Corresponding Bundle Element:

Inspiratory plateau pressures maintained < 30 cm H2O for mechanically ventilated patients.

Related Measures

Inspiratory Plateau Pressure Goal

Background:

Patients with sepsis are at increased risk for developing acute respiratory failure, and most patients with severe sepsis and septic shock will require endotracheal intubation and mechanical ventilation.  Nearly 50 percent of patients with severe sepsis will develop acute lung injury (ALI)/acute respiratory distress syndrome (ARDS).  Patients with lung injury will have bilateral patchy infiltrates on chest x-ray, low paO2:FIO2 ratios (less than 300 for ALI or less than 200 for ARDS), and pulmonary capillary wedge pressure less than 18 cm H20, although this last measure is often clinically not available. 

High tidal volumes that are coupled with high plateau pressures should be avoided in ALI/ARDS.  Clinicians should use as a starting point a reduction in tidal volumes over 1 to 2 hours to a “low” tidal volume (6 mL·kg^-1·lean body weight^-1) as a goal in conjunction with the goal of maintaining end-inspiratory plateau pressures of < 30 cm H2O. 

Mortality Reduction:

The largest trial of a volume- and pressure-limited strategy showed a 9 percent decrease of all-cause mortality in patients ventilated with tidal volumes of 6 mL/kg of estimated lean body weight (as opposed to 12 mL/kg) while aiming for a plateau pressure of < 30 cm H2O. [1]

The formal ARDSnet protocol for mechanical ventilation is available at http://www.ardsnet.org/lowvtrefcard.pdf and is encouraged for use in septic patients.

Permissive Hypercapnea:

Hypercapnia (allowing PaCO2 to increase above normal, so-called permissive hypercapnia) can be tolerated in patients with ALI/ARDS if required to minimize plateau pressures and tidal volumes.

Although an acutely elevated PCO2 may have physiologic consequences that include vasodilatation and increased heart rate, blood pressure, and cardiac output, allowing modest hypercapnia in conjunction with limiting tidal volume and minute ventilation has been demonstrated to be safe in small, nonrandomized series. [2,3]  No upper limit for PCO2 has been established. Some authorities recommend maintaining pH at > 7.20–7.25, but this has not been prospectively established. The use of hypercarbia is limited in patients with preexisting metabolic acidosis and is contraindicated in patients with increased intracranial pressure. [4]  Sodium bicarbonate infusion may be considered in select patients to facilitate use of permissive hypercarbia. [5] Experimental models suggest that respiratory acidosis may confer protection against various forms of inflammatory injury. [6]

Positive End-Expiratory Pressure:

Provide adequate supplemental oxygen to maintain a pulse oximetric saturation of > 90 percent. A minimum amount of PEEP should be set to prevent lung collapse at end expiration. Setting PEEP based on severity of oxygenation deficit and guided by the FIO2 required to maintain adequate oxygenation is one acceptable approach.

For patients supported by mechanical ventilation or who are appropriate candidates for a pressurized face mask, PEEP or continuous positive airway pressure may be used to increase mean and end-expiratory airway pressures, allowing the reduction of the oxygen concentrations below potentially toxic levels (FIO2 < 0.60).

References:

1. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. New England Journal of Medicine. 2000;342:1301–1308.
2. Hickling KG, Henderson S, Jackson R. Low mortality rate in adult respiratory distress syndrome using low-volume, pressure-limited ventilation with permissive hypercapnia: A prospective study. Critical Care Medicine. 1994;22:1568–1578.
3. Bidani A, Cardenas VJ, Zwischenberger JB. Permissive hypercapnia in acute respiratory failure. Journal of the American Medical Association. 1994;272:957–962.
4. Tasker RC. Combined lung injury, meningitis and cerebral edema: How permissive can hypercapnia be? Intensive Care Medicine. 1998;24:616–619.
5. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. New England Journal of Medicine. 2000;342:1301–1308.
6. Laffey JG, et al. Therapeutic hypercapnia reduces pulmonary and systemic injury following in vivo lung reperfusion. American Journal of Respiratory and Critical Care Medicine. 2000;162:2287–2294.

Content adapted extensively from:

• Dellinger RP, Carlet JM, Masur H, et al. Surviving Sepsis Campaign Guidelines for management of severe sepsis and septic shock. Critical Care Medicine. 2004;32:858-873.
• Sevransky JE, Levy MM,  Marini JJ. Mechanical ventilation in sepsis-induced acute lung injury/acute respiratory distress syndrome: An evidence-based review. Critical Care Medicine. 2004;32[Suppl.]:S548–S553.