Evaluation of venous flow volume of the calf muscle pump by Doppler ultrasound during active and passive kinesiotherapy: a pilot study

ORIGINAL ARTICLE

Evaluation of venous flow volume of the calf muscle pump by Doppler ultrasound during active and passive kinesiotherapy: a pilot study

Carmindo Carlos Cardoso Campos^I; Patrícia Cavalcanti de Albuquerque^II; Ivson José da Silva Braga^III

^IPhysical therapist. Graduate student, Hospital Physical Therapy, Faculdade Redentor, Rio de Janeiro, RJ, Brazil.

^IIVascular surgeon and ultrasonographer, Hospital Esperança, Recife, PE, Brazil.

^IIIMSc. in Biophysics. Professor of Biophysics and Biostatistics, Faculdade Integrada do Recife (FIR), Recife, PE, Brazil, and Universidade Salgado de Oliveira (UNIVERSO), Recife, PE, Brazil.

ABSTRACT

BACKGROUND: In-hospital physical therapists work on the effects of hypoactivity or inactivity of bedridden patients. In daily practice, contraction of the calf muscle is commonly performed by health professionals in hospitals, especially in pre- and post-operative periods as a form of reducing venous stasis and risk of deep venous thrombosis in the lower limbs.

OBJECTIVE: To assess venous flow volume at the calf muscle pump using color Doppler ultrasound during active and passive kinesiotherapy (ankle plantar flexion).

METHODS: The sample consisted of 30 individuals randomly selected and submitted to color Doppler ultrasound of the right popliteal vein, aiming to measure blood flow volume in four periods: rest, manual calf compression, active and passive ankle movement in plantar flexion. The t test was used for statistical analysis, and p ≤ 0.05 was used as an index of statistical significance.

RESULTS: The sample consisted of 16 females and 14 males. Means were as follows: age (31.57 years), height (1.68 m), weight (68.25 kg), and body mass index (24.16). Statistical analysis showed that passive ankle plantar flexion was significant when compared to baseline (p ≤ 0.000056) as to calf pump muscle activation, although not as much as active exercise (p ≤ 0.0000016). Manual compression of the triceps surae muscle in relation to passive exercise was also significant (p ≤ 0.000000081).

CONCLUSION: In this study, active ankle plantar flexion proved statistically more effective than passive exercise in calf muscle pump activation, increasing blood flow volume in the popliteal vein and minimizing venous stasis in the lower limbs.

Keywords: Physical therapy, calf muscle pump, color Doppler ultrasound.

RESUMO

CONTEXTO: O fisioterapeuta na unidade hospitalar atua sobre os efeitos da hipoatividade ou inatividade do paciente acamado. Na prática diária, a contração do músculo da panturrilha é difundida entre os profissionais de saúde no ambiente hospitalar, principalmente nos períodos de pré e pós-operatório, como forma de diminuir a estase venosa e os riscos de trombose venosa profunda nos membros inferiores.

OBJETIVO: Avaliar o volume de fluxo venoso na bomba sural, através de ultra-sonografia doppler, durante cinesioterapia ativa e passiva (flexão plantar do tornozelo).

MÉTODOS: A amostra foi constituída por 30 indivíduos escolhidos aleatoriamente e submetidos a ultra-sonografia doppler da veia poplítea direita, visando mensurar o volume de fluxo sanguíneo em quatro momentos: repouso, compressão manual da panturrilha, movimentação passiva e ativa do tornozelo em flexão plantar. Na análise dos resultados, utilizou-se o teste t, sendo utilizado um valor de p ≤ 0,05 como índice de significância estatística.

RESULTADOS: Na amostra constituída, 16 eram do sexo feminino e 14 do sexo masculino, apresentando as seguintes médias: idade (31,57 anos), altura (1,68 m), peso (68,25 kg) e índice de massa corporal (24,16). Na análise estatística, a flexão plantar do tornozelo realizada de forma passiva, quando comparada ao valor basal, é significante (p ≤ 0,000056) em relação à ativação da bomba sural, embora não tanto quanto o exercício ativo (p ≤ 0,0000016). Também mostrou significância a compressão manual do músculo tríceps sural em relação ao exercício passivo (p ≤ 0,000000081).

