Effects of graduated compression stockings,local vibration and their combination on popliteal venous blood velocity

Abstract

Objectives

The purpose of this pilot study was to examine and compare the effects of graduated compression stockings, local vibration, and combined graduated compression stockings and local vibration on popliteal venous blood velocity.

Method

Twenty-four healthy subjects received four 15 min interventions (control, graduated compression stockings alone, local vibration alone, and combined graduated compression stockings and local vibration), while resting inactive in the prone position. Popliteal vein blood velocity was investigated before (PRE) and at the end (POST) of each intervention using Doppler ultrasound.

Results

At POST, peak velocity was reported to be 26.3 ± 53.5% (p < 0.05) greater for local vibration than control (CONT). Peak velocity was 46.2 ± 54.6% (p < 0.001) and 21.1 ± 37.6% (p < 0.01) higher for graduated compression stockings than CONT and local vibration, respectively. Graduated compression stockings + local vibration presented 64.1 ± 58.0% (p < 0.001), 38.4 ± 52.4% (p < 0.001) and 15.0 ± 31.6% (p < 0.05) greater values than CONT, local vibration and graduated compression stockings, respectively.

Conclusions

This study demonstrated an increase in popliteal venous blood velocity after graduated compression stockings and local vibration application. Their combination provided the greatest effects.

Keywords

Popliteal vein Doppler ultrasound blood flow velocity graduated compression stockings local vibration

Introduction

The incidence of venous thromboembolism (VTE) presenting as deep vein thrombosis and/or pulmonary embolism in the general population is between 5 and 20 per 10,000 people per year.^1,2 Its mortality rate is high (i.e. 5–10% in the first month)^3,4 and risk of morbidity is substantial with sequelae including post-thrombotic syndrome, chronic thromboembolic hypertension and pulmonary embolism. Among the many risk factors of VTE (e.g. age, surgery, trauma, obstetric, thrombophilia, obesity, cancer, smoking, etc.), lower limb immobilisation (e.g. long distance travel, work- and computer-related seat, spinal cord injury hospitalisation, late pregnancy, plaster cast or orthosis) represents the most common potentially preventable cause in the 18–65-year age group.⁵ To reduce the burden of VTE in these cases, the use of pharmacological thromboprophylaxis (i.e. low-molecular-weight heparin)^6–8 is recommended. However, it is important to recognise that achieving full compliance with chemical thromboprophylaxis may be difficult, and that despite its use the risk of VTE remains elevated.⁸ These drugs also carry risks of adverse reactions and bleeding events. Therefore, alternative strategies to limit venous stasis should be employed whenever possible.

Physical VTE prophylaxis (i.e. intermittent pneumatic compression, neuromuscular electrical stimulation) can be associated with less complications such as lower risk of bleeding and is currently receiving considerable attention. Graduated compression stockings (GCS) are the most widely used because of their proven effectiveness in decreasing venous stasis and preventing deep venous thrombosis in hospital patients⁹ and in pregnant women,¹⁰ likely through increased venous blood velocity. In recent years, vibration has become of increasing interest to health professionals, primarily owing to reports that vibration can increase peripheral blood flow and thereby potentially provide physiological benefits in several vascular diseases.^11–13 First, peripheral blood flow enhancement was reported during and after whole-body vibration (i.e. where the participant must stand or squat on a vibrating platform).^14–16 An increase in arterial blood flow has been reported in the popliteal^17,18 and common femoral arteries after whole-body vibration exposure in patients with spinal cord injury^17–19 or Friedreich’s ataxia.²⁰ Despite promising perspectives in clinical and rehabilitation fields, whole-body vibration programmes are difficult to apply with clinical and/or aging populations who may not be able to maintain an active position on the vibratory platform. For those individuals, the use of local vibration (LV) directly applied on the relaxed muscle or its tendon may present a practical alternative to whole-body vibration.²¹ Some studies reported an increase in calf blood flow measured by plethysmography^22–24 and of lower limb skin blood flow measured by laser Doppler flowmetry.^25–29 Increased venous return after LV is also suggested by an increased cross-sectional area of the calcaneal region veins³⁰ and of the great saphenous vein.³¹ To our knowledge, no study has investigated the effect of LV on venous blood velocity, commonly measured to evaluate VTE prophylactic devices. Indeed, several studies suggest that the magnitude of increase in venous blood velocity is a good haemodynamic measure of device efficacy as higher velocities may result in decreased rate of VTE.^32–36

Therefore, the first aim of this study was to examine and compare the effects of LV and GCS on venous blood velocity (i.e. popliteal vein) using Doppler ultrasound in healthy young adults during short-term lower limb inactivity (i.e. prone position). Since the combination of different preventive methods can provide greater benefits than their isolated effects,^16,37,38 a second aim of this study was to further examine the effects of combined GCS and LV. The results of this pilot study on healthy subjects may be useful to further propose LV, GCS or their combination to prevent venous stasis and VTE risk during long-term lower limb immobilisation.

Materials and methods

Participants

Twenty-four healthy volunteers (17 men and 7 women) were recruited to participate in this study (age: 22.5 ± 2.2 years; height: 1.76 ± 0.10 m; weight: 70.4 ± 12.9 kg; body mass index: 22.5 ± 2.5 kg/m²). All subjects were physically active (i.e. 5–15 h of physical activity per week). The exclusion criteria were as follows: advanced age (>65 years), obesity (body mass index >30 kg m⁻²), medical history (previous deep venous thrombosis/pulmonary embolism, chronic venous insufficiency, varicose veins, ulcers, peripheral arterial disease, haematological disorders, recent trauma or surgery to the lower limb and diabetes), medication (anticoagulants or coagulants), pregnancy or breastfeeding and recent blood donation.³⁹ All participants received standardised verbal and written information about the experimental protocol and gave their written informed consent to participate in the investigation that was conducted according to the Declaration of Helsinki and approved by the local ethic committee. Participants were advised to avoid strenuous exercise and to maintain their sleeping, eating and drinking habits for ≥24 h, but to avoid caffeine, alcohol or other energy drinks for ≥12 h before experiments. Women were investigated on days 0–14 after menstruation.

Experimental design

The study design was a single-centre prospective crossover study. Each participant was evaluated in two different sessions separated by at least 48 h. In the first session, detailed instructions about the experimental protocol were given and subjects were familiarised with the experimental procedures. A medical history questionnaire and a written informed consent were filled out and measurements of the lower limb taken (half-leg height: 44.9 ± 2.9 cm; ankle circumference: 21.9 ± 1.5 cm; calf circumference: 37.4 ± 2.7 cm) to adjust the size of the GCS to each subject’s morphology. The experimental protocol was then performed during the second session. The experimental protocol began with a 15 min rest period in the prone position to standardise the haemodynamics and followed by four interventions each lasting 15 min and separated by a 5 min rest period in the prone position (Figure 1). Rest periods in the prone position were used between interventions to allow vascular re-equilibration.^33,39,40

Figure 1.

Schematic illustration of the experimental protocol.

Interventions

The four interventions (i) control (CONT), (ii) GCS alone (GCS), (iii) LV alone (LV) and (iv) combined GCS and LV (GCS+LV) were performed in random order for each subject (Figure 2). During the entire duration of the experimental protocol, subjects remained in the prone position. GCSs (URBAN (man) and DIAPHANE (woman), SIGVARIS, Saint-Just Saint-Rambert, France) exerting a compression between 15 and 20 mmHg were positioned by the experimenter and removed after 15 min. The LV system (VB115, VIBRASENS, Mane, France) transmitted vibrations at a frequency of 100 Hz and with a 1 mm amplitude. It was strapped by the experimenter to the Achilles tendon. LV was applied continuously for 15 min.

Figure 2.

Illustration of the interventions: GCS alone (a), LV alone (b), and combined GCS and LV (c).

Venous blood velocity measurements

Participants lay in the prone position on an examination table. They were instructed to relax, keep their breathing calm, talk only quietly, not fall asleep and not move their lower limbs during the whole experimental protocol. Right lower limb venous blood velocity was assessed with a Doppler ultrasound scanner (Aixplorer, Supersonic Imagine, Aix-en-Provence, France) using a 2–10 MHz linear probe (SuperLinear 10-2, Supersonic Imagine, Aix-en-Provence, France). All venous blood velocity measurements were taken at the popliteal vein to reflect venous outflow from the deep veins of the lower leg. The probe was positioned at the right popliteal fossa. After identification of the vein segment and marking of the optimal probe location on the skin with ink, measurements were made before (PRE) and at the end (POST) of each intervention (Figure 1). All measurements were made by the same experienced researcher.

Peak velocity (PV; cm/s), time average peak velocity (TAPV; cm/s) and time average mean velocity (TAMV; cm/s) of the popliteal vein were measured from the pulsed Doppler waveform. The probe was positioned longitudinally to the axis of the vein about 2 mm distant from the skin to minimise the effect of pressure on the vein. The Doppler ultrasound system was set to pulsed Doppler. An incident angle was maintained at 60° and a sampling volume was placed parallel to blood flow and covered the entire venous lumen.⁴¹ The pulse repetition frequency range used was 603–1500 Hz. For greater reliability, when the signal became stable, 10 images were frozen and then averaged.

Discomfort level measurements

At the end of each intervention, subjects rated their discomfort levels with a visual analogue scale by marking the level of the perceived discomfort along a 10 cm line, marked at one end ‘no discomfort’ and at the other end ‘severe discomfort’.

Statistical analyses

Statistical analyses were performed using Statistica 8 software (StatSoft Inc., Tulsa, USA). Data are presented as mean ± standard deviation (SD). All variables were normally distributed (Kolmogorov–Smirnov normality test). For ANOVA analyses, homogeneity of variance was verified by Levene’s test. A two-way repeated measures ANOVA was performed on venous blood velocity data (factors = 4 interventions (CONT, GCS, LV, GCS+LV) × 2 (PRE, POST)). A one-way repeated measures ANOVA was performed on discomfort level data (factors = 3 interventions (GCS, LV, GCS+LV)). Post hoc analyses were performed with Newman–Keuls testing when the ANOVA identified significant differences. For all statistical analyses, the statistical significance was set at p < 0.05.

Results

Venous blood velocity

Since PV, TAPV and TAMV were characterised by similar GCS- and vibration-induced variations, the following lines will only focus on PV values. All mean PV, TAPV and TAMV values are reported in Table 1. PV values recorded at PRE and POST for each intervention are shown in Figure 3. There was a significant time × intervention interaction effect (p < 0.001). PRE–POST absolute and relative changes were, respectively, −0.38 ± 1.14 cm/s and −5.1 ± 15.0% for CONT (p = 0.33), +1.26 ± 2.34 cm/s and +24.9 ± 34.3% for GCS (p < 0.01), +0.44 ± 1.40 cm/s and +9.4 ± 23.1% for LV (p = 0.67), and +2.12 ± 2.90 cm/s and +39.4 ± 52.4% for GCS+LV (p < 0.001). No differences between interventions were found at PRE (p > 0.05). At POST, PV was reported to be 26.3 ± 53.5% (p < 0.05) greater for LV than CONT; 46.2 ± 54.6% (p < 0.001) and 21.1 ± 37.6% (p < 0.01) higher for GCS than CONT and LV, respectively; and 64.1 ± 58.0% (p < 0.001), 38.4 ± 52.4% (p < 0.001) and 15.0 ± 31.6% (p < 0.05) greater for GCS+LV than CONT, LV and GCS, respectively.

Table 1.

Peak velocity (PV), time average peak velocity (TAPV), and time average mean velocity (TAMV) measurements before (PRE) and after (POST) each intervention (control (CONT), graduated compression stockings alone (GCS), local vibration alone (LV), and graduated compression stockings and local vibration simultaneous (GCS+LV)). Data are presented as mean ± SD.

	Interventions
Variables	CONT	Δ PRE–Post	GCS	Δ PRE–POST	LV	Δ PRE–POST	GCS+LV	Δ PRE–POST
PV (cm/s)
PRE	5.59 ± 1.69	−5.1%	6.23 ± 2.80	+24.9%**	5.91 ± 1.95	+9.4%	6.26 ± 2.14	+39.4%***
POST	5.20 ± 1.44		7.49 ± 2.86		6.35 ± 2.20		8.38 ± 3.34
TAPV (cm/s)
PRE	4.19 ± 1.40	−5.8%	4.34 ± 1.41	+21.6%*	4.33 ± 1.52	+5.7%	4.50 ± 1.46	+31.2%***
POST	3.84 ± 0.92		5.17 ± 1.76		4.39 ± 1.16		5.69 ± 2.28
TAMV (cm/s)
PRE	1.80 ± 0.48	−6.4%	1.84 ± 0.62	+23.0%*	1.89 ± 0.74	+4.4%	1.93 ± 0.66	+23.6%**
POST	1.65 ± 0.40		2.19 ± 0.72		1.89 ± 0.52		2.33 ± 0.99

POST values significantly different from PRE values: *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 3.

Mean peak velocity (PV) before (PRE) and after (POST) the different interventions (control (CONT), GCS alone (GCS), LV alone (LV), and combined GCS and LV (GCS+LV)). Error bars indicate SD. Values significantly different from CONT: *p < 0.05; ***p < 0.001. Values significantly different from LV: ^§§p < 0.01; ^§§§p < 0.001. Values significantly different from GCS: ^#p < 0.05.

Discomfort level

Mean discomfort levels were 0.35 ± 0.67, 2.15 ± 1.26 and 2.51 ± 1.61, respectively, for GCS, LV and GCS+LV. There was a significant intervention effect (p < 0.001) for discomfort level. Discomfort level was significantly smaller for GCS than LV (p < 0.001) or GCS+LV (p < 0.001).

Discussion

In the present study, we examined popliteal venous blood velocity in healthy, physically active volunteers while resting inactive for 15 min in a prone position. The main results are that a 15 min application of GCS or LV induces significantly greater venous blood velocity in the popliteal vein when compared with the control intervention, and that both GCS and GCS+LV have a greater effect than LV.

Since PV, TAPV and TAMV were described by similar variations, our discussion will only focus on PV data, as it represents the most consistent non-artefactual wave form detected by ultrasound^34,35 and is acknowledged by most manufacturers as a good haemodynamic measure to assess the efficacy of their systems.^32–36 All measurements were performed while the subjects were lying in the prone position in order to get closer to VTE risk situations such as bed stay. This position limits the contractions of the calf muscles and allows the most reproducible Doppler ultrasound measurements to be made.

In the control intervention, the venous blood velocity (PV) measured at the popliteal vein was non-significantly altered (−5.1%; p = 0.33) after a 15 min period in the prone position. Conversely, a 25⁴² and 41%⁴³ decrease in venous blood velocity was reported after a prolonged sitting period of 70 and 100 min, respectively. This may be the consequence of the known inactivation of the natural calf and foot muscle pumps, leading to attenuated blood flow and venous stasis. In the present study, the lack of a significant decrease in venous blood velocity may be explained by the prone position adopted and the short period of inactivity. Accordingly, Benkö et al.⁴⁴ also reported no significant change in PV at the popliteal and femoral veins after 20 min of bed rest.

In the present study, the use of GCS for 15 min significantly enhanced venous blood velocity, as demonstrated by the significant PV improvement at the end of the 15 min period (+24.9%; p < 0.01) and the 46.2% increase when comparing values at the end of the period with the control intervention. Similar findings were previously found in healthy adults after 15⁴⁵ and 20 min⁴⁴ of bed rest, as it was during prolonged sitting (range: 20–170 min) in healthy volunteers^34,42,46 or after 15 min prolonged lying in pregnant women.^47,48 However, this contrasts with some studies that reported no changes in venous blood velocity while wearing GCS in the lying position in healthy subjects,^40,49–51 chronic deep venous insufficiency patients,⁵⁰ postoperative patients,⁴⁹ late pregnancy patients⁵² and hospitalised medical patients.⁵³ Such inconsistent results about GCS-induced effects on venous blood velocity may be explained by differences in experimental protocols (i.e. duration of immobility and duration of GCS use), in the brand of GCS (i.e. size, class and ergonomics), in experimental approach (i.e. device and location) and distinct tested populations. Nonetheless, it is thought that a reduction of venous diameter and complex physiologic and biochemical phenomena would be involved in the increased venous blood velocity while wearing GCS.⁵⁴

After LV, our results demonstrated a non-significant increase in PV (+9.4%; p = 0.64). Since this counterbalanced the non-significant PV decrease reported in the control intervention, benefits of LV were further suggested by the 26.3% significantly greater PV value measured at the end of the LV cycle when compared with the control intervention. This benefit was comparable to calf blood flow increases measured by plethysmography during LV.^22–24 However, in our results, the effect of LV was significantly less pronounced than for GCS. While the present study was not designed to identify the underlying mechanisms responsible for the increased venous blood velocity reported after LV, several mechanisms may be hypothesised. Vibration has been suggested to increase arterial and microcirculatory blood flow through an increase of the local metabolism (i.e. reflex muscular contractions generated by the vibrations) and/or vasodilatation of the microcirculation (i.e. nitric oxide secretion reported after exposure to mechanical stress and neuropeptides release induced by a local axon reflex through activation of polymodal receptors), respectively. Whether or not this may also apply for increased venous blood flow remains to be determined.

Since GCS and LV both increased PV, it would be expected that using them in combination would also significantly enhance venous blood velocity. This was confirmed in the present study by the PRE–POST PV increase (+39.4%; p < 0.001) reported after GCS+LV as well as the 64.1% greater PV value at the end of the 15 min period when compared with the control intervention. While the main effect of GCS+LV was greater than for LV, this was the same as for GCS. However, the PV values measured at the end of the intervention were significantly higher for GCS+LV than for LV (+38.4%; p < 0.001) or GCS (+15.0%; p < 0.05). Similarly, additional benefits of associating several interventions have previously been reported for GCS coupled with neuromuscular electrical stimulation.^37,38

Since discomfort constitutes one of the main problems to the acceptance of preventive methods in patients, subjects in the present study were asked to rate their discomfort levels with a visual analogue scale.⁵⁵ Discomfort assessment demonstrated that LV was less comfortable than GCS. However, the LV device was well tolerated, with participants reporting, on average, only ‘mild discomfort’ (2.1 ± 1.3 cm) while using the device. As a comparison, several neuromuscular electrical stimulation studies have reported higher levels of discomfort (range: 2.6–5.4 cm)^56,57 and pain (range: 2.1–4.1 cm).^37,56 In general, most subjects found the GCS and LV devices tested to be comfortable with only a minimal increase in discomfort scores, suggesting that these devices may be easily proposed.

We should acknowledge that the present study may have some limitations. First, our sample was small and the young and physically active population did not correspond well to the patients likely to use these therapies. Furthermore, measurements in different body positions (i.e. sitting and upright) would be important in future studies to better reflect real-life situations and not just the prone position. Finally, of note is that despite peak venous velocity being the haemodynamic parameter typically reported in literature as a measure of mechanical VTE prophylaxis efficacy, controversy exists over its use as an indicator of venous blood flow.⁵⁸ Other haemodynamic parameters will have to be measured in future studies, such as calf blood flow measured by plethysmography.

In conclusion, we have demonstrated the effect of GCS and LV on venous blood velocity in popliteal vein in young healthy subjects during short-term lower limb inactivity. Our results show that the combination of GCS and LV is also an interesting solution for enhancing venous blood velocity of popliteal vein. Since the present work was a pilot study, further studies are needed to confirm whether such results may be translated to clinical populations that could benefit from such intervention with the aim to reduce the venous stasis, e.g. spinal cord injury patients, postoperative patients, hospitalised medical patients, late pregnancy patients, patients with plaster cast or orthosis. Interestingly, the use of chronic Achilles tendon LV has been previously reported to enhance force production capacities through neural adaptations in healthy subjects⁵⁹ as well as during cast immobilisation.⁶⁰ Further studies should now determine whether long-term benefits might also be observed for venous blood velocity of popliteal vein. Nonetheless, results of the present pilot study should encourage future studies in investigating the clinical applicability of combining GCS and LV in relation to VTE risk reduction.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

All participants received standardised verbal and written information about the experimental protocol and gave their written informed consent to participate in the investigation that was conducted according to the Declaration of Helsinki and approved by the local ethic committee.

Guarantor

TL.

Contributorship

LE and TL designed the study. LE performed the experiments. LE and TL analysed the data. LE and TL wrote the paper. All authors approved the final version of the manuscript.

Acknowledgements

The authors sincerely thank Dr Séverine Feasson for his contribution to Doppler ultrasound measurements, Wanda Lipski for English editing and Thibault Besson for experimental contribution. The authors also thank IVTV (project ANR-10-EQPX-06-01) for experimental support.

ORCID iD

Thomas Lapole

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