Inspiratory resistive breathing induces acute lung injury.
BACKGROUND
Resistive breathing is associated with large negative intrathoracic pressures. Increased mechanical stress induces high-permeability pulmonary edema and lung inflammation.


OBJECTIVE
To determine the effects of resistive breathing on the healthy lung.


METHODS
Anesthetized rats breathed through a two-way nonrebreathing valve. The inspiratory line was connected to a resistance setting peak inspiratory tracheal pressure at 50% of maximum (inspiratory resistive breathing), while 100% oxygen was supplied to prevent hypoxemia. Quietly breathing animals (100% oxygen) served as controls. Lung injury was evaluated after 3 and 6 hours of resistive breathing.


RESULTS
After both 3 and 6 hours of resistive breathing, lung permeability was increased, as assessed by (99m)Tc-diethylenetriaminepentaacetic acid scintigraphy and Evans blue dye extravasation. Tissue elasticity, measured on the basis of static pressure-volume curves and by the low-frequency forced oscillation technique, was also increased. After both 3 and 6 hours of resistive breathing, gravimetric measurements revealed the presence of pulmonary edema and analysis of bronchoalveolar lavage showed increased total protein content, whereas the total cell count was elevated only after 6 hours of resistive breathing. Cytokine levels were assessed in bronchoalveolar lavage fluid and lung tissue by ELISA and were increased after 6 hours compared with controls. Western blot analysis showed early activation of Src kinase via phosphorylation (at 30 min), and Erk1/2 and IκBα (nuclear factor-κB inhibitor) were phosphorylated at 3 and 6 hours. Pathology revealed the presence of lung injury after resistive breathing.


CONCLUSIONS
Resistive breathing induces acute lung injury and inflammation.
Toumpanakis
Dimitris
D
Department of Critical Care and Pulmonary Services, Evangelismos Hospital, University of Athens Medical School, Athens, Greece.
Kastis
George A
GA
Zacharatos
Panagiotis
P
Sigala
Ioanna
I
Michailidou
Tatiana
T
Kouvela
Maroussa
M
Glynos
Constantinos
C
Divangahi
Maziar
M
Roussos
Charis
C
Theocharis
Stamatios E
SE
Vassilakopoulos
Theodoros
T
D055371:Acute Lung Injury / Q000473:pathology / Q000503:physiopathology*; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002199:Capillary Permeability / Q000502:physiology; D002452:Cell Count; D016207:Cytokines / Q000032:analysis; D005260:Female; D007150:Immunohistochemistry; D008168:Lung / Q000473:pathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration; D013314:Stress, Mechanical; D014939:Work of Breathing / Q000502:physiology*
D016207:Cytokines