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The acute effects of different levels of intermittent negative pressure on peripheral circulation in patients with peripheral artery disease.

ABSTRACT: Intermittent negative pressure (INP) applied to the lower leg induces acute increase in arterial and skin blood flow. The aim of this study was to identify the optimal level of INP to increase blood flow in patients with lower extremity peripheral artery disease (PAD). We investigated the acute effects of different levels of INP in 16 subjects (7 women and 9 men, mean (SD) age 71(8) years) diagnosed with PAD. During application of INP in a pressure chamber sealed below the knee, arterial blood flow was continuously recorded in the dorsalis pedis artery or tibialis posterior artery (ultrasound Doppler), and skin blood flow was continuously recorded at the pulp of the first toe (laser Doppler). Different pressure levels (0, -10, -20, -40, and -60 mmHg) were tested in randomized order. Maximal arterial blood flow relative to baseline (median [25th, 75th percentiles]) was: 0 mmHg; 1.08 (1.02, 1.13), -10 mmHg; 1.11 (1.07, 1.17), -20 mmHg; 1.18 (1.11, 1.32), -40 mmHg; 1.39 (1.27, 1.91) and -60 mmHg; 1.48 (1.37, 1.78). Maximal laser Doppler flux (LDF) relative to baseline was: 0 mmHg; 1.06 (1.02, 1.12), -10 mmHg; 1.08 (1.05, 1.16) -20 mmHg; 1.12 (1.06, 1.27), -40 mmHg; 1.24 (1.14, 1.50) and -60 mmHg; 1.35 (1.10, 1.70). There were significantly higher maximal arterial blood flow and maximal LDF at -40 mmHg compared with -10 mmHg (P = 0.001 and P = 0.025, respectively). There were no significant differences in maximal arterial blood flow and maximal LDF between 0 and -10 mmHg (both P = 1.0), or between -40 and -60 mmHg (both P = 1.0). INP of -40 mmHg was the lowest negative pressure level that increased blood flow.

SUBMITTER: Hoel H

PROVIDER: S-EPMC6801220 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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The acute effects of different levels of intermittent negative pressure on peripheral circulation in patients with peripheral artery disease.

Hoel Henrik H Høiseth Lars Øivind LØ Sandbaek Gunnar G Sundhagen Jon Otto JO Mathiesen Iacob I Hisdal Jonny J

Physiological reports 20191001 20

Intermittent negative pressure (INP) applied to the lower leg induces acute increase in arterial and skin blood flow. The aim of this study was to identify the optimal level of INP to increase blood flow in patients with lower extremity peripheral artery disease (PAD). We investigated the acute effects of different levels of INP in 16 subjects (7 women and 9 men, mean (SD) age 71(8) years) diagnosed with PAD. During application of INP in a pressure chamber sealed below the knee, arterial blood f ...[more]

PMID: 31631579

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Project description:BackgroundIntermittent negative pressure (INP) applied to the lower leg and foot increases foot perfusion in healthy volunteers. The aim of the present study was to describe the effects of INP to the lower leg and foot on foot macro- and microcirculation in patients with lower extremity peripheral arterial disease (PAD).MethodsIn this experimental study, we analyzed foot circulation during INP in 20 patients [median (range): 75 (63-84yrs)] with PAD. One leg was placed inside an air-tight vacuum chamber connected to an INP-generator. During application of INP (alternating 10s of -40mmHg/7s of atmospheric pressure), we continuously recorded blood flow velocity in a distal foot artery (ultrasound Doppler), skin blood flow on the pulp of the first toes (laser Doppler), heart rate (ECG), and systemic blood pressure (Finometer). After a 5-min baseline sequence (no pressure), a 10-min INP sequence was applied, followed by 5-min post-INP (no pressure). To compare and quantify blood flow fluctuations between sequences, we calculated cumulative up-and-down fluctuations in arterial blood flow velocity per minute.ResultsOnset of INP induced an increase in arterial flow velocity and skin blood flow. Peak blood flow velocity was reached 3s after the onset of negative pressure, and increased 46% [(95% CI 36-57), P<0.001] above baseline. Peak skin blood flow was reached 2s after the onset of negative pressure, and increased 89% (95% CI 48-130), P<0.001) above baseline. Cumulative fluctuations per minute were significantly higher during INP-sequences compared to baseline [21 (95% CI 12-30)cm/s/min to 41 (95% CI 32-51)cm/s/min, P<0.001]. Mean INP blood flow velocity increased significantly ~12% above mean baseline blood flow velocity [(6.7 (95% CI 5.2-8.3)cm/s to 7.5 (95% CI 5.9-9.1)cm/s, P = 0.03)].ConclusionINP increases foot macro- and microcirculatory flow pulsatility in patients with PAD. Additionally, application of INP resulted in increased mean arterial blood flow velocity.

