Positive End-Expiratory Pressure after a Recruitment Maneuver Prevents Both Alveolar Collapse and Recruitment/Derecruitment

• Published in: American journal of respiratory and critical care medicine 2003-06, Vol.167 (12), p.1620-1626
• Main Authors: Halter, Jeffrey M, Steinberg, Jay M, Schiller, Henry J, DaSilva, Monica, Gatto, Louis A, Landas, Steve, Nieman, Gary F
• Format: Article
• Language: English
• Subjects: Airway Resistance; Animals; Biological and medical sciences; Disease Models, Animal; Hemodynamics; Lung Compliance; Medical sciences; Microscopy, Video; Photomicrography; Pneumology; Polysorbates; Positive-Pressure Respiration - adverse effects; Positive-Pressure Respiration - methods; Pulmonary Alveoli; Pulmonary Atelectasis - chemically induced; Pulmonary Atelectasis - pathology; Pulmonary Atelectasis - physiopathology; Pulmonary Atelectasis - prevention & control; Pulmonary Gas Exchange; Pulmonary Surfactants - antagonists & inhibitors; Recurrence; Respiratory Distress Syndrome, Adult - chemically induced; Respiratory Distress Syndrome, Adult - pathology; Respiratory Distress Syndrome, Adult - physiopathology; Respiratory Distress Syndrome, Adult - prevention & control; Respiratory Mechanics; Respiratory system : syndromes and miscellaneous diseases; Surface-Active Agents; Swine
• ISSN: 1073-449X; 1535-4970
• DOI: 10.1164/rccm.200205-435OC

We tested the hypothesis that collapsed alveoli opened by a recruitment maneuver would be unstable or recollapse without adequate positive end-expiratory pressure (PEEP) after recruitment. Surfactant deactivation was induced in pigs by Tween instillation. An in vivo microscope was placed on a lung area with significant atelectasis and the following parameters measured: (1) the number of alveoli per field and (2) alveolar stability (i.e., the change in alveolar size from peak inspiration to end expiration). We previously demonstrated that unstable alveoli cause lung injury. A recruitment maneuver (peak pressure = 45 cm H2O, PEEP = 35 cm H2O for 1 minute) was applied and alveolar number and stability were measured. Pigs were then separated into two groups with standard ventilation plus (1) 5 PEEP or (2) 10 PEEP and alveolar number and stability were again measured. The recruitment maneuver opened a significant number of alveoli, which were stable during the recruitment maneuver. Although both 5 PEEP and 10 PEEP after recruitment demonstrated improved oxygenation, alveoli ventilated with 10 PEEP were stable, whereas alveoli ventilated with 5 PEEP showed significant instability. This suggests recruitment followed by inadequate PEEP permits unstable alveoli and may result in ventilator-induced lung injury despite improved oxygenation.