Mercury Strain Gauge Plethysmography Research Articles

Influence of Lower Body Positive Pressure on Upper Airway Cross-Sectional Area in Drug-Resistant Hypertension

We previously showed that in hypertensive patients the amount of fluid displaced from the legs overnight is directly related to the severity of obstructive sleep apnea and that the rostral fluid shift was greater in drug-resistant hypertensive patients. The findings suggested that this fluid redistribution increases upper airway collapsibility, yet more direct evidence is lacking. The present study examines the effects of graded lower body positive pressure on leg fluid volume, upper airway cross-sectional area, and neck circumference in patients with drug-resistant hypertension (n=25) and controlled hypertension (n=15). In both groups, the reduction in mean upper airway cross-sectional area and oropharyngeal junction area, assessed by acoustic pharyngometry, and the increase in neck circumference, determined by mercury strain gauge plethysmography, were related to the amount of fluid displaced from the legs (R(2)=0.41, P<0.0001; R(2)=0.42, P<0.0001; and R(2)=0.47, P<0.0001, respectively). Displacement of leg fluid volume was significantly greater in patients with drug-resistant hypertension than in controlled hypertension (P<0.0001), and as a consequence, the former experienced greater reductions in mean upper airway cross-sectional area and oropharyngeal junction area (P=0.001 and P<0.0001, respectively). The findings support the concept that in hypertensive subjects, rostral fluid displacement may participate in the pathogenesis of obstructive sleep apnea by narrowing the upper airway and making it more susceptible to collapse during sleep. The exaggerated fluid volume displacement from the legs and upper airway response to lower body positive pressure in patients with drug-resistant hypertension provide additional evidence of an important link between drug-resistant hypertension and obstructive sleep apnea.

Peripheral Vascular Responses of Men and Women to LBNP

This study examined the hypothesis that women exhibit smaller vasoconstrictor responses in the calf during graded lower body negative pressure (LBNP). Selective deep oxygenated hemoglobin (Hb) assessed by near-infrared spectroscopy (NIRS) was used to examine blood flow changes in the calf. Eleven men and nine women volunteers underwent graded LBNP up to -60 mm Hg. Cardiovascular responses were measured by: NIRS on the forearm and superficial and deep calf for oxygenated and deoxygenated Hb; mercury strain gauge plethysmography for calf blood pooling; electrocardiogram for heart rate; and, photoplethysmography for blood pressure, cardiac output, and total peripheral resistance. Cardiac output was lower and total peripheral resistance higher in women; however, both men and women had similar decreases in cardiac output and increases in total peripheral resistance with LBNP. Forearm oxygenated Hb decreased from baseline throughout LBNP, and no difference was found between men and women. Female subjects had greater rates of increased blood pooling with LBNP than their male counterparts. Men had greater selective deep calf oxygenated Hb reductions compared to women during LBNP. Moreover, when the oxygenated Hb response as a function of calf blood pooling was examined with regression analyses, men had greater slopes (-0.62 +/- 0.05) than women (-0.33 +/- 0.04). The greater slopes in oxygenated Hb at given blood pooling and at each negative pressure in male subjects led us to conclude that men had greater vasoconstrictor responses in the calf during graded LBNP.

Effects of iloprost, either administered for 1 week or 4 weeks, on systemic hemodynamics, peripheral blood flow, and exercise tolerance in patients with peripheral occlusive arterial disease at leriche-fontaine stage III

