Hospital Chain Says Its Profit Will Be Lower
High hospital prices come under further scrutiny when Tenet Healthcare tells analysts to expect significantly lower profits than they had anticipated as company moves away from its aggressive pricing strategy; Centers for Medicare and Medicare Services says it will scrutinize billing of any hospital receiving excessive payments, practice that appears to be widespread; Tenet also tells analysts it plans to change how it contracts with managed care companies to rely more heavily on fixed payments; plans to offer substantial discounts to patients without insurance so they do not bear brunt of high hospital prices; chief executive Jeffrey C Barbakow tries to persuade investors that company's prospects remain bright; chart (M)