Biomedical subjects

Björn Wohlfart

Publications and source records attributed to Björn Wohlfart.

7 recordsLinked to original sources

PubMed2006

Working capacity and well-being after radical cystectomy with continent cutaneous diversion.

OBJECTIVES: The primary aim was to compare the working capacity in patients with continent urinary diversion with a control group. Secondary aims were to assess the changes in electrolyte and acid-base homeostasis and the functional status during strenuous physical activity, and finally, the well-being in the two groups. METHODS: Eleven patients who had undergone radical cystectomy and continent cutaneous diversion using an ileocolonic segment participated. The control group consisted of 12 men, matched for age and activity level. Working capacity was assessed by ergospirometry on an exercise bicycle. Venous blood samples were taken before the test, when the expiratory exchange ratio (RER) was about 1.0 and immediately after completion of the test. SF-36 was used to evaluate the subject's functional status and well-being. RESULTS: The median working capacity in the patient group was 155 (85-190) W and 155 (125-215) W in the control group (n.s.) corresponding to 72 (43-97) % and 80 (59-97) % respectively of predicted values. Peak oxygen uptake was somewhat low in both groups when compared to P-O Astrands norms. Blood tests revealed that patients developed a slight metabolic hyperchloremic acidosis, not seen in the control group. There were no differences between the groups as assessed with SF-36. CONCLUSION: Patients with a continent urinary diversion have a working capacity equal to a control group despite a slight metabolic hyperchloremic acidosis. Quality of life was similar in the two groups and corresponded well with the norms for the general Swedish population aged 65 to 74.

Acid-Base Equilibrium↗

PubMed2004

A refined technique for determining the respiratory gas exchange responses to anaerobic metabolism during progressive exercise - repeatability in a group of healthy men.

The respiratory gas exchange and ventilation during an incremental cycle exercise test were analysed in a group of 19 healthy, moderately fit men. Different computer algorithms were used to estimate the VO2 values where: (i) the rate of VCO(2) increase just exceeds the rate of VO(2) increase (DX, derivative crossing), (ii) VCO(2)/VO(2) = 1.00 (PX, point of crossing) and (iii) ventilation (VE) increases disproportionately in relation to VCO(2) (PQ, point of VCO(2) equivalent rise). The DX and PQ measurements were analysed using a new approach employing polynomial regression and the value of PX was determined following low-pass filtration of raw data. The repeatability of the measurements was evaluated with a 5-6 week interval between the tests. The correlations between tests were 0.75 at DX, 0.85 at PX and 0.62 at PQ. The mean differences between the repeated tests were not statistically significant. The repeatability of VO2, in absolute values expressed as +/-2 SD of the differences between the tests, had values of 5.0, 6.1 and 9.5 ml min(-1) kg(-1) for DX, PX and PQ, respectively. The mean value of VO(2) for each measurement point expressed as a percentage of VO(2 max) was 54% at DX, 68% at PX and 70% at PQ. The most common sequence of the measured values was DX < PX < PQ, but the sequence DX < PQ < PX was also observed. It is concluded that the gas exchange responses to developing anaerobic metabolism during progressive exercise can be characterized by a series of thresholds. However, the considerable variation in absolute values in the two testing occasions requires further attention.

Adult↗

PubMed2004

Determination of both the time constant of vO2 and DeltavO2/DeltaW from a single incremental exercise test: validation and repeatability.

A single incremental cycle exercise test including a steady-state load, combined with respiratory gas exchange, was performed with the objective of determining the time constant (tauVO(2)) and the amount of oxygen required at each load (DeltaVO(2)/DeltaW) by using a novel equation. The protocol was validated using four exercise tests at different constant loads and conventionally fitted mono-exponential functions to determine tauVO(2), and interpolation of VO(2) versus load to determine DeltaVO(2)/DeltaW. No significant differences were seen between the means of either tauVO(2) or DeltaVO(2)/DeltaW determined with the two protocols. The correlation coefficient was 0.62 for tauVO(2) and 0.48 for DeltaVO(2)/DeltaW. The absolute differences (2 SD) were 11.6 s for tauVO(2) and 1.1 ml min(-1) W(-1) for DeltaVO(2)/DeltaW. The equations were compared in the same steady-state test and good agreement of tauVO(2) was obtained (R = 0.99). The 5-6-week repeatability (incremental test) was evaluated. No statistical differences were seen between the mean of the repeated tests. The difference between the tests (2 SD) were 20 s for tauVO(2) and 1.2 ml min(-1) W(-1) for DeltaVO(2)/DeltaW. In conclusion, tauVO(2) and DeltaVO(2)/DeltaW can be determined from a single incremental test. The validation showed an acceptable agreement, although the variations in absolute values were not negligible. This could partly be explained by the natural day-to-day variation and fluctuations in incoming raw data. The test-retest variation in absolute values was considerable, which must be taken into account when using tauVO(2) and DeltaVO(2)/DeltaW for evaluation of aerobic function.

Adult↗

PubMed2004

Aerobic and functional capacity in a group of healthy women: reference values and repeatability.

