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Objective: Measurements from the pulmonary pressure-volume (PV) curve have been proposed to adjust ventilator settings. We investigated the effects of repeated construction of an inflation PV curve implemented in a standard ventilator on recruitment or derecruitment in acutely injured lungs.Design and Setting: Prospective experimental animal study in eight anesthetized and mechanically ventilated pigs.Interventions: Acute lung injury was induced by lung lavage and animals were ventilated in volume controlled mode with PEEP 10 cmH(2)O. The PV curve was constructed five times repeatedly by constant pressure rise, after which ventilation with the preset PEEP was resumed immediately. Studies of hemodynamics, lung mechanics, blood gases and computed tomography were carried out before and after maneuvers.Measurements and Results: Derecruitment was assessed as an increase in nonaerated lung volume (V(NON)), and V(PEEP) was the end-expiratory volume difference between PEEP and ZEEP. There was a significant decrease in PaO(2) from 90.4+/-33.3 to 70.9+/-36.3 mmHg and a rise in venous admixture from 47.8+/-12.7 to 59.1+/-16.6%. V(PEEP) was reduced from 244 to 202 ml. A corresponding decrease in normally aerated lung volume was observed, while regression analysis revealed increase in V(NON) depending on the amount of preexisting atelectasis.Conclusions: Repeated generation of the PV curve with a readily available tool resulted in worsened oxygenation. Derecruitment of the lungs occurred with loss of PEEP at the start of the maneuver, which could not be recovered by a maximum inflation pressure of 40 cmH(2)O. Repeated use of the investigated tool should be cautioned, and users should consider measures to preserve aerated lung volumes. [ABSTRACT FROM AUTHOR]

Objective: Earlier reports suggested that transthoracic (TTE) determination of the ratio of mitral inflow E wave velocity to early diastolic mitral annulus velocity (E/E') measured by tissue Doppler imaging (TDI) closely approximates PAOP in cardiac patients. However, the value of E/E' for PAOP assessment in ICU patients has not been evaluated. This study assessed whether the E/E' ratio provides an accurate estimation of pulmonary artery occlusion pressure (PAOP) in mechanically ventilated ICU patients.Design and Setting: Prospective, open, clinical study in the ICU of a university hospital.Patients: Twenty-three consecutive mechanically ventilated patients.Interventions: Volume expansion in 14 patients.Measurements and Results: Doppler TTE or TEE mitral inflow and TDI mitral annulus velocities were determined and compared with PAOP measured using a Swan-Ganz catheter. Of all the Doppler variables studied the best correlations were observed between PAOP and the lateral (r=0.84) and medial (r=0.76) annulus E/E' ratio and remained highly significant when the analysis was restricted to TEE (r=0.91 and 0.86) or TTE (r=0.73 and 0.61). The sensitivities and specificities of estimating PAOP at 15 mmHg or higher were, respectively, 86% and 81% for lateral E/E' above 7.5 and 76% and 80% for medial E/E' above 9. PAOP changes after volume expansion (700+/-230 ml) were limited and accurately assessed by repeated E/E' determinations.Conclusions: In mechanically ventilated ICU patients TTE or TEE E/E' determinations using TDI closely approximate PAOP. [ABSTRACT FROM AUTHOR]