Using Doppler signal power to detect changes in vessel size: a feasibility study using a wall-less flow phantom

Deverson, Stephanie; Evans, David H.

doi:10.1016/s0301-5629(99)00148-9

Cited by 7 publications

(4 citation statements)

References 40 publications

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“…A number of authors have used the spectral power of Doppler signals to show that middle cerebral artery diameter does not change during thigh cuff application and release 14 and during hypocapnia and hypercapnia, 35 but a recent study has cast doubt on the usefulness of this method of assessing vessel diameter. 36 We believe, however, that significant change in middle cerebral artery diameter is unlikely during thigh cuff application and release, 37 lower body negative pressure, 38 Valsalva maneuver, 28,39 or supine rest. Nevertheless, we have not directly measured middle cerebral artery diameter, and caution must therefore be exercised in interpreting our results.…”

Section: Discussionmentioning

confidence: 98%

Dynamic Cerebral Autoregulation Is Unaffected by Aging

Carey

Eames

Blake

et al. 2000

Stroke

120

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Background and Purpose-Normal aging is associated with marked changes in the cardiovascular and cerebrovascular systems. Although cerebral autoregulation (CA) is impaired in certain disease states, the effect of age per se on dynamic CA in humans is unknown and the focus of this study. Methods-Twenty-seven young subjects (Յ40 years) and 27 older subjects (Ն55 years), matched for sex and systolic blood pressure (BP), underwent measurement of cerebral blood flow velocity by transcranial Doppler ultrasound and noninvasive beat-to-beat arterial BP measurement during induced and spontaneous dynamic BP stimuli. A standard dynamic autoregulatory index (ARI) was derived for each spontaneous and induced dynamic BP stimulus to include the step response, as well as cardiac baroreceptor sensitivity (BRS), for the 2 groups. Results-The mean age of the young group was 29Ϯ5 years, and that of the older group was 68Ϯ5 years. Cardiac BRS was reduced in the older group (8.6Ϯ4.5 versus 16.9Ϯ8.8 ms/mm Hg; PϽ0.0001). However, no age-related differences were demonstrated in step response plots or in ARI values for any pressor or depressor dynamic BP stimulus (Pϭ0.62), with mean ARI values for all stimuli combined being 4.9Ϯ1.8 for the young group and 5.0Ϯ2.3 for the older group. Conclusions-Although increasing age is associated with a decrease in cardiac BRS, dynamic CA, as assessed by step response analysis as well as cerebral blood flow responses to transient and induced BP stimuli, is unaffected by aging.

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Section: Discussionmentioning

confidence: 98%

Dynamic Cerebral Autoregulation Is Unaffected by Aging

Carey

Eames

Blake

et al. 2000

Stroke

120

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“…Maximizing the

\overset{P}{true}

signal permits the assumption that the entire cross‐sectional area of the MCA is fully captured within the sample volume of the TCD's transmitted signal and that any changes in the

\overset{P}{true}

signal that ensue represent a change in MCA calibre (Deverson & Evans, ). Though no in vivo validation studies have been performed, changes in the

\overset{P}{true}

signal as an index of changes in cross‐sectional area of the insonated artery has been validated using flow phantoms (Deverson & Evans, ; Hatab et al., ; Saini, Maulik, Nanda, & Rosenzweig, ), which remain the gold standard for validation of non‐invasive techniques used in humans to assess CBF such as duplex ultrasonography (Rominger et al., ) and neuroimaging (Taviani et al., ). Finally, to minimize the impact of TCD probe movement on signal quality, participants were instructed to remain as still as possible during the entire experimental protocol.…”

Section: Methodsmentioning

confidence: 99%

Vascular responses to hypoxia are not impaired in obstructive sleep apnoea patients free of overt cardiovascular disease

