Respiratory suppression and swallowing from introduction of fluids into the laryngeal region of the lamb.

Introduction of 0.9% NaCl or undiluted fetal tracheal fluid into the laryngeal region produced no suppression of breathing in lambs during the perinatal period. As NaCl or tracheal fluid solutions were increasingly diluted with water, progressively greater respiratory suppression associated with rapid swallowing was observed. Introduction of amniotic fluid was associated with variable suppression of respiration. The swallowing induced by the dilute solutions was as rapid as two swallows per sec. Lambs 3 months of age swallowed when water was introduced into the laryngeal region, but were able to alternate swallows between breaths without suppression of breathing.