![]() The frequency commonly is initiated at 5 Hz in adults, with inspiratory time set to 33%. Initial ∆P is titrated upward until a visible “wiggle” of the patient’s body from shoulder to mid-thigh occurs. Because HFOV is more suitable for maintaining than recruiting lung volume, an initial recruitment maneuver should be performed as an adjunct before the transition from conventional ventilation. HFOV also may be contraindicated in patients with traumatic brain injuries and increased intracranial pressure, as CO 2 removal may be difficult to achieve.ĭuring the patient’s initial transition to HFOV, mPaw typically is set 5 cm H 2O above the mPaw of the current setting on conventional ventilation. Potential contraindications for HFOV include obstructive lung disease and intolerance to the heavy sedation or neuromuscular blocking agents (NMBAs) that this method generally warrants. Controlling mPaw to maintain adequate lung volume may mitigate the risk of repetitive airspace opening and closing. HFOV may be indicated when ALI/ARDS doesn’t respond to conventional mechanical ventilation therapies, such as intermittent recruitment maneuvers with positive end-expiratory pressure or pressure-control ventilation. This oscillatory pressure amplitude, or delta P (∆P), is titrated to achieve acceptable CO 2 elimination. The power setting (amplitude) on the ventilator controls the distance the “speaker” travels from its resting position, which controls displaced tidal volume (VT). ![]() As the “speaker” moves forward and backward, a portion of the flow is displaced in and out of the circuit and the patient respectively. It may be adjusted by changing either the flow rates delivered to the system or the pressure threshold of the mushroom valve, which controls outflow of gas from the system.Īn oscillating piston pump similar to the woofer of a loudspeaker vibrates the pressurized gas at a frequency that’s generally set between 3 and 15 Hz (1 Hz = 60 cycles/minute). Typically, mPaw is set at 25 to 35 cm H 2O to maintain adequate lung volume for effective oxygenation. This flow produces a constant applied airway pressure or mean airway pressure (mPaw) similar to that of high-flow continuous positive-airway pressure (CPAP). ![]() HFOV delivers a constant flow of heated, humidified gas, providing flow rates of 20 to 60 L/minute. HFOV has been studied across all patient ranges as a lung-protective strategy for ALI/ARDS refractory to conventional ventilation. Used for neonatal, pediatric, and adult forms of respiratory failure, HFOV differs from conventional mechanical ventilation by maintaining open lung volume through a constant mean airway pressure to achieve effective oxygenation, while oscillation removes CO 2. To maintain effective oxygenation and ventilation, patients with ALI/ARDS require measures to protect the lungs, such as HFOV. But you may not know that high-frequency oscillatory ventilation (HFOV) can be used as a lung-protective strategy and rescue mode for patients who have this syndrome of acute, persistent lung inflammation with increased vascular permeability. You’re probably aware that acute lung injury and acute respiratory distress syndrome (ALI/ARDS) carry a high mortality.
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