VENTILATION, RESPIRATORY CENTER OUTPUT, AND CONTRIBUTION OF THE RIB CAGE AND ABDOMINAL COMPONENTS TO VENTILATION DURING CO2 RE-BREATHING IN CHILDREN WITH CYSTIC-FIBROSIS

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Abstract
Although there is extensive research into the control of breathing adults with chronic obstructive lung disease, there is little information in this area in children with cystic fibrosis (CF). To investigate the respiratory response of children with CF to CO2 under hyperoxic conditions, a standard CO2 rebreathing technique was used in 14 children with CF. Their response to CO2 was evaluated in terms of ventilation (.ovrhdot.VE), mean inspiratory flow rate (VT/Tl) and the pressure generated at the mouth after 0.1 s of an inspiratory effort against an occlusion (PO.1). To understand the contributions of the rib cage and abdominal components to ventilation, the volume change in each compartment was assessed by attaching magnetometers to the chest and abdomen. Overall changes in lung volume were assessed in a volume displacement plethysmograph. When corrected for the height of the child, the slope of .ovrhdot.VE vs. end tidal CO2 (PETCO2), and the slope of VT/TI vs. PET[end tidal partial pressure]CO2 correlated significantly with the degree of airway obstruction as expressed by the forced expiratory flow between 25 and 75% of vital capacity. The values for PO.1 were all within the normal range and showed no correlation with the degree of airway obstruction. The contribution of the rib cage and abdomen to ventilation during rebreathing was similar to that previously reported for adults. No changes were observed in functional residual capacity during rebreathing. Tests involving a mechanical response to CO2 correlated with the degree of airway obstruction, but there was no evidence that the neuromuscular drive was abnormal.

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