High-frequency Percussive Ventilation Improves Oxygenation in Patients With ARDS: Mechanical Ventilation
The piston is driven by a high-pressure gas supply at a high-frequency rate of 200 to 900 beats/min, superimposed on a conventional inspiratory/expiratory pressure-controlled cycle that is set at a rate of 10 to 15 breaths/min. There are five control parameters: (1) peak inspiratory pressure (PIP), (2) inspiratory time (Ti), (3) Te, (4) positive end-expiratory pressure (PEEP) and continuous positive airway pressure (CPAP), and (5) percussive frequency. The Vt of both types of breaths is determined by the set PIP, the set Ti, and the lung compliance. The high-frequency breath volume is also determined by the pressure difference between PEEP and CPAP. The PEEP and CPAP are used in combination. This is a unique feature of the VDR that allows progressive exhalation in subtidal volumes rather than rapid elimination of the entire exhaled volume. The endotracheal tube cuff is left partially deflated to allow for a continuous air leak through the trachea. Humidification during HFPV may be difficult, and failure to adequately humidify the large volumes of air passing through the circuit may result in erosion and desiccation of the mucosa, potentially leading to airway obstruction. A high-volume dual nebulizer is included in the ventilator circuit to deliver water at 30 mg/L of air to raise the humidity of circulating air to 100%. zyrtec tablets
Oxygenation is controlled by the Fio2, PEEP/CPAP, PIP, Ti, and frequency. Ventilation is governed by the relationship between Ti and Te, PIP, and frequency. Typical starting settings are a high-frequency rate of 500 beats/min superimposed on a rate of 12 breaths/min, a peak pressure of two thirds the pressure used on the conventional ventilator, a Ti/Te of 1:1, and a PEEP/CPAP of 10. Adjustments are made on the basis of values obtained by monitoring continuous arterial oxygen saturation (Sao2) and arterial blood gas levels. The mean airway pressure (MAP) is measured by the ventilator and displayed continuously.