lung protective ventilation; low tidal volume ventilation; permissive hypercapnia

Introduction

The practice of allowing pCO2 to increase (hypercapnia) in order to maintain acceptably low airway pressures.

• this diminishes barotrauma from airway pressures necessary to maintain normal or lower pCO2.
• in general, permissive hypercapnia leads to improved outcomes.

Indications

• Acute Respiratory Distress Syndrome (ARDS)
• may be of benefit during general anesthesia for surgery

Benefit/risk

• number needed to treat (NNT) for ARDS
  • 10 for 1 life save at 28 days of hospitalization
  • 12 for 1 life saved at hospital discharge

Procedure

• mechanical ventilation providing a tidal volume of <= 6 ml/kg with plateau pressure of <= 30 cm H2O
• peak inspiratory pressure < 30-35 mm Hg
• provision of adequate PEEP (5-8 cm H2O) to prevent collapse of unstable alveoli during expiration

* contrast with convention mechanical ventilation defined as providing a tidal volume of 10-15 ml/kg range with a plateau pressure of > 30 cm H2O

Management

• adjust fraction of inspired oxygen (fiO2) & positive end-expiratory pressure (PEEP) to meet the following goals:
  • partial pressure of oxygen (PaO2) = 55-80 mm Hg
  • arterial pH = 7.30-7.45
  • plateau pressure <= 30 cm H2O

More general terms

• mechanical ventilation (assisted ventilation)