Impact of Chest Wall Modifications and Lung Injury on the Correspondence Between Airway and Transpulmonary Driving Pressures. Issue 8 (August 2015)

• Record Type: Journal Article
• Authors: Cortes-Puentes, Gustavo A.; Keenan, Joseph C.; Adams, Alexander B.; Parker, Emily D.; Dries, David J.; Marini, John J.
• Is Part Of: Critical care medicine. Volume 43:Issue 8(2015)
• Publication Date: 2015-08
• Subjects: Critical care medicine -- Periodicals; Soins intensifs -- Périodiques; 616.028
• DOI: 10.1097/CCM.0000000000001036
• Languages: English
• ISSNs: 0090-3493

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Objective:</title> <p>Recent interest has arisen in airway driving pressure (DP<sub>AW</sub>), the quotient of tidal volume (<italic>V</italic><sub>T</sub>), and respiratory system compliance (<italic>C</italic><sub>RS</sub>), which could serve as a direct and easily measured marker for ventilator-induced lung injury risk. We aimed to test the correspondence between DP<sub>AW</sub> and transpulmonary driving pressure (DP<sub>TP</sub>)—the quotient of V<sub>T</sub> and lung compliance (C<sub>L</sub>), in response to intra-abdominal hypertension and changes in positive end-expiratory pressure during different models of lung pathology.</p> </sec> <sec> <title>Design:</title> <p>Well-controlled experimental setting that allowed reversible modification of chest wall compliance (C<sub>CW</sub>) in a variety of models of lung pathology.</p> </sec> <sec> <title>Setting:</title> <p>Large animal laboratory of a university-affiliated hospital.</p> </sec> <sec> <title>Subjects:</title> <p>Ten deeply anesthetized swine.</p> </sec> <sec> <title>Interventions:</title> <p>Application of intra-abdominal pressures of 0 and 20 cm H<sub>2</sub>O at positive end-expiratory pressure of 1 and 10 cm H<sub>2</sub>O, under volume-controlled mechanical ventilation in the settings of normal lungs (baseline), unilateral whole-lung atelectasis, and unilateral and bilateral lung injuries caused by saline lavage.</p> </sec> <sec> <title>Measurements and Main Results:</title> <p>Pulmonary mechanics including esophageal pressure and calculations of DP<sub>AW</sub>, DP<sub>TP</sub>, <italic>C</italic><sub>RS</sub>, <italic>C</italic><sub>L</sub>, and <italic>C</italic><sub>CW</sub>. When compared with normal intra-abdominal pressures, intra-abdominal hypertension increased DP<sub>AW</sub>, during both "normal lung conditions" (<italic>p</italic> < 0.0001) and "unilateral atelectasis" (<italic>p</italic> = 0.0026). In contrast, DP<sub>TP</sub> remained virtually unaffected by changes in positive end-expiratory pressure or intra-abdominal pressures in both conditions. During unilateral lung injury, both DP<sub>AW</sub> and DP<sub>TP</sub> were increased by the presence of intra-abdominal hypertension (<italic>p</italic> < 0.0001 and <italic>p</italic> = 0.0222, respectively). During bilateral lung injury, intra-abdominal hypertension increased both DP<sub>AW</sub> (at positive end-expiratory pressure of 1 cm H<sub>2</sub>O, <italic>p</italic> < 0.0001; and at positive end-expiratory pressure of 10 cm H<sub>2</sub>O, <italic>p</italic> = 0.0091) and DP<sub>TP</sub> (at positive end-expiratory pressure of 1 cm H<sub>2</sub>O, <italic>p</italic> = 0.0510; and at positive end-expiratory pressure of 10 cm H<sub>2</sub>O, <italic>p</italic> = 0.0335).</p> </sec> <sec> <title>Conclusions:</title> <p>Our data indicate that DP<sub>AW</sub> is influenced by reductions in chest wall compliance and by underlying lung properties. As with other measures of pulmonary mechanics that are based on unmodified <italic>P</italic><sub>AW</sub>, caution is advised in attempting to attribute hazard or safety to any specific absolute value of DP<sub>AW</sub>.</p> </sec> </abstract>