Breathing pattern and transcutaneous oxygen tension during motor activity in preterm infants.

We studied breathing pattern and transcutaneous oxygen tension (TcPO2) during episodes of sustained generalized motor activity in 18 hospitalized preterm infants. We used a newly developed quantitative method for assessing minute ventilation in infants during vigorous motor activity. We recorded respiratory air flow, tidal volume, esophageal pressure, TcPO2, and electromyograms of various muscle groups. We observed a distinctive pattern of breathing ("exertional breathing pattern") that was invariably associated with episodes of "squirming" motor activity. This breathing pattern is characterized by reduced minute volume, intermittent Valsalva maneuvers, and obstructed inspiratory effects (obstructive apnea). Episodes of squirming with the accompanying altered breathing pattern were usually followed by a decrease in TcPO2. These episodes occurred spontaneously or could be induced by sensory stimulation. They appear to be a significant cause of obstructive apnea and TcPO2 instability in hospitalized preterm infants, and were responsible for 30% of sudden decreases in TcP[O2 of 10 mmHg or greater.