Prognostic value of the pulmonary dead-space fraction during the first 6 days of acute respiratory distress syndrome.
BACKGROUND
The ratio of pulmonary dead space to tidal volume (VD/VT) in acute respiratory distress syndrome (ARDS) is reported to be between 0.35 and 0.55. However, VD/VT has seldom been measured with consideration to the evolving pathophysiology of ARDS.


METHODS
We made serial VD/VT measurements with 59 patients who required mechanical ventilation for > or = 6 days. We measured VD/VT within 24 h of the point at which the patient met the American-European Consensus Conference criteria for ARDS, and we repeated the VD/VT measurement on ARDS days 2, 3, and 6 with a bedside metabolic monitor during volume-regulated ventilation. We analyzed the changes in VD/VT over the 6-day period to determine whether VD/VT has a significant association with mortality.


RESULTS
VD/VT was significantly higher in nonsurvivors on day 1 (0.61 +/- 0.09 vs 0.54 +/- 0.08, p < 0.05), day 2 (0.63 +/- 0.09 vs 0.53 +/- 0.09, p < 0.001), day 3 (0.64 +/- 0.09 vs 0.53 +/- 0.09, p < 0.001), and day 6 (0.66 +/- 0.09 vs 0.51 +/- 0.08, p < 0.001).


CONCLUSIONS
In ARDS a sustained VD/VT elevation is characteristic of nonsurvivors, so dead-space measurements made beyond the first 24 hours may have prognostic value.
Cardiovascular Research Institute, Department of Anesthesia, University of California, San Francisco, USA. rkallet@sfghsom.ucsf.edu.
Richard H
RH
Kallet
James A
JA
Alonso
Jean-François
JF
Pittet
Michael A
MA
Matthay
D000367:Age Factors; D015331:Cohort Studies; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D011175:Positive-Pressure Respiration / Q000379:methods; D011379:Prognosis; D011659:Pulmonary Gas Exchange; D012126:Respiratory Dead Space / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D015656:Respiratory Mechanics; D018570:Risk Assessment; D012737:Sex Factors; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome