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Biomedical subjects

H N Mayrovitz

Publications and source records attributed to H N Mayrovitz.

At least 19 recordsLinked to original sources
PubMed2006

Hand volume estimates based on a geometric algorithm in comparison to water displacement.

Assessing changes in upper extremity limb volume during lymphedema therapy is important for determining treatment efficacy and documenting outcomes. Although arm volumes may be determined by tape measure, the suitability of circumference measurements to estimate hand volumes is questionable because of the deviation in circularity of hand shape. Our aim was to develop an alternative measurement procedure and algorithm for routine use to estimate hand volumes. A caliper was used to measure hand width and depth in 33 subjects (66 hands) and volumes (VE) were calculated using an elliptical frustum model. Using regression analysis and limits of agreement (LOA), VE was compared to volumes determined by water displacement (VW), to volumes calculated from tape-measure determined circumferences (VC), and to a trapezoidal model (VT). VW and VE (mean +/- SD) were similar (363 +/- 98 vs. 362 +/-100 ml) and highly correlated; VE = 1.01VW -3.1 ml, r=0.986, p<0.001, with LOA of +/- 33.5 ml and +/- 9.9 %. In contrast, VC (480 +/- 138 ml) and VT (432 +/- 122 ml) significantly overestimated volume (p<0.0001). These results indicate that the elliptical algorithm can be a useful alternative to water displacement when hand volumes are needed and the water displacement method is contra-indicated, impractical to implement, too time consuming or not available.

Adult↗
PubMed2005

Foot volume estimates based on a geometric algorithm in comparison to water displacement.

Assessing lower extremity limb volume and its change during and after lymphedema therapy is important for determining treatment efficacy and documenting outcomes. Although leg volumes may be determined by tape measure and other methods, there is no metric method to routinely assess foot volumes. Exclusion of foot volumes can under- or overestimate therapeutic progress. Our aim was to develop and test a metric measurement procedure and algorithm for practicing therapists to use to estimate foot volumes. The method uses a caliper and ruler to measure foot dimensions at standardized locations and calculates foot volume (VM) by a mathematical algorithm. VM was compared to volumes measured by water displacement (Vw) in 30 subjects (60 feet) using regression analysis and limits of agreement (LOA). Vw and VM (mean +/- sd) were similar 857 +/- 150 ml vs. 859 +/- 154 ml, and were highly correlated VM = 1.00Vw + 1.67 ml, r = 0.965, p < 0.001. The LOA for absolute volume differences and percentages were respectively +/- 79.6 ml and +/- 9.28 %. These results indicate that this metric method can be a useful alternative to water displacement when foot volumes are needed, but the water displacement method is contraindicated, impractical to implement, too time consuming or is not available.

Adult↗
PubMed2005

Transcutaneous oxygen tension in arms of women with unilateral postmastectomy lymphedema.

Previous reports suggest that skin blood flow is reduced in arms of women with lymphedema due to breast cancer treatment. Since tissue oxygenation depends on blood flow, we sought to determine if transcutaneous oxygen tension (TcPO2) is also reduced and if so, if therapy that reduces edema has a beneficial effect. TcPO2 was measured in fibrotic areas of affected arms and in corresponding sites on non-affected arms of 15 women with unilateral arm lymphedema before and after CDP therapy sequences. Fibrosis was assessed by indentation recovery times (IRT) after applying an indenter-like device to tissue. Volumes and edema percentages were determined from circumferences using automated software calculations. Treatment significantly (p < 0.01) reduced arm edema from 28.6 +/- 22.9% to 18.1 +/- 17.7% (mean +/- SD) and fibrotic segment edema from 42.6 +/- 30.1% to 25.0 +/- 20.4%, and softened fibrotic tissue judged by reductions in IRT (88.7 +/- 60.7 sec vs. 23.1 +/- 38.8 sec, p < 0.001). TcPO2 did not differ between arms initially and did not change with treatment, being 60.1 +/- 8.8 mmHg at the start and 61.8 +/- 9.2 mmHg at the end of treatment. Thus, despite significant amounts of initial edema, TcPO2 was not initially less in affected arms nor was it changed by therapy that improved both edema and fibrosis.

