High-Frequency Jet Ventilation

High-Frequency Jet Ventilation

The essence of high-frequency jet ventilation utilizes the concept of delivering very small tidal volumes at a high frequency. The method of high-frequency jet ventilation was first introduced in the 1960s by Douglas Sanders which permitted continuous ventilation for patients without interrupting surgical practices used in various procedures. This technique used an open-rigid bronchoscope attached to an adapter which provided a pressure regulated oxygen supply as well as applying a manual valve allowing adjustment of ventilation frequency to the patient. Oxygen was then delivered typically at low tidal volumes and high frequency through a small bore nozzle placed within the bronchoscope (OXFORD). This method was

The jet ventilator can then deliver to the patient rapid, yet small volumes of pressurized gas into the upper airway at rates ranging anywhere from 150 to 600 breaths per minute while exhalation is achieved through passive recoil of the lungs. For this system to work effectively, an open-ventilator circuit is required along with the use of a Continuous Mechanical Ventilation mode to ensure appropriate oxygenation and ventilation to the patient is achieved. Due to the small tidal volumes delivered at a high frequency, the actual measurement of volume delivered to the patient is difficult to determine but is approximated that it is close to the anatomical dead space of the patient. Jet Ventilation can be effectively used for a wide variety of patient dimensions from pediatrics to adults, providing adequate tidal volumes for variable lung capacities and compliances (Andrea L Lampland). A study by Carlon et al compared three hundred nine patients on mechanical ventilation, 157 of the patients were on a volume-cycled ventilator and 152 of the patients on high-frequency jet ventilation. The study measured the number of patients who could not reach a therapeutic respiratory goal from the ventilatory support they were placed on and was then switched over to the other form of ventilation. They concluded that those patients who required to switch over to

Common forms seen in practice involve supraglottic, ingraglottic, transtracheal, and by means of a rigid bronchoscope. Laryngeal surgeries are common procedures where these alternative methods of high-frequency jet ventilation must be utilized. Typically with laryngeal procedures, an endotracheal tube cannot be used for intubation in order for surgical access to be obtained. Rather, a metal, small bore needle is passed within a laryngoscope and inserted through the vocal cords and is either controlled manually or by use of a mechanical devices to control rate and volume delivered to the patient. During the procedure, oxygen concentration levels must be kept to a minimum in order to prevent combustion as the surgical site is located extremely close to where oxygen delivery is supplied. However, oxygen requirements vary from each patient and should be carefully considered when using jet ventilation support. Jet ventilation is usually tolerable by most patients, however those who are morbidly obese, have an inflexible neck or thorax, present with chronic stages of obstructive or restrictive lung diseases including fibrosis or poor alveolar diffusion should avoid jet ventilation as hypoventilation can become a