The present invention is directed to methods and apparatus for sealing a puncture or incision formed percutaneously in tissue separating two internal portions of the body of a living being with an anchor, a sealing plug and a filament connecting the anchor and sealing plug. The enclosure includes a five-sided open bottom air tight cavity comprising a liquid volume fluidly coupled to a gas volume creating a gas-fluid coupling layer, rising in elevation within cavity. By averaging and watching for correlations, the present AGC identifies the pulse rate and pulse widths and over a fairly short period of time predicts when the next pulse is coming.