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Effects of Sigh on Regional Lung Strain and Ventilation Heterogeneity in Acute Respiratory Failure Patients Undergoing Assisted Mechanical Ventilation*

Mauri, Tommaso MD1,2; Eronia, Nilde MD1; Abbruzzese, Chiara MD3; Marcolin, Roberto MD3; Coppadoro, Andrea MD4; Spadaro, Savino MD5; Patroniti, Nicolo’ MD1,3; Bellani, Giacomo MD, PhD1,3; Pesenti, Antonio MD1,3

doi: 10.1097/CCM.0000000000001083
Clinical Investigations

Objective: In acute respiratory failure patients undergoing pressure support ventilation, a short cyclic recruitment maneuver (Sigh) might induce reaeration of collapsed lung regions, possibly decreasing regional lung strain and improving the homogeneity of ventilation distribution. We aimed to describe the regional effects of different Sigh rates on reaeration, strain, and ventilation heterogeneity, as measured by thoracic electrical impedance tomography.

Design: Prospective, randomized, cross-over study.

Setting: General ICU of a single university-affiliated hospital.

Patients: We enrolled 20 critically ill patients intubated and mechanically ventilated with PaO2/FIO2 up to 300 mm Hg and positive end-expiratory pressure at least 5 cm H2O (15 with acute respiratory distress syndrome), undergoing pressure support ventilation as per clinical decision.

Interventions: Sigh was added to pressure support ventilation as a 35 cm H2O continuous positive airway pressure period lasting 3–4 seconds at different rates (no-Sigh vs 0.5, 1, and 2 Sigh(s)/min). All study phases were randomly performed and lasted 20 minutes.

Measurements and Main Results: In the last minutes of each phase, we measured arterial blood gases, changes in end-expiratory lung volume of nondependent and dependent regions, tidal volume reaching nondependent and dependent lung (Vtnondep and Vtdep), dynamic intratidal ventilation heterogeneity, defined as the average ratio of Vt reaching nondependent/Vt reaching dependent lung regions along inspiration (VtHit). With Sigh, oxygenation improved (p < 0.001 vs no-Sigh), end-expiratory lung volume of nondependent and dependent regions increased (p < 0.01 vs no-Sigh), Vtnondep showed a trend to reduction, and Vtdep significantly decreased (p = 0.11 and p < 0.01 vs no-Sigh, respectively). VtHit decreased only when Sigh was delivered at 0.5/min (p < 0.05 vs no-Sigh), while it did not vary during the other two phases.

Conclusions: Sigh decreases regional lung strain and intratidal ventilation heterogeneity. Our study generates the hypothesis that in ventilated acute respiratory failure patients, Sigh may enhance regional lung protection.

Supplemental Digital Content is available in the text.

1Department of Health Science, University of Milan-Bicocca, Monza, Italy.

2Department of Anesthesia, Critical Care and Pain Medicine, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy.

3Department of Emergency Medicine, San Gerardo Hospital, Monza, Italy.

4Department of Emergency Medicine, A. Manzoni Hospital, Lecco, Italy.

5Department of Medical Surgical and Experimental Medicine, Section of Anesthesia and Intensive Care, University of Ferrara, Ferrara, Italy.

*See also p. 2021.

This work was performed in the general ICU of the Department of Emergency Medicine, San Gerardo Hospital, Monza, Italy.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (

Supported, in part, by institutional funding of the Department of Health Science, University of Milan-Bicocca, Monza, Italy, and by an unrestricted research grant from Drager GmbH, Lubeck, Germany, to the Department of Emergency, San Gerardo Hospital, Monza, Italy. The supporting company did not have any formal requirement for financial or technical reports as well as no claim to any intellectual property rights that resulted from the study. The supporting company had no role in study conception, design and conduction, data analysis, and/or writing of the article.

Dr. Pesenti’s institution received grant support from Drager Company, Lubeck, Germany. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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