Evaluation of forearm vascular resistance during orthostatic stress: Velocity is proportional to flow and size doesn't matter.

BACKGROUND: The upright posture imposes a significant challenge to blood pressure regulation that is compensated through baroreflex-mediated increases in heart rate and vascular resistance. Orthostatic cardiac responses are easily inferred from heart rate, but vascular resistance responses are harder to elucidate. One approach is to determine vascular resistance as arterial pressure/blood flow, where blood flow is inferred from ultrasound-based measurements of brachial blood velocity. This relies on the as yet unvalidated assumption that brachial artery diameter does not change during orthostatic stress, and so velocity is proportional to flow. It is also unknown whether the orthostatic vascular resistance response is related to initial blood vessel diameter. METHODS: We determined beat-to-beat heart rate (ECG), blood pressure (Portapres) and vascular resistance (Doppler ultrasound) during a combined orthostatic stress test (head-upright tilting and lower body negative pressure) continued until presyncope. Participants were 16 men (aged 38.4±2.3 years) who lived permanently at high altitude (4450m). RESULTS: The supine brachial diameter ranged from 2.9-5.6mm. Brachial diameter did not change during orthostatic stress (supine: 4.19±0.2mm; tilt: 4.20±0.2mm; -20mmHg lower body negative pressure: 4.19±0.2mm, p = 0.811). There was no significant correlation between supine brachial artery diameter and the maximum vascular resistance response (r = 0.323; p = 0.29). Forearm vascular resistance responses evaluated using brachial arterial flow and velocity were strongly correlated (r = 0.989, p<0.00001) and demonstrated high equivalency with minimal bias (-6.34±24.4%). DISCUSSION: During severe orthostatic stress the diameter of the brachial artery remains constant, supporting use of brachial velocity for accurate continuous non-invasive orthostatic vascular resistance responses. The magnitude of the orthostatic forearm vascular resistance response was unrelated to the baseline brachial arterial diameter, suggesting that upstream vessel size does not matter in the ability to mount a vasoconstrictor response to orthostasis.

Middle cerebral artery blood flows by combining TCD velocities and MRA diameters: in vitro and in vivo validations.

Non-invasive transcranial Doppler (TCD) is widely used for blood velocity (BV, cm/sec) measurements in the human middle cerebral artery (MCA). MCABV measurements are accepted as linear with MCA blood flow (MCABF). Magnetic resonance angiography (MRA) provides measurements of MCA lumen diameters that can be combined with TCD MCABV to calculate MCABF (mL/min). We tested the precision and accuracy of this method against a flow phantom and in vivo proximal internal carotid artery blood flow (ICABF). In vitro precision (repeated measures) and accuracy (vs. time collection) gave correlations coefficients of 0.97 and 0.98, respectively (both p < 0.05). In vivo precision (repeated measures) and accuracy (vs. ICABF) gave correlation coefficients of 0.90 (left and right), 0.94 (left) and 0.93 (right) (all p < 0.05). Bilateral MCABF in 35 adults were similar (left, 168 ± 72 mL/min; right, 180 ± 69 mL/min; p > 0.05). Results suggest that blood velocity by TCD and lumen diameter by MRA can be combined to estimate absolute values of MCABF.

Middle cerebral artery resistivity and pulsatility indices in systemic lupus erythematosus: evidence for hyperperfusion.

