Mode of ventilation

The mode of ventilation should be tailored to the needs of the patient. In the emergent situation, the practitioner may need to order initial settings quickly. SIMV and A/C are versatile modes that can be used for initial settings. In patients with a good respiratory drive and mild-to-moderate respiratory failure, PSV is a good initial choice.

Tidal volume

Observations of the adverse effects of barotrauma and volutrauma have led to recommendations of lower tidal volumes than in years past, when tidal volumes of 10-15 mL/kg were routinely used.

An initial TV of 5-8 mL/kg of ideal body weight is generally indicated, with the lowest values recommended in the presence of obstructive airway disease and ARDS. The goal is to adjust the TV so that plateau pressures are less than 35 cm H₂ O.

Respiratory rate

A respiratory rate (RR) of 8-12 breaths per minute is recommended for patients not requiring hyperventilation for the treatment of toxic or metabolic acidosis, or intracranial injury. High rates allow less time for exhalation, increase mean airway pressure, and cause air trapping in patients with obstructive airway disease. The initial rate may be as low as 5-6 breaths per minute in asthmatic patients when using a permissive hypercapnic techniquSupplemental oxygen therapy

The lowest FiO₂ that produces an arterial oxygen saturation (SaO₂) greater than 90% and a PaO₂ greater than 60 mm Hg is recommended. No data indicate that prolonged use of an FiO₂ less than 0.4 damages parenchymal cells.

Inspiration/expiration ratio

The normal inspiration/expiration (I/E) ratio to start is 1:2. This is reduced to 1:4 or 1:5 in the presence of obstructive airway disease in order to avoid air-trapping (breath stacking) and auto-PEEP or intrinsic PEEP (iPEEP). Use of inverse I/E may be appropriate in certain patients with complex compliance problems in the setting of ARDS.