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.)