedation and intranasal flumazenil to reverse it. CO2 exchange was measured every 2.5 h; twice a day, cognitive testing and meals were preceded by placebo or flumazenil. Return to sedated state was produced with either placebo or diazepam. In the drug phase, initial diazepam doses (10 to 40 mg) were followed by maintenance doses to achieve sedation corresponding to Alertness Scores of 3 or 4. RESULTS: In the drug phase, subjects received a total of 360-495 mg of diazepam (with doses of 5-40 mg), average alertness score was 3.75, and mean Vco2 was 14% less than in the placebo phase (0.212 vs. 0.248 L x min(-)). Subjects were 21-36% less active when sedated with diazepam. The mean flumazenil dose to restore full alertness was 0.36 mg, with subjects being conversant and oriented within 5 min, performing cognitive tasks at 86-97% of their baseline. Subjects could follow instructions and ambulate independently, though unsteadily 6 h after final flumazenil dose; at 72 h they exhibited normal cognitive and physical functions. DISCUSSION: Reversible sedation to lower crew metabolism in a disabled submarine may be effective, safe, and practical.

Hypoxia due to shunts in pig lung treated with O2 and fluorocarbon-derived intravascular microbubbles.

RATIONALE: Earlier work has shown that experimental conditions calling for improved tissue oxygenation could be assisted by i.v. infusion of a dodecafluoropentane emulsion (DDFPe) forming oxygen-transporting microbubbles. OBJECTIVES: The present work investigated the effect of DDFPe on hypoxia due to experimental shunts in the pig lung. METHODS: Nineteen O(2) breathing, anesthetized pigs had glass beads administered into the trachea so as to significantly depress arterial oxygen tension (PaO(2)). PaO(2) was recorded for up to 12 hrs while 0.1 ml/kg DDFPe was administered 1-3 times. MAIN RESULTS: The animals were divided into two groups based on arterial oxygen saturation (SaO(2)) after shunt induction, combined with oxygen breathing: the "SaO(2) >90% group" (n=6) and the "SaO(2) <90% group" (n=13). In the "SaO(2) <90% group," the PaO(2) increased stepwise with each infusion from 56.6+/-2.9 to 88.6+/-14.6 mmHG (P

Respiratory muscle training reduces the work of breathing at depth.

Resistance respiratory muscle training (RRMT) increases respiratory muscle and swimming performance at depths down to 17 msw. It is unknown if RRMT improves swimming performance at greater depths and if the improvements are associated with a reduced work of breathing (WOB), altered respiratory mechanics and/or improved respiratory muscle performance. Eight male subjects (30.3 +/- 6.0 years) were tested swimming underwater in a hyperbaric chamber at 37 m of depth against a pre-determined load (70% VO(2)) until exhausted. End expiratory lung volume (EELV) was determined by subtracting inspiratory capacity from total lung capacity throughout the swims. The mechanical WOB on the lung was calculated as the integrated product of the transpulmonary pressure and ventilatory flow. Maximal expiratory (P EMAX) and inspiratory pressures (P IMAX) were measured pre- and post-RRMT. RRMT was performed every 30 s against spring loaded inspiratory and expiratory valves 30 min/day, 5 days/week, for 4 weeks. RRMT increased P (IMAX) and P (EMAX) by 40% (110 +/- 11 cmH2O (SD) vs. 155 +/- 22, p < 0.001) and 30% (148 +/- 33 cmH2O vs. 192 +/- 49, p < 0.001), respectively, respiratory endurance by 75% (19.7 +/- 15.4 min vs. 34.4 +/- 27.3, p = 0.010), and swimming endurance by 87% (26.4 +/- 9.7 min vs. 49.4 +/- 21.6, p = 0.004). The longer swimming time was associated with reduced V(E) and V(A) (p < 0.001), f(b) (p < 0.001), V(CO(2)) (p < 0.001) and WOB (p < 0.001). There were no changes in EELV post-RRMT. These results suggest the improved exercise performance post-RRMT was associated with stronger respiratory muscles, a decreased f b, and a reduced WOB.

Recommendations to improve identification of hereditary and familial colorectal cancer in Europe.

