Potassium and ventilation during positive and negative work inpatients with chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD),reduced ventilatory reserves limit exercise tolerance. In these patients, the ventilatoryrequirements of eccentric exercise (negative work, W_neg) are lower thanthose of concentric exercise (positive work, W_pos) at similar workloads.In this study, we investigated the relationship between plasma potassium levels and ventilationduring W_pos and W_neg in these patients. Twelvepatients with stable COPD [mean (SD) FEV₁ 46% (16) of predicted]performed W_pos and W_neg on a cycle ergometer(6 min of exercise; interval ≥1 h) in a randomized order at a constant workload of50% of the individual maximum (positive) work capacity. Minute ventilation (V_E) and arterial plasma potassium concentration ([K⁺]_a) were measured at rest, and at 1-min intervals during exercise and during 3 min ofrecovery. V_E increased less during W_neg thanduring W_pos [6 (range 3–26) vs. 18 (range 8–28) l min^?1; P<0·01]. V_E during W_neg was reduced in proportion to VCO ₂.The increase in [K⁺]_a during W_pos and W_neg [0·45 (range 0·26–0·75) and0·34 (range 0·1–0·97) mM ] did not differsignificantly. V_E was closely correlated with VCO ₂ during both types of exercise. V_E was also closelycorrelated with [K⁺]_a, but the slope of the relationship between[K⁺]_a and V_E was steeper during W_pos than during W_neg [39·1 (range15·2–88·6) vs. 18·3 (range7·2–37·3) l min^?1 mM ^?1; P=0·012]. In contrast, the slope of the relationship betweenVCO ₂ and V_E was similar during bothtypes of exercise [27?8 (range 19·2–37·1) vs. 32·1 (range19·8–48·4)]. Thus, for a given increase in [K⁺]_a, the increase in V_E was significantly less during W_neg. In patients with COPD, potassium did not explain the difference inexercise ventilation between W_neg and W_pos, andmay not play a significant role in the control of breathing during low-intensity exercise.     

Evaluation of a modified acetylene rebreathing method for the determination of cardiac output

Summary. In order to evaluate a computerized modified acetylene rebreathing method for the determination of cardiac output, 15 healthy subjects were studied at different levels of their maximal oxygen uptake (V?o_2max). Submaximal exercise was performed on a cycle ergometer and maximal exercise on a treadmill. Oxygen uptake, heart rate, and cardiac output (acetylene method) were determined in all test situations. In seven subjects simultaneous determinations of cardiac output were made by a modified acetylene rebreathing method (Q?_A) and a dye dilution method (Q?_D) Furthermore, a new resting rebreathing technique was used. The methodological error for (Q?_A)(means of double samples) was 0·37 litre min^-1 (2·8%) in the same individual at 150 W. The corresponding values between individuals were 0·71 (rest), 0·41 (50 W), 0·69 (150 W), and 0·40 litre min^-1 (V?o_2max). Thus the methodological error of the modified acetylene method was very low. There was a significant difference (P<0·01), however, between the acetylene method and the dye dilution method, which showed a lower value for Q?_A at all levels. This was probably due to the long response time of the mass spectrometer combined with anatomical and physiological arteriovenous shunt effects in the lungs during exercise. When these factors were considered the correcting formula was:Q?_Ac=Q?_A+0·005·Q²_A There was no significant difference between the corrected cardiac output values (Q?_Ac) and the corresponding Q?_D values. In conclusion, this modified acetylene rebreathing method is a very useful non-invasive method for measuring cardiac output at rest as well as during heavy exercise.     

Accuracy and responsiveness of the stepwatch activity monitor and ActivPAL in patients with COPD when walking with and without a rollator

Purpose: To evaluate the measurement properties of the StepWatch^? Activity Monitor (SAM) and ActivPAL in COPD. Method: Whilst wearing both monitors, participants performed walking tasks at two self-selected speeds, with and without a rollator. Steps obtained using the monitors were compared with that measured by direct observation. Results: Twenty participants aged 73?±?9 years (FEV₁?=?35?±?13% pred; 8 males) completed the study. Average speeds for the slow and normal walking tasks were 34?±?7 m·min^?1and 46?±?10 m·min^?1, respectively. Agreement between steps recorded by the SAM with steps counted was similar irrespective of speed or rollator use (p?=?0.63) with a mean difference and limit of agreement (LOA) of 2 steps·min^?1 and 6 steps·min^?1, respectively. Agreement for the ActivPAL was worse at slow speeds (mean difference 7 steps·min^?1; LOA 10 steps·min^?1) compared with normal speeds (mean difference 4 steps·min^?1; LOA 5 steps·min^?1) (p?=?0.03), but was unaffected by rollator use. The change in step rate between slow and normal walking via direct observation was 12?±?7 steps·min^?1 which was similar to that detected by the SAM (12?±?6 steps·min^?1) and ActivPAL (14?±?7 steps·min^?1). Conclusions: The SAM can be used to detect steps in people who walk very slowly including those who use a rollator. Both devices were sensitive to small changes.

