The Hering-Breuer reflex in anesthetized infants: end-inspiratory vs. end-expiratory occlusion technique

1 Department of Anaesthesia, Montreal Children's Hospital, Montreal, Quebec, Canada H3H 1P3; 2 Portex Anaesthesia, Intensive Therapy and Respiratory Medicine Unit, Institute of Child Health, London, WC1N 1EH, United Kingdom; and 3 Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, People's Republic of China Both end-inspiratory (EIO) and end-expiratory (EEO) occlusions have been used to measure the strength of the Hering-Breuer inflation reflex (HBIR) in infants. The purpose of this study was to compare both techniques in anesthetized infants. In each infant, HBIR activity was calculated as the relative prolongation of expiratory and inspiratory time during EIO and EEO, respectively. Respiratory drive was assessed from the change in airway pressure during inspiratory effort against the occlusion, both at a fixed time interval of 100 ms (P 0.1 ) and a fixed proportion (10%) of the occluded inspiratory time (P 10% ). Twenty-two infants [age 14.3 ± 6.4 (SD) mo] were studied. No HBIR activity was present during EIO [ 11.8 ± 15.9 (SD) %]. By contrast, there was significant, albeit weak, reflex activity during EEO [HBIR: 27.2 ± 17.4%]. A strong HBIR (up to 310%) was elicited in six of seven infants in whom EIO was repeated after lung inflation. P 0.1 was similar during both types of occlusions, whereas mean ± SD P 10% was lower during EEO than during EIO: 0.198 ± 0.09 vs. 0.367 ± 0.15 kPa, respectively ( P