Aged↗
PubMed2003

Limb volume estimates based on limb elliptical vs. circular cross section models.

Limb volumes, as would be estimated by the widely used right circular truncated cone model (right circular frustum), were analytically compared to volume estimates that would be obtained if limbs were represented by an elliptical cross section. A general expression for the ratio of circular to elliptical limb segmental volumes was developed in terms of the ratio of minimum to maximum limb radial dimensions. Analytical results showed that in general the elliptical representation resulted in smaller calculated limb volumes, with the difference increasing as the ratio of minimum to maximum limb dimension became smaller. However, differences in estimated limb volume between circular and elliptic representations were less than 5% if the minimum to maximum limb dimensions at measured circumference sites were greater than 0.64. It is concluded that although limbs deviate from circularity, the added work of determining minimum and maximum dimensions for each circumference measured, as is needed to employ elliptical models, is warranted only for extreme differences in limb radial dimensions or possibly for research purposes.

Anatomy, Cross-Sectional↗
PubMed2001

Effects of permanent magnets on resting skin blood perfusion in healthy persons assessed by laser Doppler flowmetry and imaging.

Effects on skin blood perfusion of permanent ceramic magnets [0.1 T (1000 G) surface field], individually (disk shaped, 4 cm diameter x 1 cm thick) or in the form of a 11 x 7 in pad ( approximately 28 x 17.8 cm) with an array of 16 rectangular magnets (4.5 x 2.2 cm), were investigated in 16 female volunteers (27.4 +/- 1.7 years, range 21-48 years) using three separate protocols. In protocol A, a disk magnet was placed on the palmar surface of the hand in contact with the thenar eminence (n = 5). In protocol B, the magnet was placed on the hand dorsum overlying the thenar eminence (n = 5). In protocol C, the entire palm and fingers rested on the magnetic pad (n = 6). Magnets were in place for 36 min on one hand, and a sham was in place on the other hand. Blood perfusion was measured on the middle finger dorsum by laser Doppler flowmetry (LDF) and on the index finger by laser Doppler imaging (LDI). Perfusion measurements were simultaneously taken in sham and magnet exposed hands, before and during the entire magnet exposure interval. Magnetic field effects were tested by comparing skin blood perfusion sequences in magnet and sham exposed regions. Results showed no significant changes in either LDF or LDI perfusion at magnet or sham sites during exposure, nor were there any significant differences between sham and magnet sites for any protocol. Measurements of skin temperature at the LDF measurement sites also showed no significant change. It is concluded that in the healthy subjects studied with normal, unstressed circulation, magnets of the type and for the duration used, showed no detectible effect on skin blood perfusion in the anatomical area studied.

Adult↗
PubMed1999

Blood perfusion hyperaemia in response to graded loading of human heels assessed by laser-Doppler imaging.

Heel pressure ulcers are important clinical, humanitarian and economic problems arising in part from localized blood flow deficits during loading and inadequate flow recovery. Because there are few data available with regard to the intrinsic physiological responses of heel skin to pressure-induced ischaemia, the present study was undertaken to characterize the main features of the post-loading hyperaemic response. Laser-Doppler perfusion imaging was used to measure hyperaemia in 14 vascularly normal women who were subjected to sequential local heel loading with graded magnitudes (30-140 mmHg) and durations (2.5-20 min). Peak heel perfusion produced by local heating to 44 degrees C for 5 min was used as a comparison standard. All heel loads and durations resulted in hyperaemic responses, with the largest increase in peak response occurring between heel loads of 60 and 120 mmHg. During this transition, peak hyperaemia increased from about 32% to 79% of the local maximal microvascular vasodilatory capacity. Recovery times also increased with both load duration and magnitude, with the longest recovery time being about 7.5 min. Hyperaemic responses and recovery times were analytically dependent on the heel load pressure duration product, with evidence of suppression of the peak response at 1500 mmHg min and a levelling off of recovery time at higher pressure durations. These findings serve to characterize normal physiological perfusion responses to pressure-induced ischaemia at an anatomical site prone to pressure ulceration. The results suggest the possibility of a 'critical' heel loading, above which a near-maximum response is elicited and beyond which vasodilatory recovery potential is blunted.

Adult↗
PubMed1998

Compression-induced pulsatile blood flow changes in human legs.

Initial and sustained (7-h) impacts of foot-to-knee compression bandaging on leg arterial pulsatile blood flow were assessed by nuclear magnetic resonance flowmetry in eight healthy supine subjects. A widely used bandaging method (zinc impregnated gauze + Coban) and a slight variant (Coban only) were applied one week apart to one leg. Blood flow was measured on each day of bandage application before and after bandaging and after 7 h of normal activity. Initial mean sub-bandage pressures (lateral gaiter) were between 28.4 and 28.9 mmHg but were significantly reduced after 7 h to 16.3-19.4 mmHg. Overall below-knee pulsatile blood perfusion was initially significantly increased by both methods mainly due to increased proximal blood flow. Bandaging was also associated with a decrease in blood perfusion of the nonbandaged control leg mainly due to a decrease in distal blood flow. Neither of these effects were sustained after 7 h. The fact that neither sub-bandage pressure nor blood flow was sustained may indicate a causal linkage, a concept consistent with the finding of a linear relationship between afternoon blood flow and sub-bandage pressure reductions. The implications of the present findings for venous ulcer therapy are speculative and based on the concept that arterial pulsatile flow augmentation is a positive feature. If so, more frequent bandage changes to provide transient flow stimulation or use of bandages to better maintain sub-bandage pressure to sustain flow increases may be useful.

Adult↗
PubMed1998

Posturally induced leg vasoconstrictive responses: relationship to standing duration, impedance and volume changes.

Shifting legs to a gravity-dependent position provokes a physiological vasoconstrictive response that forms the basis of several diagnostic tests based on initial (< 5 min) blood perfusion decreases. However, it is not known if responses are maintained over longer duration and if they depend on the volume shifted to the limb during the manoeuvre. These issues were investigated by measurements of blood perfusion changes on foot and ankle (laser Doppler) and below-knee volume and impedance changes induced by 30 min of standing in 10 healthy volunteers. Initial perfusion decreases were 66.4% +/- 2.6% and 49.3% +/- 3.8% for ankle and foot dorsum, respectively, and were fully maintained during sustained standing without evidence of 'vasodilator escape'. Response magnitudes were not dependent on leg volume changes using geometric or impedance measures. A close correlation (r2 = 0.78) between impedance and volume changes suggests the former as a useful way of assessing dynamic limb volume changes. Sustained vasoconstrictive responses make it unlikely that extending the duration of such tests would offer more, diagnostic information than is currently available.

Adult↗
PubMed1998

Compression bandaging effects on lower extremity peripheral and sub-bandage skin blood perfusion.

Laser-Doppler blood perfusion was simultaneously measured on both great toes and the lateral upper-calf before and during fore-foot-to-knee compression bandaging of one test-leg in ten vascularly healthy female volunteers. Two bandaging methods were sequentially used separated by a 30 minutes interval. Bandage A consisted of a layer of zinc impregnated gauze and an elastic wrap; bandage B had the elastic wrap only. Sub-bandage pressures of the test-leg were measured at distal and proximal lateral below-knee standardized sites. The study purpose was to determine the effects of moderate compression pressure achieved for bandages A under and distal to bandaged regions. Initial (mean +/- sem_ sub-bandage pressure achieved for bandages A and B were similar, being respectively 32.9 +/- 2.8 and 28.4 +/- 3.9 mm Hg. Both bandages types were associated with significant reductions in test-leg toe blood perfusion amounting to 44.2 +/- 13.1 percent and 27.5 +/- 10.5 percent for bandages A and B respectively. Contrastingly, test-leg sub-bandage blood perfusion did not differ from its pre-bandage baseline mean level for either bandage type. These findings show that a widely used bandaging method and a slight variant each significantly reduces distal (toe) blood perfusion without reducing sub-bandage skin perfusion. Absence of sub-bandage perfusion decreases may be related to a partially compensating reflex vasodilatory response, but such effects if present are inadequate to prevent reductions in distal perfusion. These results reinforce the need for due care and risk-benefit consideration with respect to therapeutic compression levels.

