A guide to venous thromboembolism risk factor assessment

An examination of acute physiological and perceptual responses following blood flow restriction exercise using a traditional research device or novel, automated system

Objective. To compare the acute physiological and perceptual responses to blood flow restriction (BFR) exercise using a traditional research device or novel, automated system.Methods. Forty-four resistance trained individuals performed four sets of unilateral elbow flexion exercise (30% one-repetition maximum) to volitional failure using two distinct restrictive devices [SmartCuffs PRO BFR Model (SMARTCUFF), Hokanson E20 Rapid Inflation device (HOKANSON)] and with two levels of BFR [40% limb occlusion pressure (LOP), 80% LOP]. Blood pressure (BP), muscle thickness (MT), and isometric strength (ISO) were assessed prior to and following exercise. Perceptual responses [ratings of perceived exertion (RPE), discomfort] were assessed prior to exercise and following each exercise set.Main results. Data are displayed as means (SD). Immediately following exercise with 40% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 1 of exercise, RPE was greater with SMARTCUFF compared to HOKANSON (p< 0.05). In addition, only following Set 2 of exercise, discomfort was greater with HOKANSON compared to SMARTCUFF (p< 0.001). Immediately following exercise with 80% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 4 of exercise, RPE was greater with HOKANSON compared to SMARTCUFF (p< 0.05). In addition, following all exercise sets, discomfort was greater with HOKANSON compared to SMARTCUFF (p< 0.001). For repetitions completed with 40% LOP there were no statistical differences between SMARTCUFF and HOKANSON across any exercise sets. For repetitions completed with 80% LOP there were no statistical differences between SMARTCUFF and HOKANSON across Set 1 of exercise (p= 0.34), however, for Sets 2-4 of exercise, significantly greater number of repetitions were completed during SMARTCUFF than HOKANSON.Significance. The present study provides valuable insight into the efficacy of a novel, automated BFR system (SMARTCUFF) eliciting comparable acute physiological responses to BFR exercise and in some cases favorable perceptual responses when compared to a traditional research device (HOKANSON).

Comparing the acute responses between a manual and automated blood flow restriction system

The purpose of this study was to compare acute responses between manual and automated blood flow restriction (BFR) systems.

Methods

A total of 33 individuals completed this study. On visit 1, arterial occlusion pressure (AOP, mm Hg), cardiovascular responses, and discomfort (RPE-D) were measured with each BFR system at rest. On visit 2, unilateral bicep curls were completed [30% one-repetition maximum; 50% AOP] with one system per arm. Muscle thickness (MT, cm) and maximal force (N) were assessed before (pre), immediately (post-0), 5 min (post-5), and 10 min (post-10) post-exercise. Ratings of perceived exertion (RPE-E) and ratings of perceived discomfort (RPE-D) were assessed throughout the exercise. AOP and repetitions were compared with Bayesian paired t-tests. Other outcomes were compared with Bayesian RMANOVAs. BF10 represents the likelihood of the best model vs. the null. The results are presented as mean ± SD.

Results

Supine cardiovascular responses and RPE-D were similar for manual and automated (all BF10 ≤ 0.2). Supine AOP for manual (157 ± 20) was higher than that of automated (142 ± 17; BF10 = 44496.0), but similar while standing (manual: 141 ± 17; automated: 141 ± 22; BF10 = 0.2). MT (time, BF10 = 6.047e + 40) increased from Pre (3.9 ± 0.7) to Post-0 (4.4 ± 0.8; BF10 = 2.969e + 28), with Post-0 higher than Post-5 (4.3 ± 0.8) and Post-10 (4.3 ± 0.8; both BF10 ≥ 275.2). Force (time, BF10 = 1.246e + 29) decreased from Pre (234.5 ± 79.2) to Post-0 (149.8 ± 52.3; BF10 = 2.720e + 22) and increased from Post-0 to Post-5 (193.3 ± 72.7; BF10 = 1.744e + 13), with Post-5 to Post-10 (194.0 ± 70.6; BF10 = 0.2) being similar. RPE-E increased over sets. RPE-D was lower for manual than automated. Repetitions per set were higher for manual (Set 1: 37 ± 18; Set 4: 9 ± 5) than automated (Set 1: 30 ± 7; Set 4: 7 ± 3; all BF10 ≥ 9.7).

Conclusion

Under the same relative pressure, responses are mostly similar between BFR systems, although a manual system led to lower exercise discomfort and more repetitions.

Sustained success of a Caprini postoperative venous thromboembolism prevention protocol over one decade

BACKGROUND

The objective of this study was to review the long-term efficacy of a post-operative venous thromboembolism (VTE) prevention program at our institution.

METHODS

We performed a review of the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) data at our hospital from January 2008-December 2022. The primary outcome was risk-adjusted VTE events.

RESULTS

In 2009, a postoperative general surgery patient was three times more likely to have a postoperative VTE event than predicted (O/E ratio 3.02, 95% CI 1.99-4.40). After implementing a mandatory VTE risk assessment model and a risk-commensurate prophylaxis protocol in the electronic medical record in 2011, the odds ratio of a patient developing a postoperative VTE declined to 0.70 by 2014 (95% CI 0.40-1.23). This success persisted through 2022.

CONCLUSIONS

Since the implementation of a standardized postoperative VTE prevention program in 2011, our institution has sustained a desirably low likelihood of VTE events in general surgery patients.

The Impact of Different Ischemic Preconditioning Pressures on Pain Sensitivity and Resistance Exercise Performance

ABSTRACT

Kataoka, R, Song, JS, Yamada, Y, Hammert, WB, Seffrin, A, Spitz, RW, Wong, V, Kang, A, and Loenneke, JP. The impact of different ischemic preconditioning pressures on pain sensitivity and resistance exercise performance. J Strength Cond Res 38(5): 864-872, 2024-To determine (a) the impact of ischemic preconditioning pressures (applied as a % of arterial occlusion pressure [AOP]) on pressure pain threshold (PPT) and resistance exercise performance and (b) whether changes in performance could be explained by changes in PPT. Subjects ( n = 39) completed 4 protocols in a randomized order: (a) ischemic preconditioning (IPC) at 110% AOP (IPC 110%), (b) IPC at 150% AOP (IPC 150%), (c) IPC at 10% AOP (Sham), and (d) time-matched control (CON). Each protocol included 4 cycles of 5 minutes of occlusion followed by 5 minutes of reperfusion. Pressure pain threshold was taken before and after. Discomfort ratings were given at the end of each cycle. Every visit finished with 2 sets of 75-second maximal isokinetic unilateral elbow flexion or extension. Overall, IPC 110% and IPC 150% resulted in similar increases in PPT relative to CON [110%: difference of 0.36 (0.18, 0.54) kg·m -2 ; 150%: difference of 0.377 (0.15, 0.59) kg·m -2 ] and Sham. Both resulted in greater discomfort than Sham and CON, with IPC 150% inducing greater discomfort than IPC 110% (BF 10 : 14.74). There were no differences between the conditions for total work (BF 10 : 0.23), peak torque (BF 10 : 0.035), or average power (BF 10 : 0.159). We did not find evidence that PPT mediated performance. We did not detect changes in performance with 2 different relative pressures greater than AOP. Our mean applied pressures were lower than those used previously. There might be a minimal level of pressure (e.g., >150% of AOP) that is required to induce ergogenic effects of ischemic preconditioning.

Blood flow restriction augments the cross-education effect of isometric handgrip training

INTRODUCTION

The application of blood flow restriction (BFR) to low-intensity exercise may be able to increase strength not only in the trained limb but also in the homologous untrained limb. Whether this effect is repeatable and how that change compares to that observed with higher intensity exercise is unknown.

PURPOSE

Examine whether low-intensity training with BFR enhances the cross-education of strength compared to exercise without BFR and maximal efforts.

METHODS

A total of 179 participants completed the 6-week study, with 135 individuals performing isometric handgrip training over 18 sessions. Participants were randomly assigned to one of four groups: 1) low-intensity (4 × 2 min of 30% MVC; LI, n = 47), 2) low-intensity with blood flow restriction (LI + 50% arterial occlusion pressure; LI-BFR, n = 41), 3) maximal effort (4 × 5 s of 100% MVC; MAX, n = 47), and 4) non-exercise control (CON, n = 44).

RESULTS

LI-BFR was the only group that observed a cross-education in strength (CON: 0.64 SD 2.9 kg, LI: 0.95 SD 3.6 kg, BFR-LI: 2.7 SD 3.3 kg, MAX: 0.80 SD 3.1 kg). In the trained hand, MAX observed the greatest change in strength (4.8 SD 3.3 kg) followed by LI-BFR (2.8 SD 4.0 kg). LI was not different from CON. Muscle thickness did not change in the untrained arm, but ulna muscle thickness was increased within the trained arm of the LI-BFR group (0.06 SD 0.11 cm).

CONCLUSION

Incorporating BFR into low-intensity isometric training led to a cross-education effect on strength that was greater than all other groups (including high-intensity training).