Twenty patients, 15 males and 5 females, aged 50–71 years, with peripheral obstructive arterial disease at Fontaine stage III and requiring hospitalization, were randomized to two different iloprost treatment schedules: iloprost i.v. infusion, up to 2 ng/kg/minute for 6 hours/day for 28 days (Group A) or iloprost i.v. infusion, up to 1.5 ng/kg/minute, for 16 hours/day for 7 days (Group B). At baseline, after 7 days (end of treatment, Group B only) and after 28 days (end of study) the following measurements were done: blood pressure and heart rate, ankle/arm pressure index, first flow, peak flow, time to regression (by means of mercury strain-gauge plethysmography), stroke volume, cardiac output, ejection fraction (by means of 2D-echocardiography and echo-Doppler), exercise tolerance (by means of treadmill test), and rest pain (by means of visual analogue scale). Both treatment schedules resulted in significant improvement in plethysmographic parameters and exercise tolerance (both maximal and pain free) with concomitant reduction in rest pain. These effects were long lasting as evident by the results observed in Group B where the absolute data after 3 weeks of drug withdrawal were superimposable to those of Group A. On the contrary, only mild effects were evident on systemic hemodynamics, which tended to wane off as the infusion was stopped. From the results of this pilot study it is possible to conclude that treatment with iloprost at lower dosage (up to 1.5 ng/kg/minute) for 16 hour/day for 7 days, in patients at Fontaine stage III, seems to result in the same therapeutic benefits of the currently used schedule (up to 2 ng/kg/minute for 6 hour/day for 28 days). If confirmed by larger clinical experience, these data have clear implication in terms of patient comfort and cost containment.

Post-prandial endothelial dysfunction is ameliorated following weight loss in obese premenopausal women

SummaryBackgroundEndothelial dysfunction and postprandial hyperglycemia represent independent risk factors for cardiovascular diseases. Obesity is connected with endothelial impairments; however, it is unclear whether weight loss can modify endothelial function during the postprandial period. The aim of this study was to evaluate endothelial response (post-ischemic forearm blood flow, PIFBF) in a fasted state and following ingestion of 75g glucose before and after very low caloric diet (VLCD).Material/Methods40 obese premenopausal women (age 39.6±7.8 years, BMI 34.3±3.2 kg/m2) participated in 4-week very low caloric diet (VLCD, 800kcal/day). Before and after VLCD, the baseline blood flow and PIFBF were measured using a mercury strain gauge plethysmography in fasting state as well as 1 hour after ingestion of 75 g glucose.ResultsDietary intervention resulted in a 7% weight loss (p<0.05) and a decrease in insulin resistance index HOMA-IR (2.44±1.25 vs. 1.66±0.81, p<0.05). Before VLCD intervention, PIFBF following oral glucose challenge decreased by 8.2±9.1 ml/min/100 g tissue, while after weight loss identical stimulus increased PIFBF by 4.2±8.9 ml/min/100 g tissue (p<0.05). Plasma ICAM-1 and VCAM-1 decreased by 8% and 10%, respectively, throughout the study.ConclusionsPostprandial endothelial dysfunction is ameliorated following weight loss in obese women. This finding demonstrates the beneficial effects of weight reduction on atherosclerosis risk.

A diet enriched with mackerel (Scomber scombrus)–derived products improves the endothelial function in a senior population (Prevención de las Enfermedades Cardiovasculares: Estudio Santoña – PECES project)

Regular consumption of fish reduces cardiovascular risks. Here, we investigate if the consumption of products with mackerel (Scomber scombrus) with 8.82 g of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) content per 100 g of product improves parameters of endothelial function in a controlled population. Subjects maintained a 12-week diet with products with mackerel. The population consisted of 58 senior subjects (12 withdrawals, 25 women), aged 82.08 +/- 8.13 years (Group A). Twenty-three senior subjects (13 women) on a regular diet were used as the control group (Group B). Subjects of Group A received 57 portions throughout 12 weeks (four to five portions a week of products with a mean EPA + DHA content of 2.5 g a day). A continuous follow-up and a final evaluation were performed to determine the level of consumption. Plasma samples were stored at -70 degrees C for a biochemical study. Endothelial function was analysed by reactive hyperemia with a mercury strain gauge plethysmography with measurement of blood flow in the forearm, both baseline and at the end of the 12-week diet. Endothelium-dependent vasodilatation significantly increased in Group A subjects (P < 0.001). No changes were found in Group B. The subgroup analyses showed that improvements were produced in Group A subjects without cardiovascular disease (P < 0.001). Nitrites/nitrates and von Willebrand factor plasma concentrations were higher in participants after the 12-week diet. The consumption of mackerel meat products improves endothelium-dependent, flow-mediated vasodilatation in a senior population. This finding might explain some of the cardioprotective effects of fish consumption.