Adult↗
PubMed1998

Heel-skin microvascular blood perfusion responses to sustained pressure loading and unloading.

OBJECTIVE: Sustained heel pressure during surgery and during acute and long-term care residence can cause heel blood flow deprivation sufficient to cause pressure ulcers. Because little is known about the amount and distribution of heel blood perfusion changes under these conditions, the aim of this study was to characterize the main features of these changes. METHODS: Heel blood perfusion by laser Doppler imaging (LDI, 40 x 40 mm scans) was measured in 11 vascularly normal persons before (10 minutes), during heel loading (40 minutes) and after off-loading (20 minutes). Loading was done with subjects supine and one heel on a transparent plate through which LDI data were obtained during loading. Analyses were on progressively increasing areas around the central compression site using 10 x 10, 20 x 20, 30 x 30, and 40 x 40 mm assay areas at each of multiple time points during the 70-minute test. RESULTS: (1) Heel perfusion is rapidly and significantly reduced on loading (P < 0.01) with the greatest reduction within the central heel area; (2) perfusion remains uniformly depressed throughout the loading interval; (3) off-loading is associated with a rapid onset, specially heterogeneous hyperemia which exceeds baseline (P < 0.01) for 10 minutes. CONCLUSIONS: The present seminal findings may serve as a guide to develop sorely needed microvascular tests to help classify heel breakdown risk on a patient-by-patient basis.

Adult↗
PubMed1997

Effects of compression bandaging on leg pulsatile blood flow.

Leg external compression bandaging is the mainstay of venous ulcer treatment, yet little is known about the impact of therapeutic compression levels on arterial haemodynamics. In this study, the effect of foot-to-knee, four-layer compression bandaging on below-knee arterial pulsatile blood flow was assessed by nuclear magnetic resonance flowmetry. In 14 healthy supine subjects bilateral flow measurements at five below-knee sites without compression, and after compressing one leg to an average malleolar sub-bandage pressure of 40.7 +/- 4.0 mmHg, revealed a potentially important new phenomenon. The forefoot-to-knee compression bandaging caused a highly significant (P < 0.001) increase in the bandaged leg pulsatile blood flow owing to increases in both peak flow and pulse width. It is hypothesized that arteriolar vasodilatation, induced either myogenically by reduced transmural pressure or by vasodilatory substance release triggered by increased venous shear stress, produce the observed compression-related phenomenon. Whatever the mechanism(s), the finding of a compression-associated pulsatile flow increase suggests a previously undiscovered arterial linkage, which may play a role in the well-documented beneficial effects of compression bandaging in venous ulcer treatment. A possible impact of the arterial flow-pulse increase is speculated to effect venous ulcer outcome via a decrease in leucocyte effects in the distal microvasculature, as a consequence of the more vigorous haemodynamic state.

Adult↗
PubMed1997

Heel blood perfusion responses to pressure loading and unloading in women.

