Breathing intolerance index: a new indicator for ventilator use

The purpose was to study the efficacy of a proposed breathing intolerance index for justifying ventilator use by patients with pulmonary or chest wall diseases and to compare with values obtained from healthy controls. A total of 42 patients with lung/chest wall disease, including 11 ventilator users and 25 age-matched controls, were studied. The breathing intolerance index was defined as (Ti/Ttot) x (Vt/VC), where Ti = inspiratory time of one breath (in seconds), Ttot = total time of one breath (in seconds), Vt = tidal volume (in milliliters) at rest, and VC = vital capacity (in milliliters). A digital spirometer with custom computer software was used. The examinations were completed uneventfully. The mean breathing intolerance index values of the 25 healthy volunteers, the 31 nonventilator user patients, and the 11 users of nocturnal noninvasive positive-pressure ventilation were 0.050 +/- 0.009 (mean +/- standard deviation), 0.087 +/- 0.022, and 0.186 +/- 0.038, respectively. The breathing intolerance indices of the ventilator users were significantly greater (P < 0.0001) than those of the other nonventilator user groups, and there was no overlap in values. Ventilator users have a significantly higher breathing intolerance index than nonventilator users. The index may be useful for justifying ventilator use.