BACKGROUND AND PURPOSE: Systemic lupus erythematosus (SLE) is associated with significant cerebrovascular and neuropsychiatric disease for which multiple pathogeneses have been proposed. Although global cerebral hypoperfusion has been proposed, there are limited data about intracerebral arterial hemodynamics. Transcranial Doppler (TCD) allows portable, high temporal and spatial resolution, noninvasive blood velocity measurements in the middle cerebral arteries, and calculations of standard resistivity (RI) and pulsatility (PI) indices. RI and PI correlate with cerebral hemispheric arteriolar tone, blood flow resistances, and impedances. Accordingly, we hypothesized that there would be significant differences (p < 0.05) in RI and PI between SLE patients and healthy, age and gender matched controls. METHODS: TCD was used to measure RI and PI bilaterally on 34 stable SLE patients (35 ± 11 years) and 15 control subjects (34 ± 10 years). Patients and controls had similar, normal blood pressures and were examined in the supine position during normal, resting respiration. RI and PI were determined by a blinded, experienced observer. RESULTS: There were no significant differences in RI and PI bilaterally within each cohort. However, SLE patients had significantly lower average RI and PI values compared with controls: 0.45 ± 0.10 versus 0.52 ± 0.05 (p < 0.05); and 0.65 ± 0.19 versus 0.77 ± 0.12, (p < 0.05); respectively. CONCLUSIONS: These preliminary data suggest that RI and PI values in the human middle cerebral artery are significantly lower in SLE compared with controls. These indices indicate that middle cerebral arterial resistances and impedances are decreased in SLE. Under normotensive conditions, the results are consistent with hyperperfusion in SLE with increased arteriolar dilation and increased cerebral blood flow.

Noninvasive transthoracic and transesophageal Doppler echocardiographic measurements of human coronary blood flow velocity: In vitro flow phantom validation.

Coronary angiography is limited in assessing the hemodynamic significance of a coronary lesion or the state of the coronary microcirculation. Noninvasive transthoracic (TTE) and transesophageal (TEE) Doppler echocardiography have been used to measure coronary blood flow velocity and coronary flow reserve and thus the physiology of the coronary vasculature (normal, stable or unstable lesions). A fundamental, in vitro validation of these methods with a tissue and blood mimicking flow phantom has not been reported. Accordingly, Bland-Altman 95% confidence levels for precision (repeated measures) and accuracy (comparison with time collection) were determined for both TTE and TEE measurements of simulated coronary diastolic blood velocities in 2 mm and 4 mm vessels at the normal in vivo depths of 40 mm and 60 mm. The Doppler angle was set at 45 degrees and flow velocities were varied within a normal in vivo range of 0- 150 cm/s. Confidence levels for precisions and accuracies were similar between TTE and TEE and ranged from ± 6 cm/s to ± 13 cm/s or approximately 10-15% over the range of the measured velocities. These in vitro results in a controlled flow phantom suggest that technically adequate TTE and TEE can be used to reliably measure epicardial coronary conduit artery blood flow velocities.

Arterial distensibility in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease that is atherogenic. Decreased arterial distensibility (AD) is a risk factor for cardiovascular disease, and this precursor may be associated with SLE. Accordingly, we tested the hypothesis that patients with SLE will have significantly (p < 0.05) decreased AD when compared to normal, healthy age, and gender matched controls. Noninvasive, high resolution ultrasound was performed on 30 patients with chronic SLE and 16 age and gender matched controls. All were female. Maximum systolic and minimum diastolic diameters (mm) and intima-media thickness (IMT, mm) in the right common carotid artery were measured from M-mode images. In vitro arterial models were used for quality control. With a single, blinded observer, the 95% confidence levels for accuracy and precision for noninvasive systolic and diastolic tonometric arm blood pressures (SBP, DBP) and carotid sonographic diameters were approximately 5 mmHg and approximately 0.10 mm, respectively. Derived measurements for strain (%), stiffness (units), and AD (units) were determined by published arterial mechanical models and algorithms. Results (mean/standard deviation) were as follows: (patients/controls; # =p<0.05) Age 39/11, 35/11 years; SBP 130/20, 117/8# mmHg; DBP 82/11, 74/9# mmHg; strain 11/4, 11/4 %); stiffness 19/10, 17/11 units; IMT 0.44/0.08, 0.41/0.06 mm; AD 3.10/1.49, 3.30/1.63 units. There were no statistically significant differences (p<0.05) in measurements of AD and IMT in the common carotid artery between relatively young SLE patients and well matched controls.

Doppler ultrasound determination of the distribution of human cardiac output: effects of age and physical stresses.

