Emergency Services in U.S. Found Uneven
NY Times survey of ambulance services finds wide variations in efficiency and capabilities of rescue systems; emergency med systems have improved but deficiencies still exist that undoubtedly cost tens of thousands of lives each yr; survey finds more than 1/2 of US ambulances are inadequately equipped for advanced life-saving techniqes, many major cities lack central emergency phone number and ambulances in some cities seriously compromise victim's chance of survival because of long response time; illus (M)