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Can air plethysmography evaluate the severity of chronic venous insufficiency?
(Portuguese PDF version)

Carlos Alberto Engelhorn,¹ Cristina Veronese Beffa,² Galvane Bochi,³ Renata Corrêa Pullig,² Maria Fernanda Cassou,³ Sérgio Salles Cunha⁴

1. Ph.D. in Vascular Surgery. Professor of Angiology, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, PR, Brazil.
2. Vascular Surgeon, Santa Casa de Misericórdia de Curitiba, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, PR, Brazil.
3. Resident doctor, Santa Casa de Misericórdia de Curitiba, Pontifícia Universidade Católica do Paraná (PUCPR), Curitiba, PR, Brazil.
4. PhD, Clinical Research Director, Jobst Vascular Center, USA.

Correspondence:
Carlos Alberto Engelhorn
Rua Deputado Heitor Alencar Furtado, 1720/901
CEP 81200-110 - Curitiba, PR, Brazil
Phone and Fax: +55 41 279.1241
E-mail: engelhor@bsi.com.br

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ABSTRACT

Objective: To determine which plethysmographic parameters allow the discrimination among the mild, moderate and severe degrees of chronic venous insufficiency according to the clinical classification CEAP, suggested by the Society of Vascular Surgery.

Method: During an 8-month period, 88 limbs in 47 patients were evaluated. They presented clinical signs of chronic venous insufficiency categorized as classes 1 to 6, divided into three groups: Group A - mild chronic venous insufficiency (classes 1 and 2); Group B - moderate chronic venous insufficiency (class 3) and Group C - severe chronic venous insufficiency (classes 4, 5 and 6). Venous hemodynamics evaluation was performed with air plethysmography and the parameters that showed differences between the classes of chronic venous insufficiency were analyzed statistically.

Results: There were no statistically significant differences between the plethysmographic parameters of groups A and B. There were statistical differences when group C was compared with groups A and B in relation to 90% of the venous filling time (P < 0.0001) and the venous filling index (P < 0.0001).

Conclusion: It is possible to determine the severity of the chronic venous insufficiency by air plethysmography. The venous filling index is the parameter which best determines the clinical severity of the venous disease.

Key-words: venous insufficiency, plethysmography.

J Vasc Br 2004;3(4):311-6

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Chronic venous insufficiency (CVI) of the lower limbs may be a consequence of occlusion, reflux, muscle pump dysfunction or a combination of these etiologies.^1-3 Symptoms include edema, dermatosclerosis, eczema, pigmentation, and ulcer. Over the past years, air plethysmography has been used to assess venous hemodynamics.⁴ The standard equipment and exam technique currently employed to treat CVI were developed by Professor Andrew Nicolaides, in order to study volume variations in the calf in response to postural alterations and exercise.^5,6

Air plethysmography adds quantitative and objective data to the anatomical assessment of non-invasive image methods in the study of chronic venous insufficiency (CVI). It is also useful to detect hemodynamic alterations in the venous system, whether they are due to obstruction, primary or secondary valve insufficiency, or calf pump alteration. However, its correlation to CVI severity has not been established.^2,7,8

This paper aims at correlating air plethysmography parameter values with the different classes of CVI, according to the CEAP classification reported in the American Venous Forum, as well as determining which plethysmographic parameters allow the discrimination among the mild, moderate and severe degrees of CVI.

METHODS

Population

Venous hemodynamics evaluation was performed in 88 lower limbs in 48 patients, three males and 45 females. Patients who presented clinical signs of chronic venous insufficiency (classes 1 to 6 in the CEAP classification), independently of etiology and anatomical location of the reflux were included in the study.

Exclusion criteria were being pregnant, having undergone varicose veins surgery, having orthopedic disorders such as genu valgum, genu varum and reduced ankle mobility, collagenosis, and difficulties in cooperating with the exam.

The evaluated lower limbs were divided into three groups: group A, patients with mild chronic venous insufficiency (CEAP classes 1 and 2); group B, moderate CVI (class 3); and group C, severe chronic venous insufficiency (classes 4, 5, and 6).