The combined effectiveness of therapeutic ultrasound, electrical stimulations, and blood flow restriction to treat symptoms of muscle damage

This study assessed whether symptoms of muscle damage could be reduced by a combination of therapeutic ultrasound and electrical stimulations, and whether this could be enhanced by blood flow restriction. Before and 48 h after performing eccentric elbow flexion exercises, individuals completed assessments of muscle damage. A 10-min therapeutic ultrasound and electrical stimulation treatment was then applied with and without blood flow restriction to assess short (5 min) and long-term (24 h) improvements. Twenty-three individuals completed the study (11 females). Data were analysed using Bayesian repeated measures ANOVAs. The damaging exercise increased discomfort (BF10 = 2.93e14) and relaxed joint angle (BF10 = 2425.90) while decreasing pain pressure threshold (BF10 = 289.71). Each of these variables was acutely improved with the combination treatment protocol (all BF10 ≥ 74) with no added effect of blood flow restriction. A combination of therapeutic ultrasound and interferential electrical stimulations appeared effective at acutely alleviating symptoms of muscle damage with no additive effect of blood flow restriction.

Blood flow restriction augments exercise-induced pressure pain thresholds over repetition and effort matched conditions

We sought to determine the effects of blood flow restriction (BFR) on exercise-induced hypoalgesia, specifically using low-load (LL) resistance exercise (30% 1RM) protocols that accounted for each individual's local muscular endurance capabilities. Forty-four participants completed four conditions: (1) 70% of maximal BFR repetitions with blood flow restriction (LL+BFR exercise); (2) 70% maximal BFR repetitions without LL+BFR (LL exercise); (3) 70% maximal free flow repetitions (LL+EFFORT exercise); (4) time-matched, non-exercise control (CON). Pressure pain threshold (PPT) was measured before and after exercise. Ischaemic pain threshold and tolerance was assessed only at post. The change in upper body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.15 (0.35) kg/cm2], LL+EFFORT exercise [difference of 0.23 (0.45) kg/cm2], and the CON condition. The change in lower body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.40 (0.55) kg/cm2], LL+EFFORT exercise [difference of 0.36 (0.62) kg/cm2], and the CON condition. Ischaemic pain thresholds and tolerances did not change. Submaximal exercise with BFR resulted in systemic increases in PPT but had no influence on ischaemic pain sensitivity. This effect is likely unique to BFR as we did not see changes in the effort matched free flow condition.

Post-occlusive reactive hyperemia in habituated caffeine users: Effects of abstaining versus consuming typical doses

BACKGROUND

Post-occlusive reactive hyperemia (PORH) typically requires caffeine abstinence. For habitual users, it is unknown if abstinence affects PORH.

OBJECTIVE

Compare PORH after habitual users consume or abstain from caffeine.

METHODS

On separate visits (within-subject), PORH was measured in 30 participants without abstinence from typical caffeine doses (CAFF) and with abstinence (ABS). Measurements included baseline and peak hyperemic velocity, tissue saturation index slopes during ischemia (Slope 1) and following cuff deflation (Slope 2), resting arterial occlusion pressure (AOP), heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure. All variables were compared using Bayesian paired t-tests. BF10 = likelihood of alternative vs null. Results are mean±SD.

RESULTS

Comparing baseline velocity (cm/s) between CAFF (9.3±4.8) and ABS (7.5±4.9) yielded anecdotal evidence (BF10 = 1.0). Peak hyperemic velocity (cm/s) was similar (CAFF = 77.3±16.7; ABS = 77.6±19.0, BF10 = 0.20). For slopes (TSI% /s), CAFF Slope 1 = -0.11±0.04 and Slope 2 = 1.9±0.46 were similar (both BF10≤0.20) to ABS Slope 1 = -0.12±0.03 and Slope 2 = 1.8±0.42. SBP and DBP (mmHg) were both similar (CAFF SBP = 116.0±9.8, DBP = 69.6±5.8; ABS SBP = 115.5±10.7, DBP = 69.5±5.4; both BF10≤0.22). Comparing AOP (mmHg) (CAFF = 146.6±15.0; ABS = 143.0±16.4) yielded anecdotal evidence (BF10 = 0.46). HR (bpm) was similar (CAFF = 66.5±12.3; ABS = 66.9±13.0; BF10 = 0.20).

CONCLUSIONS

In habitual users, consuming or abstaining from typical caffeine doses does not appear to affect post-occlusive reactive hyperemia.

The Hypoalgesic Effect of Low-Load Exercise to Failure Is Not Augmented by Blood Flow Restriction

Purpose: To 1) examine whether blood flow restriction would provide an additional exercise-induced hypoalgesic response at an upper and lower limb when it is incorporated with low-load resistance exercise until failure, and 2) examine if increases in blood pressure and discomfort, with blood flow restricted exercise, would mediate the exercise-induced hypoalgesia over exercise without blood flow restriction. Methods: Forty healthy young participants completed two trials: four sets of unilateral knee extension exercise to failure at 30% of one-repetition maximum, with and without blood flow restriction. Pressure pain thresholds were assessed before (twice) and 5-min post exercise at an upper and lower limb. Blood pressure and discomfort ratings were recorded to examine mediating effects on exercise-induced hypoalgesia with blood flow restricted exercise. Results: Pressure pain threshold increased following both exercise conditions compared to a control, without any differences between exercise conditions at the upper (exercise conditions vs. control: ~0.37 kg/cm2) and lower (exercise conditions vs. control: ~0.60 kg/cm2) limb. The total number of repetitions was lower for exercise with blood flow restriction compared to exercise alone [median difference (95% credible interval) of -27.0 (-29.8, -24.4) repetitions]. There were no mediating effects of changes in blood pressure, nor changes in discomfort, for the changes in pressure pain threshold at either the upper or lower limb. Conclusion: The addition of blood flow restriction to low-load exercise induces a similar hypoalgesic response to that of non-blood flow restricted exercise, with a fewer number of repetitions.

Skeletal Muscle Adaptations to High-Load Resistance Training With Pre-Exercise Blood Flow Restriction

ABSTRACT

Hammert, WB, Moreno, EN, Martin, CC, Jessee, MB, and Buckner, SL. Skeletal muscle adaptations to high-load resistance training with pre-exercise blood flow restriction. J Strength Cond Res 37(12): 2381-2388, 2023-This study aimed to determine if blood flow restriction (BFR) could augment adaptations to a high-load training protocol that was inadequate for muscle growth. Forty nontrained individuals had each arm assigned to 1 of 3 elbow flexion protocols: (a) high-load resistance training [TRAD; 4 sets to muscular failure at 70% 1 repetition maximum (1RM)], (b) low repetition high-load resistance training with pre-exercise BFR (PreBFR; 4 sets of 3 repetitions at 70% 1RM + 3 min of pre-exercise BFR), and (c) low repetition high-load resistance training (LRTRAD); 4 sets of 3 repetitions at 70% 1RM). Muscle thickness (MT), 1RM strength, and local muscular endurance (LME) of the elbow flexors were measured before and after 8 weeks. An alpha level of 0.05 was used for all comparisons. For the 50% site, MT increased for TRAD (0.211 cm, 95% confidence interval [95% CI]: 0.143-0.280), PreBFR (0.105 cm, 95% CI: 0.034-0.175), and LRTRAD (0.073 cm, 95% CI: 0.000-0.146). The change for TRAD was greater than PreBFR and LRTRAD. For the 60% site, MT increased for TRAD (0.235 cm, 95% CI: 0.153-0.317), PreBFR (0.097 cm, 95% CI: 0.014-0.180), and LRTRAD (0.082 cm, 95% CI: 0.000-0.164). The change for TRAD was greater than PreBFR and LRTRAD. For the 70% site MT increased for TRAD (0.308 cm, 95% CI: 0.247-0.369), PreBFR (0.103 cm, 95% CI: 0.041-0.166), and LRTRAD (0.070 cm, 95% CI: 0.004-0.137). The change for TRAD was greater than PreBFR and LRTRAD. One repetition maximum and LME significantly increased for each condition, with no differences between conditions. Collapsed across conditions 1RM strength increased 2.094 kg (95% CI: 1.771-2.416) and LME increased 7.0 repetitions (95% CI: 5.7-8.3). In conclusion, the application of BFR to low-repetition, high-load training did not enhance the adaptative response.

Improved interference control after exercise with blood flow restriction and cooling is associated with but not mediated by increased lactate

BACKGROUND

To evaluate the effects of recumbent sprint interval exercise with and without blood flow restriction and body cooling on interference control and whether the changes in interference control can be explained by the changes in blood lactate.

METHODS

85 participants (22 SD 3 years old) completed 1 familiarization visit and then 5 experimental visits in a randomized order: exercise only (Ex), exercise with blood flow restriction (ExB), exercise with cooling (ExC), and exercise with blood flow restriction and cooling (ExBC), and non-exercise control (Con). Measurements of blood lactate and the Stroop Color Word Test were performed before and after exercise. Each bout began with a 15-minute low-moderate intensity warm-up, followed by five 20-second "all out" sprints separated by 40 s of active recovery. Bayes Factors (BF10) quantified evidence for or against the null hypothesis. Within-subject mediation analysis quantified the indirect effect of changes in blood lactate (mediator) on the change in interference control (each exercise condition vs. Con).

