Comparison of pleural pressure measuring instruments

OBJECTIVE The objective of this study was to compare the accuracy of a handheld digital manometer (DM) and U-tube (UT) manometer with an electronic transducer (ET) manometer during thoracentesis. METHODS Thirty-three consecutive patients undergoing thoracentesis were enrolled in the study. Pleural pressure (Ppl) measurements were made using a handheld DM (Compass; Mirador Biomedical), a UT water manometer, and an ET (reference instrument). End-expiratory Ppl was recorded after catheter insertion, after each aspiration of 240 mL, and prior to catheter removal. Volume of fluid removed, symptoms during thoracentesis, pleural elastance, and pleural fluid chemistry were also evaluated. RESULTS A total of 594 Ppl measurements were made in 30 patients during their thoracenteses. There was a strong linear correlation coefficient between elastance for the DM and ET ( r = 0.9582, P r = 0.0448, P = .84). Among the 15 patients who developed cough, recorded ET pressures ranged from −9 to +9 cm H 2 O at the time of symptom development, with a mean (SD) of −2.93 (4.89) cm H 2 O. ET and DM measurements among those patients with cough had a low correlation between these measurements ( R 2 = 0.104, P = .24). Nine patients developed chest discomfort and had ET pressures that ranged from −26 to +6 cm H 2 O, with a mean (SD) of −7.89 (9.97) cm H 2 O. CONCLUSIONS The handheld DM provided a valid and easy-to-use method to measure Ppl during thoracentesis. Future studies are needed to investigate its usefulness in predicting clinically meaningful outcomes.