9-16 624074/07
9 P/V tool maneuver option
The lower inflection point of the inflation pressure/
volume curve (LIP)
The LIP is the point of maximal curvature below the linear por-
tion of the inflation P/V curve, or the point where the rate of
increase in respiratory system compliance is maximal. This point
is where alveoli start to open as airway pressure increases. The
recommendation is to set positive end expiratory pressure
(PEEP) at that level or slightly above
1
.
The difference in volume between the two curves (dv)
The difference between the inflation and the deflation limb,
also called hysteresis, can have several meanings. Recent publi-
cations suggest that in patients with acute lung injury or acute
respiratory distress syndrome hysteresis could indicate the
volume that might be gained by increasing PEEP or by using
a special maneuver to open alveoli (recruitment maneuver)
2
.
The linear compliance of the inflation pressure/volume curve
(Clin)
This part of the curve is where the maximal compliance is
obtained. In that zone, a change in volume requires a minimal
increase in pressure. The recommendation is to set PEEP and
tidal volume to obtain tidal ventilation in that zone2.
The upper inflection point of the inflation pressure/volume
curve (UIP)
The UIP is the point of maximal curvature at the end of the
linear portion of the inflation PV curve, or the point where the
rate of decrease in respiratory system compliance is maximal.
This point is where all recruitable alveoli are open and start to
overinflate. The recommendation is to set the tidal volume to
obtain a plateau pressure below that point2.
1. Tobin MJ. Advances in mechanical ventilation. N Engl J Med.
2001;344:1986-96.
2. Hickling KG. The pressure-volume curve is greatly modified by recruitment.
A mathematical model of ARDS lungs. Am J Respir Crit Care Med.
1998;158:194-202.
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