Eva Rivas1, Ebymar Arismendi2, Alvar Agustí3, Marcelo Sanchez4, Salvadora Delgado5, Concepción Gistau6, Peter D Wagner7, Roberto Rodriguez-Roisin8. 1. Servei d'Anestesiologia, University of California, San Diego (UCSD), San Diego, CA; Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA. 2. Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA; CIBER Enfermedades Respiratorias (CIBERES), University of California, San Diego (UCSD), San Diego, CA. 3. Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA; Servei de Pneumologia (Institut Clínic del Tòrax [ICT]), University of California, San Diego (UCSD), San Diego, CA; CIBER Enfermedades Respiratorias (CIBERES), University of California, San Diego (UCSD), San Diego, CA. 4. Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA; Centre de Diagnòstic per la Imatge (CDI), University of California, San Diego (UCSD), San Diego, CA. 5. Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA; Servei de Cirurgia Gastrointestinal, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain. 6. Servei de Pneumologia (Institut Clínic del Tòrax [ICT]), University of California, San Diego (UCSD), San Diego, CA; CIBER Enfermedades Respiratorias (CIBERES), University of California, San Diego (UCSD), San Diego, CA. 7. Department of Medicine, University of California, San Diego (UCSD), San Diego, CA. 8. Institut d'investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Fundació Clínic per a la Recerca Biomédica (FCRB), University of California, San Diego (UCSD), San Diego, CA; Servei de Pneumologia (Institut Clínic del Tòrax [ICT]), University of California, San Diego (UCSD), San Diego, CA; CIBER Enfermedades Respiratorias (CIBERES), University of California, San Diego (UCSD), San Diego, CA. Electronic address: rororo@clinic.ub.es.
Abstract
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.
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 obesewomen (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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