[Clinical application of the tidal flow-volume curve--a computer simulation].
BACKGROUND
Since the tidal flow-volume (V-V) curve obtained during mechanical ventilation is difficult to interpret, there have been few reports on how to interpret it.


METHODS
The tidal V-V curve during mechanical ventilation was analyzed using a computer simulation. Ventilatory modes, the time constant of a patient's respiratory system (TC), spontaneous breathing during mechanical ventilation, airway obstructions, and circuit leakage were simulated.


RESULTS
The inspiratory shape depended on ventilatory modes and was affected by TC only in pressure-regulated breathing. The expiratory shape was not dependent on ventilatory modes and was influenced by TC. Spontaneous breathing synchronized with the mandatory ventilatory phase increased the flow rate. Characteristic double expiratory flow pattern was observed in spontaneous expiration during the inspiratory phase of the ventilator. A dip in the expiratory tidal V-V curve was observed with a peripheral airway obstruction model. A central airway obstruction attenuated the slope of the expiratory phase. In circuit leakage, the tidal V-V curve did not return to the origin at the end of the expiration.


CONCLUSIONS
New findings on the tidal V-V curve were observed and this systematic analysis will be helpful in clinical respiratory care.
Masahide
M
Ohtsuka
D000402:Airway Obstruction / Q000503:physiopathology*; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D008991:Monitoring, Physiologic; D012121:Respiration, Artificial; D012137:Respiratory System / Q000503:physiopathology*; D013990:Tidal Volume / Q000502:physiology*