PREDICTION OF THE NEED FOR MECHANICAL VENTILATION IN ACUTE SEVERE ASTHMA

Unwarranted long delays in treating asthmatic patients requiring assis ted mechanical ventilation (AMV) could be associated with higher death rates. The objective of the study was to identify which were the best predictive characteristics of patients with acute severe asthma (ASA) who required AMV. For this purpose, we reviewed retrospectively the h ospital record of every patient with ASA admitted to the intensive car e unit (ICU) from 1981 to 1991 (38 with AMV and 38 without AMV). Twent y-seven variables were obtained from the history, physical examination , laboratory tests, blood gases and treatment. Using a multivariate di scriminant analysis, the most powerful predictor of patients needing A MV was a function that consisted of eight variables: arterial pH, numb er of previous admissions to ICU, asthma severity, time elapsed since last visiting a physician, respiratory rate, age, systolic pressure an d heart rate. With this function, 33 of 38 mechanically ventilated pat ients were well classified (sensitivity: 0.89) and the overall accurac y of the test was 92% (70 out of 76 cases). The positive and negative predictive values of the function for mechanical ventilation were 0.96 and 0.90, respectively. We conclude that the application of the calcu lated final discriminant function could be appropriate to decide which patients with ASA require AMV.