RESULTS

Bayesian pairwise comparisons found that only ExC [σ: -0.37 (-0.59, -0.15)] and ExBC [σ: -0.3 (-0.53, -0.09)] produced changes in incongruent reaction time different from that of Con. There was also evidence that all exercise conditions increased blood lactate (BF10 = 8.65e+29 - 1.9e+32) and improved congruent reaction time (BF10 = 4.01 - 15.371) compared to that of Con. There was no evidence to show that changes in lactate mediated the change in incongruent reaction time.

CONCLUSIONS

Both exercise with body cooling and when body cooling was combined with blood flow restriction presented favorable changes in incongruent reaction time (a marker of interference control), which might not be explained by the changes in systemic blood lactate concentration.

Acute muscular and cardiovascular responses to high load training with pre-exercise blood flow restriction

PURPOSE

The purpose of this study is to examine the acute muscular and cardiovascular responses to applying blood flow restriction (BFR) before high-load training.

METHODS

Forty trained individuals visited the lab on three occasions. On Visit 1, participants completed paperwork and performed strength assessments. During Visits 2 and 3, participants completed four exercise conditions (one in each arm during each visit) as follows: (1) traditional resistance training (TRAD), (2) low load training with BFR (LLBFR), (3) low repetition high load training with pre-exercise BFR (PreBFR), and (4) low repetition traditional training (LRTRAD). Blood pressure, muscle thickness (MT), and isometric strength (ISO) were measured before and after exercise.

RESULTS

Data are displayed as means (SD). Immediately following exercise, MT in TRAD was greater compared with PreBFR (mean difference = 0.18[0.30] cm, p < 0.001) and LRTRAD (mean difference = 0.28[0.30] cm, p < 0.001). In addition, LLBFR demonstrated greater MT compared with PreBFR (mean difference = 0.24[0.30] cm, p < 0.001]. Immediately following exercise, ISO was lower in TRAD compared with PreBFR (mean difference = 33.8[46.9]N, p < 0.001) and the LRTRAD condition (mean difference = 32.8[50.4]N, p < 0.001). In addition, ISO was lower in LLBFR compared with PreBFR (mean difference = 43.9 [47.4]N, p < 0.001) and LRTRAD (mean difference = 42.9 [43.8]N, p < 0.001). Immediately following exercise, systolic blood pressure was greater in TRAD compared with PreBFR and LRTRAD.

CONCLUSION

The application of BFR before engaging in high-load training does not seem to augment the muscular responses to exercise when compared with traditional high loads alone; however, it may pose less demand on the cardiovascular system.

Classification of deep vein thrombosis stages using convolutional neural network of electromyogram with vibrotactile stimulation toward developing an early diagnostic tool: A preliminary study on a pig model

Deep vein thrombosis (DVT) can lead to life-threatening disorders; however, it can only be recognized after its symptom appear. This study proposed a novel method that can detect the early stage of DVT using electromyography (EMG) signals with vibration stimuli using the convolutional neural networks (CNN) algorithm. The feasibility of the method was tested with eight legs before and after the surgical induction of DVT at nine-time points. Furthermore, perfusion pressure (PP), intracompartmental pressure (IP), and shear elastic modulus (SEM) of the tibialis anterior were also collected. In the proposed method, principal component analysis (PCA) and CNN were used to analyze the EMG data and classify it before and after the DVT stages. The cross-validation was performed in two strategies. One is for each leg and the other is the leave-one-leg-out (LOLO), test without any predicted information, for considering the practical diagnostic tool. The results showed that PCA-CNN can classify before and after DVT stages with an average accuracy of 100% (each leg) and 68.4±20.5% (LOLO). Moreover, all-time points (before induction of DVT and eight-time points after DVT) were classified with an average accuracy of 72.0±11.9% which is substantially higher accuracy than the chance levels (11% for 9-class classification). Based on the experimental results in the pig model, the proposed CNN-based method can classify the before- and after-DVT stages with high accuracy. The experimental results can provide a basis for further developing an early diagnostic tool for DVT using only EMG signals with vibration stimuli.

Effect of Increased Pressure Pain Threshold on Resistance Exercise Performance With Blood Flow Restriction

ABSTRACT

Kataoka, R, Song, JS, Bell, ZW, Wong, V, Spitz, RW, Yamada, Y, and Loenneke, JP. Effect of increased pressure pain threshold on resistance exercise performance with blood flow restriction. J Strength Cond Res XX(X): 000-000, 2022-This study aimed to examine whether increasing pressure pain threshold (PPT) through isometric handgrip exercise (HG) affects the number of repetitions completed and discomfort with knee extension exercise (KE) with blood flow restriction (BFR), and examine whether performing additional exercise leads to a further increase in PPT. Forty-one participants completed 2 trials: rest followed by low-load KE with BFR at 80% of resting arterial occlusion pressure (Rest + KE BFR) and low-intensity (30% of maximal strength) HG exercise followed by KE with BFR (HG + KE BFR). Pressure pain threshold was measured before and after exercise at the forearm and tibialis anterior. Results are presented as median difference (95% credible interval). Pressure pain threshold increased at the forearm (Bayes factor [BF10]: 5.2 × 107) and tibialis anterior (BF10: 1.5 × 106) after HG exercise. However, this did not lead to greater repetitions being completed with BFR exercise (0.2 [-0.1, 0.6] repetitions, BF10: 0.07). Pressure pain threshold after BFR exercise was not augmented over that observed with HG exercise (0.02 [-0.15, 0.2] kg·cm-2, BF10: 0.175) at the forearm. More data are needed in the lower body to determine which model best fits the data (BF10: 0.84). Discomfort with BFR exercise was not different between conditions (1.0 [-2.3, 4.4] arbitrary units, BF10: 0.10). The pain-reducing effect of prior exercise did not change the repetitions completed with BFR exercise, suggesting that the change in PPT may not have been great enough to alter performance. Performing additional exercise did not elicit further increases in PPT nor was perceived discomfort to BFR exercise altered by changes in PPT.

Comparative Perceptual, Affective, and Cardiovascular Responses between Resistance Exercise with and without Blood Flow Restriction in Older Adults

Older adults and patients with chronic disease presenting with muscle weakness or musculoskeletal disorders may benefit from low-load resistance exercise (LLRE) with blood flow restriction (BFR). LLRE-BFR has been shown to increase muscle size, strength, and endurance comparable to traditional resistance exercise but without the use of heavy loads. However, potential negative effects from LLRE-BFR present as a barrier to participation and limit its wider use. This study examined the perceptual, affective, and cardiovascular responses to a bout of LLRE-BFR and compared the responses to LLRE and moderate-load resistance exercise (MLRE). Twenty older adults (64.3 ± 4.2 years) performed LLRE-BFR, LLRE and MLRE consisting of 4 sets of leg press and knee extension, in a randomised crossover design. LLRE-BFR was more demanding than LLRE and MLRE through increased pain (p ≤ 0.024, d = 0.8-1.4) and reduced affect (p ≤ 0.048, d = -0.5--0.9). Despite this, LLRE-BFR was enjoyed and promoted a positive affective response (p ≤ 0.035, d = 0.5-0.9) following exercise comparable to MLRE. This study supports the use of LLRE-BFR for older adults and encourages future research to examine the safety, acceptability, and efficacy of LLRE-BFR in patients with chronic disease.

A comparison of variability between absolute and relative blood flow restriction pressures

Recommendations are that blood flow restriction (BFR) be applied relative to arterial occlusion pressure (AOP) to provide a similar stimulus.

PURPOSE

Compare variability of the change in blood flow, shear rate, and discomfort between recommended relative pressures and an absolute pressure.

METHODS

During one visit, brachial arterial blood flow was measured in 91 participants using pulse-wave Doppler ultrasonography. After 5-min seated rest, AOP was measured. Following another 5-min rest, blood flow and discomfort were assessed twice before cuff inflation as controls (C1 and C2), then again with a cuff inflated to each BFR pressure (all measures separated by 1-min). Change scores from C1 to all subsequent measures were calculated (i.e., C2-C1; 40%AOP-C1; 80%AOP-C1; 100mmHg-C1). Variability of the changes were compared via pairwise modified Pitman-Morgan tests (α=.008).

RESULTS

Variance (95%CI) of the change for blood flow (mL/min), shear rate (1/sec), and discomfort (AU) had similar trends. C2-C1 differed from all conditions (all p<.001), 40%AOP-C1 differed from 80%AOP-C1 and 100mmHg-C1 (all p<.001), which did not differ (both p≥.117). Blood flow: C2-C1=469.79 (357.90, 644.07), 40%AOP-C1=1263.18 (962.34, 1731.80), 80%AOP-C1=1752.90 (1335.42, 2403.18), 100mmHg-C1=1603.18 (1221.36, 2197.92); Shear rate: C2-C1=6248.24 (4760.10, 8566.15), 40%AOP-C1=14625.30 (11142.06, 20050.95), 80%AOP-C1=22064.02 (16809.13, 30249.27), 100mmHg-C1=20778.76 (15829.98, 28487.21); Discomfort: C2-C1=0.07 (0.05, 0.08), 40%AOP-C1=2.03 (1.55, 2.78), 80%AOP-C1=4.26 (3.25, 5.84), 100mmHg-C1=4.50 (3.43, 6.17).

