End-expiratory lung volume assessment using helium and carbon dioxide in an experimental model of pediatric...

Capnoperitoneum during laparoscopy leads to cranial shift of the diaphragm, loss in lung volume, and risk of impaired gas exchange. Infants are susceptible to these changes and bedside assessment of lung volume during laparoscopy might assist with optimizing the ventilation. Thus, the primary aim was to investigate the monitoring value of a continuous end-expiratory lung volume (EELV) assessment method based on CO₂ dynamics ( $$ ) in a pediatric capnoperitoneum model by evaluating the correlation and trending ability against helium washout (EELV_He ).

Intra-abdominal pressure (IAP) was randomly varied between 0, 6, and 12 mm Hg with CO₂ insufflation, while positive end-expiratory pressure (PEEP) levels of 3, 6, and 9 cm H₂ O were randomly applied in eight anesthetized and mechanically ventilated chinchilla rabbits. Concomitant $$ and EELV_He and lung clearance index (LCI) were obtained under each experimental condition.

Significant correlations were found between $$ and EELV_He before capnoperitoneum (r = .85, P < .001), although increased IAP distorted this relationship. The negative influence of IAP was counteracted by the application of PEEP 9, which restored the correlation between $$ and EELV_He and resulted in 100% concordance rate between the methods regarding changes in lung volume. EELV_He and LCI showed a curvilinear relationship, and an EELV_He of approximately 20 mL kg^-1 , determined with a receiver operating characteristic curve, was associated with near-normal LCI values.

In this animal model of pediatric capnoperitoneum, reliable assessment of changes in EELV based on $$ requires an open lung strategy, defined as EELV above approximately 20 mL kg^-1 .