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Invasive Mechanical Ventilation

ARMA trial – low tidal volume ventilation
6 mL/kg vs 12 mL/kg reduced mortality from 40% to 30%

Plateau pressure < 30 cm H2O
Often requires permissive hypercapnia and high FiO2

“open-lung” strategy of high PEEP does not offer an advantage over lower PEEP levels sufficient to improve oxygenation

CVP goal
Study found CVP < 4 in patients without renal dysfxn had no effect on mortality but reduced length of stay

Early steroids may reduce duration

No improvement in mortality

Prone positioning


Chronic Obstructive Lung Disease
Watch for auto-PEEP
Failure to fully expire breath before initiation of next breath causes air-trapping and pressure build up. Signs…

  • Vent dyssynchrony
  • Patient discomfort
  • Hypotension (impaired venous return)


Look at waveform to see if expiratory airflow is ceasing before next breath
Check end expiratory pressure during an end-expiratory pause

Treatment of autoPEEP
Prolong expiratory phase (increase inspiratory flow rate)
Lower minute ventilation (either lower tidal volume or rr)

Acute on chronic hypercapnia
Immediate correct to a normal PCO2 in a chronic COPD patient will unmask a severe metabolic alkalosis due to compensatory bicarb retention
Elevated airway pressures, hyperinflation, vent dyssnchrony

Strategies: lower minute volume, permissive hypercapnia, neuromuscular blocking agents


Ventilator-associated pneumonia
PNA with onset >48h after invasive ventilation started
10-25% of intubated patients

HOB 30 degrees reduces risk
Send sputum
ABX for one week are sufficient

Last Updated August 29, 2010