| Description |
This research determined the incidence of clinically significant errors in the bedside measurement of pulmonary capillary wedge pressure (Pw). Routine Pw measurements were compared to Pw's confirmed by the following more stringent criteria: a) Pw less than the mean pulmonary artery pressure (PAP); b) atrial waveform; c) free-flow through the catheter and blood vessel; and e) aspiration of capillary blood. One hundred and forty-three comparisons were made in 53 ICU ¦ patients being monitored with a Swan-Ganz catheter. Technical problems identified by the careful waveform analysis required to confirm the Pw were present in 41% of the initial measurements. These technical problems included: inadequate waveform (15%), poor dynamic response (20%), overinflation (4%), and suspect Pw (13%). Seventy-five percent of the technical problems were easily corrected by removing air bubbles, tightening loose connections, withdrawing or advancing the catheter 1 to 2 cm, increasing balloon volume, or irrigating the catheter. The remaining problems required catheter repositioning to resolve. The overall incidence of clinically significant errors (? 4 mmHg) was 17%. When a technical problem was present, the incidence of an error ? 4 mmHg was 23%. If the technical problem was not easily corrected and required catheter repositioning to resolve, the incidence of an error ? 4 mmHg was 53%. In the absence of technical problems, an error of ? 4 mmHg occurred in only 4% of the measurements. Aspiration of capillary blood was the only criterion which detected these errors. The criteria used to confirm the Pw requires careful waveform analysis (Criteria 1,2,3) and aspiration of capillary blood (Criteria 4). These criteria identify problems which can lead to errors in the Pw measurements. Identification and correction of technical problems, using waveform analysis improved the accuracy of the Pw measurement and can decrease the incidence of a clinical significant error from M% to only 4%. Waveform analysis, using Criteria 1, 2 and 3 should be done routinely in the critical care setting when measuring the Pw. Capillary blood aspiration (Criterion 4) offers only minimal improvement in the accuracy of the Pw measurement (4%) and is not warranted on a routine basis. |
