Enhanced Pause (Penh)

Enhanced Pause (Penh) is a unit-less index of airway hyper-reactivity. Penh is derived from the expiratory side of the respiratory waveform in a flow whole body plethysmograph. In this region, conditioning effects (heating and humidification) are minimal and resistance effects dominate.

While Penh is not a pure measure of resistance, it is a useful indicator – an opinion supported by a large body of published articles. Further, use of the Penh parameter is the only commercial option for studying such a wide range of pulmonary parameters on conscious, unrestrained animals. All other methods – most also sold by Buxco – involve restraint or anesthesia.

It should be clearly stated that this position on Penh is disputed by a number of influential researchers. It is supported by others.

So long as the controversy persists, Buxco recommends investigators confirm discoveries made using Penh with other direct and more widely-accepted methods such as invasive resistance and compliance (anesthetized) or non-invasive airway mechanics (conscious, restrained).