PT  - JOURNAL ARTICLE
AU  - Kallet, Richard H
AU  - Daniel, Brian M
AU  - Garcia, Oscar
AU  - Matthay, Michael A
TI  - Accuracy of Physiologic Dead Space Measurements in Patients With Acute Respiratory Distress Syndrome Using Volumetric Capnography: Comparison With the Metabolic Monitor Method
DP  - 2005 Apr 01
TA  - Respiratory Care
PG  - 462--467
VI  - 50
IP  - 4
4099  - http://rc.rcjournal.com/content/50/4/462.short
4100  - http://rc.rcjournal.com/content/50/4/462.full
AB  - BACKGROUND: Volumetric capnography is an alternative method of measuring expired carbon dioxide partial pressure (PeCO2) and physiologic dead-space-to-tidal-volume ratio (VD/VT) during mechanical ventilation. In this method, PeCO2 is measured at the Y-adapter of the ventilator circuit, thus eliminating the effects of compression volume contamination and the need to apply a correction factor. We investigated the accuracy of volumetric capnography in measuring VD/VT, compared to both uncorrected and corrected measurements, using a metabolic monitor in patients with acute respiratory distress syndrome (ARDS). METHODS: There were 90 measurements of VD/VT made in 23 patients with ARDS. The PeCO2 was measured during a 5-min expired-gas collection period with a Delta-trac metabolic monitor, and was corrected for compression volume contamination using a standard formula. Simultaneous measurements of PeCO2 and VD/VT were obtained using volumetric capnography. RESULTS: VD/VT measured by volumetric capnography was strongly correlated with both the uncorrected (r2 = 0.93, p < 0.0001) and corrected (r2 = 0.89, p < 0.0001) measurements of VD/VT made using the metabolic monitor technique. Measurements of VD/VT made with volumetric capnography had a bias of 0.02 and a precision of 0.05 when compared to the VD/VT corrected for estimated compression volume contamination. CONCLUSION: Volumetric capnography measurements of VD/VT in mechanically-ventilated patients with ARDS are as accurate as those obtained by metabolic monitor technique.