Beaudin

Hanly

Raneri

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?Does treatment of obstructive sleep apnoea (OSA) with nocturnal oxygen or continuous positive airway pressure (CPAP) improve hypoxic vascular responses, which are reportedly impaired in OSA? What is the main finding and its importance?Cerebrovascular and cardiovascular hypoxic responses were not impaired in OSA patients free of overt cardiovascular disease and known risk factors, and were not altered by nocturnal oxygen or CPAP treatment. We conclude that this OSA patient phenotype has normal vascular responses to hypoxia and is unlikely to obtain long term cardiovascular benefits from nocturnal oxygen or CPAP therapy. Abstract Cerebral blood flow (CBF) and cardiovascular responses to hypoxia are reportedly impaired in obstructive sleep apnoea (OSA) patients and corrected by continuous positive airway pressure (CPAP), beneficial effects that are ascribed to correction of OSA‐related intermittent hypoxia (IH). However, CPAP corrects both IH and ancillary OSA features (i.e. intermittent hypercapnia, sympathetic activation, blood pressure surges, negative intrathoracic pressure swings and sleep fragmentation). Whether correction of these ancillary OSA features contribute to CPAP's beneficial effects on vascular hypoxic responses is unknown. Nocturnal oxygen corrects OSA‐induced IH, but apnoeas and ancillary features persist. Thus, we examined the effects of nocturnal oxygen and CPAP on cerebrovascular and cardiovascular hypoxic responses in untreated OSA patients. Responses were assessed in 52 OSA patients free of overt cardiovascular disease and known risk factors at baseline, after 2 weeks of nocturnal oxygen (n = 26) or no treatment (n = 26), and after ∼4 weeks of CPAP treatment (n = 40). Twenty‐two age‐matched controls were assessed at baseline and follow‐up visits. Resting, isocapnic euoxia mean blood pressure was decreased following nocturnal oxygen (−3.6 ± 6.0 mmHg; P = 0.006) and CPAP (−4.5 ± 7.5 mmHg; P < 0.001) while cerebrovascular conductance was increased with CPAP (P = 0.001). However, these changes were not different from controls. Unexpectedly, OSA patients and controls had similar hypoxic vascular responses at baseline that were not changed by either nocturnal oxygen or CPAP. We conclude that OSA patients free of overt cardiovascular disease and known risk factors did not have impaired cerebrovascular or cardiovascular responses to hypoxia and are unlikely to obtain long term cardiovascular benefits from nocturnal oxygen or CPAP therapy.

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“…Therefore the mean vessel diameter can be slightly underestimated, and the vessel wall distension can be over-estimated. Caution should be shown when attempting to relate the changes in PDI area to the changes in vessel size of peripheral arteries (DEVERSON and EVANS, 2000). A lower PDI threshold value (Th=6-10) is recommended for the BA and DPA.…”

confidence: 99%

“…From the PDI, we can obtain the cross-sectional area of blood flow for large arteries with low levels of inaccuracy (STEINKE et aL, 1997;HOSKINS et al, 1998;DEVERSON and EVANS, 2000).…”

mentioning

confidence: 99%

Non-invasive assessment of arterial distension waveforms using gradient-based Hough transform and power Doppler ultrasound imaging

Shau

Chong

et al. 2001

Med. Biol. Eng. Comput.

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The peripheral arterial vessel often appears as an elliptic shape under the constraints of the surrounding tissues. In this study, the gradient-based Hough transform was used to detect the central location of the ellipse and the lumen area of the arterial vessel non-invasively using power Doppler imaging. Sequential ultrasound images were used to construct arterial distension waveforms in both the major- and minor-axis directions for a few cardiac cycles. The common carotid arteries (CCAs) for nine healthy male volunteers (mean age 24 years), in the sitting position, were investigated in vivo. The CCAs (n = 9) had a mean diameter of 5.83mm, and the pulsatile diameter distension was 13.7+/-1.9%. The brachial artery and dorsalis pedis artery for five healthy male volunteers (mean age 26 years), in the supine position, had mean diameters of 4.03mm and 2.83mm and distensions of 16.7+/-4.6% and 15.5+/-5.4%, respectively. The movement of the arterial centre location during the cardiac cycle reflected the asymmetry of the reaction forces produced by the surrounding soft tissues. The present method can obtain the response of vessel distension to pulse pressure, as well as the constrained conditions of the arteries.

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Using Doppler signal power to detect changes in vessel size: a feasibility study using a wall-less flow phantom

Cited by 7 publications

References 40 publications

Dynamic Cerebral Autoregulation Is Unaffected by Aging

Dynamic Cerebral Autoregulation Is Unaffected by Aging

Vascular responses to hypoxia are not impaired in obstructive sleep apnoea patients free of overt cardiovascular disease

Non-invasive assessment of arterial distension waveforms using gradient-based Hough transform and power Doppler ultrasound imaging

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