[The application of "expiration holding" in measuring end expiration pulmonary artery wedge pressure in patients undergoing mechanical ventilation].

OBJECTIVE

To find an accurate and convenient method of measuring end expiratory pulmonary artery wedge pressure (eePAWP) by "expiration holding" function of ventilator and "pulmonary artery wedge pressure (PAWP) Review" software of monitor.

METHODS

Twelve patients with introduction of pulmonary artery catheter and undergoing mechanical ventilation were selected. Fifty measurements were randomly selected for the comparison of the differences between automatic measurement and expiration holding method in each patient. There were 21 cases underwent single positive pressure ventilation and 29 cases with positive pressure ventilation mixed with spontaneous breathing. All measurements were first divided into <8 mm Hg (1 mm Hg=0.133 kPa) or ≥8 mm Hg groups according to respiratory variability (RV). They were then divided into automatic measurement group and expiration holding group according to PAWP measurement, and the difference in the results between two groups were recorded.

RESULTS

In 21 cases with single positive pressure ventilation, in 12 cases PAWP (mm Hg) of automatic measurement group was higher than that of expiration holding group (12-16 vs. 9-14) when RVP<8 mm Hg, but the difference between two groups was not obvious, and measurements were similar occasionally. In automatic measurement group PAWP (mm Hg) was higher than that of expiration holding group (13-20 vs. 9-15) in 9 cases when RV≥8 mm Hg, the difference was obvious. Neither RVP<8 mm Hg nor RV≥8 mm Hg, the statistical difference was significant (all P<0.01). In 29 cases, when positive pressure ventilation was mixed with spontaneous breathing, RVP<8 mm Hg (n=13), RV≥8 mm Hg (n=16), most of the results in automatic measurement group were higher than those of expiration holding group (11-18 vs. 10-17), and only 4 of them were lower than expiration holding group (11-20 vs. 14-23). There was no statistically significant difference between two groups (all P>0.05).

CONCLUSION

Expiration holding measurement is a better method that can identify the eePAWP, and it reflects the true hemodynamic status more accurately and quickly whether positive pressure ventilation only or positive pressure ventilation mixed with spontaneous breathing is given.