Marc D. Fisicaro MD (Resident in Anesthesiology),

1. Using the capnograph to confirm lung isolation when using a bronchial blocker Marc D. Fisicaro MD (Resident in Anesthesiology), David P. Maguire MD (Associate Professor of Anesthesiology), Valerie E. Armstead MD, FAAP (Professor of Anesthesiology) Department of Anesthesiology, Thomas Jefferson University/Jefferson Medical College, Philadelphia, PA 19107-5092, USA Received 15 October 2008; revised 5 August 2009; accepted 16 September 2009 Journal of Clinical Anesthesia (2010) 22, 557–559

2. Bronchial blocker; Capnography; Lung isolation; Thoracotomy Keywords:

3. Abstract The endotracheal tube and bronchial blocker combination is an accepted lung isolation technique used during thoracic surgery. A reliable and inexpensive method of confirming lung isolation that uses capnographic monitoring of the bronchial blocker central lumen is presented. As the bronchial blocker balloon is inflated, lung isolation is confirmed when the normal respiratory variation of carbon dioxide (CO2) is replaced by a persistent plateau CO2 waveform.

5. The bronchial blocker is an accepted lung isolation technique used during thoracic surgery. The Univent™ tube, the Uniblocker™ , and the Arndt™ bronchial blocker are commercially available bronchial blockers manufactured with continuous central lumens used for deflating the lung and for applying continuous positive airway pressure (CPAP), if needed. A bronchial blocker is placed in the appropriate bronchus using bronchoscopic guidance, and the attached balloon is then inflated to occlude the bronchus and isolate the lung. 1. Introduction

6. Two techniques have been described to confirm lung isolation using a bronchial blocker, but they are cumbersome to use during surgery. A reliable, convenient, and inexpensive technique for using the capnograph and the bronchial blocker's central lumen to confirm lung isolation while achieving proper cuff inflation pressure is presented.

7. 2. Case report The trachea of a 62 year-old woman undergoing rightsided video-assisted thoracoscopic surgery (VATS) and right lower lobectomy was intubated using a Univent™ tube following induction of general anesthesia. The tube's integral bronchial blocker was then positioned in the right mainstem bronchus using bronchoscopic guidance.

8. At this time, a gas sampling line was placed on the central lumen of the bronchial blocker and connected to a three-way stopcock that had been placed on the capnograph nipple. The gas sampling line from the breathing circuit was connected to the other port of the stopcock. The stopcock was turned to allow sampling from the bronchial blocker's central lumen; a normal capnograph tracing was seen (Fig. 1).

9. Fig. 1 Normal capnograph from the central lumen of the bronchial blocker before the bronchial cuff was inflated

10. While monitoring the bronchial blocker's distal lumen, air was injected into the blocker's balloon in one mL increments. After a total of 4 mL of air had been injected into the balloon, the normal capnograph trace was replaced by a persistent CO2 plateau (Fig. 2A, B);

11. Fig. 2 Capnographs showing persistent carbon dioxide (CO2) after 4 mL of air was injected into the bronchial cuff. A. The lack of respiratory variation in the capnograph tracing confirmed that the bronchial blocker tip was isolated from respiratory gases and that the blocker's balloon had occluded the right mainstem bronchus.

12. B. Note on a similar capnograph that, despite the loss of variation the CO2 trace, the pressure trace remains unchanged, indicating continued ventilation of the dependent lung. etCO2 = end-tidal carbon dioxide, FiCO2 = inspired carbon dioxide concentration, PLAT = plateau, PEEP = positive end expiratory pressure.

13. The lack of respiratory variation in the capnograph tracing confirmed that the bronchial blocker's tip was isolated from respiratory gases and that its balloon had occluded the right mainstem bronchus. Once isolation was confirmed, the stopcock was turned to allow gas sampling from the ETT.

14. If there were concerns about surgical manipulation of the operative site or a change in patient position, the stopcock was momentarily returned to the bronchial blocker position to confirm lung isolation and adequate balloon inflation. This maneuver was performed just long enough to confirm the presence of the characteristic plateau pattern of the capnograph (usually less than 15 sec).

15. The Univent™ tube is an established modality providing one-lung ventilation during thoracic surgery. One difficulty with the Univent™ tube, and bronchial blockers generally, is determining the balloon inflation volume required to isolate the lung. If the balloon is under-inflated, the surgical lung will continue to be ventilated, which will adversely affect surgical exposure and delay the procedure. 3. Discussion

16. If the balloon is over-inflated, bronchial blocker cuff pressure increases as does the pressure exerted against the bronchus, which could increase the risk of bronchial trauma and rupture. Inflating the balloon with the minimum amount of air needed to isolate the bronchus should optimize operating conditions while minimizing the risk of bronchial rupture.

17. The optimum amount of air needed to isolate the right mainstem bronchus was easily determined. This technique is simple and inexpensive, and it is performed with equipment normally found in an operating room.

18. This technique also allows a relatively quick method to recheck for maintenance of lung isolation by a simple turn of the stopcock to the bronchial blocker's lumen, if patient position is changed or if there is manipulation of the surgical site by retractors.

19. As these intermittent reaffirmations of lung isolation were of short duration (15 sec or less), complete lung deflation and occlusion of the bronchial blocker's central lumen as a result of the 200 mL/min gas sampling from the Datex monitor or the anesthesia machine was not encountered.

20. Although the end-tidal CO2 (etCO2) tracing required for confirmation of correct technique for lung isolation was reassuring, there are cases where this pattern may indicate problems.

21. Prolonged etCO2 plateau phase without the capnogram's return to baseline is also seen with an incompetent expiratory valve in a circle system. Other situations that may affect the plateau and baseline of capnograms include exhaustion of, or other problems with, the CO2 absorbent system, ventilator malfunction, and system leaks.

22. Hannallah et al. described a similar technique to verify lung isolation when using double-lumen tubes during thoracic surgery. This technique was also found to be successful when using the Arndt™, Uniblocker™, and Univent™tube bronchial blockers during both right and left thoracic procedures.

23. In conclusion, a technique that uses capnographic monitoring of the central lumen of the Univent™ tube bronchial blocker to verify lung isolation during one-lung ventilation is presented. This simple technique will improve the quality and safety of lung isolation during thoracic procedures when using bronchial blockers equipped with a continuous central lumen.

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