A novel intermittent pneumatic compression boot to improve venous haemodynamics

Venous ulcers, caused by venous hypertension, affects 0.5-1% of the general population (up to 640,000 Britons), especially the elderly with poor mobility. This common malady is difficult to manage, expensive to treat, and often recurs. Common treatments include external static (bandage) and dynamic (Intermittent Pneumatic Compression (IPC)) compression. Although several important applications for IPC have emerged, the optimal magnitudes of cuff pressures and related timing parameters have not been determined. The primary goal of this dissertation was to investigate the sensitivity of the healthy cohort’s haemodynamics to changes in cuff pressure magnitudes and timing parameters. This study measures the velocity-time integral to assess venous flow changes. i) the optimum pressure to maximise venous return, ii) the optimum deflation time that will maximise venous return and iii) whether IPC should be personalised to patients. More analytically this thesis explores: 1. the relationship between cuffs’ pressure and velocity time integral (stroke distance) during IPC 2. the haemodynamic effects of IPC across genders and ages 3. the impact of deflation time across different set of cuff pressures, gender and ages. A novel IPC device was designed and prototyped to provide adjustable parameters (pressures, time), safety, and reliability. This device used a real-time, non-invasive method (Doppler ultrasound) to collect data on the haemodynamics of the popliteal vein. After several preliminary tests to help define IPC design and device reliability, forty healthy participants were recruited and tested, using different sets of compression pressures and cuff inflation and deflation timing values. Strong positive relationships between cuff pressure magnitude and mean stroke distance was observed for deflation times of 10 seconds (Stroke distance of 234, 434 and 557 AU for pressure magnitudes of 60, 80 and 100 mmHg, an increase of 86% from 60 mmHg to 80 mmHg and 28% from 80 mmHg to 100 mmHg; p<0.001, R=0.620), 20 second (Stroke distance of 263, 430 and 596 AU iv for pressure magnitudes of 60, 80 and 100 mmHg, an increase of 96% from 60 mmHg to 80 mmHg and 21% from 80 mmHg to 100 mmHg; p<0.001, R=0.629), and 30 second (Stroke distance of 274, 451 and 628 AU for pressure magnitudes of 60, 80 and 100 mmHg, an increase of 108% from 60 mmHg to 80 mmHg and 17% from 80 mmHg to 100 mmHg; p<0.001, R=0.609). Mean stroke distance did not saturate at 80mm Hg and was not significantly related to deflation times, irrespective of the magnitude of applied cuff pressure, but did saturate below 20-second deflation times. Mean stroke distance was not affected by gender or age across deflation times and pressure levels. To conclude, the main determinant of haemodynamic effects was the magnitude of cuff compression pressure, irrespective of sex or age. The optimum compression pressures in the standing position to obtain maximum stroke distance were the set of 120/100/80 mmHg for the ankle/lower calf/upper calf levels respectively. The value of foot compression was negligible. This investigation sets the foundation for future research in pathological groups and further refinement of this technology.