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Ann Thorac Surg 2003;75:635-636
© 2003 The Society of Thoracic Surgeons
a Department of Anesthesiology, Hospital Privado de Communidad, Cordoba 4545, 7600 Mar del Plata, Argentina
b Department of Anesthesiology, University Clinic Hamburg–Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
e-mail: gtusman{at}hotmail.com
e-mail: shb{at}tomedix.com
To the Editor:
We appreciate the interesting remarks of Drs 
entürk and Tu
rul concerning our report [1]. We will address a few issues.
First, a "pneumatic" maneuver was done after lobectomy to evaluate the bronchial sutures of the nondependent lung. This maneuver is performed after all lobectomies in our hospital as part of the routine surgical protocol irrespective of the use of an alveolar recruitment strategy (ARS). For study purposes (as opposed to the clinical routine), we used the ARS as a "pneumatic" maneuver, as pointed out in the Protocol section of our study [1]. Following the protocol design, we performed the ARS during one-lung ventilation (OLV) to compare its effects on arterial oxygenation under similar conditions before and after the recruitment maneuver. We never suggested the use of a recruitment maneuver once hypoxemia becomes a problem during OLV.
Anesthesia-induced atelectasis appears within 5 minutes after induction and causes part of the shunting in the dependent (ventilated) lung during OLV. Therefore, the main message of our article was to treat the atelectasis before OLV so as to use its positive impact on arterial oxygen tension during OLV. The ARS decreases the ventilation-perfusion mismatch. Consequently, with only one ARS, an open lung condition can be achieved, thus increasing both oxygenation and respiratory compliance [2, 3]. This condition can be maintained during the entire operation provided that sufficient levels of positive end-expiratory pressure are applied after the ARS to keep the lung open [2, 3].
Second, we agree with Drs entürk and Turul regarding the clinical advantages of pressure-controlled ventilation, which were clearly demonstrated in their study [4]. This method improves the distribution of inspired gases and controls peak inspiratory pressure. They cited Jordan and colleagues [5] when they wrote that "both hypoxia and high respiratory pressures should be avoided during OLV." This was also the major objective of our approach, as seen in the Results section [1]. Oxygenation during OLV reached values almost as high as during two-lung ventilation, but only after performing the ARS (although the differences were not significant compared with OLV values before ARS). As Rothen and coauthors [6] pointed out in anesthetized patients without lung injury, peak airway pressure of 40 cm H2O is needed to open atelectatic zones. In our study, these 40 cm H2O were applied in a controlled fashion for only ten breaths. In sick lungs (eg, during and after pneumonectomy) on the other hand, the main mechanisms of ventilator-induced lung injury are "shear forces" and tidal recruitment, as they are observed in the transitional zones between the open and collapsed lungs.
In an atelectatic lung, even low tidal ventilation can induce lung injury [7]. For this reason, we believe that as a net result, a recruitment maneuver should protect collapse-prone lungs despite ten respiratory cycles at a peak pressure of 40 cm H2O. The ARS will be less injurious than continuous shear stress in atelectatic lungs during hours of mechanical ventilation. By using a recruitment maneuver of up to 40 cm H2O of peak pressure, similar to our strategy, Amato and associates [8] demonstrated an improvement in survival when applying their "open lung approach" in patients with acute respiratory distress syndrome. It has been demonstrated in both healthy and sick lungs that recruitment maneuvers are not harmful [2, 6, 8, 9].
In summary, the ARS improved arterial oxygenation during OLV. We suggest that this simple maneuver be performed during two-lung ventilation before OLV to avoid intraoperative hypoxemia and to increase the margin of safety.
References
rul M., Çamci E., Karadeniz H., entürk M., Pembeci K., Akpir K. Comparison of volume controlled with pressure controlled ventilation during one-lung anaesthesia. Br J Anaesth 1997;79:306-310.
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