A New Index of the Intrapulmonary Mixture of Inspired Air
Open Access
- 1 March 1952
- Vol. 7 (1) , 111-116
- https://doi.org/10.1136/thx.7.1.111
Abstract
A relatively simple index of intrapulmonary mixing of inspired air is provided by an estimate of the 1. of ventilation required to wash each 1. of the functional residual air (F. R. A.) free of N2 while the subject breathes pure O2. This is termed the "lung clearance index", and is calculated by the formula: Liters ventilation required to wash 90% F.R.A. free of No 90% F.R.A. The 90% mixing point was selected because this point is more accurately detd. on the shape of the mixing curve than the moment of complete mixing. Mixing studies on 23 normal and 27 emphysematous subjects are reported and the results variously expressed by 4 indices. Of these indices, the lung clearance index is the simplest and most satisfactory in separating normal from emphysematous subjects.Keywords
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