Expiratory Hold vs Clamping/Transducing for Intrinsic PEEP Determination in the Siemens 900C

Abstract

Background

Various investigators have commented on the possible underestimation of intrinsic PEEP (PEEP;) when the expiratory hold function on microprocessor ventilators equipped with high-compressible-volume circuits is used. Although several ventilators incorporate this method of measuring PEEP;, comparisons with other accepted methods have been infrequent.

Methods

In an in-vitro lung model, we examined the difference between the clamping/transducing method and the use of the expiratory hold function of the Siemens 900C ventilator equipped with a low-compressible-volume circuit. Seven different PEEP; levels ranging from 3-26 cm H₂O were generated through random alterations in minute ventilation and inspiratory to expiratory ratio. For each method the measurement was repeated three times at each level of PEEP¡. Data analysis was performed employing the technique of Bland.

Results

The mean (SD) difference between the two methods was -0.13 (1.14) cm H₂O, a value close to zero showing good agreement between the two methods. The mean difference between the two methods did not increase as PEEP; increased. The maximum difference between the two methods of determining PEEP; lay within ±2 standard deviations of the mean, that is, within ±2.28 cm H₂O. This value is within a predetermined clinically acceptable range of ±2.5 cm H₂O.

Conclusion

In this laboratory study, we found no significant difference in the results obtained with PEEP; measurement using the clamping/transducing method and with the expiratory hold function of the Siemens 900C ventilator when the ventilator is equipped with a low-compressible-volume circuit.