Venous surgery for the treatment of chronic venous insufficiency with respect to global venous haemodynamics and clinical symptoms

SummaryOur goal was to document changes in venous drainage function ΔV and venous refill times to and th achieved with venous surgery and compare them with preoperative measurements acquired using a variety of venous function tests. Preoperative measurements were performed with two pressure cuffs to predict postoperative outcome; they were compared with actual postoperative measurements made without a pressure cuff. In addition we also analyzed whether the postoperative improvement in venous haemodynamics was correlated with an improvement in clinical findings and symptoms. Patients, methods: 64 patients (14 men and 50 women) were enrolled into the study. Inclusion criteria were Doppler sonographic evidence of insufficiency of the saphenous veins and impaired venous haemodynamics, which form the medical indication for venous surgery. Before and after surgery a variety of diagnostic tests of venous function were carried out simultaneously with the patient in a seated position and performing dorsal extensions: mercury strain gauge plethysmography (MSGP) at the forefoot and calf, phlebodynamometry (PDM), light reflection rheography (LRR), digital photoplethysmography (DPPG) with Elcat measuring head and with Laumann Elcat measuring head, universal light reflection plethysmography (ULP). Results: All the examined methods are suitable for monitoring progress and evaluating therapeutic success after the selective surgical removal of insufficient vein segments. All examination methods showed that refill times t0 and th were significantly improved 6 weeks after venous surgery. The postoperative results of ΔV, t0 and th were most reliably predicted by MSGP (forefoot). ΔV, to and th values determined with MSGP at the calf differed significantly from those acquired with PDM, so MSGP (calf) should not be used for preoperative screening. Conclusions: A close correlation between improvement of clinical symptoms and improvement in venous haemodynamics was found. Selection of the suitable preoperative measurement method makes it possible to accurately predict postoperative outcome.

Near‐infrared spectroscopy provides an index of blood flow and vasoconstriction in calf skeletal muscle during lower body negative pressure

Near-infrared spectroscopy (NIRS) has been used previously for forearm blood flow estimation at rest and during exercise. In this study we applied NIRS to selectively monitor deep calf oxygenated haemoglobin (Hb) responses in order to estimate blood flow changes in the calf muscle during lower body negative pressure (LBNP). The purpose of this study was to test the hypothesis that changes in calf skeletal muscle oxygenated-Hb, after the removal of superficial tissue responses, were related to blood flow changes during orthostatic stress, and to determine the efficacy of using NIRS measurements as an index of vasoconstriction. Twenty-nine subjects participated in this study. All attempted a graded LBNP trial from baseline (0 mmHg) to -60 mmHg LBNP in 10 mmHg steps at 5-min intervals. Calf blood flow changes were estimated by oxygenated-Hb responses in relation to changes in mercury strain gauge plethysmography and muscle sympathetic nerve activity (MSNA). Calf selective deep oxygenated-Hb decreased continuously from -10 mmHg LBNP. Regression analysis showed that oxygenated-Hb was significantly related to declines in plethysmography evaluations of blood flow [oxygenated-Hb = (-1.57 +/- 0.26) + (1.86 +/- 0.49) plethysmography, r(2) = 0.87 +/- 0.09]. Changes in MSNA (total activity) were also inversely related to oxygenated-Hb (slope < 0, P = 0.037; r(2) = 0.52 +/- 0.15). These results suggest that changes in selective deep calf oxygenated-Hb can be utilized to estimate calf muscle blood flow changes that are most likely caused by vasoconstriction during graded LBNP.

