The effects of surgically treated pulmonary stenosis on lung growth and cardiopulmonary function in children during rest and exercise

The effects of high pulmonary blood flow and pressure on pulmonary developm ent are well understood, but the effect of low pulmonary flow/pressure is n ot. Pulmonary stenosis (PS) was therefore used as a model to determine its effect on lung development, which was assessed noninvasively by carbon mono xide transfer at rest and during exercise. One hundred and six control children (55 males, 8-16 yrs) and 11 children w ith isolated valvar or subvalvar PS surgically corrected greater than or eq ual to 10 yrs prior to the study without residual stenosis/regurgitation we re evaluated. Measurements of effective pulmonary blood flow, stroke volume , arteriovenous oxygen difference (AVO), transfer factor and transfer const ant, alveolar ventilation and anaerobic threshold were performed using a ma ss spectrometer. Data from the normal children allowed calculation of z-sco res for the study group matched for age, sex, pubertal stage and surface ar ea. PS children at rest had a significantly lower forced expired volume in one second, cardiac frequency and transfer constant with a raised oxygen consum ption and AVO which persisted on exercise. During exercise, the cardiac fre quency was 12 beats.min(-1) slower and AVO 0.017 L greater than controls (p <0.05), A persistently mildly raised effective functional residual capacity (0.2 L.m(-2)) during exercise led to a reduced transfer constant (0.35 mmo l.min(-1).kPa(-1).L-1), although the percentage rise (28%) from rest to pea k exercise was normal. The percentage fall in stroke volume from the penult imate exercise stage to peak exercise stage was greater in PS children (24% , 95% confidence interval 11-37) than control children (2.4, -2-10, p<0.005 ), In conclusion, although the effects are small, pulmonary stenosis does affe ct cardiopulmonary function after surgery. This needs to be considered when contemplating the timing of treatment.