Peak oxygen uptake and mortality in children with cystic fibrosis

Area of Science:

• Pediatric Pulmonology
• Cardiopulmonary Exercise Testing
• Clinical Outcomes Research

Background:

• Single peak oxygen uptake (VO2) measurements predict mortality in cystic fibrosis (CF).
• Longitudinal studies of serial VO2 measurements in pediatric CF patients are lacking.
• Previous research focused on single time-point assessments, necessitating a longitudinal approach.

Purpose of the Study:

• To determine if initial, final, or rate of decline in forced expiratory volume in 1 second (FEV1) or peak VO2 better predicts mortality in children with CF.
• To evaluate the prognostic value of serial cardiopulmonary exercise testing data in pediatric CF.
• To establish predictors of mortality in pediatric CF patients.

Main Methods:

• Twenty-eight children (8-17 years) with CF underwent annual pulmonary function and maximal exercise tests over 5 years.
• FEV1 and peak VO2, their changes over time, and subsequent survival (7-8 years) were analyzed.
• Kaplan-Meier curves and Cox proportional hazard models were used for statistical analysis.

Main Results:

• Peak VO2 declined annually in 70% of patients (mean decline: 2.1 ml/min/kg).
• Rate of decline and final peak VO2, but not initial peak VO2, significantly predicted mortality.
• FEV1's initial, final, and rate of decline were all significant mortality predictors.
• Patients with final peak VO2 <32 ml/min/kg had increased mortality; those with peak VO2 >45 ml/min/kg had no deaths.

Conclusions:

• Higher peak VO2 is associated with longer survival in CF patients.
• Serial measurements of peak VO2 and FEV1 provide significant prognostic information.
• Cardiopulmonary exercise testing is a valuable tool for risk stratification in pediatric CF.