['To determine characteristics of breathing patterns prior to respiratory pauses in extremely low birth weight (ELBW) infants breathing spontaneously under proportional assist ventilation (PAV).', 'Thirteen infants (mean +/- SD: gestational age 25 +/- 1 weeks; birth weight 753 +/- 149 g; age 4 +/- 3 days) were studied. Recordings were obtained under PAV over two-hour periods on two consecutive days. The last 10 breaths preceding respiratory pauses were analyzed.', 'Tidal volume, inspiratory and expiratory peak flow, and mean inspiratory flow decreased in the last breaths prior to respiratory pauses compared to all other breaths (p < 0.001). Of all apneas 89% were preceded by a decrease in tidal volume of at least 33% (435/487; p < 0.001). The positive predictive value of a decrease in tidal volume to predict an apnea was 26% (435/1640; p < 0.001).'] Does antecedents of respiratory pause in extremely low birth weight infants supported by proportional assist ventilation?