By 1946 American research in positive pressure breathing (PPB) and mechanical pressure culminated in the partial pressure suit introduced by Henry and Drury of the University of Southern California. Added to trunk bladders and the helmet were gas-filled tubes running down the arms and legs, which were tied to the suit material with tapes. When these capstan tubes were inflated, the inelastic and tightly fitted cloth of the arms and legs was drawn up tight, thereby applying mechanical pressure to the limbs.
The suit was intended to give protection against decompression in high altitude aircraft, allowing time to bring the craft down to safe altitudes. For such short periods, nearly complete coverage of the trunk with breathing bladders proved useful, but these bladders plus the anti-G suit bladders on the legs made the pilot hot, since perspiration could not evaporate. The full bladders were used in a later suit by McGuire. Temperature regulation continued to be a severe problem, since more than 50% of the skin was covered by impermeable layers. The suit was useful in aircraft operating at very high altitudes, and it had been tested in a chamber to 60,000 m, but it was never intended to be used by an active man in a space vacuum.