Familial colorectal cancer (CRC) accounts for 10-15% of all CRCs. In about 5% of all cases, CRC is associated with a highly penetrant dominant inherited syndrome. The most common inherited form of non-polyposis CRC is the Lynch syndrome which is responsible for about 2-4% of all cases. Surveillance of individuals at high risk for CRC prevents the development of advanced CRC. About 1 million individuals in Western Europe are at risk for Lynch syndrome. We performed a survey to evaluate the strategies currently used to identify individuals at high risk for CRC in 14 Western European countries. Questionnaires were distributed amongst members of a European collaborative group of experts that aims to improve the prognosis of families with hereditary CRC. The survey showed that in all countries obtaining a family history followed by referral to clinical genetics centres of suspected cases was the main strategy to identify familial and hereditary CRC. In five out of seven countries with a (regional or national) CRC population screening program, attention was paid in the program to the detection of familial CRC. In only one country were special campaigns organized to increase the awareness of familial CRC among the general population. In almost all countries, the family history is assessed when a patient visits a general practitioner or hospital. However, the quality of family history taking was felt to be rather poor. Microsatellite instability testing (MSI) or immunohistochemical analysis (IHC) of CRC are usually recommended as tools to select high-risk patients for genetic testing and are performed in most countries in patients suspected of Lynch syndrome. In one country, IHC was recommended in all new cases of CRC. In most countries there are no specific programs on cancer genetics in the teaching curriculum for medical doctors. In conclusion, the outcome of this survey and the discussions within an European expert group may be used to improve the strategies to identify individuals at high risk of CRC. More attention should be given to increasing the awareness of the general population of hereditary CRC. Immunohistochemical analysis or MSI-analysis of all CRCs may be an effective tool for identifying all Lynch syndrome families. The cost-effectiveness of this approach should be further evaluated. All countries with a CRC population screening program should obtain a full family history as part of patient assessment.

The physiology and pathophysiology of human breath-hold diving.

This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive. However, a remarkable, and so far poorly understood, variation in individual disposition for such problems exists. Mortality connected with breath-hold diving is primarily concentrated to less well-trained recreational divers and competitive spearfishermen who fall victim to hypoxia. Particularly vulnerable are probably also individuals with preexisting cardiac problems and possibly, essentially healthy divers who may have suffered severe alternobaric vertigo as a complication to inadequate pressure equilibration of the middle ears. The specific topics discussed include the diving response and its expression by the cardiovascular system, which exhibits hypertension, bradycardia, oxygen conservation, arrhythmias, and contraction of the spleen. The respiratory system is challenged by compression of the lungs with barotrauma of descent, intrapulmonary hemorrhage, edema, and the effects of glossopharyngeal insufflation and exsufflation. Various mechanisms associated with hypoxia and loss of consciousness are discussed, including hyperventilation, ascent blackout, fasting, and excessive postexercise O(2) consumption. The potential for high nitrogen pressure in the lungs to cause decompression sickness and N(2) narcosis is also illuminated.

Isocapnic hyperpnea training improves performance in competitive male runners.

The effects of voluntary isocapnic hyperpnea (VIH) training (10 h over 4 weeks, 30 min/day) on ventilatory system and running performance were studied in 15 male competitive runners, 8 of whom trained twice weekly for 3 more months. Control subjects (n = 7) performed sham-VIH. Vital capacity (VC), FEV1, maximum voluntary ventilation (MVV), maximal inspiratory and expiratory mouth pressures, VO2max, 4-mile run time, treadmill run time to exhaustion at 80% VO2max, serum lactate, total ventilation (V(E)), oxygen consumption (VO2) oxygen saturation and cardiac output were measured before and after 4 weeks of VIH. Respiratory parameters and 4-mile run time were measured monthly during the 3-month maintenance period. There were no significant changes in post-VIH VC and FEV1 but MVV improved significantly (+10%). Maximal inspiratory and expiratory mouth pressures, arterial oxygen saturation and cardiac output did not change post-VIH. Respiratory and running performances were better 7- versus 1 day after VIH. Seven days post-VIH, respiratory endurance (+208%) and treadmill run time (+50%) increased significantly accompanied by significant reductions in respiratory frequency (-6%), V(E) (-7%), VO2 (-6%) and lactate (-18%) during the treadmill run. Post-VIH 4-mile run time did not improve in the control group whereas it improved in the experimental group (-4%) and remained improved over a 3 month period of reduced VIH frequency. The improvements cannot be ascribed to improved blood oxygen delivery to muscle or to psychological factors.

