[Estimation of the position of right-sided double-lumen endobronchial tubes with spirometry in elderly patients]

To study the accuracy of position estimation of right-sided double-lumen endobronchial tubes (DLTs) without carinal hook in elderly patients according to the changes of inspiratory peak airway pressure (Ppeak), lung compliance (Cdyn), pressure-volume loop (P-V loop), and flow-volume loop (F-V loop).

Ninety-six elderly patients undergoing thoracic surgery were intubated with right-sided Mallinckrodt DLTs, the depth of which was determined based on the regressive equation. After 15 min of two lung ventilation (TLV), the Ppeak showed a more than 50% increase from the baseline in 22 patients when switching to one lung ventilation (OLV) with Cdyn less than 50% of the baseline and Ppeak in excess of 22 cmH(2)O. In these 22 cases, the position of the DLT was determined by fiberoptic bronchoscope (FOB) and adjusted to the precise position at 15 min of OLV.

DLTs were inserted into the right middle bronchi in 19 cases and the right lower lobe bronchi in 3 cases. At 124-/+39 s after OLV, the SpO(2) began to decrease, and the Ppeak of OLV increased by 91.0% and Cdyn decreased by 62.7%. The slope of P-V curve was reduced and the P-V loop extended, with reduced increment of the expiratory limb and the area of the F-V loop, so that the tips of the DLT were withdrawn by 0.5 to 1.9 cm. The Ppeak of OLV increased only by 43.4% when DLT was in correct position, and was Cdyn decreased by 33.6% ( P<0.01).

When changes of Ppeak and Cdyn in excess of above guidelines occurs after switching from TLV to OLV in the elderly patients, FOB should be applied to determine the tip position of DLT before SpO(2) reduction takes place.