CONCLUSÃO: Neste estudo, a flexão plantar do tornozelo de forma ativa mostrou-se estatisticamente mais eficaz do que a passiva na ativação da bomba sural, aumentando o volume do fluxo de sangue na veia poplítea e diminuindo a estase venosa nos membros inferiores.

Palavras-chave: Fisioterapia, bomba sural, ultra-sonografia Doppler em cores.

Introduction

Changing an individual into a patient includes a number of experiences marked by fragmentation and loss of autonomy. The condition of being bedridden and distortion of spatial relations brings to medical practice the concern with the effects triggered by immobility and with quality of care.¹

Hospital stay generates reduction in movement and immobility in bed. It may cause severe complications in different systems of the human organism, such as significant reduction in muscle protein synthesis, which starts in the first 9 hours of bed restriction,^2,3 causing reduction in muscle mass and peripheral muscle strength, proliferation of connective tissue in joints, in addition to favoring occurrence of muscle shortening and contractures and reduction in bone mass.^3-5 It also predisposes to occurrence of depressive cases and irritability,^4,6 increased blood concentration of cortisol and exacerbation of the level of muscle catabolism.^2,3 Prolonged time in bed sometimes is a more severe risk factor than baseline disease.⁷

A study conducted in 2008 observed that the most frequently adopted position by patients during hospital stay were lying and sitting (55.5%), while walking was 1.73% (25 minutes a day).⁸ Prolonged immobility in bed generates venous stasis, which is a defined and addictive condition of risk for acquired states of hypercoagulability, and may result in deep venous thrombosis (DVT).^9-11

Fighting the negative effects of immobilization can be performed by physical activity in patients during hospital stay.^12-16 Movement of the lower limbs, especially by walking, facilitates return of venous blood in this segment due to action of the calf muscle pump, reducing possibility of common venous stasis in bedridden patients.^17,18 An exercise program during hospital stay should include the lower limbs to improve the muscle function of the calf muscle pump and help recovery from venous problems.^18-20

Pathogenesis of venous thrombosis is also associated with presence of the triad venous: stasis, endothelial lesion of the vascular wall and hypercoagulability, described for the first time in 1856 by Virchow.^21-27 It occurs in 1% of the population per year – more than 500,000 people, and is the third most frequent cardiovascular disease.²⁵ It has a multifactorial nature, with association and synergism of constitutional and acquired factors.^9,28 Prophylactic treatments improve venous blood flow or reduce blood coagulability.²³ Thrombus formation may easily occur in the postoperative period at the level of valve cusps of deep veins, especially of the lower limbs. Risk of thromboembolic accidents persists for a period of 3-4 weeks after surgery²² and considerably increases hospital costs.⁹ The highest incidence of DVT occurs in the fourth postoperative day, and a second peak occurs on the 14th day.^11,22

In a recent review, it was recommended that hospitalized patients should be submitted to protocols of preventive anticoagulation, according to risk stratification, and that all patients should be submitted to physical measures, such as early walking, physical therapy, active or passive movement, active exercises of the lower limbs, and elastic stockings of intermittent pneumatic compression. These procedures reduced in 60% the relative risk of venous thromboembolism.^{9,10,21-24,27,28}

Physical therapists in hospital units can work on the effects of hypoactivity and inactivity of bedridden patients. In daily practice, contraction of the calf muscle and activation of the calf muscle pump have been unanimously used by health professionals in the hospital setting, especially before and after surgeries, as a way to reduce venous stasis of the lower limbs. All articles relative to evaluation of calf muscle pump blood flow are performed with the patient standing erect, but none reported evaluation of this mechanism with the patient in the supine position. However, such procedure is the most common during hospital stay, and in this moment physical therapy exercises are performed more frequently.

This study aims at evaluating venous flow volume in the calf muscle pump using Doppler ultrasound during active and passive kinesiotherapy (ankle plantar flexion), as well as its effectiveness as a form of minimizing venous stasis in this segment.

Materials and methods

This study was carried out between May and June 2008. It was approved by the Research Ethic Committee according to norms of research involving human subjects, resolution 196/96, no. 62/2008.

The sample was comprised of 30 individuals of both genders randomly chosen. To be included in the study patients should be in the age group 21-40 years and sign an informed consent term. Therefore, exclusion criteria were all participants aged less than 21 years, as they could not legally sign the consent term, and older than 40 years because they have higher risk for DVT. Anamnesis was performed before the Doppler ultrasound to verify whether there was any exclusion factor (Table 1).

Table 1 - Click to enlarge

The examination was performed with the patient in prone position with lower limbs free from any clothes. The patient's feet remained outside the examination table to allow for ankle mobilization. Firstly, right popliteal vein diameter was evaluated using color Doppler ultrasound; next, blood flow velocity was measured at four intervals:

- At rest, with no type of mobilization – baseline flow volume;

- After maneuver of calf manual compression;

- Requiring total ankle relaxation with passive ankle mobilization, generating plantar flexion and foot hyperextension – passive kinesiotherapy;

- After active ankle mobilization by the participant, with contraction of the triceps surae, generating plantar flexion and foot hyperextension – active kinesiotherapy.

Between intervals there was a rest period so that the calf muscle pump could be filled by venous blood, allowing reliable responses at each interval.

Blood flow volume of the popliteal vein was evaluated by vein diameter and flow velocity using the following formula: flow in mL/min = area (cm²) x mean velocity (cm/s) x 60. Examinations were performed by a single examiner. A color Doppler ultrasound device and an 8-11 MHz transducer were used (GE LOGIC 500^®).

This is an experimental inferential study. The t test and the Statistica package^® (version 5.1) were used for analysis of results, and p ≤ 0.05 was set as an index of statistical significance.

Results

In the sample comprised of 30 random patients, 16 were female and 14 were male, and had the following means: age (31.57 years), height (1.68 m), weight (68.25 kg) and body mass index (BMI) (24,16). In anamnesis none of the patients had exclusion factors. Only three patients reported practicing routine physical activity. Three sedentary patients had higher BMI in the sample (30.86/30.30/31.48), and blood flow volume measured during active movement was lower than most patients. Figure 1 shows a sample of images of venous blood flow obtained by Doppler ultrasound at each interval.

After measuring venous blood flow volume of all participants, mean values for each interval were obtained. Results showed that active kinesiotherapy (exercise) had blood flow volume higher than the baseline value and passive kinesiotherapy; it was only lower than manual compression (Table 2).

Figure 2 shows all venous flow volume values in the popliteal vein, by participant, at each study interval.

According to the statistical analysis, a significance test was performed between study intervals and had the following results: passive ankle plantar flexion is significant when compared with the baseline value (p ≤ 0.000056), although not as much as the active exercise (p ≤ 0.0000016). Manual compression of triceps surae, when compared with passive mobilization, showed a great significant index (p ≤ 0.000000081), as well as when compared with active mobilization (p ≤ 0.0008). Significance between active and passive exercise was also significant (p ≤ 0.000006). Therefore, active ankle plantar flexion proved to be more efficacious than passive in the activation of the calf muscle pump, with increase in blood flow volume in the popliteal vein, minimizing venous stasis in the lower limbs.

Discussion

Although the literature reports the efficacy of the calf muscle pump in venous return in the lower limbs, no studies confirmed its effectiveness with the individuals in supine position, which is the most adopted position during hospital stay and when ankle plantar flexion exercises are performed.

Doppler ultrasound in the popliteal vein showed that active ankle plantar flexion generates increased blood flow volume due to efficacy of the calf muscle pump, triggered by recruitment and effective contraction of all muscles. This results in increased venous flow volume in the lower limb when compared with the baseline value and with passive exercise, causing reduction in venous stasis in this segment. Figure 1D shows flow volume in the popliteal vein when the movement is active.