CONCLUSION

Contrary to previous suggestions, applying relative pressures does not necessarily guarantee a similar stimulus. It seems that higher pressures produce more variable changes even if the external pressure applied is made relative to each individual. This article is protected by copyright. All rights reserved.

A Useful Blood Flow Restriction Training Risk Stratification for Exercise and Rehabilitation

Blood flow restriction training (BFRT) is a modality with growing interest in the last decade and has been recognized as a critical tool in rehabilitation medicine, athletic and clinical populations. Besides its potential for positive benefits, BFRT has the capability to induce adverse responses. BFRT may evoke increased blood pressure, abnormal cardiovascular responses and impact vascular health. Furthermore, some important concerns with the use of BFRT exists for individuals with established cardiovascular disease (e.g., hypertension, diabetes mellitus, and chronic kidney disease patients). In addition, considering the potential risks of thrombosis promoted by BFRT in medically compromised populations, BFRT use warrants caution for patients that already display impaired blood coagulability, loss of antithrombotic mechanisms in the vessel wall, and stasis caused by immobility (e.g., COVID-19 patients, diabetes mellitus, hypertension, chronic kidney disease, cardiovascular disease, orthopedic post-surgery, anabolic steroid and ergogenic substance users, rheumatoid arthritis, and pregnant/postpartum women). To avoid untoward outcomes and ensure that BFRT is properly used, efficacy endpoints such as a questionnaire for risk stratification involving a review of the patient’s medical history, signs, and symptoms indicative of underlying pathology is strongly advised. Here we present a model for BFRT pre-participation screening to theoretically reduce risk by excluding people with comorbidities or medically complex histories that could unnecessarily heighten intra- and/or post-exercise occurrence of adverse events. We propose this risk stratification tool as a framework to allow clinicians to use their knowledge, skills and expertise to assess and manage any risks related to the delivery of an appropriate BFRT exercise program. The questionnaires for risk stratification are adapted to guide clinicians for the referral, assessment, and suggestion of other modalities/approaches if/when necessary. Finally, the risk stratification might serve as a guideline for clinical protocols and future randomized controlled trial studies.

Blood flow restriction maintains blood pressure upon head-up tilt

BACKGROUND

Orthostatic intolerance occurs in some astronauts following space flight. Although orthostatic blood pressure responses should normalize in the weeks following the return to Earth, there may be situations where an immediate short-term solution is necessary (e.g., emergency evacuation).

PURPOSE

The purpose of this study was to examine different levels of blood flow restriction on changes in blood pressure and heart rate when transitioning from supine to a head-up tilt and determine whether this change differs based on sex.

METHODS

Eighty-nine participants (45 men, 44 women) completed the three visits with different pressures (Sham, Moderate, and High) in a randomized order. Cuffs were placed on the most proximal area of the thighs. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and eight more times separated by 45 seconds.

RESULTS

Data are presented as mean (SD). The change in systolic (High > Moderate > Sham) [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4) mmHg, and Moderate vs Sham: 2.4 (8.4) mmHg] and diastolic pressure (High > Moderate = Sham) [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3) mmHg] differed across applied pressures. The change in heart rate was initially greatest in the sham-pressure but increased the greatest in the high-pressure condition by the end of the head-up tilt period. Additionally, there was no influence of sex.

CONCLUSION

Blood flow restriction applied in this study increased blood pressure in a pressure-dependent manner upon head-up tilt.

Muscle growth adaptations to high-load training and low-load training with blood flow restriction in calf muscles

PURPOSE

To compare muscle growth adaptations between traditional high-load training and low-load training with blood flow restriction (BFR) in the calf muscles over 6 weeks.

METHODS

27 trained individuals performed calf exercise in both legs for 6 weeks. Each leg was randomly assigned to one of the two conditions: (1) Traditional (70% of 1RM) training (TRAD); and (2) Low-load (30% of 1RM) training with BFR. In addition, subjects performed standing calf raises with or without BFR. Measures were taken pre- and post-intervention.

RESULTS

For the posterior muscle site, there was no condition (BFR vs. TRAD) × time (pre vs. post) interaction (p = 0.15). In addition, there was no main effect for condition (p = 0.83) or time (p = 0.20). For the lateral muscle site, there was no condition × time interaction (p = 0.47). In addition, there was no main effect for condition (p = 0.10) or time (p = 0.57). For the medial muscle site, there was no condition × time interaction (p = 0.60). In addition, there was no main effect for condition (p = 0.44) or time (p = 0.72). For RPE, there was no condition × time interaction. However, there was a main effect for condition (p < 0.05) with BFR having higher RPE. For discomfort, there was no condition × time interaction. However, there was a main effect for condition (p < 0.001) with the BFR condition displaying higher discomfort.

CONCLUSION

No muscle growth was detected in the calf musculature. BFR was not more effective at eliciting muscle hypertrophy compared to traditional training. However, it was accompanied with higher exertion and discomfort.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets for potential treatment of deep venous thrombosis

Current thrombolytic therapies for deep venous thrombosis are limited due to the wide side effect profile. Contrast mediated sonothrombolysis is a promising approach for thrombus treatment. The current study examines the effectiveness of in vitro streptokinase (SK) loaded phase-change nanodroplet (PCND) mediated sonothrombolysis at 7 MHz for the diagnosis of deep venous thrombosis. Lecithin shell and perfluorohexane core nanodroplets were prepared via the thin-film hydration method and morphologically characterized. Sonothrombolysis was performed at 7 MHz at different mechanical indexes of samples i.e., only sonothrombolysis, PCND mediated sonothrombolysis, sonothrombolysis with SK and SK loaded PCND mediated sonothrombolysis. Thrombolysis efficacy was assessed by measuring clot weight changes during 30 min US exposure, recording the mean gray intensity from the US images of the clot by computer software ImageJ, and spectrophotometric quantification of the hemoglobin in the clot lysate. In 15 minutes of sonothrombolysis performed at high mechanical index (0.9 and 1.2), SK loaded PCNDs showed a 48.61% and 74.29% reduction of mean gray intensity. At 0.9 and 1.2 MI, 86% and 92% weight loss was noted for SK-loaded PCNDs in confidence with spectrophotometric results. A significant difference (P < 0.05) was noted for SK-loaded PCND mediated sonothrombolysis compared to other groups. Loading of SK inside the PCNDs enhanced the efficacy of sonothrombolysis. An increase in MI and time also increased the efficacy of sonothrombolysis. This in vitro study showed the potential use of SK-loaded perfluorohexane core PCNDs as sonothrombolytic agents for deep venous thrombosis.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets.

Hypoalgesia following isometric handgrip exercise with and without blood flow restriction is not mediated by discomfort nor changes in systolic blood pressure

The purpose was to examine the effect of isometric handgrip exercise with and without blood flow restriction on exercise-induced hypoalgesia at a local and non-local site, and its underlying mechanisms. Sixty participants (21 males & 39 females, 18-35 years old) completed 3 trials: four sets of 2-minute isometric handgrip exercise at 30% of maximum handgrip strength; isometric handgrip exercise with blood flow restriction at 50% of arterial occlusion pressure; and a non-exercise time-matched control. Pain thresholds increased similarly in both exercise conditions at a local (exercise conditions: ~0.45 kg/cm², control: ~-0.04 kg/cm²) and non-local site (exercise conditions: ~0.37 kg/cm², control: ~-0.16 kg/cm²). Blood flow restriction induced greater feelings of discomfort compared to exercise alone [median difference (95% credible interval) of 4.5 (0.5, 8.6) arbitrary units]. Blood pressure increased immediately after exercise (systolic: 10.3 mmHg, diastolic: 7.7 mmHg) and decreased in recovery. There was no within participant correlation between changes in discomfort and pressure pain threshold. A bout of isometric handgrip exercise with or without blood flow restriction can provide exercise-induced hypoalgesia at a local and non-local site. However, discomfort and changes in systolic blood pressure do not explain this response.

Effects of isometric handgrip exercise with or without blood flow restriction on interference control and feelings

The purpose of this study was to investigate whether isometric handgrip exercise, with or without blood flow restriction, would alter interference control and feelings. 60 healthy young adults completed three experimental visits, consisting of four sets of 2 min isometric handgrip exercise, at 30% of maximal strength with or without blood flow restriction (50% of arterial occlusion pressure), or a non-exercise/time-matched control. Exercise-induced feeling inventory and Stroop Color Word Test were performed at pre- and ~10-min post-exercise, respectively. Bayes factors (BF₁₀ ) quantified the evidence for or against the null. There were no changes or differences between conditions for interference control following exercise with or without blood flow restriction (Incongruent BF₁₀ : 0.155; Stroop Interference BF₁₀ : 0.082). There were also no differences in the error rate as well as no differences between conditions for changes in 'positivity' or 'revitalization'. Feelings of 'tranquility' were reduced relative to a control following exercise with (median δ [95% credible interval]: -0.74 (-1.05, -0.45), BF₁₀ : 5515.7) and without (median δ: -0.72 [-1.02, -0.41], BF₁₀ : 571.3) blood flow restriction. These changes were not different between exercise conditions. Feelings of 'physical exhaustion' were increased relative to a control following exercise without blood flow restriction (median δ: 0.35[0.09, 0.61], BF₁₀ : 5.84). However, this increase was not different from the same exercise with blood flow restriction. These results suggest that 1) isometric handgrip exercise could be performed without impairing interference control, even when blood flow restriction is added, and that 2) changes in feelings occur independent of changes in interference control.

