Light Sedation during Acute Respiratory Failure

Abstract

Light sedation is commonly used in the ICU to decrease adverse effects of heavy sedation (hemodynamic, gastrointestinal, neuropsychiatric, neuromuscular). Is this strategy feasible in case of acute respiratory failure? Profound sedation has negative effects on respiratory mechanics, ventilation variability, and diaphragm atrophy. Light sedation allows promoting assisted ventilatory modes (namely pressure support ventilation PSV). Spontaneous breathing keeps active contraction of diaphragm resulting in reopening of inferior lobes and a decrease in lung opening and closing phenomenon. PSV can also promote better gaz exchanges. However, main drawbacks of PSV need to be taken into account, including patient/ventilator asynchrony and uncontrolled tidal volume. Hence, in case of important inspiratory efforts, airway pressures will be considered safe whereas transpulmonary pressures could be very high, increasing the risk for barotrauma. Studies on light sedation (daily interruption, nurse driven protocols) often included as high as 50% of patients presenting respiratory insufficiency. Pilot studies suggest that assisted ventilator modes can be used early in the course of respiratory failure (in ARDS also), but randomized controlled studies are still needed.