Study objectives: Bilevel pressure ventilation has had proven success in the treatment of acute respiratory failure (ARF). The purpose of this study was to identify patient characteristics early in the course of acute illness that can predict the successful use of bilevel pressure ventilation.
Methods: Ventilatory assistance using a ventilatory support system (BiPAP model ST-D; Respironics; Murrysville, PA) was considered a treatment option for stable patients with ARF. The system was titrated to patient comfort. Once stable settings had been achieved for 30 min, a posttrial arterial blood gas (ABG) measurement was obtained. Patient charts were reviewed for pretrial and posttrial ABG levels, along with demographics, APACHE (acute physiology and chronic health evaluation) II score, Glasgow Coma Scale (GCS), and length of stay (LOS) data.
Results: Bilevel pressure ventilation trials were performed on 58 patients. In 43 patients (74.1%), the trials were successful. Of the 15 patients (25.9%) in whom the trials were not successful, 13 patients required intubation. The pretrial ABG levels did not predict success, as there were no significant differences between the success and failure groups for pH and PaCO2, respectively: 7.26 vs 7.26 mm Hg and 75.3 vs 72.8 mm Hg. After 30 min, posttrial ABG levels for pH and PaCO2 predicted successful avoidance of intubation: 7.34 vs 7.27 mm Hg (p < 0.002) and 61.9 vs 73.0 mm Hg (p < 0.04), respectively. There were no significant differences between the success and failure groups in age, gender, GCS, or APACHE II. There were differences between the success and failure groups for LOS data (ventilator days, ICU days, and hospital days): 1.8 vs 10.4 days (p < 0.01), 4.2 vs 12.3 days (p < 0.02), and 7.5 vs 15.6 days (p < 0.02), respectively.
Conclusion: Successful treatment with bilevel pressure ventilation could not be predicted by pretrial data (including pH and PaCO2) obtained in the emergency department; however, a successful outcome could be determined quickly with a 30-min trial. Successful treatment with bilevel pressure ventilation significantly reduced LOS data.
Clinical implications: Our inability to predict success based on initial data supports the use of bilevel pressure ventilation trials for all stable patients with ARF. If the patient's condition fails to improve within 30 min, intubation and mechanical ventilation is indicated.