Implications for Rehabilitation

• The evaluation of physical activity (PA) before and after pulmonary rehabilitation in people with chronic obstructive pulmonary disease (COPD) has evolved to be an important outcome measure.

• Selecting an appropriate device to obtain valid measures of PA remains a challenge, especially for those individuals who walk slowly or use a rollator to assist with ambulation.

• The StepWatchTM Activity Monitor and the ActivPAL have been shown in this study to be sensitive to small changes in step rate, thus these devices can be used to assess changes in physical activity in individuals with COPD such as following pulmonary rehabilitation, including those who walk slowly or use a walking aid such as a rollator.

     

动态增强MRI鉴别诊断不典型乳腺癌与纤维腺瘤

目的 探讨动态增强MRI（DCE-MRI）定量参数对不典型乳腺癌和纤维腺瘤的鉴别诊断价值。方法 收集经病理证实的不典型乳腺癌30例（不典型乳腺癌组）和纤维腺瘤32例（纤维腺瘤组）患者。对所有患者均进行DCE-MR检查,获取血流动力学参数容量转移常数（K_trans）、速率常数（K_ep）、血管外细胞外间隙容积分数（V_e）、血浆分数（V_p）,比较两组各参数的统计学差异,并评价其诊断效能。结果 不典型乳腺癌组K_trans、K_ep、V_e、V_p分别为（1.49±0.55）min^-1、（0.70±0.02）min^-1、0.78±0.19、0.26±0.13,纤维腺瘤组K_trans、K_ep、V_e、V_p分别为（0.64±0.23）min^-1、（0.30±0.23）min^-1、0.63±0.25、0.33±0.14;两组间K_trans、V_e、K_ep差异有统计学意义（P均<0.01）,V_p差异无统计学意义（P=0.05）。K_trans、K_ep、V_e诊断不典型乳腺癌和纤维腺瘤的曲线下面积分别为0.94、0.88、0.68,敏感度为86.7%、86.7%、83.3%,特异度为93.7%、81.2%、46.9%。结论 DCE-MRI可准确评估病变的微循环,对纤维腺瘤和不典型乳腺癌的诊断及鉴别诊断具有较高的临床应用价值。     

Autonomic nervous function at rest in aerobically trained and untrained oldermen

Therelationship between aerobictraining, vagal influence on the heart and ageing was examined by assessing aerobic fitness andresting heart rate variability in trained and untrained older men. Subjects were 11 trained cyclistsand runners (mean age=6±61·6 years) and 11 untrained, age-matchedmen (mean age=66±1·2 years). Heart rate variability testing involvedsubjects lying supine for 25 min during which subjects’ breathing was paced andmonitored (7·5 breaths min^?1). Heart rate variability was assessedthrough time series analysis (HRV_ts) of the interbeat interval. Results indicated thattrained older men (3·55±0·21 l min^?1) hadsignificantly (P<0·05) greater VO _2maxthan that of control subjects (2·35±0·15 l min^?1).Also, trained older men (52±1·8 beats min^?1) hadsignificantly (P<0·05) lower supine resting heart rate than that of controlsubjects (65±4·2 beats min^?1). HRV_ts at highfrequencies was greater for trained men (5·98±0·22) than for untrainedmen (5·23±0·32). These data suggest that regular aerobic exercise inolder men is associated with greater levels of HRV_ts at rest.     

