Cardiorespiratory Dynamics of Sedated Pigs Submitted to Diff erent Inspired Oxygen Fractions under Controlled Mechanical Ventilation*

ABSTRACT Background: Individuals submitted to situations of deep sedation have a marked decrease in their ventilatory capacity. The provision of adequate ventilation and oxygenation in critically ill patients submitted to sedation in intensive therapy has been the subject of special care. In such cases, exposure to low inspired oxygen fractions (F I O 2 ) is a factor that can infl uence alveolar perfusion and respiratory performance. The aim of this study is to evaluate the effects of three inspired oxygen fractions (80%, 60% or 40%) on the cardiorespiratory dynamics of pigs submitted to mechanical ventilation by intermittent positive pressure in deep sedation with propofol-remifentanil. Material, Methods & Results: Twenty crossbred pigs weighing between 17 and 25 kg and aged between 60 and 90 days were used. Each animal was submitted to deep sedation for 2h in randomly assigned F I O 2 (80%, 60% or 40%). Scores such as heart and respiratory rate, blood pressure, respirometry (PaO 2 , P(A-a)O 2 , P IP , V min ), physiological dead space, pulmonary shunt and blood gas analysis (pH, PaO 2 , PaCO 2 , HCO 3 ) were observed, evaluated and compared. Patients were evaluated after sedation was induced with propofol (12 mg.k