Project description:BackgroundCurrent guidelines recommend treating hypertension in patients with peripheral artery disease (PAD) to reduce the risk of cardiac events and stroke, but the effect of reducing blood pressure on lower extremity PAD events is largely unknown. We investigated the association of blood pressure with lower extremity PAD events using data from the ALLHAT trial (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial).MethodsALLHAT investigated the effect of different antihypertensive medication classes (chlorthalidone, amlodipine, lisinopril, or doxazosin) on cardiovascular events. With the use of these data, the primary outcome in our analysis was time to first lower extremity PAD event, defined as PAD-related hospitalization, procedures, medical treatment, or PAD-related death. Given the availability of longitudinal standardized blood pressure measurements, we analyzed systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure as time-varying categorical variables (reference categories 120-129 mm Hg for SBP, 70-79 mm Hg for DBP, and 45-54 mm Hg for pulse pressure) in separate models. We used extended Cox regression with death as a competing risk to calculate the association of each blood pressure component with PAD events, and report the results as subdistribution hazard ratios and 95% CIs.ResultsThe present analysis included 33 357 patients with an average age of 67.4 years, 53.1% men, 59.7% white race, and 36.2% with diabetes mellitus. The median baseline blood pressure was 146/84 mm Hg. Participants were followed for a median of 4.3 (interquartile range, 3.6-5.3) years, during which time 1489 (4.5%) had a lower extremity PAD event, and 4148 (12.4%) died. In models adjusted for demographic and clinical characteristics, SBP <120 mm Hg was associated with a 26% (CI, 5%-52%; P=0.015) higher hazard and SBP≥160 mm Hg was associated with a 21% (CI, 0%-48%; P=0.050) higher hazard for a PAD event, in comparison with SBP 120 to 129 mm Hg. In contrast, lower, but not higher, DBP was associated with a higher hazard of PAD events: for DBP <60 mm Hg (hazard ratio, 1.72; CI, 1.38-2.16). Pulse pressure had a U-shaped association with PAD events.ConclusionsIn this reanalysis of data from ALLHAT, we found a higher rate of lower extremity PAD events with higher and lower SBP and pulse pressure and with lower DBP. Given the recent revised blood pressure guidelines advocating lower SBP targets for overall cardiovascular risk reduction, further refinement of optimal blood pressure targets specific to PAD is needed.Clinical trial registrationURL: https://www.clinicaltrials.gov . Unique identifier: NCT00000542.

Project description:Background: Variable pressure support ventilation (vPSV) is an assisted ventilation mode that varies the level of pressure support on a breath-by-breath basis to restore the physiological variability of breathing activity. We aimed to compare the effects of vPSV at different levels of variability and pressure support (ΔP S) in patients with acute respiratory distress syndrome (ARDS). Methods: This study was a crossover randomized clinical trial. We included patients with mild to moderate ARDS already ventilated in conventional pressure support ventilation (PSV). The study consisted of two blocks of interventions, and variability during vPSV was set as the coefficient of variation of the ΔP S level. In the first block, the effects of three levels of variability were tested at constant ΔP S: 0% (PSV0%, conventional PSV), 15% (vPSV15%), and 30% (vPSV30%). In the second block, two levels of variability (0% and variability set to achieve ±5 cmH2O variability) were tested at two ΔPS levels (baseline ΔP S and ΔP S reduced by 5 cmH2O from baseline). The following four ventilation strategies were tested in the second block: PSV with baseline ΔP S and 0% variability (PSVBL) or ±5 cmH2O variability (vPSVBL), PSV with ΔPS reduced by 5 cmH2O and 0% variability (PSV-5) or ±5 cmH2O variability (vPSV-5). Outcomes included gas exchange, respiratory mechanics, and patient-ventilator asynchronies. Results: The study enrolled 20 patients. In the first block of interventions, oxygenation and respiratory mechanics parameters did not differ between vPSV15% and vPSV30% compared with PSV0%. The variability of tidal volume (V T) was higher with vPSV15% and vPSV30% compared with PSV0%. The incidence of asynchronies and the variability of transpulmonary pressure (P L) were higher with vPSV30% compared with PSV0%. In the second block of interventions, different levels of pressure support with and without variability did not change oxygenation. The variability of V T and P L was higher with vPSV-5 compared with PSV-5, but not with vPSVBL compared with PSVBL. Conclusion: In patients with mild-moderate ARDS, the addition of variability did not improve oxygenation at different pressure support levels. Moreover, high variability levels were associated with worse patient-ventilator synchrony. Clinical Trial Registration: www.clinicaltrials.gov, identifier: NCT01683669.

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The acute effects of different levels of intermittent negative pressure on peripheral circulation in patients with peripheral artery disease.

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The acute effects of different levels of intermittent negative pressure on peripheral circulation in patients with peripheral artery disease.

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