The venous hemodynamic evaluation of all patients using air plethysmography was performed in the evening, using Narcosul equipment (Universidade Federal do Rio Grande do Sul), according to the technique described by Christopoulos et al.⁹ ( Figure 1).

Figure 1 - Examination technique of air plethysmography.

The evaluation starts with the patient in the supine position. The lower limb under study is elevated at 45°. Venous emptying is allowed for 5 minutes. A pneumatic cuff is coupled to a computerized sensor and positioned around the leg, from the knee to near the malleolar line, and then filled with air up to 6 mmHg. This allows the equipment to be calibrated, which is done through an injection of 50 ml of air. After the equipment is calibrated, the patient is asked to stand, keeping the limb under study at rest. This step allows filling of the veins through their points of reflux and through the arterial influx up to a maximum value that corresponds to the venous volume (VV). It is known that the parameter defined as 90% of the venous filling time (VFT90) corresponds to the average venous filling index up to 90% of the VV. Venous filling index (VFI) is defined as 90% VV/VFT90. With the limb filled with blood, the patient performs a dorsiflexion movement of the ankle. The volume of blood ejected (EV) by the calf is then registered. The ejection fraction (EF) is calculated as EF = EV/VVx100%. Afterwards, with the limb filled with blood, a series of ten consecutive dorsiflexion movements of the ankle is performed in order to calculate the residual volume (RV) and the residual volume fraction (RVF) of blood. RV is measured during exercise and in relation to the zero final volume. RVF is calculated as RV/VVx100%. The patient then returns to the supine position with the leg elevated and at rest.

The plethysmographic parameters used to compare the groups in this study were: VV, RVF, VFI, EF, and VFT90 (Figures 2 and 3).

Figure 2 - Normal air plethysmography examination performed in a patient with mild chronic venous insufficiency (class 2).

Figure 3 - Altered venous filling index in a patient with severe chronic venous insufficiency (class 5).

Statistical analysis

The average values of plethysmographic parameters (VV, RVF, VFI, EF, and VFT90) and the level of CVI were compared in groups A, B, and C using the non-parametric test Mann-Whitney to independent samples. The minimum significance level (significance probability) adopted was of 5% (0.05).

RESULTS

Mean age was 38 years in group A (22 to 63 years), 37 (22 to 59 years) in group B, and 42 (31 to 66 years) in group C.

Out of 88 extremities evaluated, 11 were class 1, 21 class 2, 37 class 3, five class 4, seven class 5, and seven class 6 (Figure 4).

Figure 4 - Distribution of lower limbs according to chronic venous insufficiency level (CEAP).

Comparing the studied groups (Table 1), there were no statistically significant differences in plethysmographic parameters between mild and moderate degrees of CVI. However, when group C (severe CVI) was compared to groups A and B, there was a significant difference in the values of average venous filling index (VFT90) (P < 0.0001) and VFI (P < 0.0001). Examples of normal and altered exams can be seen in Figures 2 and 3.

Table 1 - Statistical comparison of the plethysmographic parameters among groups

Data	Test result	Tabled value	Significance
Group A versus Group B
VV (ml)	1.877	p = 0.060	NS
EF (%)	0.653	p = 0.514	NS
RVF (%)	0.963	p = 0.335	NS
VFT90 (s)	0.217	p = 0.829	NS
VFI (ml/s)	1.498	p = 0.134	NS
Group A versus Group C
VV (ml)	1.510	p = 0.131	NS
EF (%)	0.431	p = 0.666	NS
RVF (%)	1.803	p = 0.071	NS
VFT90 (s)	3.341	P < 0.0001	S
VFI (ml/s)	4.277	P < 0.0001	S
Group B versus Group C
VV (ml)	0.061	p = 0.952	NS
EF (%)	0.671	p = 0.502	NS
RVF (%)	1.031	p = 0.302	NS
VFT90 (s)	3.593	P < 0.0001	S
VFI (ml/s)	3.610	P < 0.0001	S

VV = venous volume; EF = ejection fraction; RVF = residual volume fraction; VFT 90 = 90% of the venous filling time; VFI = venous filling index.

