title: Respiratory mechanical effects of surgical pneumoperitoneum in humans.
abstract: Pneumoperitoneum for laparoscopic surgery is known to stiffen the chest wall and respiratory system, but its effects on resting pleural pressure in humans are unknown. We hypothesized that pneumoperitoneum would raise abdominal pressure, push the diaphragm into the thorax, raise pleural pressure, and squeeze the lung, which would become stiffer at low volumes as in severe obesity. Nineteen predominantly obese laparoscopic patients without pulmonary disease were studied supine (level), under neuromuscular blockade, before and after insufflation of CO2 to a gas pressure of 20 cmH2O. Esophageal pressure (Pes) and airway pressure (Pao) were measured to estimate pleural pressure and transpulmonary pressure (Pl = Pao - Pes). Changes in relaxation volume (Vrel, at Pao = 0) were estimated from changes in expiratory reserve volume, the volume extracted between Vrel, and the volume at Pao = -25 cmH2O. Inflation pressure-volume (Pao-Vl) curves from Vrel were assessed for evidence of lung compression due to high Pl. Respiratory mechanics were measured during ventilation with a positive end-expiratory pressure of 0 and 7 cmH2O. Pneumoperitoneum stiffened the chest wall and the respiratory system (increased elastance), but did not stiffen the lung, and positive end-expiratory pressure reduced Ecw during pneumoperitoneum. Contrary to our expectations, pneumoperitoneum at Vrel did not significantly change Pes [8.7 (3.4) to 7.6 (3.2) cmH2O; means (SD)] or expiratory reserve volume [183 (142) to 155 (114) ml]. The inflation Pao-Vl curve above Vrel did not show evidence of increased lung compression with pneumoperitoneum. These results in predominantly obese subjects can be explained by the inspiratory effects of abdominal pressure on the rib cage.
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; sloring@bidmc.harvard.edu.
authors.forename: Stephen H
authors.identifier: http://orcid.org/0000-0002-6277-3979
authors.initials: SH
authors.lastname: Loring
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
authors.forename: Negin
authors.initials: N
authors.lastname: Behazin
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
authors.forename: Aileen
authors.initials: A
authors.lastname: Novero
authors.affiliation: Soroka University Medical Center, Beer Sheva, Israel; and.
authors.forename: Victor
authors.initials: V
authors.lastname: Novack
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
authors.forename: Stephanie B
authors.initials: SB
authors.lastname: Jones
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts.
authors.forename: Carl R
authors.initials: CR
authors.lastname: O'Donnell
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Talmor
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D010535:Laparoscopy; D008168:Lung / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011028:Pneumoperitoneum, Artificial; D011175:Positive-Pressure Respiration; D015656:Respiratory Mechanics / Q000502:physiology*; D055815:Young Adult
keywords: diaphragm; esophageal balloon; esophageal pressure; laparoscopy; respiratory mechanics