| Abstract | Positive end-expiratory pressure (PEEP) is a standard treatment for patients with refractory hypoxemia
due to an acute restrictive pathology. The therapeutic range of PEEP can be quite narrow. PEEP therapy
has been optimized using invasive variables such as oxygen transport and pulmonary shunt, and
noninvasive variables such as compliance; however, the measurements are complex. We constructed a
computerized PEEP-optimization system consisting of a Siemens 900C ventilator, Siemens prototype
sulfur hexafluoride analyzer, Siemens 940 lung mechanics analyzer, and a DEC 11/23 microcomputer. The
user may choose from three different noninvasive PEEP titration algorithms: maximizing static total
respiratory system compliance (CTR), maximizing functional residual capacity(FRC)-based compliance
(CFRC), and normalizing FRC. The device was tested in six dogs with pulmonary injury induced by oleic
acid. The system was constrained to 3-cm H2O PEEP steps at 20-min intervals. The algorithm normalizing
FRC reached optimal PEEP levels in 40 min, with a mean difference from the desired FRC of 15 +/- 48
(SEM) ml. This corresponds to a mean percent error of 1.0% +/- 2.63%. The CFRC and CTR algorithms
reached optimal PEEP levels in 60 and 40 min, respectively, and maintained a maximal compliance for
85% of the time. This system provides fully automated noninvasive PEEP titration and is flexible enough to
incorporate easily any other PEEP titration algorithms. It should improve patient care by guaranteeing that
PEEP therapy is truly optimized throughout the patient's recovery. |