Several types of fenestrated tubes are available: "Lo-Profile" tracheostomy tube (Portex Inc.), Low-pressure cuffed tracheostomy tube (Shiley Medical, Mallinckrodt Inc.), and Tracoe flex tracheostomy tubes (Boston Medical Products) are examples of cuffed or cuffless precut fenestrated tracheostomy tubes. These are available in a variety of sizes (Figure 38-2).16 The fenestration is a hole in the outer cannula. When the inner cannula is removed, the fenestration is open, providing airflow through the vocal cords, thus allowing speech. These are double cannula tubes, which permit speech when the cuff is deflated, the inner cannula is removed, and the tube is plugged. When the cuff is inflated and the inner cannula is in place, positive
pressure ventilation is possible and protection from aspiration of material into the lower airway is provided. Patients are considered candidates for a cuffed fenestrated tracheostomy tube when swallowing function is adequate. Airway protection can be evaluated with a modified barium swallow or a bedside test using blue-stained ice chips or water. Prior to the use of these devices, patients must 1) be able to protect their lower airway, 2) be able to clear secretions with minimal assistance, 3) have only a modest amount of secretions, and 4) be capable of spontaneous ventilation for at least a 2-hour period.
Upper airway patency should be evaluated prior to the placement of a fenestrated tube. A simple bedside method is to remove the tracheostomy tube, occlude the stoma with gauze, and evaluate the patient's breathing pattern using the patient's natural airway. If a patient has difficulty breathing, as evidenced by inspiratory stridor or retractions, then the fenestrated tube should not be placed.
To insure proper alignment of the fenestration within the tracheal lumen, either a lateral neck x-ray or bedside measurements should be obtained (Figure 38-3). At the bedside, the distance from the skin to the anterior and posterior tracheal walls can be measured using a simple technique. A sterile pipe cleaner, as depicted, is useful for this approach. These maneuvers help to avoid occlusion of the fenestration with tracheal tissue, by insuring proper position within the tracheal lumen. This procedure should be performed for cuffless fenestration as well.
Manufactured prefenestrated tubes may be adequate for only a small percentage of patients, due to anatomical variation and pathology. Serious upper airway obstruction has been reported in the presence of improperly positioned fenestrations.17 Therefore, custom fenestrated tubes can be ordered or, in some cases, crafted at the bedside. The size of the fenestration generally should not be larger than the lumen of the tracheostomy tube; large fenestrations allow more contact with the tracheal wall, often stimulate granulation tissue growth, and weaken the structure of the tube. It is suggested that this type of tube be examined by direct vision (flashlight or flexible bronchoscope) on a routine basis.18
figure 38-3 Bedside technique of measuring for fenestration.
An alternative approach is to use a nonfenestrated tracheostomy tube with the cuff deflated and the proximal opening occluded or "capped" to provide the ability to talk as air flows around the tube and through the cords. This method can be dangerous due to resistance and the substantial effort required to move air up and around the nonfenestrated tube through the upper airway.19 If this method is used, monitor the patient's pattern and rate of respiration for increased effort to breathe, and listen to airflow characteristics over the lateral neck with a stethoscope. Patients may have difficulty clearing secretions using a nonfenestrated capped tracheostomy tube. Pulse oximetry is recommended throughout the entire weaning procedure.
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