Normal values for QT intervals in ECG during ramp exercise on bicycle

Summary. The relation between QT interval and heart rate during ramp exercise tests on a bicycle was investigated in 37 healthy individuals (21 women) without regular medication and with a normal thallium-201 exercise scintigram (mean age 52–9 ± 8–3, range 38–68). The test started at 20 W and the load increased by 10 W min^-1. A 12-lead ECG was recorded twice every min and mean complexes (during a 15 s period) were calculated by computer. At rest the QT interval (in s) corrected for heart rate (QT_C) for women and men was 0–408 ± 0–004 and 0–399 ± 0–005, respectively, P > 0–05). During exercise there was no difference in QT interval between women and men or between younger (<50 years) and older (> 50 years) individuals. A straight line was used to describe the relation between QT interval and heart rate (beats min^-1; QT = 0–459–12–3xlO^-4*HR). A 95% prediction interval around the regression line was determined using a non-parametric statistical method. When QT_C was calculated using Bazett's formula with a cut-off value of QT_c= 0–46, 19 individuals (11 women) had a prolonged QT interval during exercise. It is concluded that the relation between QT interval and heart rate can during exercise be described by a straight line for normal individuals. It is not valid to use Bazett's formula for correction of QT intervals during ramp exercise tests.     

Intensity of Nordic Walking in young females with different peak O2 consumption

The purpose of this cross‐sectional study was to determine the physiological reaction to the different intensity Nordic Walking exercise in young females with different aerobic capacity values. Twenty‐eight 19–24‐year‐old female university students participated in the study. Their peak O₂ consumption (VO₂ peak kg^?1) and individual ventilatory threshold (IVT) were measured using a continuous incremental protocol until volitional exhaustion on treadmill. The subjects were analysed as a whole group (n = 28) and were also divided into three groups based on the measured VO₂ peak kg^?1 (Difference between groups is 1 SD) as follows: 1. >46 ml min^?1 kg^?1 (n = 8), 2. 41–46 ml min^?1 kg^?1 (n = 12) and 3. <41 ml min^?1 kg^?1 (n = 8). The second test consisted of four times 1 km Nordic Walking with increasing speed on the 200 m indoor track, performed as a continuous study (Step 1 – slow walking, Step 2 – usual speed walking, Step 3 – faster speed walking and Step 4 – maximal speed walking). During the walking test expired gas was sampled breath‐by‐breath and heart rate (HR) was recorded continuously. Ratings of perceived exertion (RPE) were asked using the Borg RPE scale separately for every 1 km of the walking test. No significant differences emerged between groups in HR of IVT (172·4 ± 10·3–176·4 ± 4·9 beats min^?1) or maximal HR (190·1 ± 7·3–191·6 ± 7·8 beats min^?1) during the treadmill test. During maximal speed walking the speed (7·4 ± 0·4–7·5 ± 0·6 km h^?1) and O₂ consumption (30·4 ± 3·9–34·0 ± 4·5 ml min^?1 kg^?1) were relatively similar between groups (P > 0·05). However, during maximal speed walking, the O₂ consumption in the second and third groups was similar with the IVT (94·9 ± 17·5% and 99·4 ± 15·5%, respectively) but in the first group it was only 75·5 ± 8·0% from IVT. Mean HR during the maximal speed walking was in the first group 151·6 ± 12·5 beats min^?1, in the second (169·7 ± 10·3 beats min^?1) and the third (173·1 ± 15·8 beats min^?1) groups it was comparable with the calculated IVT level. The Borg RPE was very low in every group (11·9 ± 2·0–14·4 ± 2·3) and the relationship with VO₂and HR was not significant during maximal speed Nordic Walking. In summary, the present study indicated that walking is an acceptable exercise for young females independent of their initial VO₂ peak level. However, females with low initial VO₂ peak can be recommended to exercise with the subjective ‘faster speed walking’. In contrast, females with high initial VO₂ peak should exercise with maximal speed.     

The influence of a fast ramp rate on peak cardiopulmonary parameters during arm crank ergometry

The influence of a very fast ramp rate on cardiopulmonary variables at ventilatory threshold and peak exercise during a maximal arm crank exercise test has not been extensively studied. Considering that short arm crank tests could be sufficient to achieve maximal oxygen consumption (VO₂), it would be of practical interest to explore this possibility. Thus, this study aimed to analyse the influence of a fast ramp rate (20 W min^?1) on the cardiopulmonary responses of healthy individuals during a maximal arm crank ergometry test. Seventeen healthy individuals performed maximal cardiopulmonary exercise tests (Ultima CardiO2; Medical Graphics Corporation, St Louis, USA) in arm ergometer (Angio, LODE, Groningen, The Netherlands) following two protocols in random order: fast protocol (increment: 2 w/6 s) and slow protocol (increment: 1 w/6 s). The fast protocol was repeated 60–90 days after the 1st test to evaluate protocol reproducibility. Both protocols elicited the same peak VO₂ (fast: 23·51 ± 6·00 versus slow: 23·28 ± 7·77 ml kg^?1 min^?1; P = 0·12) but peak power load in the fast ramp protocol was higher than the one in the slow ramp protocol (119 ± 43 versus. 102 ± 39 W, P < 0·001). There was no other difference in ventilatory threshold and peak exercise variables when 1st and 2nd fast protocols were compared. Fast protocol seems to be useful when healthy young individuals perform arm cardiopulmonary exercise test. The usefulness of this protocol in other populations remains to be evaluated.     

