Bleb mechanics during subcutaneous injection into ex vivo pork bellies

During large volume subcutaneous injections, liquid can accumulate and create a bleb around the injection site. Predicting the size of this bleb is important because it affects the rate the fluid absorbs into the body and because it may be linked to patient discomfort. In vivo pig tests have documented how the bleb height, area, and pressure vary over a range of infused liquid viscosities, flow rates, and injection volumes. However, there are inconsistencies between the various experiments and prevailing models based on poromechanics. Here we carry out systematic experiments with ex vivo tissue that replicate and extend the previous in vivo studies. Our results demonstrate that in vivo and ex vivo tissue exhibit comparable bleb dynamics over the injection timescales and highlight that certain assumptions in the current theoretical models are questionable.