Remifentanil improves breathing pattern and reduces inspiratory workload in tachypneic patients.

BACKGROUND Properly titrated opiates decrease respiratory rate but do not affect tidal volume or induce respiratory acidosis. OBJECTIVE To determine whether remifentanil improves breathing pattern or reduces inspiratory effort in patients with acute respiratory failure and tachypnea or rapid shallow breathing. METHODS We studied 14 patients who developed tachypnea and/or rapid shallow breathing if the pressure support level was reduced. During pressure support ventilation, each patient received 30-min infusions, separated by 30 min, of remifentanil and placebo. Measurements were obtained before commencing and before stopping each infusion, and after 3 min of unassisted breathing. The main outcomes were rapid shallow breathing index and change in pressure-time product. RESULTS Remifentanil did not significantly affect tidal volume. During pressure support ventilation, remifentanil infusion reduced respiratory rate, pressure-time product, and cardiovascular double product (heart rate × systolic arterial pressure) without modifying the sedation score. Mean P(aCO(2)) showed a small and clinically negligible increase during remifentanil, but P(aCO(2)) increased more in the hypercapnic patients than in the normocapnic patients. Remifentanil reduced the rapid shallow breathing index after 3 min of unassisted breathing. CONCLUSIONS Remifentanil improved respiratory pattern and decreased inspiratory muscles effort in patients with tachypnea or rapid shallow breathing, but did not affect oxygenation or sedation. Though the acid-base balance did not show clinically relevant changes on average, we cannot exclude the possibility that remifentanil might prolong weaning in hypercapnic patients. (Clinical-Trials.gov registration NCT00665119.)