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Biomedical subjects

Kevin McCully

Publications and source records attributed to Kevin McCully.

6 recordsLinked to original sources
PubMed2006

Doppler ultrasound assessment of posterior tibial artery size in humans.

PURPOSE: The difference between structural remodeling and changes in tone of peripheral arteries in the lower extremities has not been evaluated. The purpose of this study was to (1) evaluate the day-to-day reproducibility and interobserver reliability (IOR) of posterior tibial artery (PTA) diameter measurements and (2) evaluate the effect of posture on PTA diameter at rest (Drest), during 10 minutes of proximal cuff occlusion (Dmin), and after the release of cuff occlusion (Dmax), as well as range (Dmax - Dmin) and constriction [(Dmax - Drest)/(Dmax - Dmin) x 100] in vivo. METHODS: We used B-mode sonography to image the PTA during each condition. RESULTS: Day-to-day reliability was good for Drest (intraclass correlation coefficient [ICC] 0.95; mean difference 4.2%), Dmin (ICC 0.93; mean difference 5.4%), and Dmax (ICC 0.99; mean difference 2.2%). The coefficient of repeatability for IOR was 70.5 microm, with a mean interobserver error of 4.7 microm. The seated position decreased Drest (2.6 +/- 0.2 to 2.4 +/- 0.3 mm; p = 0.002), increased Dmin (2.1 +/- 0.2 to 2.4 +/- 0.2 mm; p = 0.001), and decreased Dmax (3.1 +/- 0.4 to 2.8 +/- 0.3 mm; p < 0.001) compared with the supine position. The seated position also decreased arterial range (Dmax - Dmin) from 0.9 +/- 0.2 to 0.5 +/- 0.1 mm (p = 0.003) and increased basal arterial constriction from 57 +/- 19% to 105 +/- 27% (p = 0.007). CONCLUSIONS: The system employed for measuring PTA diameter yields unbiased and consistent estimates. Furthermore, lower extremity arterial constriction and range change with posture in a manner consistent with known changes in autonomic activity.

Adult↗
PubMed2006

Upper vs lower extremity arterial function after spinal cord injury.

BACKGROUND/OBJECTIVE: The purpose of the study was to determine whether arterial diameter, flow-mediated dilatation (FMD), and arterial range are affected by spinal cord injury (SCI). We assessed arm (radial) and leg (posterior-tibial) arteries that are comparable in size and function to determine whether (a) arterial function is reduced in individuals with SCI vs nondisabled subjects and (b) decrements to SCI arterial function are greater in the legs vs arms. PARTICIPANTS: Eighteen men with chronic (9.8 +/- 6.3 years) SCI (T2 to T11; American Spinal Injury Association A) and 13 nondisabled subjects matched for age (33.1 +/- 4.8 vs 29.8 +/- 8.2 years old, respectively), height, and weight (BMI = 25.3 +/- 5.8 vs 26.6 +/- 5.5 kg/m2, respectively). METHODS: Radial and posterior tibial artery B-mode ultrasound images were continuously captured to measure resting diameter, occluded diameter, and postischemic diameters. Hierarchical linear modeling accounted for the nested experimental design. RESULTS: Individuals with SCI have lower systemic (arm + leg) FMD than nondisabled subjects (9.3% vs 12.3%, respectively; P= 0.035), primarily because of reduced leg FMD (11.5 +/- 3.1% vs 7.0 +/- 2.8% for SCI arms vs legs, respectively; P = 0.010). Persons with SCI also had lower arterial range than nondisabled subjects (0.79 vs 1.00 mm, respectively; P = 0.043), primarily because of the legs (0.81 +/- 0.09 vs 0.56 +/- 0.11 mm for SCI arms vs legs, respectively; P = 0.030). CONCLUSION: Leg arterial function seems to deteriorate at greater rates compared to the arms for individuals with SCI. Interventions to improve cardiovascular health should include measurements taken in the legs.

Adult↗
PubMed2004

Relationship between blood velocity and conduit artery diameter and the effects of smoking on vascular responsiveness.

