Influence of duration mechanics measured of occlusion time on respiratory with the single‐breath technique in infants

To determine the effect of the length of end‐inspiratory occlusion on the values of respiratory system compliance (C rs and resistance (R rs ) calculated from the single‐breath technique, 6 infants with cystic fibrosis were studied. End‐inspiratory occlusions lasted between 0.3 and 1.2 seconds, and between 8 and 32 separate occlusions were made in each infant. Examination of the individual data showed a systematic tendency for C, to decrease as the length of the airway occlusion increased, with statistical significance reached in two subjects. Using a random effects model, it was demonstrated that there was a decrease of 0.1 5 Ml/cmH 2 O in C rs for each 0.1 s increase in occlusion time. The influence of length of plateau time for C, was similar to that of total occlusion time. No such tendency was seen for R rs . These data reinforce the current emphasis on greater standardization in the methodologies used for infant lung function testing and for more fully reporting methodological details. Pediatr Pulmonol. 1994; 17:250–257. © 1994 Wiley‐Liss, Inc.