Hazard ratios for prolonged mechanical ventilation status over one year of follow up. Plot of hazard ratios (solid line) and 95% confidence intervals (dashed lines) for DRG 541/542 patients versus short-term mechanical ventilation patients, determined using a time-varying piecewise-constant nonproportional survival model. The shaded areas represent time periods with statistically significant hazard ratios. The hazard ratios vary over time, predicting an early (< 30 days after intubation) lower risk for death for DRG 541/542 relative to short-term ventilation patients, but a higher risk for mortality between days 60 and 100 as the slope of short-term ventilation mortality levels off (also see Figure 2). Hazard ratios are adjusted by day one APS, pre-admission Charlson score, age, and pre-admission ADLs. APS, Acute Physiology Score; ADL, activity of daily living; DRG, diagnosis related group.