- every patient should be maintained on at least 5 cm H2O of PEEP; - objective of optimal PEEP is to reduce the intrapulmonary
Shunt; - since
cardiac output may also be decreased, fluid administration or vasoactive drugs may also be required to restore
Cardiac Output; - if pulmonary
wedge pressure is grossly elevated, fluid infusion may be contraindicated and diuretics, vasodilators (nitroglycerin and nitroprusside), or inotropes (dobutamine & amrinone) may be needed; - if
IMV rather than assist control is used, less depression of cardiac output may be produced by therapeutic PEEP but only if the patient has some spontaneous ventilation; - improvement in
Cardiac Output with
IMV is due to a reduction in intrathoracic presssure on inspiration and an increase in venous return; - in post operative patients, increasing FiO2 is usually not effective rather "The treatment of Hypoxia is PEEP" - major problem in post operative hypoxia is Atelectasis, and resultant Ventilation Perfusion Mismatch. - begin at 5 cm H2O; then incr by: 2.5 increments up to 12 cm; (at times PEEP levels of 20-25 will be required)
- Adjusting PEEP: - PEEP is usually begun at 5 cm H2O & is increased by 2-3 cm increments; - as long as @compliance[
Compliance is normal, PEEP may be increased to about 10 cm H2O with little risk of complications; - optimum setting: - Continue to increase PEEP until Pulmonary
Shunt < 15-20% or the PaO2/FiO2 ratio exceeds 250; - Alternatively, adjust PEEP until attaining adequate
oxygenation (Hb > 90) at non toxic O2 levels (<50%) - Problem: Over PEEPing may decrease @DXCO[
CO; -
Swan Ganz needed if PEEP > 12 cm H2O ----------------------
Mechanisms of impaired renal function with PEEP. Does positive end-expiratory pressure significantly reduce airway blood flow . Effect of different levels of positive end-expiratory pressure on lung water content.
