Breathing intolerance index: A new indicator for ventilator use

Objectives: 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. Design: 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. Results: 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. Conclusions: Ventilator users have a significantly higher breathing intolerance index than nonventilator users. The index may be useful for justifying ventilator use.