USE OF NONINVASIVE POSITIVE PRESSURE VENT ILATION FOR CARDIOGENIC PULMONARY-EDEMA IN EMERGENCY CARE UNITS

The work reported by I'Her et ai. in this issue of io Presse Medicale demonstrates the feasibility of applying simple intensive care techniq ues in situations frequently encountered in emergency care units. Thes e authors used a face mask for continuous positive pressure ventilatio n in patients over 70 years oi age admitted for respiratory distress r elated to cardiogenic pulmonary edema. in these elderly patients, the authors noted an improvement in blood gases, respiratory rate and hear t rate and did nor observe any secondary effect Acute respiratory fail ure was cured in 90% of the cases without referral to the intensive ca re unit The mechanism of action of continuous positive airway pressure , or spontaneous ventilation with positive expiratory pressure, is dif ferent from simple oxygen therapy. Two mechanisms are intimately relat ed. The main effect is ventilatory assistance resulting from a ''re-ae ration'' of the pulmonary parenchyma which increases compliance and re duces work required to overcome elastic retraction forces. likewise th e increased pulmonary volume reduces pulmonary resistance. Positive ai rway pressure also has an effect on left ventricular function; indeed, after load is reduced by the reduction in the large negative intratho racic pressure swing. lower energy expenditure required for respiratio n also greatly reduces total oxygen consumption and improved blood gas es favor oxygen supply to the myocardium. The contraindications of con tinuous positive airway pressure are related to abnormal central of th e upper airways and major hemodynamic disorders. Prudence is also requ ired in case of shock due to the risk of major respiratry muscle fatig ue. The question could also be raised as to the risk in elderly patien ts where cardiogenic pulmonary edema is often associated with a certai n degree of chronic bronchitis. It is now known that these patients ha ve an intrinsic positive expiratory pressure which considerably increa ses respiratory work Symptomatic treatment in this type of disorder is mechanical and continuous positive airway pressure diminishes this wo rk. Cardiogenic pulmonary edema in the elderly is thus an excellent in dication for spontaneous Ventilation with positive expiratory pressure . improvement in these simple techniques, their widespread use and a b etter understanding of their limitations remain important challenges f or the future. (C) 1998, Masson, Paris.