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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 97/6/2083    most recent 00588.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Darquenne, C. Articles by Prisk, G. K. Search for Related Content PubMed PubMed Citation Articles by Darquenne, C. Articles by Prisk, G. K.

Effect of small flow reversals on aerosol mixing in the alveolar region of the human lung

Department of Medicine, University of California at San Diego, La Jolla, California 92093-0931

Submitted 9 June 2004 ; accepted in final form 3 August 2004

It has been suggested that irreversibility of alveolar flow combined with a stretched and folded pattern of streamlines can lead to a sudden increase in mixing in the lung. To determine whether this phenomenon is operative in the human lung in vivo, we performed a series of bolus studies with a protocol designed to induce complex folding patterns. Boli of 0.5- and 1-µm-diameter particles were inhaled at penetration volumes (V_p) of 300 and 1,200 ml in eight subjects during short periods of microgravity aboard the National Aeronautics and Space Administration Microgravity Research Aircraft. Inspiration was from residual volume to 1 liter above 1 G functional residual capacity. This was followed by a 10-s breathhold, during which up to seven 100-ml flow reversals (FR) were imposed at V_p = 300 ml and up to four 500-ml FR at V_p = 1,200 ml, and by an expiration to residual volume. Bolus dispersion and deposition were calculated from aerosol concentration and flow rate continuously monitored at the mouth. There was no significant increase in dispersion and deposition with increasing FR except for dispersion between 0 and 7 FR at V_p = 300 ml with 0.5-µm-diameter particles, and this increase was small. This suggested that either the phenomenon of stretch and fold did not occur within the number of FR we performed or that it had already occurred during the one breathing cycle included in the basic maneuver. We speculate that the phenomenon occurred during the basic maneuver, which is consistent with the high degree of dispersion and deposition observed previously in microgravity.

stretch and fold; acinar mixing; aerosol bolus; microgravity