Lower Leg Blood flow Responses to Vasodilatory and Vasoconstrictor Stimuli

Determination of vascular “health” generally centers on vasodilatory properties. Arguably, the “health” of the vasculature is affected by the interplay of both vasodilatory and vasoconstrictor controllers, which together contribute to physical performance. PURPOSE: To assess lower leg blood flow responses to a series of vascular stimuli, including arterial occlusion, dynamic exercise, and a cold pressor test. It was hypothesized that the magnitude of the vasodilatory and vasoconstrictor responses would be interrelated. METHODS: Measures of vascular function were examined in 12 individuals on two separate occasions [age=21±1 yrs] using mercury strain gauge plethysmography. Lower leg blood flow responses were assessed in the right leg, at rest, following 5 minutes of thigh occlusion at 240mmHg, immediately following 15 repetitions of plantar flexion at 60% of MVC, and following 1 minute of left foot submersion in ice water. RESULTS: The average blood flow responses for each condition were as follows: resting arterial inflow, 2.27±1.06; post-occlusion peak blood flow, 19.42 ±6.37; post-exercise blood flow, 27.37±14.95; and blood flow following the cold pressor test, 1.53±0.89 ml/100ml/min. The flow responses following plantar flexion were significantly higher then reactive hyperemia, which were significantly greater then blood flow at rest, which were significantly greater then the flow response following the cold pressor test. As expected, there were significant associations between peak post-occlusion blood flow and post exercise blood flow (r2=0.55). In addition, there were significant associations between the change in blood flow following the cold pressor test and peak post-occlusion blood flow (r2=0.25), and post exercise blood flow (r2=0.37). Finally, peak post-occlusion blood flow (r=0.48), post exercise blood flow (r=0.57), and the change in blood flow following the cold pressor test (r=−0.64) were significantly related to plantar flexion MVC. CONCLUSIONS: The magnitude of the vasodilatory and vasoconstrictor response is significantly related. Moreover, those with the greatest flow changes also have the greatest calf strength. These findings confirm the interplay between these vascular controllers, and may provide an even greater understanding of vascular fitness.

Biophysical characteristics of medical compression stockings

Summary Aim: Haemodynamic effectivity of 13 compression stockings in correlation with its physical characteristics. Patients, methods: In a prospective study, 42 patients in clinical stage C1–4 were examined with dynamic mercury strain gauge plethysmography to determine the effects of 13 different compression stockings in compression classes 2 and 3 (CEN) on venous haemodynamics. At the same time that venous function measurement was monitored, the pressure exerted by the compression stockings was measured under resting conditions and during standardized exercises by the patients. Results: Resting pressure measured while the patient was reclining corresponded to the in vitro textile data for the corresponding compression class in all of the stockings. The compression stockings improved venous refill times t0 and t1/2 to a statistically significant degree. The differences in the improvement in refill times t0 and t1/2 was found to depend on the quotient of maximum working pressure during movement over resting pressure (pW/pR) while standing (r = 0.90, p &lt; 0.01 ). The improvement of the expelled volume correlated with decrease of resting pressure from ankle to calf (r = 0.86, p &lt;0.01 ). Conclusion: Compression stockings that exert the same resting pressure at ankle level in reclining patients can still have different effects on venous haemodynamics. The haemodynamic effectivity of the various compression materials is determined above all by the degree of stiffness, which can be characterized in vivo as the ratio of maximum working pressure to resting pressure (pW/pR) while standing.

Differences in Vascular Reactivity Between Men and Women

The purpose of this study was to compare the gender and age-related differences in vascular reactivity in healthy men and women across a wide age range. Fifty-seven men and 61 women between 20 and 89 years of age, free of cardiovascular disease and risk factors, were categorized into younger (20-39 years), middle-aged (40-59 years), and older (60-89 years) age groups. Subjects were characterized on body weight and height, body mass index (BMI), and calf blood flow under resting, postocclusive reactive hyperemic (PORH), and maximal hyperemic conditions in the lower extremity with use of venous occlusion mercury strain-gauge plethysmography. Similar baseline characteristics were observed among age groups, whereas men had greater body weight (p<0.05), higher BMI values (p<0.05), and a trend toward higher ankle-brachial index (ABI) values (p=0.054) than women. While calf blood flow measurements were similar for men and women at rest and at maximal hyperemic conditions, women had a greater percentage change in calf blood flow from rest to PORH than men (p=0.046). After adjusting for body weight, BMI, and ABI, the percentage change in calf blood flow from rest to PORH was no longer significantly higher in the women (p>0.05). Furthermore, the percentage change in calf blood flow from rest to PORH was negatively related to body weight (r = -0.30, p<0.01) and to BMI (r = -0.26, p<0.01) in the men and women. No differences (p>0.05) in the calf blood flow measures were observed among the age groups. In a healthy cohort free of cardiovascular disease, increased BMI accounted for poorer vascular reactivity in men compared to women regardless of age.