Plasma lipid and lipoprotein profiles in pre- and post-menopausal middle-aged runners

Summary. Plasma lipid and lipoprotein profiles were compared in middle-aged trained and untrained women before and after menopause. Subjects were assigned to one of four groups: (1) pre-menopausal trained (Pre-T: n= 17, aged 42 ±5 years, body fat 19±5%, training distance 53 ±20 km week^-1, V?o_2max 49 ±4 ml kg^-1 min^-1, mean±SD); (2) pre-menopausal untrained (Pre-UT: n= 26, 42 ±5 years, 24 ±7%, 34 ±6 ml kg^-1 min^-1); (3) post-menopausal trained (Post-T: n= 16, 54 ±3 years, 20 ±4%, 43 ±19 km week^-1, 41 ±5 ml kg^-1 min^-1); and (4) post-menopausal untrained (Post-UT: n= 15, 55 ±3 years, 25 ±6%, 31 ±3 ml kg^-1 min^-1). There were no significant differences in total cholesterol (range 173–194 mg dl^-1), triglyceride (56–72 mg dl^-1), and HDL-cholesterol (HDLC: 76–85 mg dl^-1) among the four groups. LDL-cholesterol (LDLC) in the post-menopausal women (Post-T: 96 ±32 mg dl^-1; Post-UT: 104 ±23 mg dl^-1) tended to be higher than in the premenopausal women (Pre-T: 86 ± 25 mg dl^-1, Pre-UT: 81 ± 23 mg dl^-1). LDLC/HDLC ratio in Post-UT (1·42 ±0·38 unit) was higher than in the pre-menopausal women (Pre-T: 1·03±0·31 unit, P<0·01; Pre-UT: 1·10±0·38 unit, P<0·05), whereas the ratio in Post-T (1·20 ±0·38 unit) was not different from those of the pre-menopausal groups. These results suggest that endurance running protects against the increase in LDLC/HDLC ratio that frequently occurs after menopause.     

Assessment of V̇o2peak and Exercise Capacity After Stroke: A Validity Study of the Human Activity Profile Questionnaire

ObjectiveTo investigate the concurrent validity of the Human Activity Profile (HAP) in individuals after stroke to provide the peak oxygen uptake (V?o_2peak) and the construct validity of the HAP to assess exercise capacity, and to provide equations based on the HAP outcomes to estimate the distance covered in the Incremental Shuttle Walking Test (ISWT).DesignCross-sectional study.SettingUniversity laboratory.ParticipantsIndividuals (N=57) aged 54±11 years who have experienced stroke.InterventionNot applicable.Main Outcome MeasuresAgreement between the V?o_2peak provided by the HAP (lifestyle energy consumption [LEC] outcome, in mL/kg^?1/min^?1) and the criterion standard measure of the V?o_2peak (mL/kg^?1/min^?1), obtained through the symptom-limited Cardiopulmonary Exercise Test (CPET). Correlation between the HAP outcomes (LEC, maximum activity score [MAS], and adjusted activity score [AAS]) and the construct measure: the distance covered (in meters) in the ISWT. An equation to estimate the distance covered in the ISWT was determined.ResultsHigh magnitude agreement was found between the V?o_2peak, in mL/kg^?1/min^?1, obtained by the symptom-limited CPET and the value of V?o_2peak, in mL/kg^?1/min^?1, provided by the HAP (LEC) (intraclass correlation coefficient, 0.75; P<.001). Low to moderate magnitude correlations were found between the distance covered in the ISWT and the HAP (LEC/MAS/AAS) (0.34≤ρ≤0.58). The equation to estimate the distance covered in the ISWT explained 31% of the variability of the ISWT (ISWT_estimated, –361.91+(9.646xAAS)).ConclusionThe HAP questionnaire is a clinically applicable way to provide a valid value of V?o_2peak (in mL/kg^?1/min^?1) and to assess the exercise capacity of individuals after stroke. Furthermore, an equation to estimate the distance covered in the submaximal field exercise test (ISWT) based on the result of the AAS (in points) was provided.     

