Abstract: AIM This study compared the diagnosis values of normal respiration, Valsalva maneuver, and deep cough in right heart contrast transthoracic echocardiography (cTTE ) for right to left shunt in patent foramen ovale (PFO). METHODS A total of 396 patients requiring diagnostic exclusion of paradoxical embolism were conducted cTTE. Patients with microbubbles appearing in the left heart were diagnosed as right to left shunt: 1 to 10 microbubbles/frame were classed mild shunt; 11 to 30 microbubbles/frame were classed moderate shunt; >30 microbubbles/frame were classed severe shunt. The present investigation compared normal respiration, standard Valsalva maneuver, and deep cough in the diagnosis of right to left shunt and explored potential mechanisms. RESULTS 119 cases of PFO with right to left shunt were detected using cTTE, including 28 cases of mild shunt, 60 cases of moderate shunt, and 31 cases of severe shunt. There was no difference between standard valsalva maneover and deep cough in detecting moderate and severe shunt. However, there was a significant difference between standard valsalva maneover and deep cough in detecting mild shunt. Deep cough detected more cases than standard valsalva maneover (P<0.05). CONCLUSION Deep cough has a greater detection rate than standard Valsalva maneuver in detecting mild shunt PFO using cTTE.