Physiological Considerations for Compression Bandaging

Transcription

1 Physiological Considerations for Compression Bandaging Harvey N. Mayrovitz, Ph.D. Professor of Physiology College of Medical Sciences Nova Southeastern University

2 At the completion of this presentation participants will be able to: 1. State the difference between edema and lymphedema 2. State at least one process that can cause edema 3. Describe the basic processes involved in lymphatic transport 4. Describe long-stretch and short-stretch bandages and their use 5. Contrast the effects of resting vs. working pressures 6. Describe Laplace s law as it applies to bandaging

3 Relationship to Wound Healing Impediments to Healing Blood Flow Oxygenation Infection Tissue Environment Deficit Origins Arterial Venous Microvascular Lymphatic Localized Edema/Lymphedema Compression Therapy

4 Circulation Schema O 2 CO 2 Capillary H 2 O Vein Lymphatics Arterioles Artery

5 Normal Fluid Balance Resorption Blood Capillary Filtration P = 25 mmhg P A 35 mmhg 15 P V ~27 liters/day ~30 liters/day ~3 liters/day (10% of filtered) protein Lymphatic Capillary

6 Increased Venous Pressure or Capillary Permeability 20 P V Resorption Blood Capillary Filtration P A 35 mmhg Less Resorption More Filtration Lymphatic Capillary

7 If Net Filtration Exceeds Lymphatic Transport Capacity Overload = Edema + [Protein] = Lymphedema Therapy Options Reduce Filtration Increase Transport

8 Normal Lymph Transport Lymphangion Contraction Skeletal Muscle Pump Arterial Pulsations Body Movements Respiration All are Dynamic Processes

9 Lymphatic Capillaries Lumen Lymphatic Capillary P L P L > P T EC Anchoring Filaments P T Blood Capillary Lumen EC P L +P T P L < P T

10 Lymphatic Hearts Peristaltic-like contractions propel lymph to next segment Lymph Capillary Lymphangion (lymph micro heart) Walls have a muscular media Valve Lymphangion Lymph Capillary Contraction force is preload and afterload dependent - analogous to heart

11 Calf Muscle Pump and Normal Valves Relaxed Contracted Superficial Deep Superficial Deep Skin Fascia Skin Fascia

12 Calf Muscle Pump and Valve Dysfunction Relaxed Contracted Veins Distended Resting Venous Pressure INCREASED High pressure transmitted to Superficial Veins Pump Efficiency Reduced

13 Venous Valve Dysfunction Chronic venous hypertension due to Chronic venous insufficiency (CVI) predisposes to developing venous ulcers Increased Ambulatory Venous Pressure Venous Pressure Resting CVI Normal

14 External Compression Tissue Pressure Arteriolar Vasodilation Nitric Oxide Normalize Permeability Vein Diameter Velocity Shear Stress WBC Adherence Trans-locate Volume Venous Pressure Promote Fluid Absorption

15 Types of Compression Bandage Bandage-like Pumps Stockings Short-Stretch Long -Stretch Short-Stretch Dynamic Prevention Maintenance

16 Arrangement Superficial Drains Skin and Subcutis Skin Facia Deep Vascular Sheath Muscle Bone

17 Vascular Sheath L L V A V Arterial Pulsations Can Mechanically Augment Lymph Transport

18 Arterial Flow Pulses Below Knee Blood Flow via Nuclear Magnetic Resonance ml/min Control Leg Treated Leg Before Bandage ml/min With Bandage Increased pulses likely augment Lymph/venous transport

19 Compartments Tibia Anterior Tibial Anterior Greater Saphenous Fibula Lateral Deep Posterior Posterior Tibial Superficial Posterior Peroneal Skin Lesser Saphenous Want Therapy to Affect Superficial and Deep

20 Pressures of Interest Tibialis m. Tibia 1 Sub-bandage Surface Contact 2 Fibula Peroneus Tissue Interstitial Popliteus m. Tibialis m. Soleus m. Gastroc m. 3 Compression Bandage or Device Skin Intramuscular

21 Edema and Tissue Pressure Normal P T P T Loose Fibrous Trabeculae

22 Resting (Static) Pressure Muscles Relaxed Pressure due to bandage tension (T) projecting an inward radial pressure (P) T R Compression Bandage or Device Laplace s Law P ~ T R Superficial vessels affected the most

23 Pressure Gradient Concept Compression Applied at Constant Tension P ~ T R Increasing R Decreasing P Mimics Normal Intravascular Pressure Gradient

24 Working (Dynamic) Pressure Contracted Muscles Positive affect on deeper vessels P Bandage acts as a restraint to muscle expansion Pressure is developed from within P ~ Contraction Force x Rigidity

25 Dynamic Pressure (DP) Dynamic Pressure Depends on Bandage Material Features Form fitted steel pipe short stretch long stretch No external compression 0 Bandage Stretchibility

26 Tissue Pressure (P T ) Working vs. Resting Pressures Role of Compression Material Emptying Resting Filling Short Stretch Filling Long Stretch Time

27 Overall Impact of Compression Depends on both working and resting pressures P U Upstream Pressure P A Vein or Lymphatic Tissue Pressure P T Filling: Inflow ~ P U - P T Emptying: Outflow ~ DV ~ DP T Best: Adequate resting P T and High DP T

28 Sub-Bandage Pressure Measurements Electronic Pressure Readout Electronic Sensor* Pneumatic Sensor* Compression set at various static levels to compare dynamic sub-bandage pressures achieved with different bandages during calf muscle contraction and relaxation *Pneumatic sensor: Talley Oxford Pressure Monitor *Electronic Sensor:

29 mmhg mmhg Dynamic (Working) Pressures 150 Static Static Pressures Set by Compression Dynamic Dynamic pressures via calf muscle contraction 150 Comparison of Different Bandage Types Efficient Dynamic Pressure Inefficient Low Dynamic Pressure 0 Cohesive Elastic Multilayer

30 Multiple Choice Questions 1. According to Laplace s law, if a limb is bandaged with constant tension, then the contact pressure experienced by the limb will be: a) greater where the limb is widest b) greater where the limb is narrowest* c) equal at all sites since the tension is constant d) least over areas of bony prominence such as the malleolus 2. A short-stretch bandage, as compared to a long-stretch: a) results in a greater resting pressure b) affects the deep vessels more than the superficial vessels c) results in a greater working pressure* d) has a greater effect on underlying blood vessels at rest 3. A short-stretch bandage provides more efficient venous and lymphatic filling and emptying because it produces: a) greater working pressure and greater resting pressure b) reduced working pressure and reduced resting pressure c) greater working pressure and reduced resting pressure* d) reduced working pressure and greater resting pressure References 1. Mayrovitz HN, Larsen PB. Effects of compression bandaging on leg pulsatile blood flow. Clinical Physiology 1997;17: Mayrovitz HN. Compression-Induced pulsatile blood flow changes in human legs. Clinical Physiology, 1997;18: Mayrovitz HN, Delgado M., Smith J. Compression bandaging effects lower extremity peripheral and sub- bandage skin blood perfusion. Wounds 1997;9: Mayrovitz HN, Sims N (2003) Effects of ankle-to-knee external pressures on skin blood perfusion in the compressed leg and non-compressed foot. Adv Skin Wound Care 2003;16: