Primary clinical investigation of cardiopulmonary exercise gas exchange in pulmonary hypertension patients with and without right-to-left shunt

Abstract

Objective: The aim of this study is to determine the changes of gas exchange parameters during ramp incremental cardiopulmonary exercise test (CPET) in patients with pulmonary hypertension (PH) could identify the right to left shunt (R-L Shunt). Methods: We did a retrospective analysis of exercise gas exchange parameters for 73 PH patients and 14 normal subjects as control, in Fuwai Hospital from October 2016 to August 2017, who did CPET with signature on content form. The gas exchange data of CPET were double-blindly independently interpreted by four export-doctors. According to the reading results of CPET, the PH patients were divided into four groups: ① R-L shunt positive group, ② R-L shunt suspicious group, ③R-L shunt negative group, ④late open R-L Shunt positive group. Results: Minute ventilation (VE), ventilatory equivalents for carbon dioxide and oxygen (VE/VCO2, VE/VO2), end-tidal partial pressure of oxygen (PETO2)in R-L shunt positive group were significantly increased ((7.36 ± 2.72) L/min, (1.84± 3.59), (5.02 ±4.34), (3.75±2.64) mmHg) at the beginning of exercise, and were also significantly higher than the control ((4.26 ± 2.59) L/min, (2.22± 2.08), (1.46 ±4.68), (3.96 ± 2.82) mmHg); Partial pressure of carbon dioxide in end expiratory gas (PETCO2) was decreased (-1.63 ±1.66) mmHg, and was significantly lower than control (2.22 ± 2.08) mmHg (P<0.01). Respiratory quotient (RER), carbon dioxide, VE/VCO2, VE/VO2, PETO2 in late open R-L Shunt positive group were suddenly increased ((0.40 ± 0.08), (11.07 ± 5.60),(30.55 ±7.89), (13.72 ±2.21) mmHg) at the end of exercise near the peak, significantly higher than control too ((0.38± 0.12), (5.67± 4.60), (4.54 ± 3.83), (5.51± 4.24) mmHg); PETCO2 was suddenly decreased at the end of the exercise compared to the resting stage (-6.82 ± 1.96) mmHg, and was significantly different from the control (5.67 ±4.60) mmHg. Carbon dioxide ventilatory efficiency, oxygen uptake ventilatory efficiency relative to the peak power (-8.38 ±3.24, -13.14 ± 6.47) at the recovery stage in late open R-L shunt positive group are significantly lower than control (6.22 ±2.87, 16.56± 4.20) (P<0.01). Conclusion: Cardiopulmonary function and ventilation efficiency of patients withpulmonary hypertension are significantly decreased; pulmonary hypertension and right to left shunt in patients not only resting ventilation efficiency is limited more serious; The characteristics of R-L shunt are the sudden increase of PETO2, VE/ VCO2, VE, RER and sudden decrease of PETCO2 and VO2/ VE at the beginning of exercise, and commonly companied with decreased SpO2. For the delay open R-L shunt, these changes occurred near the peak exercise rather than the beginning, and these characteristic changes quickly reversed after stopping exercise.