A NEW CLINICAL METHOD FOR THE ASSESSMENT OF PENILE ENDOTHELIAL FUNCTION USING THE FLOW MEDIATED DILATION WITH PLETHYSMOGRAPHY TECHNIQUE

Penile endothelial function (EnF) is 1 of the major factors involved in the pathophysiology of erectile dysfunction. EnF assessment could offer crucial information on the etiology and degree of severity of cavernosal vascular pathology. In the present study we propose a new technique for the evaluation of penile EnF and test its applicability using strain gauge plethysmography. A total of 23 healthy subjects (13 younger and 10 older than 40 years) with no history of erectile dysfunction were studied. The flow mediated dilation technique was applied to the arm and penis in both age groups for the assessment of EnF. Baseline blood flow and the sequential flow recordings after rapid cessation of 5 minutes of ischemia were obtained in both organs. Baseline flow in the penis was significantly higher (approximately 3-fold) than that in the forearm and was not affected by age in either organ. Both measures of penile EnF, ie area under the flow-time curve (AUC) and maximal flow obtained after ischemia were significantly lower in the older group compared to the younger group (p <0.01 and p <0.02, respectively). Individual penile AUC and maximal flow were significantly correlated with age (r = 0.55, p <0.01 and r = 0.50, p <0.02, respectively). Finally a positive, significant correlation existed between penile and forearm AUC (p <0.05, r = 0.48). The implementation of the flow mediated dilation technique using mercury strain gauge plethysmography is simple and applicable for the assessment of penile EnF. Endothelial function parameters in the penis were found to correlate with those in the forearm, thus support for the validity of the technique is given. Further strength for the validity of this procedure in the penis comes from the comparison between the forearm and penis, and the relation to subject age.

Post-exercise Hypotension after Resistance Exercise and Diminished Sympathetic Vascular Responsiveness in Older Women

1348 The general view is that post-exercise hypotension (PEH) arises from a reduction in systemic vascular resistance. However, no hemodynamic data are available to support this hypothesis following resistance exercise (RE) in older women. PURPOSE: This study examined hemodynamic responses during and for 1-hour after two knee extension RE conditions (15-RM and 5-RM) in 16 young (mean age = 21 ± 2.3 yrs) and 16 older (mean age = 69 ± 2.3 yrs) women. METHODS: Hypotension was measure as the magnitude of blood pressure (BP) drop below baseline following single bouts of 5-RM and 15-RM RE. Continuous BP and ECG data were acquired at 200Hz, converted to tachograms, re-sampled at 4Hz, and smoothed using a low-pass digital filter with a cutoff frequency of 0.05 Hz. Heart rate and BP data are reported at rest, peak exercise, and throughout 1-hour of recovery. Heart rate variability data were derived from 5-minute segments at rest and after both RE conditions. Forearm vascular resistance (FVR) was derived using mercury strain gauge plethysmography, and reported at rest and every 3 to 5 minutes during recovery. ANOVA with repeated measures was used to examine the effects of test period, age, and exercise condition. RESULTS: ANOVA revealed a significant effect of test condition on BP that was modified by a test condition by age interaction. Older adults had a greater magnitude of PEH in systolic, diastolic and mean arterial pressure (MAP) following RE in comparison to the young group (e.g., max MAP PEH = −2.4 ± 2.0; −9.7 ± 1.5 mm Hg in young and older women, respectively). FVR following RE was also subject to a test condition by age interaction (p = 0.03), increasing above baseline in the young adults at all time periods in recovery, but changing little in older adults. The natural log of normalized low-frequency heart rate variability (lnLFnu) was subject to a main effect of test condition (p = 0.001), but did not differ between age groups. Pearson correlation revealed that lnLFnu was related to recovery of MAP (r = 0.66 and 0.79; p<0.001 in young and older women, respectively) and FVR (r = 0.93 and 0.95; p<0.001 in young and older women, respectively); however, the beta value was higher among young (MAP beta = 0.95, FVR beta = 13.1) in comparison to older women (MAP beta = 0.51, FVR beta = 9.8). CONCLUSIONS: Age group differences in PEH after RE, characterized by a greater drop in BP in older adults, may be attributed to smaller increases in vascular resistance. The similar behavior of lnLFnu across age groups, paired with age-related differences in the LFnu vs. MAP and FVR slopes is consistent with older adults having stiffer and less reactive blood vessels, possibly contributing to a greater magnitude of PEH in older women.

