PDF《Tracheostomy Tubes and Related》

498 RESPIRATORY CARE ? APRIL

2005 VOL

50 NO

4 resistance through Shiley tracheostomy tubes at 11.47, 3.96, 1.75, and 0.69 cm H2O/L/s for size 4, 6, 8, and

10 adult tubes, respectively. If the OD is too large, leak with the cuff deflated will be decreased, and this will affect the ability to use the upper airway with cuff deflation (eg, speech). A tube with a larger OD will also be more diffi- cult to pass through the stoma. A 10-mm OD tube is usually appropriate for adult women, and an 11-mm OD tube is usually appropriate for adult men as an initial tra- cheostomy tube size. Differences in tracheostomy tube length between tubes of the same ID but from different manufacturers are not commonly appreciated (Table 2), and this can have important clinical implications (Fig. 4). Tracheostomy tubes can be angled or curved (Fig. 5), a feature that can be used to improve the fit of the tube in the trachea. The shape of the tube should conform as closely as possible to the anatomy of the airway. Because the trachea is essentially straight, the curved tube may not conform to the shape of the trachea, potentially allowing for compression of the membranous part of the trachea, while the tip may traumatize the anterior portion. If the curved tube is too short, it can obstruct against the poste- rior tracheal wall (Fig. 6), which can be remedied by using either a larger tube, an angled tube, a tube with a flexible shaft, or a tube with extra length. Angled tracheostomy tubes have a curved portion and a straight portion. They enter the trachea at a less acute angle and may cause less pressure at the stoma. Because the portion of the tube that extends into the trachea is straight and conforms more closely to the natural anatomy of the airway, the angled tube may be better centered in the trachea and cause less pressure along the tracheal wall. Tracheostomy tubes are available in standard length or extra length. Extra-length tubes are constructed with extra proximal length (horizontal extra length) or with extra distal length (vertical extra length) (Fig. 7). In the case of one manufacturer, extra distal length is achieved by a dou- ble cuff design (Fig.

8 and Table 3). This design also allows the cuffs to be alternatively inflated and deflated, which may reduce the risk of tracheal-wall injury, although this has never been subjected to appropriate clinical study. Extra proximal length facilitates tracheostomy tube place- ment in patients with a large neck (eg, obese patients). Extra distal length facilitates placement in patients with tracheal malacia or tracheal anomalies. Care must be taken to avoid inappropriate use of these tubes, which may in- duce distal obstruction of the tube. Rumbak et al5 reported a series of

37 patients in whom substantial tracheal ob- struction (tracheal malacia, tracheal stenosis, or granula- tion tissue formation) caused failure to wean from me- chanical ventilation. In

34 of the

37 patients, the obstruction was relieved by use of a longer tube, which effectively........