Respiratory muscle training improves swimming endurance in divers.

Respiratory muscles can fatigue during prolonged and maximal exercise, thus reducing performance. The respiratory system is challenged during underwater exercise due to increased hydrostatic pressure and breathing resistance. The purpose of this study was to determine if two different respiratory muscle training protocols enhance respiratory function and swimming performance in divers. Thirty male subjects (23.4 +/- 4.3 years) participated. They were randomized to a placebo (PRMT), endurance (ERMT), or resistance respiratory muscle training (RRMT) protocol. Training sessions were 30 min/day, 5 days/week, for 4 weeks. PRMT consisted of 10-s breath-holds once/minute, ERMT consisted of isocapnic hyperpnea, and RRMT consisted of a vital capacity maneuver against 50 cm H(2)O resistance every 30 s. The PRMT group had no significant changes in any measured variable. Underwater and surface endurance swim time to exhaustion significantly increased after RRMT (66%, P < 0.001; 33%, P = 0.003) and ERMT (26%, P = 0.038; 38%, P < 0.001). Breathing frequency (f (b)) during the underwater endurance swim decreased in RRMT (23%, P = 0.034) and tidal volume (V (T)) increased in both the RRMT (12%, P = 0.004) and ERMT (7%, P = 0.027) groups. Respiratory endurance increased in ERMT (216.7%) and RRMT (30.7%). Maximal inspiratory and expiratory pressures increased following RRMT (12%, P = 0.015, and 15%, P = 0.011, respectively). Results from this study indicate that respiratory muscle fatigue is a limiting factor for underwater swimming performance, and that targeted respiratory muscle training (RRMT > ERMT) improves respiratory muscle and underwater swimming performance.

Intravascular fluorocarbon-stabilized microbubbles protect against fatal anemia in rats.

It has earlier been hypothesized that intravascular microbubbles, derived from a dodecafluoropentane (DDFP) emulsion, can transport physiologically significant amounts of oxygen in the animal body. To test this notion, anesthetized oxygen breathing rats were rendered severely anemic by bleeding and volume replacement. Rats treated with 0.014 ml/kg of DDFP in a 2% emulsion had normal circulatory parameters and behaved normally when waking up from anesthesia while controls died during anesthesia. Oxygen-breathing intact rats given 0.01 ml/kg of DDFP had muscle oxygen tensions which, for about 2.5 hours, exceeded those of controls by 50-100%. It was further verified in vitro that DDFP-derived microbubbles can exchange oxygen with a surrounding aqueous medium. Extrapolation from these experiments indicates that less than 1 ml of DDFP, in emulsion-form, could provide for the resting oxygen consumption of an adult person. This suggests various therapeutic uses of the emulsion.

Predictive genetic testing for hereditary breast and ovarian cancer: psychological distress and illness representations 1 year following disclosure.

This prospective study evaluates emotional functioning and illness representations in 68 unaffected women (34 carriers/34 noncarriers) 1 year after predictive testing for BRCA1/2 mutations when offered within a multidisciplinary approach. Carriers had higher subjective risk perception of breast cancer than noncarriers. Carriers who did not have prophylactic oophorectomy had the highest risk perception of ovarian cancer. No differences were found between carriers and noncarriers regarding perceived seriousness and perceived control of breast and ovarian cancer. Mean levels of distress were within normal ranges. Only few women showed an overall pattern of clinically elevated distress. Cancer-specific distress and state-anxiety significantly decreased in noncarriers from pre- to posttest while general distress remained about the same. There were no significant changes in distress in the group of carriers except for ovarian cancer distress which significantly decreased from pre- to posttest. Our study did not reveal adverse effects of predictive testing when offered in the context of a multidisciplinary approach.