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CRITICAL CARE AND TRAUMA

The Effects of Lung Recruitment on the Phase III Slope of Volumetric Capnography in Morbidly Obese Patients

Stephan H. Böhm, MD^*, Stefan Maisch, MD^*, Alexandra von Sandersleben, MD^*, Oliver Thamm, MD^*, Isabel Passoni, PhD, Jorge Martinez Arca, MSc, and Gerardo Tusman, MD

From the *Clinic of Anesthesiology, University Hospital, Hamburg-Eppendorf, Hamburg, Germany; currently at Clinic of Plastic and Reconstructive Surgery, Burn Care Center, Hospital Cologne-Merheim, University of Witten/Herdecke, Germany; Department of Bioengineering, University of Mar del Plata, Argentina; and Department of Anesthesiology, Hospital Privado de Comunidad, Mar del Plata, Argentina.

Address correspondence to Stephan H. Böhm, MD, CSEM Centre Suisse d’Electronique et de Microtechnique SA, Research Centre for Nanomedicine, Medical Sensors, Schulstr. 1, CH-7302 Landquart, Switzerland. Address e-mail to shb{at}csem.ch.

BACKGROUND: In this study, we analyzed the effect of the alveolar recruitment strategy (ARS) and positive end-expiratory pressure (PEEP) titration on Phase III slope (S_III) of volumetric capnography (VC) in morbidly obese patients.

METHODS: Eleven anesthetized morbidly obese patients were studied. Lungs were ventilated with tidal volumes of 10 mL · kg^–1, respiratory rates of 12–14 bpm, inspiration:expiration ratio of 1:2, and Fio₂ of 0.4. ARS was performed by increasing PEEP in steps of five from 0 end-expiratory pressure to 15 cm H₂O. During lung recruitment, plateau pressure was limited to 50 cm H₂O, whereas tidal volume was increased to the ventilator’s maximum value of 1400 mL, and PEEP was increased to 20 cm H₂O for 2 min. Thereafter, PEEP was reduced in steps of 5 cm H₂O, from 15 to 0. VC, arterial blood gases, and lung mechanics data were determined for each PEEP step.

RESULTS: S_III decreased from 0.014 ± 0.006 to 0.005 ± 0.005 mm Hg/mL when 0 end-expiratory pressure was compared against 15 cm H₂O of PEEP after ARS (15_ARS, P < 0.05). This decrement in S_III was accompanied by increases in Pao₂ (27%, P < 0.002) and compliance (32%, P < 0.001), whereas Paco₂ decreased by 8% (P < 0.038) when comparing values before and after ARS. A good prediction of the lung recruitment effect by S_III was derived from the receiver operating characteristic curve analysis (area under the curve of 0.81, sensitivity of 0.75, and specificity of 0.74; P < 0.001).

CONCLUSION: The S_III in VC was useful to detect the optimal level of PEEP after lung recruitment in anesthetized morbidly obese patients.

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				S. H. Bohm, O. C. Thamm, A. von Sandersleben, K. Bangert, T. E. Langwieler, G. Tusman, T. G. Strate, and T. G. Standl Alveolar Recruitment Strategy and High Positive End-Expiratory Pressure Levels Do Not Affect Hemodynamics in Morbidly Obese Intravascular Volume-Loaded Patients Anesth. Analg., July 1, 2009; 109(1): 160 - 163. [Abstract] [Full Text] [PDF]