The Relationship Between Muscle Size and Strength Does not Depend on Echo Intensity in Healthy Young Adults

Muscle quality is typically defined as muscle strength relative to muscle size. Echo intensity has gained popularity as an index of skeletal muscle quality. There is common agreement that muscle size is related to strength at baseline and echo intensity is purported to impact this relationship. Thus, the purpose of this study was to examine whether echo intensity can be used as a physiological marker for muscle quality by investigating the moderating effect of echo intensity on the relationship between muscle size and strength. A sample of 96 participants was used for the upper body analysis and a separate sample of 96 participants was used for the lower body analysis. Echo intensity, muscle thickness, and strength measurements were measured on each limb. For strength, participants performed unilateral elbow flexion (upper body analysis) and knee extension (lower body analysis) to quantify 1-repetition maximum. Muscle thickness and echo intensity were determined from images captured using B-mode ultrasound. Muscle size correlated with muscle strength for all limbs. However, the relationship between muscle size and strength was not significantly moderated by echo intensity for Arm 1 (b = 0.042, p = 0.54) or Arm 2 (b = -0.002, p = 0.97). At the proximal site, no significant moderating effect of echo intensity was found in Leg 1 (b = 0.037, p = 0.67) or Leg 2 (b = -0.085, p = 0.29). Similarly, no significant moderating effect was observed at the distal site for Leg 1 (b = 0.03, p = 0.69) or Leg 2 (b = -0.026, p = 0.75). The results would indicate that the relationship between muscle size and strength does not depend on echo intensity. Therefore, the use of echo intensity as an index of muscle quality in healthy young adults may need to be reconsidered.

Unilateral, bilateral, and alternating muscle actions elicit similar muscular responses during low load blood flow restriction exercise

PURPOSE

Compare acute muscular responses to unilateral, bilateral, and alternating blood flow restriction (BFR) exercise.

METHODS

Maximal strength was tested on visit one. On visits 2-4, 2-10 days apart, 19 participants completed 4 sets of knee extensions (30% one-repetition maximum) with BFR (40% arterial occlusion pressure) to momentary failure (inability to lift load) using each muscle action (counterbalanced order). Ultrasound muscle thickness was measured at 60% and 70% of the anterior thigh before (Pre), immediately (Post-0), and 5 min (Post-5) after exercise. Surface electromyography and tissue deoxygenation were measured throughout. Results, presented as means, were analyzed with a three-way (sex by time by condition) Bayesian RMANOVA.

RESULTS

There was a time by sex interaction (BF_inclusion: 5.489) for left leg 60% muscle thickness (cm). However, changes from Pre to Post-0 (males: 0.39 vs females: 0.26; BF₁₀: 0.839), Post-0 to Post-5 (males: - 0.05 vs females: - 0.06; BF₁₀: 0.456), and Pre to Post-5 (males: 0.34 vs females: 0.20; BF₁₀: 0.935) did not differ across sex. For electromyography (%MVC), there was a sex by condition interaction (BF_inclusion: 550.472) with alternating having higher muscle excitation for females (16) than males (9; BF₁₀: 5.097). Tissue deoxygenation (e.g. channel 1, µM) increased more for males (sets 1: 11.17; 2: 2.91; 3: 3.69; 4: 3.38) than females (sets 1: 4.49; 2: 0.24; 3: - 0.10; 4: - 0.06) from beginning to end of sets (all BF_inclusion ≥ 4.295e + 7). For repetitions, there was an interaction (BF_inclusion: 17.533), with alternating completing more than bilateral and unilateral for set one (100; 56; 50, respectively) and two (34; 16; 18, respectively).

CONCLUSION

Alternating, bilateral, and unilateral BFR exercise elicit similar acute muscular responses.

Association of Prolonged-Duration Chemoprophylaxis With Venous Thromboembolism in High-risk Patients With Head and Neck Cancer

Importance

Venous thromboembolism (VTE) is associated with substantial morbidity and is the most common factor associated with preventable death among hospitalized patients. Data from otolaryngologic studies suggest that the risk of VTE may be underestimated among high-risk patients, particularly among those undergoing oncologic procedures. The incorporation of prolonged-duration chemoprophylaxis (PDC) into preventive therapy has been associated with substantial decreases in VTE incidence among patients undergoing oncologic surgery. However, bleeding remains a major concern among otolaryngologists, and substantial variation exists in the use of thromboprophylaxis.

Objective

To assess the association between PDC and VTE in high-risk patients with head and neck cancer undergoing oncologic procedures.

Design, Setting, and Participants

This retrospective cohort study identified 750 patients with biopsy-confirmed head and neck cancer and a Caprini risk score of 8 or higher who underwent inpatient oncologic surgery at a tertiary care referral center between January 1, 2014, and February 1, 2020. After exclusions, 247 patients were included in the study; patients were divided into 2 cohorts, traditional and PDC, based on the duration of prophylaxis. Univariate and multivariate analyses were performed to examine the development of VTE and bleeding-associated complications during the 30-day postoperative period. Data were analyzed from April 1 to April 30, 2020.

Exposures

PDC, defined as 7 or more postoperative days of chemoprophylaxis.

Main Outcomes and Measures

VTE and bleeding events during the 30-day postoperative period.

Results

Among 247 patients (mean [SD] age, 63.1 [11.1] years; 180 men [72.9%]) included in the study, 106 patients (42.9%) received traditional prophylaxis, and 141 patients (57.1%) received PDC. The incidence of VTE was 5 of 106 patients (4.7%) in the traditional cohort and 1 of 141 patients (0.7%) in the PDC cohort (odds ratio [OR], 0.15; 95% CI, 0.003-1.33). In the multivariate logistic regression analysis, PDC was independently associated with reductions in the risk of VTE (OR, 0.04; 95% CI, 0.001-0.46). The incidence of bleeding events was 1 of 106 patients (0.9%) in the traditional cohort and 6 of 141 patients (4.3%) in the PDC cohort (OR, 4.64; 95% CI, 0.55-217.00).

Conclusions and Relevance

The use of chemoprophylaxis for high-risk patients with head and neck cancer remains a high-priority topic. The results of this study suggest that PDC may be associated with reductions in VTE among this patient population. However, the associated increase in nonfatal bleeding events warrants careful consideration and further highlights the need to determine an optimal duration for chemoprophylaxis among this distinct cohort.

Classification and treatment of endothermal heat-induced thrombosis: Recommendations from the American Venous Forum and the Society for Vascular Surgery

The American Venous Forum (AVF) and the Society for Vascular Surgery set forth these guidelines for the management of endothermal heat-induced thrombosis (EHIT). The guidelines serve to compile the body of literature on EHIT and to put forth evidence-based recommendations. The guidelines are divided into the following categories: classification of EHIT, risk factors and prevention, and treatment of EHIT. One major feature is to standardize the reporting under one classification system. The Kabnick and Lawrence classification systems are now combined into the AVF EHIT classification system. The novel classification system affords standardization in reporting but also allows continued combined evaluation with the current body of literature. Recommendations codify the use of duplex ultrasound for the diagnosis of EHIT. Risk factor assessments and methods of prevention including mechanical prophylaxis, chemical prophylaxis, and ablation distance are discussed. Treatment guidelines are tailored to the AVF EHIT class (ie, I, II, III, IV). Reference is made to the use of surveillance, antiplatelet therapy, and anticoagulants as deemed indicated, and the recommendations incorporate the use of the novel direct oral anticoagulants. Last, EHIT management as it relates to the great and small saphenous veins is discussed.

Classification and treatment of endothermal heat-induced thrombosis: Recommendations from the American Venous Forum and the Society for Vascular Surgery This Practice Guidelines document has been co-published in Phlebology [DOI: 10.1177/0268355520953759] and Journal of Vascular Surgery: Venous and Lymphatic Disorders [DOI: 10.1016/j.jvsv.2020.06.008]. The publications are identical except for minor stylistic and spelling differences in keeping with each journal's style. The contribution has been published under a Attribution-Non Commercial-No Derivatives 4.0 International (CC BY-NC-ND 4.0), (https://creativecommons.org/licenses/by-nc-nd/4.0/)

The American Venous Forum (AVF) and the Society for Vascular Surgery set forth these guidelines for the management of endothermal heat-induced thrombosis (EHIT). The guidelines serve to compile the body of literature on EHIT and to put forth evidence-based recommendations. The guidelines are divided into the following categories: classification of EHIT, risk factors and prevention, and treatment of EHIT.