Effect of exercise training and detraining on gas exchange kinetics in patients with chronic obstructive pulmonary disease

Symptom-limited incremental exercise tests are used to estimate the training effect on patients with chronic obstructive pulmonary disease (COPD). However, there is a need for objective parameters for measurement on submaximal exercise testing. The purpose of this study was to assess the usefulness of measurement of oxygen uptake (V?O₂) kinetics during a constant work rate exercise test of patients with COPD after exercise training. Eleven patients with COPD performed exercise tests before and after cycle ergometer training on 3 days per week for 8 weeks; they then went without training for 5 months and performed the same tests. They performed an incremental exercise test to symptom-limited maximum and a constant work rate exercise test for 6 min on a cycle ergometer. The time constant of V?O₂ during the onset of constant work rate exercise was significantly decreased (from 63·5±7·8 s to 53·2±8·0 s) after exercise training (P=0·021), but was significantly increased (to 73·4±14·9 s) after 5 months without training (P=0·001). The oxygen pulse at steady state during constant work rate exercise testing was significantly increased after exercise training but decreased 5 months later. The change in blood lactate from rest to steady state during constant work rate exercise was significantly decreased after exercise training, but increased 5 months later. Measurement of the time constant of V?O₂ and oxygen pulse during constant work rate exercise are useful for the objective evaluation of the training effect of patients with COPD.     

The lymphocyte Na+/H+ antiport: activation in primary hypertension and during chronic NaCl-loading

Abstract. Increased activity of the Na⁺/H⁺ antiport may be a major abnormality in essential hypertension. The activity of this transport system was investigated in lymphocytes from 13 patients with untreated essential hypertension (Ht) and 13 normotensive control subjects (Nt) on an ad libitum (130–170 mmol d^-1) NaCl intake. Furthermore, the effects of different states of NaCl balance on lymphocyte Na⁺/H⁺ antiport were evaluated in two groups of Nt volunteers receiving 20 vs. 300 mmol d^-1 (n= 8) and 85 vs. 200 mmol d^-1 (n= 14) of NaCl for 1 week each and in seven Ht patients (20 vs. 300 mmol NaCl d^-1 for 1 week each). Additionally, during the 20 and 300 mmol/d NaCl intake red blood cell membrane transport was studied in eight subjects. For the determination of lymphocyte antiport activity, cells were loaded with the cytosolic pH (pH_i) indicator bis-carboxyethyl carboxyfluorescein (BCECF-AM) and acidified by addition of different amounts of Na⁺-propionate (5–40 mM). Initial pH_i-recovery was taken as the activity of the antiport system and plotted against pH_i-values after acidification. Non-linear regression analysis yielded higher ’apparent’ maximal transport rates in Ht than Nt (Nt: 2·00 pL 0·22; Ht: (3·81 pL 0·59)·10^-3 s^-1; P < 0·025). In contrast, baseline pH_i-values and pH_i-values at half-maximal activity (pK) were identical in Nt and Ht. In normotensive control subjects on an NaCl intake of 20, 85, 200 and 300 mmol d^-1 for 7 d, ’apparent’ maximal transport rates averaged 2.75 0·20, 2·89 0·17, 2·81 ± 0·18 and (3·62 ± 0·25) · 10^-3 s^-1, respectively. Thus, antiport activity was significantly (P < 0·05) stimulated on the 300 mmol d^-1 intake as compared to the three other NaCl intakes. The extreme intakes of NaCl (20 vs. 300 mmol d^-1) in normotensive volunteers did not affect the erythrocyte Na⁺/K⁺ pump, Na⁺/K⁺ cotransport and Na⁺/Li⁺ countertransport. Our study supports the concept that a group of patients with primary hypertension exhibit an activated Na⁺/H⁺ antiport. Furthermore, our data demonstrate that a chronic high intake of NaCl is associated with an increase in lymphocyte antiport activity towards the high values observed in primary hypertension.     