Due to its high spatial, temporal, and dynamic resolution, noninvasive Doppler ultrasound can be used to determine the distribution of phasic cardiac output in humans. The effects of ageing and various common physical stresses on combined human major central and regional blood flows have not been reported. We tested the hypothesis that there are no significant age-related differences in steady-state human central and regional hemodynamics during leg exercise, hypoxia, eating, and standing. We used noninvasive, image-guided Doppler flowmetry (approximately 7% linearity, approximately 11% accuracy) to measure absolute values and percent changes (%C) in phasic blood flows in the following major arteries: ascending aorta (CO, cardiac output), common carotid (CQ, brain), subclavian (SQ, arm), renal (RQ, kidney), superior mesenteric (MQ, gut), and common femoral (FQ, leg). Mean arm cuff blood pressure (BP), heart rate (HR), stroke volume (SV), and total peripheral resistance (PR) were also determined. We studied 16 young (Y, 24/3 years, 8 males) and 16 elderly (E, 73/2 years, 7 males) healthy, lean adults during separate experiments of: 50% submaximal leg exercise; 12% oxygen breathing; ~700 calorie meal; and 70 degrees upright tilt. Exercise results (X/SD) are given as Y(%C) then E(%C) where (+) represents p<0.05 vs resting, fasting control: HR: 78/8+,66/7+; BP: 6/5,8/6; SV: - 15/5+,21/4+; CO: 96/11+,87/9+; PR: -83/13+,- 76/10+; CQ: 16/8+,14/6+; SQ: -6/8,-12/8; MQ: -21/11+,-15/11; RQ: -14/8/-12/7; FQ: 919/88+,898/74 Importantly, there were no significant (p<0.05) age-related differences in the percentage changes in any of these hemodynamic variables. Similar results were found during hypoxia, eating, and standing. We conclude that although physical stresses significantly (p<0.05) affects various central and regional hemodynamics, there are no significant age-related differences in these variables between healthy, successfully aged, 20 and 70 year old cohorts. These data suggest that given an appropriate genetic template and behavior free of significant trauma and disease states, cardiovascular control mechanisms and the distributions of cardiac output during common, daily, physical stresses are maintained with age through 70 years of life.

Cardiac output measurements in congenital heart disease: validation of a simple, portable Doppler method.

Noninvasive Doppler cardiac output measurements are clinical standards in adults and children. Presently, these standard Doppler methods generally require relatively expensive and large imaging equipment with complex signal-processing techniques. Thus, universal access to these important measurements has been limited. Simple, portable Doppler methods have been validated previously and applied to infants and children without cardiac disease. Nevertheless, these specific, inexpensive techniques have not been validated in children with complex congenital heart disease. Accordingly, we compared a noninvasive, suprasternal, non-image-guided, pulsed Doppler cardiac output with standard invasive Fick cardiac outputs in 20 patients (age range, 1 month to 15 years) with congenital heart disease. Doppler cardiac output was displayed by multiplying the mean velocity with an operator-selected angiographic or echographic estimate of the aortic diameter. The values from linear regression analysis were r = 0.96; Doppler cardiac output = 0.98 x Fick cardiac output - 0.08 L/min (range, 0.55-3.10 L/min). The 95% confidence limits were less than 35% of the mean of Doppler and Fick cardiac outputs across the range of measurements. We conclude that relatively linear and accurate measurements of cardiac output can be made by this simple, inexpensive, portable method in selected infants and children with various forms of congenital heart disease.

Human middle cerebral artery blood velocity during sexual intercourse.

