Analysis of atelectasis, ventilated, and hyperinflated lung during mechanical ventilation by dynamic CT.
OBJECTIVE
To study the dynamics of lung compartments by dynamic CT (dCT) imaging during uninterrupted pressure-controlled ventilation (PCV) and different positive end-expiratory pressure (PEEP) settings in healthy and damaged lungs.


METHODS
Experimental animal investigation.


METHODS
Experimental animal facility of a university department.


METHODS
In seven anesthetized pigs, static inspiratory pressure volume curves were obtained to identify the individual lower inflection point (LIP) before and after saline solution lung lavage. During PCV, PEEP was adjusted 5 millibars (mbar) below the individually determined LIP (LIP - 5), at the LIP, and 5 mbar above the LIP (LIP + 5).


RESULTS
Measurements were repeated before and after induction of lung damage. Hemodynamics, arterial and mixed venous blood gases, and dCT imaging in one juxtadiaphragmatic slice (effective temporal resolution of 100 ms) were assessed during uninterrupted PCV in series of three successive respiratory cycles. The mean fractional area (FA) of the hyperinflated lung (FA-H), mean FA of ventilated lung, mean FA of poorly ventilated lung, and mean FA of nonventilated lung (FA-NV), and the change in FA of the whole lung area (DeltaFA) were compared at different PEEP settings. Calculated pulmonary shunt (Qs/Qt) was compared to FA-NV. LIP + 5 decreased the amount of atelectasis (FA-NV) and increased hyperinflation (FA-H) in healthy and injured lungs. Cyclic changes of atelectasis (DeltaFA-NV) and hyperinflation (DeltaFA-H) were observed in both healthy and injured lungs. In the injured but not in the healthy lungs, the amount of cyclic changes of atelectasis and hyperinflation were independent from the adjusted PEEP level. FA-NV correlated with the calculated Qs/Qt, with a slight overestimation (mean +/- SEM, 2.1 +/- 4.1%).


CONCLUSIONS
dCT imaging allows the following: (1) the quantification of the extent of atelectasis, ventilated, poorly ventilated, and hyperinflated lung parenchyma during ongoing mechanical ventilation; (2) the detection and quantification of repeated recruitment and derecruitment, as well as hyperinflation; and (3) an estimation of Qs/Qt. dCT adds promising functional information for the respiratory treatment of early ARDS.
David
Matthias
M
Department of Anesthesiology, Johannes Gutenberg-University, Mainz, Germany. david@mail.uni-mainz.de
Karmrodt
Jens
J
Bletz
Carsten
C
David
Sybil
S
Herweling
Annette
A
Kauczor
Hans-Ulrich
HU
Markstaller
Klaus
K
D000818:Animals; D002245:Carbon Dioxide; D006439:Hemodynamics; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000503:physiopathology; D010100:Oxygen; D011175:Positive-Pressure Respiration; D011650:Pulmonary Alveoli / Q000503:physiopathology; D001261:Pulmonary Atelectasis / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome; D013552:Swine; D007507:Therapeutic Irrigation; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed / Q000379:methods*
D002245:Carbon Dioxide; D010100:Oxygen