Blood Flow Restriction Training for Athletes: A Systematic Review

Background: Blood flow restriction (BFR) is a novel technique involving the use of a cuff/tourniquet system positioned around the proximal end of an extremity to maintain arterial flow while restricting venous return. Purpose: To analyze the available literature regarding the use of BFR to supplement traditional resistance training in healthy athletes. Study Design: Systematic review. Methods: A systematic review was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. From November to December 2018, studies that examined the effects of BFR training in athletes were identified using PubMed and OVID Medline. Reference lists from selected articles were analyzed for additional studies. The inclusion criteria for full article review were randomized studies with control groups that implemented BFR training into athletes’ resistance training workouts. Case reports and review studies were excluded. The following data were extracted: patient demographics, study design, training protocol, occlusive cuff location/pressure, maximum strength improvements, muscle size measurements, markers of sports performance (eg, sprint time, agility tests, and jump measurements), and other study-specific markers (eg, electromyography, muscular torque, and muscular endurance). Results: The initial search identified 237 articles. After removal of duplicates and screening of titles, abstracts, and full articles, 10 studies were identified that met the inclusion criteria. Seven of 9 (78%) studies found a significant increase in strength associated with use of BFR training as compared with control; 4 of 8 (50%) noted significant increases in muscle size associated with BFR training; and 3 of 4 (75%) reported significant improvements in sport-specific measurements in the groups that used BFR training. Occlusive cuff pressure varied across studies, from 110 to 240 mm HG. Conclusion: The literature appears to support that BFR can lead to improvements in strength, muscle size, and markers of sports performance in healthy athletes. Combining traditional resistance training with BFR may allow athletes to maximize athletic performance and remain in good health. Additional studies should be conducted to find an optimal occlusive pressure to maximize training improvements. Registration: CRD42019118025 (PROSPERO).

A minimally-occlusive cuff method utilizing ultrasound vascular imaging for stress-free blood pressure measurement

Objective Occlusive cuff inflation in ambulatory blood pressure (BP) monitoring disturbs the daily life of the user, and affects efficacy of monitoring. To overcome this limitation, we have developed a novel minimally-occlusive cuff method for stress-free measurement of BP. This study aimed to experimentally evaluate the reliability of this method, and improve the precision of this method by implementing a machine learning algorithm. Methods In this method, a thin-plate-type ultrasound probe (Size: 5.6mm-thickness × 28mm × 26mm; weight: 10g) is placed between the cuff and the skin, and used to measure the ultrasonic dimension of the artery (Figure 1). The cuff pressure (Pc), arterial dimension at systole (Ds) and diastole (Dd), systolic BP (SBP) and diastolic BP (DBP) during cuff inflation are theoretically related by the following equations, SBP-Pc = P0·Exp[α·Ds] DBP-Pc = P0·Exp[α·Dd] Where P0 and α are constants, and α indicates arterial stiffness. Since multiple sets of the two equations can be defined over multiple cardiac beats while measuring Pc, Ds and Dd during mild cuff inflation (Pc is controlled less than 50 mmHg, Figure 1), it is possible to estimate SBP (SBPe) and DBP (DBPe) as solutions of the equations. In 6 anesthetized dogs, we attached the cuff and the probe to the right thigh to get SBPe and DBPe, which were one-time calibrated in each animal against reference SBP and DBP measured by using an intra-arterial catheter. We also determined the pulse arrival time (PAT), which is a commonly employed parameter in cuff-less BP monitoring. In all the dogs, BP was changed extensively by infusing noradrenaline or sodium nitroprusside. Results DBPe correlated tightly with DBP with a coefficient of determination (R2) of 0.85±0.08, and predicted DBP with error of 3.9±7.9 mmHg after one-time calibration (Figure 2). PAT correlated poorly with DBP (R2=0.49±0.17), and predicted DBP less accurately than this method. SBPe correlated well with SBP (R2=0.78±0.08) (Figure 3). However, even after one-time calibration, difference between SBPe and SBP was 2.6±18.9 mmHg, which was not acceptable. To improve the precision in SBP prediction, we used supervised machine learning approach with use of a support vector algorithm (Python, Scikit-learn), which regressed feature variables (SBPe, DBPe, Ds, Dd heart rate, and PAT) against teacher signal (reference SBP). The support vector algorithm, once trained, predicted SBP with acceptable accuracy with error of 0.7±6.9 mmHg (Figure 3). Conclusions This method reliably tracks BP changes without occlusive cuff inflation. Once calibrated, this method measures DBP accurately. With the aid of machine learning, precision in SBP prediction was greatly improved to an acceptable level. This method with machine learning approach has potential for stress-free BP measurement in ambulatory BP monitoring. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Japan Society for the Promotion of Science

Montreal electronic artificial urinary sphincters: Our futuristic alternatives to the AMS800™

Introduction: We aimed to present three novel remotely controlled hydromechanical artificial urinary sphincters (AUSs) and report their in-vitro and ex-vivo results.Methods: We successively developed three distinct hydromechanical AUSs on the basis of the existing AMS800™ device by incorporating an electronic pump. No changes were made to the cuff and balloon. The AUS#1 was designed as an electromagnetically controlled device. The AUS#2 and AUS#3 were conceived as Bluetooth 2.1 remotely controlled and Bluetooth 4.0 remotelycontrolled, adaptive devices, respectively. In-vitro experiments profiled occlusive cuff pressure (OCP) during a complete device cycle, with different predetermined OCP. Ex-vivo experiments were performed on a fresh pig bladder with 4 cm cuff placed around the urethra. Leak point pressure with different predetermined OCP values was successively measured during cystometry via a catheter at the bladder dome.Results: Our in-vitro and ex-vivo experiments demonstrated that these three novel AUSs provided stable and predetermined OCP — within the physiological range — and completely deflated the cuff, when required, in a limited time compatible with physiological voiding cycles.Conclusions: Our three novel, remotely controlled AUSs showed promising results that should be confirmed by in-vivo experiments focusing on efficacy and safety.

The Effect of Cuff Occlusion Protocols on Radial Strain and Arterial Haemodynamics

The purpose of this study is to compare arterial vasodilation in response to two occlusive cuff positions and various protocols under reactive hyperaemic stimulus. For determining the optimal reactive hyperaemia protocol we studied 10 healthy young adults and calculated the relative strain and haemodynamic changes of the left brachial artery with motion estimation from sequential ultrasonic images and Doppler sonograms. The results from two occlusion cuff positions (left proximal upper arm and distal forearm) showed that brachial artery vasodilation was significantly greater under upper arm occlusion than under forearm occlusion. Results from optimizing reactive hyperaemia protocols showed that the optimum occlusion pressure was 150 mmHg, with an occlusion time of 5 min. The optimum time interval for recording ultrasonic images and estimating relative strain after releasing the cuff was 45-60 s. Use of these conditions resulted in higher vasodilation and larger blood flow changes. We conclude that the magnitudes of relative strain and blood velocity are related not only to the choice of the location of cuff inflation and the magnitude of occlusion pressure and time, but also to the time interval after the release of the occlusive cuff.

Continuous measurement of blood flow in the superior sagittal sinus of the lamb

We assessed the validity of recording blood flow in the superior sagittal sinus (Qss) as a measure of cerebral blood flow (CBF). While anesthetized, 10 lambs were instrumented with a transit-time ultrasonic flow probe around the superior sagittal sinus to measure Qss, electrodes to assess sleep state, catheters to measure cerebral perfusion pressure (Pcp), and an occlusive cuff around the common brachiocephalic artery to vary blood pressure. After 72 h recovery, lambs were studied during spontaneous sleep-wake cycles to establish 1) the normal range of Qss and 2) the response rate of Qss to rapid alterations of Pcp. Subsequently, the lambs were reanesthetized, and the measurement of Qss was calibrated and validated. Qss was linearly related to the arterial inflow of 35% of the brain mass (y = 0.5 x + 1.6, r = 0.93, n = 4). Qss was greater in active sleep (154.1 +/- 45.7 ml.min-1 x 100 g-1, mean +/- SD, n = 5) than in quiet sleep (97.1 +/- 40.8 ml.min-1 x 100 g-1) and quiet wakefulness (107 +/- 44.3 ml.min-1 x 100 g-1, P < 0.05). Qss responded rapidly (within one beat) to spontaneous and to induced transient changes in Pcp. We conclude that recording blood flow in the superior sagittal sinus provides a simple, continuous, and quantitative measure of CBF from a defined area of the brain and is appropriate for studying transient changes in the cerebral circulation.