Heel pressure ulcers are significant and costly problems causing suffering and potential limb loss from infection and compromised blood flow. Heel blood perfusion (HBP) deficits accompanying loading likely affect the skin breakdown process, but little is known about the loading and off-loading changes. To clarify this issue, combined laser-Doppler Imaging (LDI) and Fluxmetry were used to assess HBP before, during, and after 40 minutes of continuous heel loading in 11 female volunteers (32-60 years). During loading, an initial decrease in HBP was followed by a gradual small recovery (p < 0.001). Off-loading resulted in a significant hyperemic response with HBP exceeding baseline by a factor of 4.72 +/- 0.63 (p = 0.001) and remaining elevated for about 10 minutes. Spatial LDI data showed that hyperemic responses are maximum near the pressure center and diminish radially. These results suggest a localized, pressure-related tissue trauma, which is compensated for by a substantial hyperperfusion. The dependence (and adequacy) of this response on clinical variables including heel pressure and duration, limb vascular status, and patient health are unknown. The present seminal data and associated methods provide a platform from which these and other important clinical parameters can be systematically studied and compared.

Adult↗
PubMed1997

Geometric, shape and area measurement considerations for diabetic neuropathic plantar ulcers.

Though neuropathic plantar ulcers are known to be "round-like," systematic quantitative data on their shape and geometric features are not readily available. A sample of 305 ulcers were retrospectively assessed to provide distribution data on quantitative geometric and shape parameters. After tracing the ulcer during the patient's initial visit, the following parameters were determined: surface area (A), maximum length (L), maximum perpendicular width (W), perimeter (p), shape factor (SF), and an ulcer regularity index (URI). SF assesses ulcer "circularity" and URI measures ulcer perimeter "smoothness" in comparison to a fictitious circle with the same contained area. SF and URI values of 1.0 correspond to 100 percent circularity and regularity. These data and the associated distributions, which are derived from a reasonably large random sample, provide a useful quantitative description of plantar ulcer geometry and shape.

Anthropometry↗
PubMed1997

Variability in skin microvascular vasodilatory responses assessed by laser-Doppler imaging.

Skin blood perfusion (SBP) responses to pressure loading and other traumatic and noxious stimuli are used to help identify patients at-risk of skin breakdown, evaluate preventive strategies and help clarify patho-physiological mechanisms in pre-ulcerative and ulcerative conditions. Often, laser-Doppler methods are used to compare vasodilatory responses at differing skin sites to evaluate skin parameter changes. Significant variations in skin microvasculature are known to be normally present, even in closely separated skin zones. In this study, spatial variability and temporal responses of SBP were evaluated with a widely used topical vasodilator (methylnicotinate, MN). A mask with nine holes (1.25 cm2 each) was placed on the volar forearm of ten volunteers. SBP was measured with laser-Doppler Imaging (LDI) prior to applying MN (15 ul, 50 mM) to six zones and 5, 10, 15, 20 and 30 minutes afterwards. Inter-zone mean SBP and inter- and intra-zone coefficients of variation (CV) were determined at each time. Results show that MN responses, when determined as zone LDI means, reached maximum at 15 minutes with no significant differences in relative responses among treated zones. Inter-zone perfusion CV's (range 0.11-0.13) were about 50 percent of intra-zone CV's (p < 0.01). We conclude that LDI perfusion responses can be obtained at different forearm skin sites with reasonable and acceptable levels of spatial variation if zone mean SBP values are used.

Adult↗
PubMed1996

Functional microcirculatory impairment: a possible source of reduced skin oxygen tension in human diabetes mellitus.

Lower extremity transcutaneous oxygen tension (TcPO2) is used in diagnostic and prognostic indicator of tissue perfusion and is reduced in diabetes mellitus. Since cardiac output, leg blood flow and microvascular perfusion each can singly or jointly effect tissue oxygenation, the relative importance of macro- vs microvascular factors has not been resolved. To clarify this issue we compared TcPO2 levels in diabetic and nondiabetic subjects in whom cardiac output, leg pulsatile blood flow, and microcirculatory perfusion parameters were noninvasively measured. In 60 diabetic and 60 nondiabetic subjects the following measurements were done on both legs during a single session evaluation: foot dorsum TcPO2 at 45 degrees using laser-Doppler, ankle-brachial index using Doppler ultrasound (ABI), and pulsatile leg blood flow using magnetic resonance flowmetry; cardiac output was determined using transthoracic bioimpedance. The diabetic and nondiabetic groups were determined to have nonsignificant differences (mean +/- SEM, DM vs NODM) with respect to age (63.3 +/- 1.1 vs 60.1 +/- 1.5 years), cardiac output (5.5 +/- 0.2 vs 5.5 +/- 0.2 l/min), leg blood flow (1.6 +/- 0.05 vs 1.7 +/- 0.06 ml/min/100 cc) and ABI. Although macrocirculatory values were equivalent, microvascular function indicators were significantly reduced in the diabetic group: TcPO2 (51.9 +/- 1.4 vs 62.9 +/- 1.3 mmHg); MVR 76.7 +/- 1.5 vs 84.9 +/- 0.9%) and were correlated only in diabetics (r2 = 0.48, P < 0.001). The findings suggest a primary linkage between the diabetic TcPO2 deficit and the microcirculatory submaximal vasodilatory response, with little if any role of macrocirculatory factors.