Ineffective ventilation during exercise in patients with chronic congestive heart failure

Summary The pathophysiologic mechanisms causing exertional breathlessness in patients with chronic congestive heart failure (CHF) are not fully understood. Therefore, we have studied whether the ventilation in such patients is ineffective during exercise. Thirteen patients with treated chronic CHF (New York Heart Association class II-IV) and eight healthy controls underwent a maximal bicycle ergometer test with continuous analysis of expired air and frequent arterial blood sampling for gas and lactate analysis. All subjects were non-smokers and none had any signs of a pulmonary disease. Peak O₂ consumption of the patients was 14.9 ±5.3 ml min^-1 kg^-1 and that of controls 33.6 ±7.5 ml min^-1 kg^-1. In patients with CHF the ratio of pulmonary dead space to tidal volume was significantly elevated at peak exercise compared with that of the controls (0.36±0.08 vs. 0.20±0.07, P<0.05). The ventilatory equivalent for CO₂ (VE:VCO₂) was also significantly higher in patients than in controls during exercise (P<0.05). Furthermore, both the ventilatory equivalents for CO₂ and O₂ (VE:VD₂) had a significant inverse correlation with peak O₂ consumption (P<0.001 for VE:VT:O₂ and P<0.05 for VE:VO₂), O₂ consumption at anaerobic threshold (P<0.01) and O₂-pulse (P<0.001) among the patients. During exercise the arterial PO₂ and PCO₂ remained normal in patients and controls. These data indicate that in patients with chronic CHF wasted ventilation is pathologically increased during exercise, and this is related to the severity of the disease. Chronic CHF is not associated with decreased ventilatory reserve, hypoxaemia or alveolar hyperventilation. The ineffectiveness of ventilation is probably an important cause of exertional breathlessness in patients with CHF.     

Effects of aerobic exercise training and yoga on the baroreflex in healthy elderly persons

It is unclear whether the age-associated reduction in baroreflex sensitivity is modifiable by exercise training. The effects of aerobic exercise training and yoga, a non-aerobic control intervention, on the baroreflex of elderly persons was determined. Baroreflex sensitivity was quantified by the α-index, at high frequency (HF; 0.15–0.35 Hz, reflecting parasympathetic activity) and mid-frequency (MF; 0.05–0.15 Hz, reflecting sympathetic activity as well), derived from spectral and cross-spectral analysis of spontaneous fluctuations in heart rate and blood pressure. Twenty-six (10 women) sedentary, healthy, normotensive elderly (mean 68 years, range 62–81 years) subjects were studied. Fourteen (4 women) of the sedentary elderly subjects completed 6 weeks of aerobic training, while the other 12 (6 women) subjects completed 6 weeks of yoga. Heart rate decreased following yoga (69 ± 8 vs. 61 ± 7 min^?1, P < 0.05) but not aerobic training (66 ± 8 vs. 63 ± 9 min^?1, P = 0.29). VO₂ max increased by 11% following yoga (P < 0.01) and by 24% following aerobic training (P < 0.01). No significant change in α_MF (6.5 ± 3.5 vs. 6.2 ± 3.0 ms mmHg^?1, P = 0.69) or α_HF (8.5 ± 4.7 vs. 8.9 ± 3.5 ms mmHg^?1, P = 0.65) occurred after aerobic training. Following yoga, α_HF (8.0 ± 3.6 vs. 11.5 ± 5.2 ms mmHg^?1, P < 0.01) but not α_MF (6.5 ± 3.0 vs. 7.6 ± 2.8 ms mmHg^?1, P = 0.29) increased. Short-duration aerobic training does not modify the α-index at α_MF or α_HF in healthy normotensive elderly subjects. α_HF but not α_MF increased following yoga, suggesting that these parameters are measuring distinct aspects of the baroreflex that are separately modifiable.     

