Περίληψη:
Objective: Linear modeling as a method of exploring respiratory
mechanics during mechanical ventilation, was compared to nonlinear
modeling for now dependence of resistance in three distinct groups of
patients, those with: (a) normal respiratory function (NRF), (b) chronic
obstructive pulmonary disease (COPD), or (c) adult respiratory distress
syndrome (ARDS). Design and patients: Airways opening pressure (Pao),
flow (V’), and volume (V) signals were recorded in 32 ICU mechanically
ventilated patients, under sedation and muscle relaxation (10 NRF, 11
COPD, 11 ARDS). All patients were ventilated with controlled mandatory
ventilation mode at three levels of end-expiratory pressure (PEEPe): 0,
5, and 10 hPa. Data were analyzed according to: (a) Pao = PE + Ers V +
Rrs V’ and (b) Pao = PE + Ers V + k(1)V’ +
k(2)’’: where Ers and Rrs represent
the intubated respiratory system (RS) elastance and resistance, k(1) and
k(2) the linear and the nonlinear RS resistive coefficients, and PE the
end-expiratory pressure. The model’s goodness of fit to the data was
evaluated by the root mean square difference of predicted minus measured
Pao values.
Results: NRF data fit both models well at all PEEPe levels. ARDS and
particularly COPD data fit the nonlinear model better. Values of k(2)
were often negative in COPD and ARDS groups, and they increased in
parallel with PEEPe. A gradual increase in PEEPe resulted in better fit
of ARDS and COPD data to both models.
Conclusions: The model of V’ dependence of resistance is more suitable
for the ARDS and particularly the COPD groups. PEEP tends to diminish
the V’ dependence of respiratory resistance during the respiratory
cycle, particularly in the COPD group, probably through an indirect
effect of the increased lung volume.
Συγγραφείς:
Vassiliou, MP
Petri, L
Amygdalou, A
Patrani, M
Psarakis,
C
Nikolaki, D
Georgiadis, G
Behrakis, PK