General comparison of plethysmographic parameters in the three groups is shown in Figure 5.

Figure 5 - Comparison of the plethysmographic parameters among groups.

DISCUSSION

CVI is a common vascular disease affecting about 20 to 30% of the Western population. Socio-economic impacts of this sometimes disabling chronic disease are seen in many of these patients, although CVI is quite simple to manage when its etiopathogeny is known.^10,11

CVI is a condition of long-term venous hypertension caused by valve leakage and/or vein blockage. Symptoms include changes in the skin and subcutaneous tissue, especially in lower extremities. Chronic alterations in macro and microcirculation seen on patients lead to a more severe manifestation of CVI: venous leg ulcer, responsible for reducing the quality of life of these individuals.^1,7,12-16

Lower limbs affected by venous chronic disease can be classified (Table 2) according to CEAP classification, which addresses the clinical signs (C), etiology (E), anatomical distribution (A), and physiopathology (P).¹⁷ This classification is recommended as a useful method for clinical assessment and documentation of patients with CVI.¹⁸

Table 2 - Clinical classification (CEAP)

Class 0	No visible or palpable signs of CVI
Class 1	Telangiectatic or reticular veins
Class 2	Varicose veins
Class 3	Edema
Class 4	Skin changes due to CVI
Class 5	Skin changes with healed ulceration
Class 6	Skin changes with active ulceration

CVI = chronic venous insufficiency.

 

Ambulatory venous pressure has been considered as a standard to assess venous reflux. However, besides its invasive nature, it is known that venous ulcer may occur even when venous pressure is normal.¹⁹

Data obtained through non-invasive methods such as air plethysmography and vascular Doppler ultrasound are complementary. Plethysmography provides global hemodynamic data of the venous system and of the muscle pump function, while ultrasound provides anatomical details of segmental or diffuse refluxes on saphenous or perforating veins. Air plethysmography can detect a good EF even in the presence of a significant reflux, identified by the ultrasound, due to calf muscle hypertrophy.³

Air plethysmography is a simple and feasible method to assess venous hemodynamics of lower limbs. VFI over 2 ml/s has a direct connection to valve reflux severity.²⁰ VFI values over 7 ml/s can be used to identify risk of ulceration.^20-22 Criado et al., in a plethysmographic study with 186 lower limbs, proved the VFI to be a good evaluation parameter of venous reflux, as well as the best way of determining clinical severity of the venous disease.⁴

Bays et al. have shown an incidence of 76% on skin alterations when VFI is over 10 ml/s.¹²

Several authors have demonstrated VFI statistical differences between normal patients and those with a severe disease. However, there were no differences among the mild, moderate and severe degrees.^23-25 Iafrati et al. suggest that such difference can be attributed to low sensitiveness of non-invasive methods or by alterations in microcirculation, and not by hemodynamic deficit of great vessels.² On the other hand, in our paper we have shown that VFI is a good parameter to differ the severe venous disease from the moderate and mild disease.

Other parameters measured by air plethysmography, including EF and RVF, can be also useful to assess valve incompetence and calf muscle function. Araki et al. have not identified statistically significant differences in VFI values among limbs with CVI in classes 5 and 6. However, EF and RVF were significantly worse in ulcerous limbs,²⁶ which could be explained by the limiting effect caused by ankle dorsiflexion movements, responsible for lesion pain.

Cordts et al. have determined RVF to be the best parameter to differ varicose veins without skin alterations (classes 2 and 3) from more severe cases (classes 4 to 6).²⁴ In our study, however, there were no significant differences in RVF concerning studied groups.

Air plethysmography presents distinct results when the same individual is examined several times because it is a patient-dependent exam. This explains the differences in studies found in the literature and in our outcomes. In some cases, results disagreeing with the disease severity were obtained, despite the parameters generally showing statistical differences among the groups.

The authors conclude that air plethysmography is a useful non-invasive diagnosis method for the assessment of CVI. In this paper, VFI is a plethysmographic parameter capable of determining the clinical severity of the venous disease.

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