ESOPHAGEAL PRESSURE MEASUREMENTS IN CARDIOPULMONARY EXERCISE TESTING

Study objectives: We sought to determine the adaptability and effectiv eness of a new esophageal balloon technique to measure changes in esop hageal pressure (Pes) as a reflection of pleural pressure with progres sive incremental exercise testing in normal subjects. Design: An 8F (0 .9 cm) esophageal balloon catheter (Smart Cath; Allied Health Products ; Riverside, Calif), a CP-100 pulmonary monitor (BiCore Monitoring Sys tems PC-100; Irvine, Calif), and a flow transducer (Var flex; Allied H ealth Products; Riverside, Calif) were connected to a breathing valve (model 2700; Hans-Rudolph Inc; Kansas City, Mo), This apparatus was th en used to measure Pes during a graded cardiopulmonary exercise test ( CPX) to symptom limitation. Setting: University-affiliated Veterans Af fairs Hospital. Participants: Eight nonsmoking volunteers with normal results of pulmonary function tests, Interventions: Plots of Delta Pes against pressure time product (PTP), minute ventilation ((V)over dot E), and oxygen consumption ((V)over dot O-2) were obtained, Pes at bas eline, anaerobic threshold (AT), and maximum oxygen consumption ((V)ov er dot O(2)max) were obtained by comparing the Pes measurements from t he computer printout to the corresponding breath-by-breath measurement s on the CPX. Measurements and results: The how transducer (Varflex) c onnection added only 20 mL of dead space to the standard mouthpiece ap paratus. The mean maximum work performance was 203 +/- 32 W, The mean (V)over dot O(2)max was 29 +/- 9 mL/kg/min. The Pes at AT was 16 +/- 3 cm H2O. The Pes at maximal exercise was 42 +/- 16 cm H2O. Conclusion: The small esophageal balloon was well tolerated by all subjects, Plot s of Delta Pes vs PTP, (V)over dot E, and (V)over dot O-2 demonstrated a linear correlation, This apparatus could be added to the standard C PX to assess the contribution of the diaphragm and respiratory muscles in patients with dyspnea.