The relationship between gas delivery patterns and the lower inflection point of the pressure-volume curve during partial liquid ventilation.
OBJECTIVE
To determine whether a positive end-expiratory pressure (PEEP) level equivalent to the lower inflection point (LIP) could be identified by evaluation of the airway pressure, flow (f1. gif" BORDER="0">), and volume vs time waveforms during partial liquid ventilation (PLV).


METHODS
Prospective application of PEEP during PLV in a healthy animal model.


METHODS
University hospital animal laboratory.


METHODS
Five healthy sheep weighing 30 kg each.


METHODS
The sequential application of 0 to 20 cm H(2)O PEEP in 2.5-cm H(2)O steps during PLV with both pressure and volume ventilation.


METHODS
Analysis of the pressure, volume, and f1. gif" BORDER="0"> waveforms as PEEP is sequentially increased.


RESULTS
At 0 cm H(2)O PEEP, VT was markedly reduced compared with PEEP VT at > or = 7.5 cm H(2)O (p < 0.05) in pressure control ventilation (PCV), and peak inspiratory pressure minus PEEP was markedly increased compared with PEEP at > or = 5.0 cm H(2)O (p < 0.05) in volume control ventilation. At 10 cm H(2)O PEEP, all waveforms began to stabilize, and no significant differences in any variable assessed were measured at > 12.5 cm H(2)O PEEP.


CONCLUSIONS
The application of PEEP during PLV markedly alters airway waveforms. Low PEEP decreases VT in PCV and increases airway pressure in VCV. The PEEP level equal to the LIP during PLV can be grossly estimated from airway waveforms. PEEP at > or = 10 cm H(2)O is needed to normalize gas delivery to functional residual capacity in the uninjured lung that is partially filled with perfluorocarbon.
Ferreyra
G
G
Department of Anaesthesia/Respiratory Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
Goddon
S
S
Fujino
Y
Y
Kacmarek
R M
RM
D000399:Air Pressure; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D004655:Emulsions; D005466:Fluorocarbons / Q000008:administration & dosage*; D005652:Functional Residual Capacity / Q000187:drug effects; D006842:Hydrocarbons, Brominated; D007322:Instillation, Drug; D008170:Lung Compliance / Q000187:drug effects; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D012016:Reference Values; D012143:Respiratory Physiological Phenomena / Q000187:drug effects; D012756:Sheep; D013990:Tidal Volume / Q000187:drug effects; D014132:Trachea
D004655:Emulsions; D005466:Fluorocarbons; D006842:Hydrocarbons, Brominated; C003072:perflubron