Twenty-five randomly selected, low or moderately fit and healthy women (22-44 years) rated their perceived physical capacity and performed an incremental cycle exercise test with respiratory gas analysis. The aerobic and functional capacity did not decrease with age. However, tauVo(2) increased with age. The mean value of the perceived physical capacity was 10 metabolic equivalents and that of Vo(2max) 2075 ml min(-1). The increasing anaerobic metabolism was determined at three points DX (where the rate of Vco(2) increase just exceeds the rate of Vo(2) increase), PX (where Vco(2)/Vo(2) = 1.0) and PQ (where ventilation increase disproportionately in relation to Vco(2)). The mean Vo(2) (% of Vo(2max)) at DX, PX and PQ were 1263 (63%), 1528 (73%) and 1620 (78%) ml min(-1), respectively. The mean value of deltaVo(2)/deltaW was 10.2 ml min(-1) W(-1) while that of tauVo(2) was 0.578 (age) + 15.6. Ten women performed a test and re-test on two consecutive days, and eight of these performed another re-test 4 weeks later. The repeatability was analysed and the variations were expressed as 2 SD of the differences between the tests. The variation was greater for the 4-week re-test than the day-to-day re-test regarding Vo(2max), o(2) at DX, PX and PQ, deltaVo(2)/deltaW and HR. The variation in Vo(2max), PX and deltaVo(2)/deltaW for the 4-week re-test was more than twice that of the previously reported 4-week variation for men. The considerable variation, especially for 4-week re-testing for women should be considered when evaluating the effects of exercise and rehabilitation.

Adult↗

PubMed2003

Reference values for the physical work capacity on a bicycle ergometer for men -- a comparison with a previous study on women.

The aim of the study was to collect new reference values for the clinical ramp exercise test on bicycle, because in our experience, the commonly used values were too low. A group of healthy men (n = 81, 20-80 years) was randomly selected from the local municipal register to achieve an even distribution in age. Data were compared with those obtained in a similar, previous study on women (n = 87). The subjects were encouraged to cycle until exhaustion (19 on the Borg scale) when maximal load, heart rate and systolic blood pressure were recorded. Maximal load (W(max)) was related to age (years) and height (m) using a non-linear function: W(max) = (244.6 x height - 92.1)/[1 + exp[0.038 x (age - 77.3)]]. Maximal heart rate (HRmax) was described by a similar function: HRmax = 203.7/[1 + exp[0.033 x (age - 104.3)]]. The maximal systolic blood pressure (BP(max)) was described by a linear function based on age: BP(max) = 0.505 x age + 192. Similar functions for the women are also given. It is suggested that 80-120% of the predicted maximal load can be taken as a reference interval for both men and women and similarly 90-110% of the maximal heart rate. In this study, 84% of the men reached a maximal load within the reference interval and 93% maximal heart rate within the reference interval. The reported values for maximal load were 104-132% of the reference values published by others.

Adult↗

PubMed2002

A novel rating scale to predict maximal exercise capacity.

To predict maximal exercise capacity, we have developed the rating of perceived capacity (RPC) scale, based on metabolic equivalents (METs). MET values from 1 to 20 were listed on a progressive scale and linked to physical activities. Test subjects rated their perceived capacity by choosing the most strenuous activity and the corresponding MET value that they could sustain for 30 min. In order to validate the RPC, 87 healthy women participated in the study (age range 21-79 years). The capacity rated from the scale (MET(RPC)) was compared with the actual work capacity in a maximal incremental ramp cycle test. The maximal load achieved at the cycle test (in W), was transformed into the unit MET (MET(test)). The mean difference between MET(RPC) and MET(test) was -1.4 (3.18) (2SD). Multiple linear regression showed that MET(test) depended significantly on MET(RPC) and age. Extended regression analysis suggested that a nonlinear correction was most appropriate in order to improve the prediction. The maximal predicted capacity was given by: MET(pred) = (5.08 + 0.70 x MET(RPC))/[1+(e(0.059 (age-87.2)))]. After this correction, the mean difference between MET(pred) and MET(test) was reduced to 0.0 (2.62) (2SD). Reference values for MET(pred) and MET(test) were also obtained. In conclusion, the RPC combined with an age correction was shown to predict accurately maximal exercise capacity; it is also quick and easy to use. Thus, RPC may be a valuable tool in the prescription of exercise and in monitoring the effects of exercise and rehabilitation.

Adult↗

PubMed2002

Repeatability of measurements of oxygen consumption, heart rate and Borg's scale in men during ergometer cycling.

The coefficient of repeatability (COR), expressed as 2-SD of differences, was calculated between two measurements of oxygen consumption (V O2), heart rate (HR) and rating of perceived exertion (RPE) during ergometer cycling by men. The two sets of measurements were performed 5 to 6 weeks apart. Nineteen healthy men performed an incremental maximal exercise test on an ergometer cycle. The load started at 50 W and increased by 5 W 20 s-1 until exhaustion was reached. At 40% of the individual maximum load of the pretest, the load was kept constant for 4 min in order to reach steady state. Gas measurements were recorded continuously by computerized instrumentation. The HR was monitored with electrocardiography (ECG) and the perceived exertion was evaluated using Borg's scale. The COR of V O2 at sub-maximal load was 14% and at maximum load 11%. The values in absolute figures were 209 and 332 ml min-1. The corresponding COR of the HR was 16% at sub-maximum load and 6% at maximum load, and an evaluation of the perceived exertion yielded CORs in absolute values of 4.8 and 1.3, respectively. The COR for V O2, HR and ratings of perceived exertion when cycling on an ergometer cycle thus indicate a better agreement between the measurements at maximum load. The COR of the heart at sub-maximal loads must be kept in mind when using HR for estimation of V O2max. The reported findings should be considered when using tests on an ergometer cycle for evaluating exercise capacity.

Adult↗