At-risk populations and the critically ill rely disproportionately on ambulance transport to emergency departments.

STUDY OBJECTIVE Emergency department (ED) crowding increases ambulance diversion. Ambulance diversion disproportionately affects individuals who rely on ambulance transport. The purpose of this study is to determine which populations rely most on ambulance transport. METHODS We queried the National Hospital Ambulatory Medical Care Survey database for 1997 to 2000 and 2003 to 2005 for patients who arrived by ambulance or personal transport. We performed bivariate analysis to assess the extent to which all patients and a subset of critically ill patients use ambulance transport relative to self-transport. RESULTS In our sample, 30,455 (15%; 95% confidence interval [CI] 15% to 16%) patients arrived by ambulance and 162,091 (85%; 95% CI 84% to 85%) arrived by walk-in/self-transport. Overall, patients with Medicare insurance were more likely to rely on ambulance transport, at 34% (95% CI 33% to 35%), than the privately insured, at 11% (95% CI 10% to 11%). Among the critically ill, privately insured patients were less likely to rely on ambulance transport, at 47% (95% CI 42% to 52%), than those with Medicare insurance (61%; 95% CI 58% to 65%), the publicly insured (60%; 95% CI 52% to 67%), or the uninsured (57%; 95% CI 49% to 64%). Among the critically ill, patients aged 15 to 24 years and those older than 74 years were most likely to rely on ambulance transport, at 63% (95% CI 53% to 72%) and 67% (95% CI 62% to 71%), respectively. Fifty-seven percent (95% CI 54% to 59%) of the critically ill used ambulance versus 15% (95% CI 14% to 15%) of noncritical patients. CONCLUSION Patients with Medicare insurance or public insurance, the uninsured, the elderly, and the critically ill disproportionately rely on ambulance transport to the ED. Ambulance diversion may disproportionately affect these populations.