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Original Research: Pulmonary Physiology |

Ventilation/Perfusion Distribution Abnormalities In Morbidly Obese Subjects Before and After Bariatric SurgeryVentilation/Perfusion Imbalance and Morbid Obesity

Eva Rivas, MD; Ebymar Arismendi, MD; Alvar Agustí, MD; Marcelo Sanchez, MD; Salvadora Delgado, MD; Concepción Gistau, MsC; Peter D. Wagner, MD; Roberto Rodriguez-Roisin, MD
Author and Funding Information

From Servei d’Anestesiologia (Dr Rivas); Institut d’investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB) (Drs Rivas, Arismendi, Agustí, Sanchez, Delgado, and Rodriguez-Roisin); Servei de Pneumologia (Institut Clínic del Tòrax [ICT]) (Drs Agustí and Rodriguez-Roisin and Ms Gistau); CIBER Enfermedades Respiratorias (CIBERES) (Drs Arismendi, Agustí, and Rodriguez-Roisin and Ms Gistau); Centre de Diagnòstic per la Imatge (CDI) (Dr Sanchez); Servei de Cirurgia Gastrointestinal (Dr Delgado), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain; and the Department of Medicine (Dr Wagner), University of California, San Diego (UCSD), San Diego, CA.

CORRESPONDENCE TO: Roberto Rodriguez-Roisin, MD, Servei Pneumologia (Institut del Tòrax), Hospital Clínic, Villarroel 170, 08036-Barcelona, Spain; e-mail: rororo@clinic.ub.es


Part of this study has been presented in abstract form at the American Thoracic Society Annual Meeting, May 21, 2014, San Diego CA.

FUNDING/SUPPORT: This study was funded by the Fondo de Investigación Sanitaria (FIS) PI 080311, CIBERES, the Generalitat de Catalunya [2014SGR661], and a grant-in-aid from Almirall.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(4):1127-1134. doi:10.1378/chest.14-1749
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BACKGROUND:  Obesity is a global and growing public health problem. Bariatric surgery (BS) is indicated in patients with morbid obesity. To our knowledge, the effects of morbid obesity and BS on ventilation/perfusion (V. a/Q. ) ratio distributions using the multiple inert gas elimination technique have never before been explored.

METHODS:  We compared respiratory and inert gas (V. a/Q.  ratio distributions) pulmonary gas exchange, breathing both ambient air and 100% oxygen, in 19 morbidly obese women (BMI, 45 kg/m2), both before and 1 year after BS, and in eight normal-weight, never smoker, age-matched, healthy women.

RESULTS:  Before BS, morbidly obese individuals had reduced arterial Po2 (76 ± 2 mm Hg) and an increased alveolar-arterial Po2 difference (27 ± 2 mm Hg) caused by small amounts of shunt (4.3% ± 1.1% of cardiac output), along with abnormally broadly unimodal blood flow dispersion (0.83 ± 0.06). During 100% oxygen breathing, shunt increased twofold in parallel with a reduction of blood flow to low V. a/Q.  units, suggesting the development of reabsorption atelectasis without reversion of hypoxic pulmonary vasoconstriction. After BS, body weight was reduced significantly (BMI, 31 kg/m2), and pulmonary gas exchange abnormalities were decreased.

CONCLUSIONS:  Morbid obesity is associated with mild to moderate shunt and V. a/Q.  imbalance. These abnormalities are reduced after BS.

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