PURPOSE: To show reasons for accepting a different and seemingly clinically useful standard for weaning success following prolonged mechanical ventilation by comparing five groups of patients free from ventilator support for increasing intervals.
METHODS: Data from all 316 post-acute-care patients admitted between 1/1/01 and 12/31/05 and free from ventilator support for >24 hours were extracted from medical records. Days free from ventilator support were used to form five groups; 1–7, 8–14, 15–21, 22–28, >28 days. The five groups were compared by: age, gender, ventilator time before weaning started, weaning time, co-morbidities and survival. Comorbidities were quantified using the Cumulative Illness Rating Scale (CIRS). Discharged patients’ deaths were obtained from the Social Security Death Index.
RESULTS: There were no group differences in age, gender, or time measures. Comorbidities: no differences between the four groups free <28 days but the group free >28 days had significantly lower co-morbidity burdens (ANOVA; p<0.05). Survival: no differences between the four groups free <28 days but the group free >28 days had significantly longer survivals (Time-to-event; p<0.001).
CONCLUSION: Comorbidities and survival analyses indicate two distinct populations defined by either > or < 28 days free in patients who had achieved >24 hours free from ventilator support. The current standard, 7 days free, does not discriminate between freedom <7 days and the three groups free from 7 to 28 days. The cut point of >28 days free selects those patients with less comorbidities and longer survivals, a population with better prognoses.
CLINICAL IMPLICATIONS: Patients requiring prolonged mechanical ventilation are a difficult to wean subset of all ventilated patients in acute hospitals. The 7-day-free-from-ventilator-support standard for weaning success used in acute hospitals seems less appropriate for this subset than the >28-days-free-from-ventilator-support. This different standard defines a more stable population with better prognoses than the 7 day standard. This different standard could perhaps be considered as the standard for successful weaning when reporting outcomes of patients requiring long-term ventilator support.
DISCLOSURE: J. Dermot Frengley, No Financial Disclosure Information; No Product/Research Disclosure Information