The effect of polyneuropathy on foot microcirculation in Type II diabetes.

The aim of this study was to investigate the influence of peripheral polyneuropathy (PNP) on skin microcirculation and foot swelling rate in the feet of patients with Type II (non-insulin-dependent) diabetes mellitus. 38 Type II diabetic patients, 24 with PNP (PNP+), 14 without PNP (PNP-), and 16 healthy control subjects were studied, first supine and subsequently sitting with the foot dependent for 50 mn. In patients with PNP, foot skin temperature was higher, (p<0.04) and capillary blood cell velocity (CBV, nailfold capillary microscopy), was lower compared to patients without PNP (222 vs 313 micro m/s respectively, p<0.03). Compared to the control subjects, the percentage reduction in skin blood flux, (LDF, laser-Doppler fluxmetry), after 10 min was higher in the PNP- and PNP+ patients (3% vs 18% and 26% respectively, p<0.02). These disturbances were most pronounced in PNP+ patients with a history of a foot ulcer. Foot swelling rate (mercury strain gauge plethysmography) in the first 10 min of dependency, was lower in patients with PNP+ compared to the control subjects (0.00165 vs 0.00286 ml.100 ml(-1)s respectively, p<0.01). In addition, we found a negative correlation (r=-0.41; p<0.01) between Valk-score (severity of PNP) and FSR. Type II diabetes PNP is associated with multiple abnormalities in the (skin) microcirculation of the foot, characterised by reduced capillary blood flow, an enhanced reduction in skin blood flux and impaired fluid filtration after sitting up. The most severe abnormalities were observed in patients with a history of foot ulceration.

A New Method for Lower Limb Volume Measurement — Laser Plethysmography: Comparison with Two Commonly Used Methods

Objective: (1) To assess agreement between laser plethysmography (LPG) and mercury strain-gauge plethysmography (MSGP) measurement of calf volume variation. (2) To assess agreement between LPG and water volumetry measurement of calf volume. Design: Pilot study to evaluate a method of measuring absolute lower leg volume and volume changes in volunteers; randomisation of the leg measured and of the order of measurement, evaluation of between-method correlation and limits of agreement. Setting: Hôpital Civil, Strasbourg. Participants: Seventeen healthy volunteers. Main outcome measures: Measurement of relative volume change by MSGP and LPG before and after venous occlusion by means of a thigh cuff inflated to 20 mmHg (zlV20) and 60 mmHg (/dV60); absolute volume of a 20 cm segment of lower limb measured by differential water plethysmography (two different volume water boots) and by LPG. Results: Comparison of LPG with MSGP led to fairly good correlation coefficients (r = 0.89 and r = 0.91 for δV20 and δV60, respectively) but also to an important dispersion of between-method differences (wide limits of agreement). There was a high degree of agreement between LPG and water volumetry: the correlation coefficient was 0.99 and limits of agreement were [− 6.7% 0.8%] but a significant bias was seen. Conclusions: Laser plethysmography is a new method for measurement of lower limb volume. When tested on inert material, very good accuracy and reproducibility were obtained. Comparison with water volumetry gave good agreement. Evaluation of reproducibility on healthy volunteers is required for complete validation of the device.

The Haemodynamic Efficacy of Six Different Compression Stockings from Compression Class 2 in Patients Suffering from Chronic Venous Insufficiency

