**2.1. Compression Therapy – Importance of External Pressure**

industrial and medical applications including geotextiles, diapers, wipes, draperies, furniture, mattress, mattress pads, apparel, etc. [4]. Each of these applications has different demands due to which the specific properties and characteristics of the nonwoven must be addressed carefully in order to design optimised fabric structure with maximum benefits. This chapter focuses on a particular end application for the nonwoven as a padding bandage used in multi-

Nonwoven padding is an essential component in a multi-layer compression system [5, 6]. Padding lies underneath compression bandage or stocking through which substantial amount of pressure is exerted on the limb of patient. Padding plays two major functions: first it helps to maintain uniform pressure around the circumference of limb, and, second, it helps in proper exchange of moisture or air for improved comfort to the patient. This chapter addresses several issues related to padding: it begins by mentioning the medical problem, identifying the product requirements, describing the role of fibre and construction, attempting theoretical modelling to understand padding behaviour, examining the structure–property relationship

Chronic venous disorder occurs due to improper functioning of venous system, especially in the lower extremity, which makes it difficult for the venous reflux to return to the heart from the legs [7, 8]. Patients suffering from such disorders have poor quality of life due to consistent pain, limited mobility, physical function, depression, social isolation and high treatment cost [9]. It has been estimated that 1% of the general population (age group: 18–64) is suffering from chronic venous disorders [10]. This rate is further increased to 4% in people over the age of 65 [11]. Furthermore, it has been anticipated that the rate will increase significantly in future due

Chronic venous disorders such as varicose veins, deep vein thrombosis, oedema, ulcers, lymphoedema, etc., happen primarily in lower limbs when the veins are not able to pump enough blood back to the heart. This improper functioning is the result of venous hypertension [12]. In most cases, venous hypertension is caused by reflux through incompetent valves, but other causes include venous outflow obstruction and failure of the calf-muscle pump owing to obesity or leg immobility. Deep vein thrombosis is the condition where the blood clots (thrombus) inside the veins, which obstructs the smooth flow of blood toward the heart [13]. The blood trying to pass through these blocked veins can increase the blood pressure in the vein, which, in turn, will overload the valves. This can lead to damage to the valves, which can further worsen the problem as these incompetent values will not be able to prevent backflow of blood. This may result in pooling of blood in the surrounding tissues, which will cause swelling (also termed as oedema). Over time, this can worsen the condition and result

layer compression system recommended for chronic venous ulcers.

and finally recommending the optimised product.

to changing lifestyle and the growing aging population.

**2. Chronic venous disorders**

164 Non-woven Fabrics

in venous ulceration (Figure 1).

Compression therapy is the cornerstone of treatment for phlebological and lymphatic condi‐ tions [7, 14-17]. The prime objective of compression therapy is to reduce the venous pressure in the affected limb region [13, 17, 18]. This finally serves several functions:

It reduces the venous diameter and increases the interstitial pressure in the surrounding, which increases the blood flow in the deep veins.

It restores the valve function by bringing the walls of the veins closer together.

It reduces blood pressure in the superficial venous system.

It reduces the pressure differences between the capillaries and the tissue to prevent backflow.

It increases the cutaneous microcirculation, favours white cell detachment from the endothe‐ lium and prevents further adhesion.

It reintegrates the interstitial liquids into the vessels.

The main parameter responsible for clinical efficiency is the interface pressure [19-26]. Interface pressure is defined as the pressure exerted by the compression system over the surface of skin. The Laplace's Law is used to predict the interface pressure (*P*), which is a function of the tension in the fabric, and the circumference of the limb [16, 21, 27]. This can be expressed as:

$$P = \frac{F}{r} \tag{1}$$

where *F* is the tension in the fabric per unit length, and *r* is the limb radius. The efficacy of the treatment is undoubtedly dependent on this interface pressure as this has to be quite accurate within certain limits and should not be below or above the prescribed level, otherwise it can lead to certain complications during treatment [25, 28]. Low pressure will not have the benefit of external compression, and very high pressure impedes the arterial flow, which can cause discomfort. The optimal pressure necessary to overcome venous hypertension is not well known, but an external pressure of 35–40 mmHg at the ankle is necessary to prevent capillary exudation in legs affected by chronic venous insufficiency [11, 26].
