Pad for generating alternating pressure

A pad for use by a patient sitting in a chair, the pad comprising a seat portion and a back portion to overlie the seat and back portion of the chair respectively, the pad, comprising:

• first and second flexible longitudinal tubes adjacent respective first and second sides of the pad;
• a plurality of first transverse tubes communicating pneumatically with the first longitudinal tube and each having a closed end remote therefrom;
• and a plurality of second transverse tubes communicating pneumatically with the second longitudinal tube and each having a closed end remote therefrom, the first tubes being disposed at a first angle such that the closed ends of the first transverse tubes are located beneath the second longitudinal tube, and the closed ends of the second transverse tubes being disposed at an angle opposite to the first angle, are located beneath the first longitudinal tube, whereby the first and second tubes are interdigitated so that the arrangement provides a shallow "v".