PARALYSIS HAS NO EFFECT ON CHEST-WALL AND RESPIRATORY SYSTEM MECHANICS OF MECHANICALLY VENTILATED, SEDATED PATIENTS

Objective: To evaluate the separate effects of sedation and paralysis on chest wall and respiratory system mechanics of mechanically ventila ted, critically ill patients. Setting: ICU of the University ''La Sapi enza'' Hospital, Rome. Patients and participants: 13 critically ill pa tients were enrolled in this study. All were affected by disease invol ving both lungs and chest wall mechanics (ARDS in 4 patients, closed c hest trauma without flail chest in 4 patients, cardiogenic pulmonary o edema with fluidic overload in 5 patients). Measurements and results: Respiratory system and chest wall mechanics were evaluated during cons tant flow controlled mechanical ventilation in basal conditions (i.e. with the patients under apnoic sedation) and after paralysis with panc uronium bromide. In details, we simultaneously recorded airflow trache al pressure, esophageal pressure and tidal volume; with the end-inspir atory and end-expiratory airway occlusion technique we could evaluate respiratory system and chest wall elastance and resistances. Lung mech anics was evaluated by subtracting chest wall from respiratory system data. All data obtained in basal conditions (with the patients sedated with thiopental or propofol) and after muscle paralysis were compared using the Student's t test for paired data. The administration of pan curonium bromide to sedated patients induced a complete muscle paralys is without producing significant modification both to the viscoelastic and to the resistive parameters of chest wall and respiratory system. Conclusions: This study demonstrates the lack of additive effects of muscle paralysis in mechanically ventilated, sedated patients. Also in view of the possible side effects of muscle paralysis, our results qu estion the usefulness of generalyzed administration of neuromuscular b locking drugs in mechanically ventilated patients.