Assessment of the development of choked flow during total liquid ventilation.
OBJECTIVE
The flow rate of a liquid drainage from the lungs is limited because of the elastic nature of the airways. This study was designed to clarify the relationship between intrapulmonary liquid volume and the development of the flow limitation or choked flow phenomenon as a function of expiratory flow rate during total liquid ventilation with perflubron.


METHODS
Prospective animal study.


METHODS
University research laboratory.


METHODS
Rabbits with a weight of 3.2 +/- 0.3 kg.


METHODS
After the rabbits were killed, the lungs were filled to functional residual capacity with perflubron, followed by administration of an additional volume of 30, 45, or 60 mL of perflubron (initial volume = functional residual capacity + additional volume).


RESULTS
In one set of five animals, the intratracheal pressure at the occurrence of choked flow was established at -20 mm Hg. In another set of six animals, we demonstrated that the volume remaining in the lung at the point of development of choked flow (Vch) was stable for the first 40 mins after the animals were killed. Flow rates of 1.25, 2.5, 3.75, 5.0, 7.5, 10.0, and 12.5 mL/sec were then applied at an additional volume of 30, 45, or 60 mL to 34 animals. Vch approximately doubled as the flow rate increased from 1.25 mL/sec to 12.5 mL/sec (p <.001). At the same flow, Vch was higher for an additional volume of 60 mL than 30 mL when the flow was > or =2.5 mL/sec.


CONCLUSIONS
From these data, we conclude that choked flow occurs at intratracheal pressure of less than -20 mm Hg, that Vch is stable for the first 40 mins after the animals are killed, and that Vch is a function of flow rate and initial volume.
Baba
Yuzo
Y
Department of Surgery, University of Michigan, Ann Arbor, USA.
Brant
David
D
Brah
Sukhjinder S
SS
Grotberg
James
J
Bartlett
Robert H
RH
Hirschl
Ronald B
RB
D000402:Airway Obstruction / Q000209:etiology / Q000503:physiopathology*; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005466:Fluorocarbons / Q000494:pharmacology; D006842:Hydrocarbons, Brominated; D021061:Liquid Ventilation / Q000009:adverse effects* / Q000379:methods*; D008168:Lung / Q000473:pathology; D008176:Lung Volume Measurements; D008297:Male; D015999:Multivariate Analysis; D011312:Pressure; D011336:Probability; D011817:Rabbits; D012120:Respiration Disorders / Q000628:therapy; D015656:Respiratory Mechanics / Q000502:physiology*; D012680:Sensitivity and Specificity; D013990:Tidal Volume; D014692:Ventilation-Perfusion Ratio
D005466:Fluorocarbons; D006842:Hydrocarbons, Brominated; C003072:perflubron