Relationship Between Pulmonary-to-Systemic-Blood-Flow Ratio (Qp:Qs) Based on Cardiac Catheterization and Indices Derived from Simultaneously Measured End Tidal CO2 (EtCO2) in Children with Complex Congenital Heart Disease

• Published in: Pediatric cardiology 2019-01, Vol.40 (1), p.182-187
• Main Authors: Chauhan, Jigar C., Deb, Rituparna
• Format: Article
• Language: English
• Subjects: Cardiac Surgery; Cardiology; Medicine; Medicine & Public Health; Original Article; Vascular Surgery
• ISSN: 0172-0643; 1432-1971
• DOI: 10.1007/s00246-018-1976-7

CO 2 removal by the lungs depends upon ventilation and pulmonary blood flow, with end tidal CO 2 (EtCO 2 ) as surrogate for it. We studied indices based on EtCO 2 measured routinely during anesthesia for cardiac catheterization, along with simultaneously calculated Qp:Qs (pulmonary-to-systemic-blood-flow ratio) in children with complex congenital heart disease to assess the relationship between these measures. A retrospective, single-center, correlational cohort study was conducted at a tertiary-care, free-standing children’s hospital. All included subjects had Qp:Qs calculated as well as EtCO 2 and PaCO 2 documented during a single cardiac catheterization. Children with stage-1 single ventricle or complex biventricular repair with highly variable Qp:Qs were defined as Group 1, and Group 2 comprised those with stage 2 or 3 repairs with less variable Qp:Qs. Exclusion criteria were uncuffed artificial airway, EtCO 2  > PaCO 2 , and abnormally high Qp:Qs. EtCO 2 indices were defined as EtCO 2 :PaCO 2 (alveolar functional fraction) and EtCO 2 gap (PaCO 2 –EtCO 2 ). Correlation coefficients were obtained between Qp:Qs and EtCO 2 indices in both groups. A total of 29 patients in Group 1 and 24 in Group 2 underwent final analysis. Even with highly variable Qp:Qs, Group 1 showed a strong correlation between Qp:Qs and EtCO 2 :PaCO 2 ( r  = 0.83, p