Although the augmentation of central hemodynamics during human sexual intercourse is well established, dynamic changes in human regional cerebral blood flow have not been reported. Noninvasive transcranial Doppler ultrasonography has been well validated and allows direct, continuous measurement of phasic blood velocity in the human middle cerebral artery (a linear index of regional cerebral blood flow). The middle cerebral artery supplies the premotor and primary sensorimotor cortical regions for the arms, upper and lower trunk, and head. Blood velocities in this vessel have been shown to increase significantly with sensory stimuli and physical stresses. Accordingly, we tested the hypothesis that human sexual intercourse increases middle cerebral artery blood velocity. We used noninvasive, transcranial Doppler ultrasonography (95% confidence limits for precision +/- 7%) to measure blood velocity in the left middle cerebral artery of 10 male and 10 female, sexually acquainted, healthy adults (age range, 23 to 47 years; mean, 30 years). To eliminate signal artifacts and allow complete freedom of motion, a modified low profile, temporal fossa transducer was secured by minimal unobtrusive forehead strapping. Continuous measurements of phasic blood velocity and heart rate were made in a private bedroom setting during rest (control), preexcitement, excitation, prepenetration, penetration, preorgasm, orgasm, and resolution with the untethered instrumented subject in the supine missionary position. Heart rate and blood velocity responses were similar in both sexes. During orgasm, the maximal heart rate increased significantly (P < 0.05): 49 +/- 44% in women, 65 +/- 32% in men, and 58 +/- 38% combined from a combined resting value of 77 +/- 11 standard deviations SD beats per minute. Importantly, blood velocity in the middle cerebral artery of the 20 subjects remained unchanged (P > 0.10) from a resting value of 56 +/- 15 cm/s. In conclusion, in both sexes, human middle cerebral artery blood velocity, a linear index of human regional cerebral blood flow, does not increase significantly (P > 0.10) during human sexual intercourse.

Arterial oxygen saturation for prediction of acute mountain sickness.

BACKGROUND: Acute mountain sickness (AMS) is a usually self-limiting syndrome encompassing headache, nausea and dizziness. AMS is seen in those that go from low to high altitudes too quickly, without allowing sufficient time to acclimatize. At present, susceptibility to AMS cannot be predicted. One feature of AMS noted in some studies is impaired gas exchange. If impaired gas exchange presages AMS then those individuals with exaggerated hypoxemia at high altitude may be more likely to develop AMS. If true, then monitoring of arterial oxygen saturation (SaO2%) may differentiate AMS-resistant individuals from those with impending AMS. METHODS: To test this hypothesis, we measured SaO2% and AMS symptom scores in 102 healthy asymptomatic climbers at 4200 m on Denali (Mt. McKinley) prior to their further ascent toward the summit at 6194 m, and on their return from higher altitudes to 4200 m. RESULTS: The results show that exaggerated hypoxemia in asymptomatic climbers prior to further ascent correlates with subsequent AMS (r = -0.48, p < 0.001). Criteria are presented for identification of 80-100% of those climbers who later become ill with AMS. CONCLUSION: We conclude that resting arterial hypoxemia is related to later development of clinical AMS, and can exclude the occurrence and caution those at risk for development of subsequent AMS. Likely mechanisms are hypoventilation relative to normally acclimatizing individuals and/or abnormalities of gas exchange. Thus, non-invasive oximetry provides a simple, specific indicator of inadequate acclimatization to high altitudes and impending AMS.

Temporal inhomogeneity in brachial artery blood flow during forearm exercise.

The purpose of this study was to measure the influences of muscle contraction and exercise intensity on brachial artery blood flow during incremental forearm wrist flexion exercise to fatigue. Twelve subjects performed incremental forearm exercise (increments of 0.1 W every 5 min) with their nondominant arms. Doppler waveforms and two-dimensional images of the brachial artery were recorded during the last 2 min of each stage. Exercise intensities were expressed as a percent of the maximal workload achieved (%WLmax). Blood flow was calculated during each of the concentric (CP), eccentric (EP), and recovery phases (RP) of the contraction cycle. Blood flow during the CP of the contraction did not increase above resting values (25.0 +/- 10.5 mL.min-1) at any intensity (100%WLmax = 21.6 +/- 6.5 mL.min-1). Conversely, blood flow during the EP and RP increased from 25.6 +/- 3.0 to 169.1 +/- 12.8 (P < 0.05), and from 24.7 +/- 3.1 to 137.9 +/- 19.5 mL.min-1 (P < 0.05), respectively from rest to maximal exercise. Time averaged blood flow increased linearly from rest to maximal exercise (75.3 +/- 26.3 to 334.6 +/- 141.6 mL.min-1, P < 0.05). Thus, a significant impairment in blood flow occurs with concentric contractions during forearm dynamic exercise. The implications of a temporal disparity in blood flow to oxygen delivery and skeletal metabolism during exercise are discussed.