High anaerobic energy release during submaximal arm exercise

Summary. The anaerobic energy release during submaximal arm (AE) and leg exercise (LE) has been estimated from O₂ deficit measured at the onset of exercise. Eight male subjects were studied during 8–10 min of arm or leg cycling at the same relative workload (53% of the peak exercise-induced increase in pulmonary oxygen uptake, VO₂). The workloads were 78 ± 4 W during AE and 173 ± 11 W during LE and Vo₂ was 1.51 ± 006 1 min^-1 for AE and 2.33 ±0.15 1 min^-1 for LE. The half-time of the Vo₂ on-response was considerably longer (P<0.01) during AE (62 ± 9 s) than during LE (33 ± 4 s) and the peak blood lactate concentration was higher (P<0.05) during AE (4.8 ± 0.5 mmol-l^-1) than during LE (3.5 ±0.4 mmol-l^-1). Oxygen deficil was 1.64 ±016 and 1.78 ±0.16 1 for AE and LE respectively. Oxygen deficit was higher during AE than during LE when related to absolute workload (P<0.01), or tc Vo₂ at steady state (P<0.001) or to limb volume (P<0.001). The proportion of the total energy demand covered by anaerobic energy release at the onset of exercise (0–8 min) was about 54% higher (P<0.01) during AE than during LE. It is concluded thai the energy release to a greater extend is covered by anaerobic processes during AE than during LE.     

Cerebral perfusion during human liver transplantation

Summary. During transplantation of the liver cerebral perfusion was monitored by transcranial Doppler determined middle cerebral artery mean flow velocity (V_mean) and pulsatility index (PI) in six fulminant hepatic failure patients and 11 patients with chronic liver disease. In both groups of patients V_mean, PI and central haemodynamic variables were recorded during (1) the last preanhepatic hour; (2) the anhepatic phase; (3) the first 15 min of reperfusion; and (4) for the following 45 min of reperfusion. No significant differences were detected between the two groups of patients with respect to changes of variables with time. The V_mean (40±13 cm s^-1 [mean±SD]), thoracic electrical impedance (TI) (30±7 Ohm), heart rate (97±19 beats min^-1), mean arterial pressure (84±9 mmHg) and arterial carbon dioxide tension (PaCO₂, 4.5±0.4 kPa) remained stable in the anhepatic phase, while cardiac output (CO, 7.6±2.7 to 5.4±1.41 min^-1), stroke volume (SV, 79±26 to 56±15 ml) and PI (1.2±0.3 to 0.9±0.2) decreased (P<0.05). During reperfusion, CO (9.9±4.01 min^-1), SV (105±40 ml), Pa_CO2 (5.5±0.6 kPa), Vmean (57±17 cm s^-1) and PI (1.2±0.2) became elevated. Taken together, during the anhepatic phase of the liver transplantation a maintained central blood volume as indicated by the constant TI served for a stable blood pressure and in turn cerebral perfusion, whereas revascularization of the graft increased cerebral perfusion concomitant with an elevated carbon dioxide tension.     

Ventilation–perfusion inequality and carbon dioxide sensitivity in hypoxaemic chronic obstructive pulmonary disease (COPD) and effects of 6 months of long‐term oxygen treatment (LTOT)

The aim of our study was to find out how blood gas disturbances in stable, eucapnic, severe chronic obstructive pulmonary disease (COPD) patients with an arterial oxygen tension (PaO₂) value of 7·7 (6·1–8·4) kPa are affected by ventilation–perfusion (V_A/Q) relationships and carbon dioxide (CO₂) sensitivity and how these parameters are influenced by 6 months of long‐term oxygen treatment (LTOT). V_A/Q ratios were measured using the multiple inert gas elimination technique (MIGET). Mouth occlusion pressure 0·1 s after onset of inspiration (Pi0·1) and minute ventilation (V_E) were measured to assess respiratory drive response (ΔPi0·1/ΔPCO₂) and hypercapnic ventilatory response (HCVR) to CO₂ rebreathing. At the start of LTOT, a normal median respiratory drive response level of 1·2 (0·2–2·3) cm H₂O/kPa and a low median HCVR as compared with healthy individuals (P<0·001) were found. However, 7·9 (0–29·8)% of the V_E, was directed towards hypoperfused lung areas. The dispersion of ventilation (log SDV; 0·47–1·76), and the dispersion of perfusion (log SDQ; 0·66–1·07) were wider than normal. The PaO₂ level correlated inversely with mean V_A/Q ratio for ventilation (V mean) and shunt. The PaCO₂ level correlated inversely with HCVR and vital capacity. After 6 months of LTOT, no significant changes in daytime blood gas levels, CO₂‐sensitivity or V_A/Q ratios were found. V_E tended to be reduced by 1·0 l min^–1. Conclusions: An elevated V mean and probably shunting are important contributing factors for the reduced PaO₂ and hypercapnic ventilatory response is a major determinant of PaCO₂ in eucapnic stable hypoxaemic COPD. Six months of LTOT does not affect blood gases, CO₂ sensitivity or ventilation–perfusion relationships.     

