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Byline: Carlo A. Volta (1), Enrico Ferri (1), Elisabetta Marangoni (1), Riccardo Ragazzi (1), Marco Verri (1), Valentina Alvisi (1), Silvia Zardi (1), Sara Bertacchini (1), Gaetano Gritti (2), Raffaele Alvisi (1) Keywords: Respiratory mechanics; Aortic surgery; Transperitoneal approach; Retroperitoneal approach; Weaning indexes Abstract: Objective Elective abdominal aneurysm repair can be performed by using the transperitoneal or the retroperitoneal approach. The latter has been described as having a better outcome, reducing the impairment of respiratory function or the incidence of lung complications. Hence, the retroperitoneal approach has been proposed for treatment of medically high-risk patients. However, the superiority of one technique or the other in preserving pulmonary function has not been conclusively demonstrated. The aim of this study was to ascertain whether the retroperitoneal and the transperitoneal approaches affect respiratory function differently. Design A prospective randomized study. Setting Two four-bed surgical-medical ICUs of a University hospital. Patients Twenty-three consecutive patients undergoing abdominal aortic aneurysm repair were randomized to the retroperitoneal (12 patients) and transperitoneal approach (11 patients). They were studied: a) within 30 min the end of surgery b) 8 h after the end of surgery and c) during a T-piece tube-weaning trial. Measurements The comparison between the two groups was based on respiratory mechanics, partitioned between lung and chest wall components, basic spirometry, tension-time index of the inspiratory muscle, weaning indexes, and length of stay both in ICU and hospital. Results The two surgical techniques do not differ in their impact on either respiratory mechanics or inspiratory muscle function or weaning indexes. However, there was a tendency for retroperitoneal patients to stay for less time both in ICU and in the hospital. Conclusions During the first 24 h after surgery, the postoperative impairment of respiratory function is independent of the surgical approach. Author Affiliation: (1) Department of Surgical, Anaesthesiological and Radiological Science, Section of Anaesthesia and Intensive Care, S. Anna Hospital, University of Ferrara, Corso Giovecca n. 203, 44100, Ferrara, Italy (2) Department of Medical and Surgical Critical Care, Section of Anaesthesia and Intensive Care, Careggi Hospital, University of Florence, Florence, Italy Article History: Received Date: 12/07/2002 Accepted Date: 04/04/2003 Online Date: 26/06/2003 Article note: This study was supported in part by a grant from M.U.R.S.T. (60%, 2001)

Byline: Carlo A. Volta (1), Elisabetta Marangoni (1), Valentina Alvisi (1), Maurizia Capuzzo (1), Riccardo Ragazzi (1), Lina Pavanelli (1), Raffaele Alvisi (1) Keywords: Expiratory flow limitation chronic obstructive pulmonary disease Least squares fitting method Compliance Resistance Positive end-expiratory pressure Abstract: Objective: Although computerized methods of analyzing respiratory system mechanics such as the least squares fitting method have been used in various patient populations, no conclusive data are available in patients with chronic obstructive pulmonary disease (COPD), probably because they may develop expiratory flow limitation (EFL). This suggests that respiratory mechanics be determined only during inspiration. Setting: Eight-bed multidisciplinary ICU of a teaching hospital. Patients: Eight non-flow-limited postvascular surgery patients and eight flow-limited COPD patients. Intervention: Patients were sedated, paralyzed for diagnostic purposes, and ventilated in volume control ventilation with constant inspiratory flow rate. Measurements: Data on resistance, compliance, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) obtained by applying the least squares fitting method during inspiration, expiration, and the overall breathing cycle were compared with those obtained by the traditional method (constant flow, end-inspiratory occlusion method). Results and conclusion: Our results indicate that (a) the presence of EFL markedly decreases the precision of resistance and compliance values measured by the LSF method, (b) the determination of respiratory variables during inspiration allows the calculation of respiratory mechanics in flow limited COPD patients, and (c) the LSF method is able to detect the presence of PEEPi,dyn if only inspiratory data are used. Author Affiliation: (1) Department of Surgical, Anesthesiological and Radiological Sciences, Section of Anesthesia and Intensive Care, Ospedale S. Anna, University of Ferrara, Corso Giovecca n. 203, 44100 Ferrara, Italy Article History: Received Date: 30/01/2001 Accepted Date: 28/09/2001 Article note: Electronic Publication

Byline: Carlo A. Volta (1), Raffaele Alvisi (1), Elisabetta Marangoni (1), Ermino R. Righini (1), Marco Verri (1), Riccardo Ragazzi (1), Valentina Alvisi (1), Enrico Ferri (1), Joseph Milic-Emili (2) Keywords: Bronchodilating agent Intravenous administration Respiratory mechanics Additional respiratory system resistance Static and dynamic intrinsic PEEP Abstract: Objective: In chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF), bronchodilating agents administered by inhalation have, in general, little effect on dynamic hyperinflation and concurrent static intrinsic positive end-expiratory pressure (PEEPi,st). Since in COPD the severely obstructed segments of the lung may not be reached by inhaled medication, we reasoned that drug efficiency may be enhanced by intravenous administration of the agent. Design: Physiological study. Setting: Two four-bed surgical-medical ICUs of a university hospital. Patients: Fourteen COPD patients were studied within 36 h from the onset of ARF. Measurements and results: Static compliance (Cst,rs), minimal (Rmin,rs) and additional (IRrs) resistance of the respiratory system, and PEEPi,st were measured before and after intravenous administration of salbutamol. All patients had limitation of air flow before and after salbutamol administration. On average, after salbutamol there was a small, though significant, decrease in Rmin,rs (-9%), IRrs (-12%) and PEEPi,st (-8%). Conclusion: The changes in resistance and PEEPi,st after intravenous administration of salbutamol were too small to be of clinical significance. Author Affiliation: (1) Department of Surgical, Anaesthesiological and Radiological Sciences, Section of Anaesthesia and Intensive Care, S. Anna Hospital, University of Ferrara, Ferrara, Corso Giovecca 203, 44100 Ferrara, Italy (2) Meakins Christie Laboratories, McGill University, Montreal, Canada Article History: Received Date: 21/12/2000 Accepted Date: 03/09/2001 Article note: Final revision received: 24 August 2001 Electronic Publication