Central vascular flow patterns in the alligator Alligator mississipiensis.

Many different flow patterns have been described through the central circulation of crocodilian reptiles. We tested the hypothesis that the vagus nerve stimulation promotes right-to-left (R-L) shunting in the alligator. Flow patterns were investigated before and during stimulation of the intact left vagus nerve using three methods. 1) Atrial and aortic PO2 were measured simultaneously and continuously by gas probes. 2) Atrial outflows were tracked with a blood tracer (helium). 3) Flows were assessed with echocardiography. Four different flow patterns were observed before vagal stimulation: left ventricular (LV) blood flowed into both the right (RAo) and left (LAo) aortas, whereas right ventricular (RV) blood flowed only into the LAo; both aortas received a mixture of LV and RV blood; only LV blood perfused both aortas; and RV blood flowed into both aortas, but LV blood flowed only into the RAo. During vagal stimulation, both aortas received a mixture of LV and RV blood in half of the animals, and in the other half, both aortas received RV blood, but LV blood flowed only into the RAo. Doppler and contrast echocardiography demonstrated swirling flow in the foramen of Panizza and the base of the LAo during systole. These data indicate that vagal stimulation either maintains or produces R-L shunting, flow patterns are variable, and blood can swirl in the foramen of Panizza and LAo base.

Hemodynamic effects of nasal and face mask continuous positive airway pressure.

Studies of the hemodynamic effects of nasal continuous positive airway pressure (n-CPAP) in normal subjects have had conflicting results. The largest study (n = 19) found no effect of up to 15 cm H2O on heart rate (HR), cardiac stroke volume (SV), or cardiac index. We hypothesized that n-CPAP, by increasing intrathoracic pressure, should decrease SV and cardiac output (CO) in a dose-dependent fashion in normal subjects. We also hypothesized that mouth position, i.e., open or closed, could affect intrathoracic pressure and thus SV and CO. Six normal subjects were tested with four levels of CPAP (5, 10, 15, and 20 cm H2O) under three mask conditions-face mask and nasal mask with the mouth open (mo) or with the mouth closed (mc). Noninvasive pulsed Doppler measurements of SV and HR were made under each condition. N-CPAP (mc) and face mask CPAP (f-CPAP) resulted in significant dose-dependent decreases of SV-24 +/- 5 ml (21%) and 33 +/- 5 ml (28%), respectively--from baseline to 20 cm H2O (p < 0.05). HR were unchanged and CO significantly decreased with n-CPAP(mc) and with f-CPAP, 1.6 +/- 0.38 L/min (23%) and 2.29 +/- 0.54 L/min (31%), respectively, from baseline to 20 cm H2O (p < 0.05). Esophageal pressure measurements verified increasing intrathoracic pressure with increasing levels of f-CPAP and n-CPAP (mc) but not with n-CPAP (mo). In conclusion, n-CPAP (mc) and f-CPAP resulted in significant and similar dose-dependent decreases in SV and CO.

Hemodynamic comparison of microsurgical repairs for large arterial defects.

Twenty-eight femoral arteries in 14 rats were used to compare transverse closures and end-to-end anastomoses in blood vessels approximately 1 mm in diameter. The transverse closures were applied to arteriectomies created by excising one-half the circumference of the vessel over a length of 1 mm. The end-to-end anastomoses were performed after resecting a 1-mm segment. Recordings were made of pre- and postrepair flow velocity and three-point diameter measurements every 5 minutes using a 20-MHz pulsed Doppler velocimeter and digimatic caliper. Maximum reductions in flow velocity were 18% and 31% for the transverse repair and end-to-end anastomosis, respectively. Otherwise, intergroup comparisons of the postrepair normalization of both flow velocity and vessel diameter showed few significant differences (P < 0.05). We conclude that arterial defects involving no more than half the diameter of the vessel can be effectively repaired in significantly less time using the transverse closure.

