Impact of speed limit: I. Chest injuries, review of 966 cases

Abstract

Traffic fatalities have decreased since the reduction in the speed limit to 55 miles per hour. However, there has been no report documenting a decrease in the severity of chest injury from automobile accidents. From January, 1968, to January, 1980, 966 patients with chest injury from automobile accidents were admitted: 463 during the period January, 1968, to December, 1973 (before speed limit change, first period), and 503 during the period January, 1974 to January, 1980 (after reduction of speed limit, second period). The mortality during the first period was 17.3% (80/463), which was 16.1% higher than second period, 14.9% (75/503), p > 0.05. There were no significant differences in number of the following chest injuries: multiple rib fractures, 77.8% (360/463) versus 73.0% (367/503); pneumothorax, 41.7% (193/463) versus 39.4% (198/503); lung contusion, 25.9% (120/463) versus 24.9% (125/503); diaphragm rupture, 3.9% (18/463) versus 4.2% (21/503); tracheoesophageal fistula, 0.4% (2/463) versus 0% (0/503); cardiac injury, 3.5% (16/463) versus 5.6% (28/503), or aortic injury, 3.2% (15/463) versus 4.0% (20/503). There were statistically significant differences in the following injuries: hemothorax, 42.1% (195/463) versus 29.2% (147/503), p < 0.01; sternum fracture, 6.7% (32/463) versus 3.8% (19/503), p < 0.01; tracheobronchial rupture, 1.5% (7/463), versus 0% (0/503), p < 0.01; and flail chest, 14.7% (68/463) versus 7.2% (36/503), p < 0.001. During the first period the following were significantly higher: first 24 hour blood replacement, average 1.9 versus 1.4 units, p < 0.05; 48 hour chest tube drainage, average 358 versus 216 ml, p < 0.001; respirator use, average 1.75 versus 0.42 days, p < 0.001; and hospitalization, average 15.0 versus 13.1 days, p < 0.05. Thus the mortality, morbidity, and severity of chest injury were lower after the reduction of the speed limit to 55 miles per hour from 70 miles per hour.