Transient changes in arterial diameter in response to transient ischemia-induced changes in arterial blood velocity have been used as an index of vascular health. The purpose of this study was to determine the relationship between blood velocity and diameter in the brachial artery by different methods of increasing blood velocity. Acute cigarette smoking was used with otherwise healthy young occasional smokers to determine the influence of endothelial-nitric oxide pathways on the arterial diameter-blood velocity relationship. Nine nonsmokers and 12 occasional smokers (<1 pack/wk) were tested. Blood flow to the forearm was manipulated to indirectly investigate the relationship between blood velocity and diameter in the brachial artery. Blood flow to forearm was manipulated through the use of 1) 5-min ischemia; 2) handgrip exercise; 3) indirect local heating; and 4) 5-min ischemia plus indirect local heating. A strong relationship was observed between blood velocity and diameter independent of the method used to increase blood velocity (R(2) = 0.89). The mean slope of the velocity-diameter relationship was not different between nonsmokers and occasional smokers who abstained from smoking at least 2 days. Acute smoking did not alter the slope of the velocity-diameter relationship although the mean intercept was decreased as a result of consistent vasoconstriction (7-10%). The mechanisms by which smoking impairs vascular health are largely unknown. These findings differ from previous smoking studies that used chronic and/or heavier smokers. The velocity-diameter relationship appears independent of the method for increasing velocity. Acute smoking in occasional smokers results in vasoconstriction without altering vascular responsiveness. The velocity-diameter relationship may be a useful measure of the progression of vascular disease.

Adult↗
PubMed2004

Running for health: how much running for how much health?

Increasing physical activity has been shown to reduce physiological markers of cardiovascular disease, such as high blood pressure, vascular endothelial cell reactivity and arterial stiffness. In this issue of Clinical Science, Hägg and colleagues have chosen the spontaneously hypertensive rat model to investigate the effect of exercise on vascular function. They found that spontaneous running increased aortic compliance and antioxidant capacity with decreased oxidative stress in mesenteric arteries, presenting support for the cardiovascular protective effects of physical activity. Two important aspects of their study include the magnitude of the running stimulus and the choice of artery to evaluate.

Animals↗
PubMed2003

Relationship between muscle architectural features and oxygenation status determined by near infrared device.

This study tested whether regional differences in oxygenation status could result from differences in muscle fiber architecture. Architectural properties, oxygen supply, and consumption in the medial head of the gastrocnemius muscle (GM) were determined in vivo in six men using B-mode ultrasound and functional near infrared (NIR) imaging devices. Fascicle length, fascicle angle, NIR-O(2) saturation (deoxygenated Hb or oxygenated Hb), and NIR-blood volume (sum of deoxygenated and oxygenated Hb) were obtained in the distal and proximal portions of the GM at rest and during contraction. Exercise consisted of 2 min of standing plantar flexion at 1 Hz with an additional load of 50% of each subject's weight. Plantar flexion produced larger decreases (Delta: difference between rest and exercise values) in NIR-O(2) saturation [mean saturation (SD) of 0.14 (0.05) vs 0.07 (0.04) optical density units] and NIR-blood volume [mean saturation (SD) of -0.23 (0.08) vs -0.13 (0.04) optical density units] in the distal compared with the proximal portion ( P<0.05 for all comparisons). It also produced larger changes (Delta) in fascicle length [mean length (SD) of -16.5 (4.7) vs -8.2 (4.2) mm] and fascicle angle (mean angle (SD) of 10.8 (1.4) degrees vs 3.9 (2.1) degrees ] in the distal compared with the proximal portion ( P<0.05 for all comparisons). There were significant correlations between DeltaNIR-O(2 )saturation and Deltafascicle length ( r=-0.84, P<0.05), and between DeltaNIR-O(2) saturation and Deltafascicle angle ( r=-0.90, P<0.05), between DeltaNIR-blood volume and Deltafascicle length ( r=0.91, P<0.05), between DeltaNIR-blood volume and Deltafascicle angle ( r=-0.85, P<0.05). In conclusion, the plantar flexion exercise produced regional differences in oxygenation status consistent with regional differences in muscle architecture.

Adult↗