Pressures For Blood Flow Restricted Exercise Cannot Be Estimated With Precision For Narrow Cuffs

Blood flow restriction pressures are set relative to the lowest pressure needed to occlude blood flow with that specific cuff. Wider cuffs (12-cm) occlude blood flow at a lower pressure than narrower cuffs (5-cm). Other factors like limb circumference also affect arterial occlusion pressure (AOP). Due to pressure output limitations of some devices, it is not always possible to occlude blood flow in the lower body with a narrow cuff. One solution is to create a formula that uses a wide cuff and thigh circumference to estimate pressure with a narrow cuff. However, this formula would need to be validated against an AOP that was measured with a narrow cuff. Purpose: Use a device capable of generating high pressures (up to 907 mmHg) to create and validate an estimation equation for the 5-cm cuff in the lower body using a 12-cm cuff AOP and thigh circumference as a predictor. Methods: One hundred seventy participants completed the study. Thigh circumference was measured in the right leg at 33% of the distance between the inguinal crease and the top of the patella with a tape measure as this is where the cuff would be applied. Following 10 minutes of rest, participants had their AOP measured with a 5-cm cuff. After an additional five minutes of rest, AOP was then measured with a 12-cm cuff. The sample was randomly allocated to a prediction group (66%) and validation group (33%). Thigh circumference and AOP measured with a 12-cm cuff, were used as predictors. A Bland-Altman plot was constructed to assess agreement. Results: Both thigh circumference and 12-cm AOP were significant predictors. The following formula was created from the prediction group. 5-cm AOP = 2.753 (12-cm AOP) + 11.428 (thigh circumference) - 707.703.In the validation group the mean difference (95% confidence interval) between the observed (336.8 mmHg) and the predicted (343.9 mmHg) 5-cm AOP was 7.1 (-11.9, 26.1) mmHg. The 95% limits of agreement were -133.6 to 147.8 mmHg. There was a negative relationship between the difference and the average of predicted and measured 5-cm AOP (B = -0.137, p = 0.000043). Conclusions: Although this was the first study to quantify AOP over 600 mmHg with a 5-cm cuff in the lower body, our equation is not valid across all levels of pressure. Therefore, when using blood flow restriction in the lower body, larger cuff widths should be employed if possible.