Airway and tissue mechanics in ventilated patients with pneumonia.
We applied the low-frequency forced oscillation technique (LFOT) to measure respiratory impedance (Zrs) at various positive end-expiratory pressures (PEEPs) in 14 sedated and intubated patients with pneumonia classified into a mild (Group 1) and a severe group (Group 2) based on lung injury scores. The Zrs spectra were fit with the constant-phase (CP) model including Newtonian resistance (R(N)) and tissue damping (G) and elastance (H), a distributed airway resistance (DR) and a distributed tissue elastance (DH) model. Using the CP model, all parameters revealed a negative PEEP dependence (p<0.001) in Group 2 and H was higher in Group 2 (p=0.014). The variability of H from the DH model was nearly significantly larger in Group 1 (p=0.061). Following bronchodilator inhalation, G significantly decreased (p=0.009). Thus, the CP model provides a robust partitioning of Zrs into tissue properties and R(N), a surrogate for airway resistance, while the distributed models suggest that lung heterogeneity decreases with increasing PEEP.
Lorx
András
A
Department of Anesthesiology and Intensive Therapy, Semmelweis University, Budapest, Hungary.
Suki
Béla
B
Hercsuth
Magdolna
M
Szabó
Barna
B
Pénzes
István
I
Boda
Krisztina
K
Hantos
Zoltán
Z
D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance / Q000187:drug effects; D001993:Bronchodilator Agents / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000188:drug therapy / Q000503:physiopathology*; D011175:Positive-Pressure Respiration / Q000379:methods; D015656:Respiratory Mechanics / Q000187:drug effects; D012720:Severity of Illness Index
D001993:Bronchodilator Agents