One major feature is to standardize the reporting under one classification system. The Kabnick and Lawrence classification systems are now combined into the AVF EHIT classification system. The novel classification system affords standardization in reporting but also allows continued combined evaluation with the current body of literature. Recommendations codify the use of duplex ultrasound for the diagnosis of EHIT. Risk factor assessments and methods of prevention including mechanical prophylaxis, chemical prophylaxis, and ablation distance are discussed.

Treatment guidelines are tailored to the AVF EHIT class (ie, I, II, III, IV). Reference is made to the use of surveillance, antiplatelet therapy, and anticoagulants as deemed indicated, and the recommendations incorporate the use of the novel direct oral anticoagulants. Last, EHIT management as it relates to the great and small saphenous veins is discussed.

Blood Flow Restriction Exercise: Effects of Sex, Cuff Width, and Cuff Pressure on Perceived Lower Body Discomfort

Narrow cuffs cause less discomfort than wide cuffs immediately following elbow flexion exercise in combination with blood flow restriction, possibly due to a balling up effect of the bicep underneath the cuff. In this study, we sought to examine the impact of cuff width, sex, and pressure on perceived discomfort in the quadriceps, following knee extensions. One hundred participants completed three separate experiments. In Experiment 1, we compared participants' discomfort at rest after using a 5 and a 12 cm cuff. In Experiment 2, we compared the discomfort from these two cuffs after four sets of exercise. In Experiment 3, we used the same exercise protocol as in Experiment 2, but we compared the discomfort between a 12 cm cuff inflated to an inappropriate pressure and a 12 cm cuff inflated to the recommended pressure. We found no sex differences in Experiments 1 and 3. In Experiment 1, the narrow cuff had higher discomfort (16 vs 12 AU). In Experiment 2, men reported higher discomfort than women, with no discomfort differences related to cuff width, though narrow cuffs were most preferred. In Experiment 3, cuffs inflated to a pressure intended for narrow cuffs were associated with higher discomfort, and participants preferred to use it less. In summary, we found no strong evidence for discomfort differences due to cuff width. There was some indication that participants preferred narrow cuffs with pressures inflated to the recommended relative pressure. Muscle shape may influence how cuff width affects discomfort.

The Effect of Blood Flow Restriction Therapy on Recovery After Experimentally Induced Muscle Weakness and Pain

Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res XX(X): 000-000, 2020-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

The rational use of thromboprophylaxis therapy in hospitalized patients and the perspectives of health care providers in Northern Cyprus

Background

Despite the presence of effective strategies and standard guidelines for the prevention of deep vein thrombosis (DVT), a considerable proportion of patients at risk of developing thromboembolism did not receive prophylaxis during hospitalization, while others received it irrationally, thus led to unwanted side effects.

Aim

This study aimed to evaluate the current thromboprophylaxis practice and management of hospitalized patients at risk of developing DVT, along with the assessment of health care providers (HCPs) knowledge, and attitudes regarding DVT prevention.

Methods

An observational study was conducted in the general wards of two leading tertiary university hospitals in Northern Cyprus in which patients from multiple clinics were enrolled to investigate the rational use of DVT prophylaxis using the Caprini risk assessment tool. Patients were also followed for possible complications two weeks post-hospitalization. A cross-sectional study followed to assess the knowledge and attitude of HCPs regarding DVT risks and prophylaxis.

Results

Of the 180 patients enrolled, 47.7% were identified as irrationally managed, 52.3% were identified as rationally managed, 77.8% of patients were identified as having a high level of risk. Notably, Four of thirteen patients who received more thromboprophylaxis developed minor complications. Additionally, 73.3% of nurses had not received DVT education. Furthermore, more than 50% of physicians and nurses achieved a low knowledge score for DVT risks and prophylaxis.

Conclusions

A high degree of irrationality in the administration of thromboprophylaxis therapy to hospitalized patients was observed. The overall scores for HCPs indicated insufficient knowledge of DVT risk assessments and prophylaxis.

Acute cardiovascular response to unilateral, bilateral, and alternating resistance exercise with blood flow restriction

AIM

Blood flow restriction (BFR) exercise is a common alternative to traditional high-load resistance exercise used to increase muscle size and strength. Some populations utilizing BFR at a low load may wish to limit their cardiovascular response to exercise. Different contraction patterns may attenuate the cardiovascular response, but this has not been compared using BFR.

PURPOSE

To compare the cardiovascular response to unilateral (UNI), bilateral (BIL), and alternating (ALT) BFR exercise contraction patterns.

METHODS

Twenty healthy participants performed four sets (30 s rest) of knee extensions to failure, using 30% one-repetition maximum, 40% arterial occlusion pressure, and each of the three contraction patterns (on different days, at the same time of day, separated by 2-10 days, randomized). Cardiovascular responses, presented as pre- to post-exercise mean changes (SD), were measured using pulse wave analysis and analyzed with Bayesian RMANOVA.

RESULTS

ALT caused greater changes in: aortic systolic [ΔmmHg: ALT = 21(8); UNI = 13(11); BIL = 15(8); BF₁₀ = 29.599], diastolic [ΔmmHg: ALT = 13(8); UNI = 7(11); BIL = 8(8); BF₁₀ = 5.175], and mean arterial [ΔmmHg: ALT = 19(8); UNI = 11(11); BIL = 13(7); BF₁₀ = 48.637] blood pressures. Aortic [ΔmmHg bpm: ALT = 4945(2340); UNI = 3294(1408); BIL = 3428 (1461); BF₁₀ = 113.659] and brachial [ΔmmHg bpm: ALT = 6134(2761); UNI = 4300(1709); BIL = 4487(1701); BF₁₀ = 31.845] rate pressure products, as well as heart rate [Δbpm: ALT = 26(14); UNI = 19(8); BIL = 19(11); BF₁₀ = 5.829] were greatest with ALT. Augmentation index [Δ%: UNI = -6(13); BIL = - 7(11); ALT = - 5(16); BF₁₀ = 0.155] and wave reflection magnitude [Δ%: UNI = - 5(9); BIL = - 4(7); ALT = - 4(7); BF₁₀ = 0.150] were not different.

CONCLUSION

Those at risk of a cardiovascular event may choose unilateral or bilateral BFR exercise over alternating until further work determines the degree to which it can be tolerated.

The acute muscular response to passive movement and blood flow restriction

PURPOSE

To compare the acute effects of passive movement combined with blood flow restriction (PM + BFR) to passive movement (PM) or blood flow restriction alone (BFR).

METHODS

A total of 20 healthy participants completed: time control (TC), PM, BFR and PM + BFR (one per leg, over 2 days; randomized). For PM, a dynamometer moved the leg through 3 sets of 15 knee extensions/flexions (90° at 45°/second). For BFR, a cuff was inflated to 80% arterial occlusion pressure on the upper leg. Measurements consisted of anterior muscle thickness at 60% and 70% of the upper leg before and after (-0, -5 and -10 min) conditions, ratings of perceived effort and discomfort before conditions and after each set, and of the vastus lateralis during conditions. Data, presented as mean (SD), were compared using Bayesian RMANOVA, except for perceived effort and discomfort, which were compared using a Friedman's test (non-parametric).

RESULTS

60% (Δcm before-after-0: TC = 0.04 [0.09], PM = -0.01 [0.15], BFR = 0.00 [0.11], PM + BFR = 0.01 [0.22]) and 70% (Δcm before-after-0: TC = 0.01 [0.09], PM = -0.01 [0.15], BFR = 0.02 [0.11], PM + BFR = -0.03 [0.22]) muscle thickness did not change. Perceived effort was greater than TC following PM (p = .05) and PM + BFR (p = .001). Perceived discomfort was greater following BFR and PM + BFR compared to TC (all p ≤ .002) and PM (all p ≤ .010). Changes in deoxygenation (e.g. channel 1; ΔμM start set 1-end set 3: TC = 0.9 [1.2], PM = -1.2 [1.9], BFR = 10.3 [2.7], PM + BFR = 10.3 [3.0]) were generally greater with BFR and PM + BFR (BF_inclusion  = 1.210e + 13).

CONCLUSION

Acute muscular responses to PM + BFR are not augmented over the effect of BFR alone.