Objective: To describe the efficacy of six different compression stockings from compression class 2 on venous haemodynamics in patients with chronic venous insufficiency (CVI). Design: An open, randomised, prospective study. Setting: University Department of Dermatology, Tübigen, Germany. Patients: Twenty-two patients (11 women, 11 men; mean age 55.1 years, SD 10.3 years) suffering from chronic venous insufficiency (CVI) at clinical stages C14EpAs, A14, Ap, PR. Interventions: The acute effect of six different compresion stockings from compression class 2 (CEN) on venous haemodynamics were measured using dynamic mercury strain gauge plethysmography. At the same time as venous function, the pressure exerted by the compression hosiery was determined under resting conditions and during exercise. Main outcome measures: Resting pressure exerted in the supine position was equivalent in all compression hosiery to the data defined in textile technology for compression class 2 (25–35 mmHg at the ankle). Compression hosiery produced a statistically significant improvement in venous refilling time t 0. The differing improvement in venous function could be explained by the quotient for maximum active pressure/resting pressure on standing (r = 0.98, p &lt;0.01). Conclusion: Compression stockings from the same compression class possess differing acute effects on venous haemodynamics. The efficacy of the various compression devices derives to an exceptional degree from the elasticity of the material, and can be characterised in vivo by the ratio between maximum pressure exerted during exercise and the resting pressure on standing.

Dynamic leg volume changes when sitting in a locked and free floating tilt oé ce chair

It is well established that prolonged sitting may lead to swelling of the lower extremities. However, activation of the vein pump system by repeated walking breaks or dynamic tiltable foot-rests have been shown to reduce foot and leg oedema. Some oé ce chairs incorporate tilt mechanisms facilitating movements of the body from the feet up. The present study was undertaken to establish whether a beneficial effect on the transcapillary fluid balance of the legs by enabling such mechanisms could be documented. An oé ce chair where the tilt mechanism could be locked or open was used for the study. The seat position and seat activity level was recorded by a transducer system developed for the study. Calf volume and calf muscle pump activity was detected by mercury strain gauge plethysmography. In the locked position there was a steady increase in volume of mean=1.2% (range=0.8–1.8%) for all participants in the 30-min study period. On the other hand, for all participants there was a decrease in calf volume (mean=0.7%, range=0.1–1.2%, p=0.008) when the tilt mechanism was open (30-min period), irrespective of what study period came first. The study showed that upward seat deflection was not associated with concomitant venous obstruction, since such obstruction was detected in less than 2% of the time period with more than 50% of maximal upward deflection. A locked seat mechanism does not prevent activation of the vein pump mechanism, but the study indicates that oé ce chairs that permit variation in seat angle per se stimulate movements of the leg. This, in turn, activates vein pumps and counteracts local oedema formation in seated working postures.

Peripheral microvascular parameters in the nephrotic syndrome

Peripheral edema, in combination with severe proteinuria and low serum albumin levels, is pathognomonic of the nephrotic syndrome, yet the exact mechanism of its formation is unknown. Two of the most important of the factors in Starling's forces controlling fluid filtration across the capillary have hitherto not been studied in nephrotic subjects. The hydrostatic capillary pressure at the finger nail-fold in actively nephrotic subjects and age and sex matched controls was studied, using direct puncture of the apex of the capillary under video microscopy, and a servonulling apparatus to give a direct measurement of capillary pressure. Capillary filtration capacity (CFC) at the calf was measured noninvasively by a modern derivative of the technique of mercury strain gauge plethysmography. Fifteen nephrotic subjects with a variety of underlying pathological lesions, and age matched controls were studied. Contrary to the assumption of the "overflow" hypothesis of edema formation, there was no evidence of capillary hypertension. The capillary pressure showed no difference between nephrotic subjects and controls: median (range) of 17.6 (12.0 to 24.2) compared with 17.3 (9.0 to 21.6) mm Hg, P = NS. CFC was significantly higher in nephrotic subjects than controls [5.23 (3.28 to 8.52) x 10(-3) versus 3.55 (2.43 to 5.28) x 10(-3) ml/min/100 g/mm Hg, P < 0.01]. An increase in CFC provides a potentially novel mechanism contributing at least in part to the formation of peripheral edema in the nephrotic syndrome.

