FORCED EXPIRATION - 50 YEARS AFTER TIFFEN EAU,ROBERT

One hundred and fifty years after the original description of spiromet ry by Hutchinson and 50 years after the definition of his famous ratio by Tiffeneau, a certain number of physiological advances have enabled a better understanding of the determinants of the forced expired mano euvre and to mitigate some of its inconveniences. This review focuses on three of these advances. The first is the influence of an inspirato ry manoeuvre which precedes a forced expiration, on the expiratory flo w. This influence is probably a consequence of viscoelastic phenomena and impose some strains on standardisation in current practice. The se cond is the possibility of detecting in a reproducible and simple fash ion, without the need for co-operation on the part of the subject, a l imitation in expiratory flow by the application of a negative expirato ry pressure at the opening of the airways (NEP for negative expiratory pressure). The third is the possibility to verify in a simple fashion the quality of the expiratory performance achieved by the patient and thus to detect an insufficient effort in the force of a falling expir atory flow.