Ischemic Preconditioning Did Not Affect Central and Peripheral Factors of Performance Fatigability After Submaximal Isometric Exercise

The present study was designed to provide further insight into the mechanistic basis for the improved exercise tolerance following ischemic preconditioning (IPC) by investigating key-determinants of performance and perceived fatigability. Using a randomized, counterbalanced, single-blind, sham-controlled, crossover design, 16 males performed an isometric time-to-exhaustion test with the knee extensors at 20% maximal voluntary torque (MVT) after an IPC and a sham treatment (SHAM). Those who improved their time-to-exhaustion following IPC performed a time-matched IPC trial corresponding to the exercise duration of SHAM (IPC_tm). Neuromuscular function was assessed before and after exercise termination during each condition (IPC, IPC_tm, and SHAM) to analyze the impact of IPC on performance fatigability and its central and peripheral determinants. Muscle oxygenation (SmO₂), muscle activity, and perceptual responses (effort and muscle pain) were recorded during exercise. Performance fatigability as well as its central and peripheral determinants were quantified as percentage pre-post changes in MVT (ΔMVT) as well as voluntary activation (ΔVA) and quadriceps twitch torque evoked by paired electrical stimuli at 100 and 10 Hz (ΔPS100 and ΔPS10⋅PS100^-1 ratio), respectively. Time-to-exhaustion, performance fatigability, its determinants, muscle activity, SmO₂, and perceptual responses during exercise were not different between IPC and SHAM. However, six participants improved their performance by >10% following IPC (299 ± 71 s) compared to SHAM (253 ± 66 s, d = 3.23). The time-matched comparisons (IPC_tm vs. SHAM) indicated that performance fatigability, its determinants, and SmO₂ were not affected, while effort perception seemed to be lower (η_p ² = 0.495) in those who improved their time-to-exhaustion. The longer time-to-exhaustion following IPC seemed to be associated with a lower effort perception (η_p ² = 0.380) and larger impairments in neuromuscular function, i.e., larger ΔMVT, ΔVA, and ΔPS10⋅PS100^-1 ratio (d = 0.71, 1.0, 0.92, respectively). IPC did neither affect exercise tolerance, performance fatigability, as well as its central and peripheral determinants, nor muscle activity, SmO₂, and perceptual responses during submaximal isometric exercise. However, IPC seemed to have an ergogenic effect in a few subjects, which might have resulted from a lower effort perception during exercise. These findings support the assumption that there are 'responders' and 'non-responders' to IPC.

Muscle swelling following blood flow-restricted exercise does not differ between cuff widths in the proximal or distal portions of the upper leg

The purpose was to understand how wider cuffs, covering larger portions of the limb, may affect acute muscle swelling when used during low-load knee extension exercise with blood flow restriction. A total of 96 individuals (53 females and 43 males) completed two visits, with visit one used for measuring maximal strength and arterial occlusion pressure (AOP), and visit two to compare between a narrow (5 cm) and a wide (12 cm) cuff for acute changes in muscle thickness and echo intensity following exercise. Ultrasound measurements were completed at a proximal and distal site within both legs, with the proximal site located beneath the cuff within the leg exercising using the wide cuff. Study findings indicate that the difference in acute changes for muscle thickness [median difference (95% credible interval) of 0.009 (-0.03, 0.05) cm] and echo intensity [median difference (95% credible interval) of 0.79 (-0.28, 1.89) AU] between cuff widths did not differ between proximal and distal sites. Additionally, acute changes in muscle thickness did not differ between cuff widths, sexes or participants who had AOP measured and those who were estimated. Lastly, acute changes in echo intensity did not differ between cuff widths and those who had AOP measured and those who were estimated. However, there was evidence showing how there might be greater reductions in echo intensity for females at the distal site. The previously observed attenuation of muscle growth under the cuff is unlikely to be related to differences in the acute muscle swelling response.

Effects of Blood Flow Restriction Training on Muscle Strength and Architecture

Korkmaz, E, Dönmez, G, Uzuner, K, BabayevaŞerife Şeyma Torgutalp, N, and Özçakar, L. Effects of blood flow restriction training on muscle strength and architecture. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to compare the effect of the traditional resistance (RES) training and low-intensity resistance training with blood flow restriction (BFR) protocols on quadriceps and hamstring muscle strength, and rectus femoris (RF) and vastus lateralis architecture, in youth team soccer players. Twenty-three young trained soccer team players were divided into 2 groups: the RES group that practiced traditional high-intensity resistance training (80% 1 repetition maximum [1RM], 4 sets, 12 rep.) (n = 12) and the BFR group that performed low-intensity resistance exercise with BFR (30% 1RM, 4 sets, 30-15-15-15 rep) (n = 11)-unilateral knee extension exercise-twice a week for 6 weeks. Muscle strength (isokinetic concentric peak torque of the quadriceps and hamstring muscles) and ultrasonographic parameters (muscle thickness, pennation angle, and fascicle length) were assessed. Bilateral knee flexor and extensor strength was increased in both groups compared with pre-exercise. The increase in dominant side extensor muscle strength (60°·s p = 0.02, ηp = 0.256, 180°·s p = 0.019, ηp = 0.271) and RF thickness (p = 0.002, ηp = 0.361) was statistically higher in the BFR group than in the RES group. These findings support that occlusion training can provide better benefits than traditional strength training to improve muscle hypertrophy. In addition, the novelty of our study is that BFR training may affect the muscle structure measured by ultrasonography.

Caprini score and surgical times linked to the risk for venous thromboembolism after robotic-assisted radical prostatectomy

OBJECTIVE

To evaluate the Caprini score as an independent predictor of venous thromboembolism (VTE) in patients undergoing robotic-assisted radical prostatectomy (RARP) and to identify appropriate cut-points for clinical use.

MATERIAL AND METHODS

We performed a retrospective review of patients who underwent RARP for prostate cancer between December 2003 and February 2016. VTE cases developed the condition within 90 days of discharge. The control group was comprised of patients whose RARP most closely preceded and followed each VTE case in time and who were matched on lymph node dissection and surgeon. The Caprini score was calculated for each patient, and the groups were compared on a number of clinical variables. Multiple logistic regression was used to evaluate whether the Caprini score was an independent predictor of VTE. Receiver operating characteristics (ROC) curves were used to establish appropriate clinical cutpoints.

RESULTS

A total of 3719 patients underwent RARP during the study period. A total of 52 (1.4%) of patients met the criteria for cases. Data were available for 97 patients who met the criteria for controls. Multiple logistic regression indicated that the Caprini score and operative time were independently both significant predictors of VTE (p=0.005 and p=0.044, respectively). ROC indicated that the Caprini score showed a significant but moderate relationship to VTE (area under curve [AOC]=0.64; p=0.004). A Caprini score >6 was the best arithmetic balance for sensitivity (61.5; 95% confidence interval [CI]: 47.0-74.7) and specificity (59.8; 95% CI: 49.3-69.6).

CONCLUSION

The Caprini score predicts postoperative VTE in patients undergoing RARP.

Anticoagulation in Patients With Advanced Chronic Kidney Disease: Walking the Fine Line Between Benefit and Harm

Chronic kidney disease affects more than 3 million Canadians and is highly associated with cardiovascular diseases that require anticoagulation, such as atrial fibrillation and venous thromboembolism. Patients with chronic kidney disease are at a problematic crossroads; they are at high risk of thrombotic conditions requiring anticoagulation and bleeding complications due to anticoagulation. The limited high-quality clinical evidence to guide decision-making in this area further compounds the dilemma. In this review, we discuss the physiology and epidemiology of bleeding and thrombosis in patients with kidney disease. We specifically focus on patients with advanced kidney disease (estimated glomerular filtration rate ≤ 30 mL/min) or who are receiving dialysis and focus on the nephrologist perspective regarding these issues. We summarize the existing evidence for anticoagulation use in the prevention of stroke with atrial fibrillation and provide practical clinical recommendations for considering anticoagulation use in this population. Last, we examine specific scenarios such as the use of a glomerular filtration rate estimating equation and dosing, the use of existing prediction tools for stroke and hemorrhage risk, current patterns of anticoagulation use (including during the dialysis procedure), and vascular calcification with vitamin K antagonist use in patients with chronic kidney disease.

Blood flow restriction augments the skeletal muscle response during very low-load resistance exercise to volitional failure

The purpose of this study was to compare the acute muscular response with resistance exercise between the following conditions [labeled (% one-repetition maximum/% arterial occlusion pressure)]: high-load (70/0), very low-load (15/0), very low-load with moderate (15/40), and high (15/80) blood flow restriction pressures. Twenty-three participants completed four sets of unilateral knee extension to failure (up to 90 repetitions) with each condition, one condition per leg, each day. Muscle thickness and maximal voluntary contraction (MVC) were measured before (Pre), immediately after (Post-0), and 15 min after (Post-15) exercise and electromyography (EMG) amplitude during exercise. Pre to Post-0 muscle thickness changes in cm [95% CI] were greater with 15/40 [0.57 (0.41, 0.73)] and 15/80 [0.49 (0.35, 0.62)] compared to 70/0 [0.33 (0.25, 0.40)]. Pre to Post-0 MVC changes in Nm [95% CI] were higher with 15/40 [-127.0 (-162.1, -91.9)] and 15/80 [-133.6 (-162.8, -104.4)] compared to 70/0 [-48.4 (-70.1, -26.6)] and 15/0 [-98.4 (-121.9, -74.9)], which were also different. Over the first three repetitions, EMG increased across sets, whereas in the last three repetitions it did not. EMG was also different between conditions and was generally greater during 70/0. Repetitions decreased across sets reaching the lowest for 70/0, and for very low loads decreased with increased pressure. In trained participants exercising to failure, lower load and the application of restriction pressure augment changes in muscle thickness and torque. The EMG amplitude was augmented by load. Training studies should compare these conditions, as the results herein suggest some muscular adaptations may differ.

