HFOV Protocols

High-frequency oscillatory ventilation (HFOV) is an alternative method of mechanical ventilation for severe acute respiratory distress syndrome (ARDS) in large patients. ARDS is a life-threatening lung condition in which the blood does not receive enough oxygen. Thus, ventilation with a low tidal volume is required. HFOV protocols enable a health care provider to determine the transpulmonary pressure (TPP) level that preserves oxygenation in the lungs. Transpulmonary pressure is the difference between the pleural space or intraaveolar pressure and intrapleural pressure in the lungs.

Initiating HFOV

• Prior to HFOV treatment, a patient's airway should be suctioned. A patient is considered for high-frequency oscillatory ventilation when he cannot maintain a target plateau pressure (Pplat) of less than 30 to 35 cmH2O, according to Viasys Healthcare. Pplat is the static end respiratory recoil pressure rating of the chest wall, lung and respiratory system. Patients who have an FiO2 level of 40 to 50 percent and are on conventional ventilation -- with a mPaw of less than 24 cmH20 -- should be switched to HFOV.

Bronchoscopy

• HFOV protocol requires that a bronchoscopy is performed prior to initiation of high-frequency oscillatory ventilation. The bronchoscopy enables visualization of the airway, measurement of the opening of the endotracheal tube and an evaluation for infection.

Sedation

• Prior to HFOV treatment, a patient should be treated with a neuromuscular blocker such as cis-atracurium. During HFOV, he should be sedated with benzodiazepine and a narcotic such as fentanyl or morphine. When the patient's mPaw is between 20 to 24 centimeters of water (cmH20), neuromuscular paralysis may no longer be necessary.

Oxygenation

• An increase in pressure amplitude of oscillation pressure and decrease in the frequency setting of HFOV results in a lowered tidal volume. In addition, partial pressure of carbon dioxide (PaCO2) is lowered. Minimum fraction of inspired oxygen (FiO2) is required for PaO2 greater than 60 millimeters of atmospheric pressure (mm Hg).

Ventilation

• In treating patients with ARDS, the principal goal of HFOV is to achieve a non-toxic FiO2 rating of less than 60 percent and reduce ventilator induced lung injury. When oxygenation is improved through HFOV, FiO2 must be reduced before mPaw is reduced. If a patient has an mPaw of 20 to 24 cmH20 and FiO2 of 40 percent, the patient should be switched from HFOV to conventional ventilation.

Oscillator Stoppage

• A backup conventional ventilation mode does not exist for HFOV; therefore, if a pressure valve or external connection becomes disconnected, decompression of the electronic circuit may cause an oscillator to stop. If an oscillator stops, a patient must be disconnected from the electronic circuit and provided with a resuscitation bag. HFOV protocol requires that a Positive End-expiratory Pressure (PEEP) valve and an oxygen source is attached to a resuscitation bag and kept near the head of a patient. PEEP is usually five to ten cmH20.