Mechanical ventilation in acute hypoxemic respiratory failure: a review of new strategies for the practicing hospitalist

Abstract

Background: The goal of mechanical ventilation in acute hypoxemic respiratory failure is to support adequate gas exchange without harming the lungs. How patients are mechanically ventilated can significantly impact their ultimate outcomes.

Methods: This review focuses on emerging evidence regarding strategies for mechanical ventilation in patients with acute hypoxemic respiratory failure including: low tidal volume ventilation in the acute respiratory distress syndrome (ARDS), novel ventilator modes as alternatives to low tidal volume ventilation, adjunctive strategies that may enhance recovery in ARDS, the use of lung-protective strategies in patients without ARDS, rescue therapies in refractory hypoxemia, and an evidence-based approach to weaning from mechanical ventilation.

Results: Once a patient is intubated and mechanically ventilated, low tidal volume ventilation remains the best strategy in ARDS. Adjunctive therapies in ARDS include a conservative fluid management strategy, as well as neuromuscular blockade and prone positioning in moderate-to-severe disease. There is also emerging evidence that a lung-protective strategy may benefit non-ARDS patients. For patients with refractory hypoxemia, extracorporeal membrane oxygenation should be considered. Once the patient demonstrates signs of recovery, the best approach to liberation from mechanical ventilation involves daily spontaneous breathing trials and protocolized assessment of readiness for extubation.

Conclusions: Prompt recognition of ARDS and use of lung-protective ventilation, as well as evidence-based adjunctive therapies, remain the cornerstones of caring for patients with acute hypoxemic respiratory failure. In the absence of contraindications, it is reasonable to consider lung-protective ventilation in non-ARDS patients as well, though the evidence supporting this practice is less conclusive.

FIG. 1

Sixty-day mortality in the Acute Respiratory Distress Syndrome (ARDS) Network trials: change over time. Sixty-day mortality reported over the last 11 years in randomized clinical trials from the ARDS Network. ARMA-12 refers to the mortality rate in the higher-tidal volume arm of the original ARDS Network trial of lower tidal volumes (And Respiratory Management of Acute Lung Injury/ARDS), whereas ARMA-6 refers to patients in the lower-tidal volume arm. FACTT fluid conservative refers to the mortality of patients enrolled into the fluid-conservative arm of the Fluid and Catheter Treatment Trial. ALTA and OMEGA refer to the combined mortalities of 2 more recent trials: Albuterol for the Treatment of ALI, and Omega-3 Fatty Acid, Gamma-Linolenic Acid, and Antioxidant Supplementation in the Management of ALI or ARDS. Figure adapted from Matthay et al.

FIG. 2

Chest radiograph findings in acute respiratory distress syndrome (ARDS). (A) Anterior-posterior portable chest radiograph of a previously healthy 28-year-old woman with severe ARDS due to aspiration. (B) Anterior-posterior chest radiograph of a 62-year-old woman with moderate ARDS due to bacterial pneumonia. (C) Anterior-posterior chest radiograph of a 52-year-old man with moderate ARDS due to influenza-related pneumonia.

FIG. 3

Airway pressure release ventilation: pressure versus time. Pressure versus time curve in airway pressure release ventilation. Spontaneous breathing appears during P high. Abbreviations: P high, the high positive end-expiratory pressure (PEEP); P low, the low PEEP; T high, the duration of P high; T low, the duration of P low. From Daoud EG. Ann Thorac Med. 2007;2:176–179. Reused pursuant to Creative Commons Attribution License.