The influence of biological sex and cuff width on muscle swelling, echo intensity, and the fatigue response to blood flow restricted exercise

The purpose was to determine if the muscle swelling, echo intensity, and fatigue responses to blood flow restriction differs based on cuff width (Experiment 1), applied pressure (Experiment 2), and sex. Ultrasound of muscle was taken before and after exercise. In Experiment 1 (n = 96), men swelled more than women and more with a narrow cuff than a wide cuff (0.60 cm vs. 0.52 cm). Expressed as a percentage change, there were no longer differences between cuffs (Narrow: 15% vs. Wide: 14%) or sex (Men: 14% vs. Women: 15%). Echo intensity remained unchanged. Women required more repetitions to reach task failure in sets 2, 3, and 4. In Experiment 2 (n = 87), men swelled more than women (Men: 0.46 cm vs. Women: 0.31 cm). Expressed as a percentage change, there were no differences. Echo intensity decreased in both conditions and to a greater extent with a higher applied pressure. If the acute muscle swelling response is important for initiating long term adaptation, then our results indicate that neither cuff width, sex, nor applied pressure will differentially impact the adaptation observed via this mechanism. Changes in echo intensity were inconsistent and the utility of this measurement may need to be reconsidered.

Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery

PURPOSE

The present study was designed to provide mechanistic insight into the time course and etiology of muscle fatigue development and recovery during and after low-intensity exercise when it is combined with blood flow restriction (BFR).

METHODS

Seventeen resistance-trained males completed four sets of low-intensity isotonic resistance exercise under two experimental conditions: knee extension exercise (i) with BFR and (ii) without BFR (CON). Neuromuscular tests were performed before, during (immediately after each set of knee extension exercise), and 1, 2, 4, and 8 min after each experimental condition. Maximal voluntary torque, quadriceps twitch torque in response to paired electrical stimuli at 10 Hz (PS10) and 100 Hz (PS100), PS10·PS100 ratio as an index of low-frequency fatigue, and voluntary activation were measured under isometric conditions. Perceptual and EMG data were recorded during each exercise condition.

RESULTS

After the first set of exercise, BFR induced significantly greater reductions in maximal voluntary torque, PS100, and PS10·PS100 ratio compared with CON. These parameters progressively declined throughout the BFR protocol but recovered substantially within 2 min postexercise when blood flow was restored. Neither a progressive decline in the course of the exercise protocol nor a substantial recovery of these parameters occurred during and after CON. Only at exercise termination, voluntary activation differed significantly between BFR and CON with greater reductions during BFR.

CONCLUSION

At the early stage of exercise, BFR exacerbated the development of muscle fatigue mainly due to a pronounced impairment in contractile function. Despite the high level of muscle fatigue during BFR exercise, the effect of BFR on muscle fatigue was diminished after 2 min of reperfusion, suggesting that BFR has a strong but short-lasting effect on neuromuscular function.

Acute skeletal muscle responses to very low-load resistance exercise with and without the application of blood flow restriction in the upper body

The purpose was to examine the acute skeletal muscle response to high load exercise and low-load exercise with and without different levels of applied pressure (BFR). A total of 22 participants completed the following four conditions: elbow flexion exercise to failure using a traditional high load [70% 1RM, (7000)], low load [15% 1RM,(1500)], low load with moderate BFR [15%1RM+40%BFR(1540)] or low load with greater BFR [15% 1RM+80%BFR(1580)]. Torque and muscle thickness were measured prior to, immediately post, and 15 min postexercise. Muscle electromyography (EMG) amplitude was measured throughout. Immediately following exercise, the 7000 condition had lower muscle thickness [4·2(1·0)cm] compared to the 1500 [4·4 (1·1)cm], 1540 [4·4(1·1)cm] and 1580 [4·5(1·0)cm] conditions. This continued 15 min post. Immediately following exercise, torque was lower in the 1500 [31·8 (20) Nm], 1540 [28·3(16·9) Nm, P<0·001] and 1580 [29·5 (17) Nm] conditions compared to the 7000 condition [40 (19) Nm]. Fifteen minutes post, 1500 and 1540 conditions demonstrated lower torque compared to the 7000 condition. For the last three repetitions percentage EMG was greater in the 7000 compared to the 1580 condition. Very low-load exercise (with or without BFR) appears to result in greater acute muscle swelling and greater muscular fatigue compared to high load exercise.

Effects of load on the acute response of muscles proximal and distal to blood flow restriction

To determine the effects of load and blood flow restriction (BFR) on muscular responses, we asked 12 participants to perform chest presses under four different conditions [30/0, 30/40, 50/0, and 50/40, presented as percentage one-repetition maximum (1RM)/percentage arterial occlusion pressure (AOP)]. Muscle thickness increased pre- to post-exercise [chest: mean 0.29, 95% confidence interval (CI) 0.21, 0.37 cm; triceps: mean 0.44, 95% CI 0.34, 0.54 cm], remaining elevated for 15 min post-exercise. Electromyography amplitude was greater with 50% 1RM and increased over time for the first three repetitions of each set of chest presses. The last three repetitions differed across time only. AOP increased from pre- to post-exercise, augmented by BFR [30/0: mean 31, 95% CI 18, 44 mmHg; 30/40: mean 39, 95% CI 28, 50 mmHg; 50/0: mean 32, 95% CI 23, 41 mmHg; 50/40: mean 46, 95% CI 32, 59 mmHg). Tranquility decreased and physical exhaustion increased from the pre- to post-condition, with both parameters returning to the baseline 15 min post-exercise level. In conclusion, load and BFR do not elicit meaningful differences in the acute response of chest press exercise taken to failure.

Muscle Adaptations to High-Load Training and Very Low-Load Training With and Without Blood Flow Restriction

An inability to lift loads great enough to disrupt muscular blood flow may impair the ability to fatigue muscles, compromising the hypertrophic response. It is unknown what level of blood flow restriction (BFR) pressure, if any, is necessary to reach failure at very low-loads [i.e., 15% one-repetition maximum (1RM)]. The purpose of this study was to investigate muscular adaptations following resistance training with a very low-load alone (15/0), with moderate BFR (15/40), or with high BFR (15/80), and compare them to traditional high-load (70/0) resistance training. Using a within/between subject design, healthy young participants (n = 40) performed four sets of unilateral knee extension to failure (up to 90 repetitions/set), twice per week for 8 weeks. Data presented as mean change (95% CI). There was a condition by time interaction for 1RM (p < 0.001), which increased for 70/0 [3.15 (2.04,4.25) kg] only. A condition by time interaction (p = 0.028) revealed greater changes in endurance for 15/80 [6 (4,8) repetitions] compared to 15/0 [4 (2,6) repetitions] and 70/0 [4 (2,5) repetitions]. There was a main effect of time for isometric MVC [change = 10.51 (3.87,17.16) Nm, p = 0.002] and isokinetic MVC at 180^°/s [change = 8.61 (5.54,11.68) Nm, p < 0.001], however there was no change in isokinetic MVC at 60^°/s [2.45 (−1.84,6.74) Nm, p = 0.261]. Anterior and lateral muscle thickness was assessed at 30, 40, 50, and 60% of the upper leg. There was no condition by time interaction for muscle thickness sites (all p ≥ 0.313). There was a main effect of time for all sites, with increases over time (all p < 0.001). With the exception of the 30% lateral site (p = 0.059) there was also a main effect of condition (all p < 0.001). Generally, 70/0 was greater. Average weekly volume increased for all conditions across the 8 weeks, and was greatest for 70/0 followed by 15/0, 15/40, then 15/80. With the exception of 1RM, changes in strength and muscle size were similar regardless of load or restriction. The workload required to elicit these changes lowered with increased BFR pressure. These findings may be pertinent to rehabilitative settings, future research, and program design.

Perceptual and arterial occlusion responses to very low load blood flow restricted exercise performed to volitional failure

PURPOSE

Studies examining perceptual and arterial occlusion responses between blood flow restricted exercise and high load exercise often prescribe an arbitrary number of repetitions, making it difficult for direct comparisons. Therefore, the purpose of this study was to compare these protocols when performed to volitional failure.

METHODS

Individuals completed four exercise conditions varying in load and pressure: (i) 15% 1RM; no restrictive pressure, (ii) 15% 1RM; 40% arterial occlusion pressure, (iii) 15% 1RM; 80% arterial occlusion pressure, and (iv) 70% 1RM; no pressure. Four sets of knee extension exercises were performed until volitional failure (or until 90 repetitions per set) was completed.

RESULTS

A total of 23 individuals completed the study. While all conditions increased arterial occlusion pressure, the greatest increases (~30%) were observed in the blood flow restriction conditions. All lower load conditions resulted in greater RPE and discomfort than that of the high load condition, but only discomfort was increased further when adding blood flow restriction.

CONCLUSION

High load exercise will likely be perceived more favourably than lower load exercise to volitional failure; however, those who are incapable or unwilling to lift heavier loads may use blood flow restriction to help reduce the volume needed to reach volitional failure, although this will likely increase discomfort.