Effects of Iloprost, Either Administered for 1 Week or 4 Weeks, on Systemic Hemodynamics, Peripheral Blood Flow, and Exercise Tolerance in Patients with Peripheral Occlusive Arterial Disease at Leriche-Fontaine Stage III

Twenty patients, 15 males and 5 females, aged 50–71 years, with peripheral obstructive arterial disease at Fontaine stage III and requiring hospitalization, were randomized to two different iloprost treatment schedules: iloprost i.v. infusion, up to 2 ng/kg/minute for 6 hours/day for 28 days (Group A) or iloprost i.v. infusion, up to 1.5 ng/kg/minute, for 16 hours/day for 7 days (Group B). At baseline, after 7 days (end of treatment, Group B only) and after 28 days (end of study) the following measurements were done: blood pressure and heart rate, ankle/arm pressure index, first flow, peak flow, time to regression (by means of mercury strain-gauge plethysmography), stroke volume, cardiac output, ejection fraction (by means of 2D-echocardiography and echo-Doppler), exercise tolerance (by means of treadmill test), and rest pain (by means of visual analogue scale). Both treatment schedules resulted in significant improvement in plethysmographic parameters and exercise tolerance (both maximal and pain free) with concomitant reduction in rest pain. These effects were long lasting as evident by the results observed in Group B where the absolute data after 3 weeks of drug withdrawal were superimposable to those of Group A. On the contrary, only mild effects were evident on systemic hemodynamics, which tended to wane off as the infusion was stopped. From the results of this pilot study it is possible to conclude that treatment with iloprost at lower dosage (up to 1.5 ng/kg/minute) for 16 hour/day for 7 days, in patients at Fontaine stage III, seems to result in the same therapeutic benefits of the currently used schedule (up to 2 ng/kg/minute for 6 hour/day for 28 days). If confirmed by larger clinical experience, these data have clear implication in terms of patient comfort and cost containment.

Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest.

Leg venous hemodynamics [venous distensibility index (VDI), arterial flow index (AFI), half-emptying time (T1/2)], and leg volumes (LV) were assessed by mercury strain-gauge plethysmography with venous occlusion and volometry, respectively, in seven men before, during, and after 42 days of 6 degrees head-down bed rest. Results showed a high increase in VDI up to day 26 of bed rest (+50% vs. control at day 26, P < 0.05), which tended to subside thereafter (+20% increase vs. control value at day 41, P < 0.05). VDI changes were associated with parallel changes in T1/2 (+54% vs. control at day 26 of bed rest, P < 0.05, and +25% vs. control at day 41, P < 0.05) and with a decrease in AFI (-49% at day 41 vs. P < 0.05). LV continuously decreased throughout bed rest (-13% vs. control at day 41, P < 0.05) but was correlated with VDI only during the first month of bed rest. These results show that during long-term 6 degrees head-down bed rest alterations of leg venous compliance are associated with impairment of venous emptying capacities and arterial flow. Changes in skeletal muscle mass and fluid shifts may account for venous changes during the first month of bed rest but, subsequently, other physiological factors, to be determined, may also be involved in leg venous hemodynamic alterations.

MYOCARDIAL HYPERTROPHY IS THE PRIMARY CARDIOVASCULAR ADAPTATION TO ENDURANCE TRAINING IN SEDENTARY MEN 804

In sedentary individuals at sea level, maximal aerobic power is determined primarily by the ability to deliver and accommodate blood flow to skeletal muscle. In order to determine the relative importance of central and/or peripheral adaptations in the cardiovascular system in response to endurance training, we measured cardiac mass (magnetic resonance imaging, MRI) and maximal vascular conductance (Gmax) before and after 3 months of training(running/cycling/swimming, 3-4 days/wk) in 5 sedentary healthy men (27± 6yrs). Maximal leg blood flow was measured by mercury strain-gauge plethysmography during reactive hyperemia produced by ischemic exercise to fatigue. Gmax in the lower leg was calculated from blood flow and mean arterial cuff pressure from the branchial artery. Results: VO2max increased by 12% (43 ± 4.6, to 48 ± 6.5 ml/kg/min; p<0.004), while both resting (95 ± 10, to 78 ± 10) and submaximal (171 ± 15, to 146 ± 14) heart rates decreased 16% and 15% respectively. There was no change in body weight (78 ± 4.8, to 77± 4.5 kg; p=0.15). LV mass increased by 7% (204 ± 29, to 219± 13g; p<0.005), with no increase in Gmax [0.396 ±.089, to 0.394 ± 0.076 (ml/min/100g) (mmHg)-1; p=0.07].Conclusion: Cardiac hypertrophy appears to be the initial primary mechanism for increasing VO2max and oxygen delivery in healthy sedentary subjects following three months of moderate endurance training.