Manometry performed at indwelling pleural catheter insertion to predict unexpandable lung.

Background: The finding of unexpandable lung (UL) at an early timepoint is of increasing importance in guiding treatment decisions in patients with malignant pleural effusion (MPE). Pleural manometry is the most common technique to delineate UL, however it has never been measured via an indwelling pleural catheter (IPC). To further the evidence base we analysed all patients in the IPC-PLUS study who had manometry performed during IPC insertion for the ability to predict substantial UL using manometry.

Methods: All patients enrolled in IPC-PLUS who had manometry performed at IPC insertion and radiographic assessment of UL at day 10 were included. Elastance curves were visually inspected for each patient. Initial pleural pressure, closing pleural pressure, and terminal elastance were analysed for their differences and predictive ability in those with substantial UL, defined as ≥25% entrapment on chest radiography.

Results: A total of 89 patients had manometry performed at IPC insertion with subsequent radiographic assessment of UL and interpretable elastance curves. Those with substantial UL had a significantly lower median closing pleural pressure (-15.00 0.00 cmHO, P=0.012) and higher terminal elastance (12.03 8.59 cmHO/L, P=0.021) compared to a combined group with no or partial UL. However, the predictive ability of these factors to discriminate substantial UL was poor, with areas under the receiver operating characteristic curves of 0.695 and 0.680 for closing pleural pressure and elastance respectively.

Conclusions: Our results suggest that manometry is not useful in accurately predicting substantial UL when used via an IPC at the time of insertion.