Blood Gas Monitoring, Transcutaneous↗
PubMed1996

Pulsatile blood flow asymmetry in paired human legs.

Average leg blood flow has been extensively measured using non-invasive methods, but knowledge concerning pulsatile flow at specific leg cross-sections in normal or vascularly impaired limbs is quite limited. The present study used nuclear magnetic resonance flowmetry to address two fundamental questions; (1) to what extent are pulsatile flow differences present between paired-legs? and (2) is paired-leg flow symmetry affected by the presence of lower extremity arterial disease (LEAD)? Comparisons of left-right leg pulsatile blood flow (ml/min), perfusion (ml/min/100cc), and arterial status index at multiple leg sites showed highly significant correlations between legs (P < 0.001) in 57 normal and 37 patients with LEAD. To evaluate symmetry, the ratio of lower to higher paired-leg flow parameter values at five below-knee sites were averaged. Results showed all ratios significantly greater in normal subjects (P < 0.001). These findings establish the distribution and range of leg flow symmetry in vascularly normal individuals and show significant symmetry reductions accompanying bilateral LEAD. Although the cause of the asymmetry is presently unknown, non-uniform disease progression between paired legs may be involved. These initial findings provide a basis for subsequent research regarding the possible use of bilateral flow asymmetry assessment to further clarify the pathophysiological progression process and the possibility of using symmetry-based parameters to develop early markers of sub-clinical peripheral arterial disease progression.

Adult↗
PubMed1994

Electrophysiologic characteristics at initiation of ventricular tachycardia and ventricular fibrillation in a canine infarct model.

Local ventricular activation time and the conduction time during sinus rhythm at the induction of ventricular tachycardia (VT) and ventricular fibrillation (VF) were investigated using a canine model of chronic myocardial infarction. Of 26 dogs studied, 15 had inducible VT, 10 had inducible VF, and 1 had no inducible arrhythmias. Bipolar local ventricular electrograms were recorded during sinus rhythm from 136 sites in 10 dogs with VT and 164 sites in 11 dogs with VF. Mean activation time in dogs with inducible VT was significantly longer than in dogs with inducible VF. Furthermore, simultaneous local ventricular electrograms were recorded during the induction of VT (74 episodes) or VF (38 episodes) from the infarct border zone at the endocardium (B-EN), the epicardium (B-EP), and normal sites (N-EN, N-EP). During VT induction, the activation time at N-EN and N-EP was significantly longer than during VF induction (N-EN: 94 +/- 21, 70 +/- 19 ms; N-EP: 83 +/- 21, 64 +/- 10 ms; p < 0.05). Conduction time was measured at the initiation of VT or VF induced by orthodromic or antidromic pacing. The conduction times of the last paced beat between N-EN and B-EP (35 +/- 11, 62 +/- 24 ms), N-EN and N-EP (35 +/- 12, 14 +/- 13 ms), B-EN and B-EP (16 +/- 10, 38 +/- 25 ms), and B-EP and N-EP (77 +/- 27, 44 +/- 12 ms) were significantly different in dogs with inducible VT (p < 0.05), but not in dogs with VF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