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise

The association between muscle oxygen uptake (VO₂) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one‐legged knee‐extension exercise at variable intensities using positron emission tomography and a‐v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI‐1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI‐2). Muscle perfusion and O₂ delivery during HI‐1 (26 ± 5 and 5·4 ± 1·0 ml 100 g^?1 min^?1) and HI‐2 (28 ± 4 and 5·8 ± 0·7 ml 100 g^?1 min^?1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g^?1 min^?1). Muscle VO₂ was also higher during both HI workloads (HI‐1 3·3 ± 0·4 and HI‐2 4·1 ± 0·6 ml 100 g^?1 min^?1) than LOW (1·4 ± 0·4 ml 100 g^?1 min^?1; P<0·01) and 25% higher during HI‐2 than HI‐1 (P<0·05). O₂ extraction was higher during HI workloads (HI‐1 62 ± 7 and HI‐2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O₂ extraction tended to be higher (P = 0·08) during HI‐2 when compared to HI‐1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one‐legged knee‐extension exercise at variable intensities, skeletal muscle perfusion and O₂ delivery are unchanged between high‐intensity workloads, whereas muscle VO₂ is increased during the second high‐intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O₂ delivery and uptake. We propose that the excess muscle VO₂ during the second high‐intensity workload is derived from working muscle cells.     

Diabetes mellitus and subjects' ageing: a study on the ATP content and ATP-related enzyme activities in human erythrocytes

Na⁺/K⁺- and Ca²⁺-ATPase are the major ATP-dependent membrane-bound enzymes that regulate the cation transmembrane gradient which is altered both in red blood cell (RBC) senescence and in RBCs of diabetic patients. In an attempt to clarify the possible connection between diabetes mellitus and ageing, we investigated the relationship between RBC ATP content, Na⁺/K⁺-ATPase, Ca²⁺-ATPase activities and ageing in healthy, insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) subjects. A significant correlation was found (r = ?0.82; P < 0.001) between RBC ATP content and subject's age only in the control group. A significant reduction in Na⁺/K⁺-ATPase activity was observed in the older group (C₂) of control subjects, in comparison with the younger (C₁) one. In both IDDM and NIDDM subjects, the enzymatic activity was significantly decreased when compared with healthy subjects of similar age (P < 0.001). A significant negative correlation was found between age and enzymatic activity in healthy subjects (r = ?0.60; P < 0.001). No difference was observed in the RBC membrane Ca²⁺-ATPase activity between younger (C₁) and older (C₂) healthy subjects. Ca²⁺-ATPase activity was significantly increased both in IDDM patients compared with C₁ (P < 0.001) and in NIDDM patients compared with C₂ (P < 0.001). The present data indicate that ageing causes a reduction in the erythrocyte ATP content in both healthy and diabetic subjects. In diabetic patients Na⁺/K⁺-ATPase activity decreases independently of age.     

Plasma lipid and lipoprotein profile in elderly female runners

Plasma lipid and lipoprotein profiles were compared in elderly female runners (RU: n= 15, aged 66 ± 5 years, body fat 20 ± 4%, training distance 35 ± 15 km week¹, V?O_2max 36 ± 4 ml kg¹ min¹, mean ± SD) and age-matched untrained women (UT: n= 28, 66 ± 4 years, body fat 26 ± 6%, V?O_2max 26 ± 3 ml kg¹ min¹). There were insignificant differences in total cholesterol (RU: 5·04 ± 0·60 vs. UT: 5·48 ± 0·85 mmol 1¹), HDL-cholesterol (RU: 1·97 ± 0·41 vs. UT: 1·91 ± 0·36 mmol 1¹) and LDL-cholesterol (RU: 2·72 ± 0·59 vs. UT: 3·03 ± 0·80 mmol 1¹) between the two groups. Plasma triglyceride concentration of the runners was significantly lower than that of the untrained women (RU: 0·80 ± 0·27 vs UT: 1·14 ± 0·36 mmol 1¹, P < 0·01). No difference was observed in the LDL-cholesterol/HDL-cholesterol ratio between the two groups (RU: 1·45 ± 0·51 vs UT: 1·64 ± 0·53 units). These results suggest that regularly performed running of 35 km week¹ in elderly women does not further elevate their HDL-cholesterol level which is already high compared to the levels found in elderly men. However, elderly female runners appear to be protected against age-related increases in the levels of triglyceride and LDL-cholesterol.