A new ventilation inhomogeneity index from multiple breath indicator gas washout tests in mechanically ventilated patients.
OBJECTIVE
a) To determine the validity of a new method to analyze indicator gas washout tests on mechanically ventilated patients. This method takes into account the difference between the end-expiratory gas fraction and the mean gas fraction in the lung and provides the end-expiratory lung volume and a new index of ventilation inhomogeneity called volumes regression index. b) To determine the validity of this index as a predictor of chronic obstructive pulmonary disease. c) To compare this index with the moment ratio index and Becklake index.


METHODS
Prospective study of diagnostic test. Criterium standards: Closed-circuit indicator gas dilution technique and Tiffeneau index.


METHODS
Surgical intensive care unit of a university hospital.


METHODS
A total of 38 mechanically ventilated postoperative patients, divided into two groups: the obstructive group (n = 21) and the nonobstructive group (n = 17), based on their preoperative lung function.


METHODS
None.


RESULTS
a) The mean coefficient of variation of all lung volume measurements in a group of nine healthy volunteers was 5%, and the difference between this technique and the closed-circuit helium dilution measurements was -2 +/- 5%. In patients, the mean coefficient of variation of the lung volume measurements was 3.5%. The volumes regression index was measured as 0.02 +/- 0.04 in a dummy lung, 0.37 +/- 0.08 in the healthy volunteers, 0.64 +/- 0.23 in the nonobstructive patients, and 1.1 +/- 0.3 in the obstructive patients. The volumes regression index provided a better correlation (r2 = .46) with preoperatively determined Tiffeneau index than the Becklake index (r2 = .11) or the moment ratio index (r2 = .18).


CONCLUSIONS
The proposed technique provides a means for accurate measurement of the end-expiratory lung volume and the amount of ventilation inhomogeneity in mechanically ventilated intensive care unit patients.
Huygen
P E
PE
Department of Surgery, University Hospital Rotterdam, The Netherlands.
Gültuna
I
I
Ince
C
C
Zwart
A
A
Bogaard
J M
JM
Feenstra
B W
BW
Bruining
H A
HA
D000328:Adult; D000368:Aged; D001827:Body Height; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006371:Helium; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology / Q000628:therapy; D008176:Lung Volume Measurements / Q000295:instrumentation / Q000379:methods*; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014797:Vital Capacity
D006371:Helium