A system, method or apparatus to detect abnormalities in delivery of a fluid may include an infusion apparatus that is controllable to cause one or more perturbations in a fluid flow (e.g., each of the one or more perturbations in the fluid flow may result in a measurable perturbed force response). A force signal representative of the perturbed force response may be used to determine an integrated perturbed force response value (e.g., using integration of the force signal over a perturbation time period； the integrated perturbed force response value being representative of an additional force caused by the at least one perturbation over an equilibrium force). A ratio between the integrated perturbed force response value and a normalizing value (e.g., based at least on a maximum perturbation force of the perturbed force response) may be used to determine if fluid flow is occluded.