Effects of prolonged head-down bed rest on physiological responses to moderate hypoxia.

To determine the effects of hypoxia on physiological responses to simulated zero-gravity, cardiopulmonary and fluid balance measurements were made in 6 subjects (acclimatized to 5,400 ft) before and during 5 degrees head-down bed rest (HDBR) over 8 d at 10,678 ft and a second time at this altitude as controls (CON). The VO2max increased by 9% after CON, but fell 3% after HDBR (p < 0.05). This reduction in work capacity during HDBR could be accounted for by inactivity. The heart rate response to a head-up tilt was greatly enhanced following HDBR, while mean blood pressure was lower. No significant negative impact of HDBR was noted on the ability to acclimatize to hypoxia in terms of pulmonary mechanics, gas exchange, circulatory or mental function measurements. No evidence of pulmonary interstitial edema or congestion was noted during HDBR at the lower PIO2 and blood rheology properties were not negatively altered. Symptoms of altitude illness were more prevalent, but not marked, during HDBR and arterial blood gases and oxygenation were not seriously effected by simulated microgravity. Declines in base excess with altitude were similar in both conditions. The study demonstrated a minimal effect of HDBR on the ability to adjust to this level of hypoxia.

Hemodynamic comparison of microsurgical closures for longitudinal arteriotomies.

Twenty-four femoral arteries in 12 rats were used to compare longitudinal and transverse closures in blood vessels approximately 1 mm in diameter. The closure techniques were applied to a simple longitudinal slit, 1 mm long, and to a longitudinal defect, 0.5 mm wide and 1 mm long. Comparisons were made of the change in pre- and postrepair flow velocities, recorded every 5 min using a 20-MHz pulsed Doppler velocimeter. Maximum reductions in flow velocity (linearly related to volume flow) were 10% and 29% for the longitudinal and transverse repairs, respectively, when applied to the longitudinal slit, and 65% and 19%, respectively, when applied to the larger arteriotomy. An analysis of variance indicates that the differences in the normalization of flow velocities during the immediate postrepair period are significant (P < 0.05). We conclude that optimal flow normalization is achieved by applying the longitudinal repair to the simple slit and the transverse repair to the larger arteriotomy.

The effect of vasodilators on pulmonary hemodynamics in high altitude pulmonary edema: a comparison.

High altitude pulmonary edema is characterized hemodynamically by a markedly restricted pulmonary vascular bed. Pulmonary vascular resistance is six to eight times higher than control values at altitude, and mean pulmonary pressure is generally elevated two to four-fold over control values. We wished to compare the effect of various vasodilators on the hemodynamics of HAPE, both to gauge their potential effectiveness in treatment of HAPE, and also to gain clues as to the mechanism of the altered pulmonary circulation. In a series of field experiments using a total of 16 subjects with HAPE and 10 well controls, we measured pulmonary hemodynamics by non-invasive Doppler echocardiography. The per cent reduction in pulmonary vascular resistance and mean pulmonary artery pressure, respectively, were 46 and 33 for oxygen, 30 and 29 for nifedipine, 29 and 25 with hydralazine, 57 and 42 with phentolamine, and 72 and 52 when oxygen and phentolamine were combined. All the vasodilators improved gas exchange, suggesting a link between edema formation and pulmonary vasoconstriction. A number of vasodilators may be useful in the treatment of HAPE; the superiority of an alpha adrenergic blocker may implicate the sympathetic nervous system in the pathophysiology of high altitude pulmonary edema.

Internal carotid flow velocity with exercise before and after acclimatization to 4,300 m.

Cerebral blood flow and O2 delivery during exercise are important for well-being at altitude but have not been studied. We expected flow to increase on arrival at altitude and then to fall as O2 saturation and hemoglobin increased, thereby maintaining cerebral O2 delivery. We used Doppler ultrasound to measure internal carotid artery flow velocity at sea level and on Pikes Peak, CO (4,300 m). In an initial study (1987, n = 7 men) done to determine the effect of brief (5-min) exercises of increasing intensity, we found at sea level that velocity [24.8 +/- 1.4 (SE) cm/s rest] increased by 15 +/- 7, 30 +/- 6, and 22 +/- 8% for cycle exercises at 33, 71, and 96% of maximal O2 uptake, respectively. During acute hypobaric hypoxia in a decompression chamber (inspired PO2 = 83 Torr), velocity (23.2 +/- 1.4 cm/s rest) increased by 33 +/- 6, 20 +/- 5, and 17 +/- 9% for exercises at 45, 72, and 98% of maximal O2 uptake, respectively. After 18 days on Pikes Peak (inspired PO2 = 87 Torr), velocity (26.6 +/- 1.5 cm/s rest) did not increase with exercise. A subsequent study (1988, n = 7 men) of the effect of prolonged exercise (45 min at approximately 100 W) found at sea level that velocity (24.8 +/- 1.7 cm/s rest) increased by 22 +/- 6, 13 +/- 5, 17 +/- 4, and 12 +/- 3% at 5, 15, 30, and 45 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular hemodynamics during exercise recovery.

The directional response of human left ventricular stroke volume during exercise recovery is unclear. Stroke volume has been reported to increase and decrease over exercise values during early recovery. The confounding variable may be posture. With the use of pulsed Doppler ultrasound, we tested the hypothesis that there is a significant difference between seated and supine stroke index (SI) during passive recovery from seated ergometer exercise. Thirteen subjects aged 26 +/- 2 yr performed two seated cycle ergometer exercise tests to 70% of predicted maximum heart rate (HR). Recovery was supine on one test and seated on the other. Cardiac index (CI), HR, and SI were calculated during rest, exercise, and 10 min of recovery. At rest, SI and CI were significantly (P less than 0.01) less and HR significantly (P less than 0.01) greater when the subjects were seated than when they were supine. At the last exercise work load, no significant differences were found in any measured variable between tests. During recovery, supine SI was maximal 180 s postexercise (99 +/- 14 ml/m2) and exceeded (P less than 0.01) resting supine (81 +/- 14 ml/m2) and peak exercise (77 +/- 14 ml/m2) SI by 22 and 29%, respectively. Seated SI was constant at peak exercise levels for 2 min. Seated and supine recovery CI never exceeded exercise values. Systolic and diastolic blood pressure recovery curves were similar in the two postures. We conclude that posture significantly affects SI during recovery from submaximal seated exercise. These results have implications for choice of recovery posture after stress testing in cardiac patients where it is desirable to minimize ventricular loading.

Effects of exercise training on common femoral artery blood flow in patients with intermittent claudication.

Exercise training is a commonly used rehabilitative therapy for patients with intermittent claudication (IC). However, it is not known whether blood flow through the major conduit vessel of the leg, the common femoral artery (CFA), increases with exercise training. We tested the hypothesis that peak CFA blood flow will increase with a supervised, lengthy, and individualized exercise training program. Subjects were 10 IC patients (eight men, two women) with a mean age of 61 +/- 7 (mean +/- SD) years who had either aortoiliac (n = 7) or femoropopliteal (n = 3) stenosis. Using noninvasive Doppler flowmetry, we measured CFA blood flow and ankle pressure at rest and after a maximum symptom-limited graded treadmill test before (T1) and after 3 (T2) and 5 (T3) months of exercise training. Variables were measured in the supine and upright postures at rest and during recovery. Total walking distance and claudication distance on the treadmill were determined for T1, T2, and T3. After training, CFA blood flow and ankle pressure were not significantly higher at rest or at 1 minute after exercise compared with pretraining despite significant increases in claudication and total walking distances. The rate of CFA blood flow recovery was slower at T3, suggesting the accrual of a larger metabolic debt during exercise due to more work performed. We conclude that changes in CFA blood flow are not responsible for measured changes in performance with exercise training in IC patients.