Statistical data show that passive ankle plantar flexion is efficacious when compared with the baseline value, although not as much as active exercise. It is interesting to notice that passive exercise does not produce muscle contraction^18,29,30 and, consequently, should not activate the calf muscle pump and increase blood flow volume. When venous flow volume was evaluated during passive exercise, the patient was requested to leave his ankle completely free and not moving it, therefore, without muscle contraction. In case there was any muscle contraction at evaluation, it was discarded and performed again. Explanation for occurrence of any type of muscle contraction during passive exercise is that, when the movement of ankle plantar flexion is performed passively in individuals that are alert and have full motor reflexes, there is a reflex response of joint protection in the last degrees of the movement.^29,30 Such response is triggered by joint receptors and, in this case, also by ankle dorsiflexor muscles, through muscle spindles and Golgi tendon organs,²⁹ as this exercise causes maximal joint opening, with possible risk of lesion. Thus, muscle fibers are distended at its maximal length, generating a "defense moment" and muscle co-contraction (activation of agonist and antagonist muscles^29,30), triggering a stop near the end of the movement arch, with activation of the calf muscle pump. This justifies increase in venous flow volume near the end of the movement arch, when there are short periods of filling, which cannot be sustained, reducing and not being immediately followed by other filling moments. Blood flow volume peaks during passive contraction proved to be inferior (Figure 1C) than those of active exercise (Figure 1D) and manual compression (Figure 1B).

Therefore, it would be interesting to perform this study in individuals who do not have motor reflexes, either temporary, such as in patients submitted to spinal anesthesia, or permanent, such as in individuals with complete spinal trauma. This might really mimic the situation in which passive exercise is performed in the patient that has no conditions of performing it actively, because he is unconscious, has marked muscle weakness or nervous and/or motor lesion. In case the hypothesis that passive exercise of the calf muscle pump is confirmedly not efficacious to increase venous flow volume, this exercise will aim at preserving and maintaining joint integrity, and not as a form of blood pumping in the lower limb.

Manual compression performed in the triceps surae is efficacious to increase blood flow volume in the popliteal artery. It is also highly efficacious when compared with passive exercise. The same occurs when compared with active exercise, but it has filling volume and reaches maximal flow volume peak abruptly (Figure 1B). This suggests that, when performing such maneuver, for example, in an ascending massage in the lower limb, we should be alert to force and pressure used, since there is a risk for endothelial lesion because veins have less developed muscle layer than arteries, facilitating possible development of venous thrombosis.²⁹ Attention should be given when using the system of intermittent pneumatic compression, using as maximal value the patient's diastolic pressure to avoid risk of lesions.¹⁸

Individuals that, at the interview, reported performing physical exercises routinely had higher popliteal vein diameters and higher blood flow volume peaks, because conditioned muscles have higher tonus, effectiveness in contraction and torque strength, showing the beneficial effects of continued physical activity over skeletal muscle and the vascular system and lower predisposition to risk of venous thrombosis.³⁰ On the other hand, sedentary individuals and those with the highest BMI had smaller popliteal vein diameter and low blood flow volume during evaluation of active movement. Although having a large calf perimeter, especially due to the thick adipose layer, the calf muscle pump was deconditioned, not favoring as expected increase in blood flow volume during exercise.

Physical therapy is an important factor to prevent venous thromboembolism, during hospital stay and after discharge, since such risk persists in some cases. Although being a pilot study that used a small sample of 30 individuals, this study statistically shows that active exercise of the calf muscle pump (ankle plantar flexion) with patients in bed, reduces venous stasis because it provides greater blood flow volume in the lower limb when compared with passive exercise. In addition, it shows that strengthening the calf muscle is able to improve venous hemodynamics in this segment.

This study could not reach any conclusion in terms of passive kinesiotherapy. A new methodology occasionally using individuals with temporary or permanent motor paralysis might be interesting as an attempt to clarify whether passive ankle plantar flexion does activate the calf muscle pump.

References

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Correspondence

Publication Dates

• Publication in this collection
  20 Feb 2009
• Date of issue
  Dec 2008

History

• Accepted
  05 Nov 2008
• Received
  19 Aug 2008