Answer: C
This is an esophageal catheter for esophageal pressure (Pes) measurement. Measurement of Pes allows for breaking down the total respiratory system compliance into its transpulmonary and chest wall components. As can be seen from the photo, the catheter has an inflatable balloon with holes inside to transmit the Pes to the transducer through the balloon. Five ml air can fully inflate the balloon, but during measurement, 0.5 to 2.5 ml air is to be injected.
For this instance of insertion, we are using it in an obese human swine flu patient being put on ECMO. We are aiming at a positive transpulmonary pressure (PEEP minus Pes at end-expiration) to optimize PEEP setting, as suggested by Daniel Talmor’s paper in NEJM (here). Pes measurement allows us to better set PEEP in this young and obese female patient who has low chest wall compliance from obesity and edema, in addition to low lung compliance from her human swine flu pneumonitis. Better management of PEEP has probably contributed to less lung injury, and allows us to wean off ECMO within five days in her case.
Reference
Talmor D, Sarge T, Malhotra A, O’Donnell CR, Ritz R, Lisbon A, Novack V, Loring SH. Mechanical ventilation guided by esophageal pressure in acute lung injury. N Engl J Med. 2008 Nov 13;359(20):2095-104. Epub 2008 Nov 11.