valsalva manoeuvre The effort to breathe out forcibly while the mouth and nose are firmly closed or the vocal cords pressed together. The valsalva manoeuvre is employed while straining at stool and in other circumstances. It causes a rise in blood pressure followed by a sharp drop and then a second sharp rise in blood pressure. This may be dangerous in people with heart disease and should be avoided. (Antonio Maria Valsalva, 1666–1723, Italian anatomist).