The Science Journal of the American Association for Respiratory Care
Pressure volume curve analysis may be a useful tool to optimize ventilatory settings in patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Few studies have reported on the safety of the PV curve measurement. We measured static inspiratory PV curves in patients with ALI/ARDS using a modified super-syringe technique, and monitored heart rate (HR), blood pressure (BP), and pulse oxygen saturation (SpO2) immediately prior to, during, and immediately following the PV curve measurement. We also monitored patients for adverse events such as clinical barotrauma. Eleven patients (PaO2/FiO2 160±11.1mm Hg. and Apache score of 25±1.9) had serial PV curves performed for 2 to 7 days. On each day the PV curve measurement was performed in triplicate. The study was terminated if the patient developed hypotension (systolic BP<90 mm Hg.) or hypoxemia (SpO2 <85%) on two successive days. The patients were excluded if they were unable to tolerate a reduction in PEEP to 0 cm H2O (ZEEP), were hemodynamically unstable, or had obstructive lung disease. Starting from ZEEP, The patients' lungs were inflated in increments of 50-100 cc with a 100 cc syringe filled with 100% oxygen until an airway pressure of 45 cm H2O was reached. We present the mean group HR and mean arterial pressure (MAP), recorded pre and post PV curve measurement, and SpO2, recorded pre, post, and at the nadir during the PV curve measurement.
|*p<0.05 vs pre values are mean ±SD|
The study was discontinued in 2 patients: in 1 because of inability to tolerate ZEEP, and in another because of subcutaneous emphysema that developed on day 3 of the study. In 1 patient the systolic BP dropped to 64 mmHg. and in a second patient the SpO2 dropped to 79%. These effects were transient and did not result in termination of the study. In all other cases measurement of the PV curve was safe and well tolerated. Although the PV curve may aid in setting ventilatory parameters to reduce VILI, physiological changes do occur. Thus careful monitoring of vital signs, oxygen saturation, and signs of barotrauma is critical when performing these types of procedures.