Objectives

1. To understand factors involved with the timing of tracheostomy including physiologic changes that occur when transitioning from translaryngeal to transtracheal intubation.
2. To understand the appropriate tracheostomy tube selection in patients with varying anatomy.
3. To understand the available options to promote speech in tracheostomized patients.
4. To understand the appropriate characteristics governing patient selection for decannulation.
5. To understand the available methods used in decannulation.

Abbreviations

PCF = peak cough flow; PEEP = positive end-expiratory pressure; Raw = airway resistance

Tracheostomies

Tracheostomies have become a therapeutic mainstay for the management of patients with chronic respiratory failure. Patients with prolonged mechanical ventilation frequently undergo tracheostomy and are eventually decannulated depending on the underlying disease process. Despite its routine use, there are few data and little consensus regarding the timing of tracheostomies; this results in a myriad of practice habits regarding the management and eventual decannulation process. This text will review the available literature and make practice recommendations for the timing, management, and decannulation of tracheostomies.

Timing of Tracheostomies

The timing of the transition from translaryngeal to tracheal intubation must begin with a comparison of physiologic factors that will be affected by this transition. Both the overall work of breathing, as defined as the area under the volume-pressure curve, and the airway resistance (Raw) decrease after tracheostomy.¹ Raw includes the resistance through both the endotracheal tube and the ventilator circuit. In patients prone to dynamic hyperinflation, a decrease in Raw results in a decrease in intrinsic positive end-expiratory pressure (PEEP or auto-PEEP). The tidal volume, respiratory rate, and thus minute ventilation tend to be equivalent in both translaryngeal and tracheal intubation.² Secretion clearance is enhanced in tracheostomy patients. Direct access to deep tracheal secretions, the minimization of anatomic dead space, and patient education for self-suctioning all improve upper airway clearance and are facilitated by tracheostomy. All of the above factors may combine to hasten a patient's eventual liberation from mechanical ventilation.

Prolonged intubation historically has been complicated by a high incidence of tracheal stenosis. This phenomenon was related to localized tracheal ischemia caused by the high-pressure cuffs previously used. Because both modern endotracheal tubes and current tracheostomy tubes use high-volume, low-pressure cuffs, tracheal mucosal ischemia has been significantly reduced. Thus, the duration of translaryngeal intubation should no longer be considered a compelling reason for converting to a tracheostomy.

Additionally, the incidence of nosocomial pneumonia has been cited as a reason to convert to tracheostomy. Prolonged mechanical ventilation has been shown to lead to an increase in nosocomial pneumonia. Recent data show that this risk may be magnified by converting to a tracheostomy. In fact, a prospective study in more than 3,000 patients demonstrated that those patients undergoing tracheostomy had a sixfold increase in the risk for developing nosocomial pneumonias compared with those who underwent translaryngeal intubation.³

The decision to perform tracheostomy must balance the risk of complications with prolonged translaryngeal intubation vs the surgical and stomal complications of tracheostomy. One study of 54 male patients demonstrated that laryngeal pathology was worse in those patients converted to a tracheostomy compared with those patients extubated 24 h later.⁴ Based on published data, the timing for performing tracheostomies should not be based solely on the length of time the patient has been orotracheally intubated. Tracheostomy is indicated if it is clear that the patient will not soon be liberated from the ventilator. The potential physiologic benefits reviewed above may assist in the weaning process.

Management of Tracheostomies

While much has been written on the indications for and the weaning of mechanical ventilation, there is a paucity of literature regarding the management and decannulation of tracheostomies in the chronically tracheostomized patient. There is a great deal of published opinion and anecdotal reporting, but randomized, controlled data are scarce.

The appropriate management of a tracheostomy actually begins with the selection of an appropriate tube. Standard tracheostomy tubes are made with a C-shaped curve that may be inappropriately short for patients with thick necks or long tracheostomy stomal tracts. In such cases, longer tubes with specialized angulations may be needed (Fig 1). For patients with especially long stomal tracts (eg, those with thick, obese necks), a flexible, kink-resistant plastic tube reinforced with metal wire can be used (Fig 2). Proper fit is essential; selection of a tube with excess length may cause increased pressure on the anterior tracheal wall, leading to microvascular ischemia and subsequent tracheal stenosis (Fig 3). A tube that is too short may not be secure in the airway and may be more subject to accidental expulsion with vigorous coughing or movement.

Unfortunately, there are very few data to guide the decision between plastic and metal tracheostomy tubes. Plastic tubes offer the advantage of an endotracheal cuff that facilitates mechanical ventilation. Ventilation through a metal tracheostomy tube can produce significant air leakage. This air leak may lead to intolerable tachypnea in patients demanding high minute volumes and therefore may be poorly tolerated in this population. Lastly, tube diameter must be considered when selecting the proper tracheostomy tube. Smaller tubes lead to higher Raw, and small, uncuffed tubes can lead to significant air leakage as with the metal tubes. Recall that resistance to airflow is inversely proportional to the radius to the fourth power of the conducting tube; ie , the smaller the lumen, the higher the Raw. This was demonstrated experimentally by Mullins and his colleagues.⁵ They calculated both Raw and work of breathing using tracheostomy tubes ranging in size from 4 to 10. The Raw declined by 45% when changing from a size 6 to size 8 tracheostomy tube and by 40% when changing from a size 8 to a size 10. Work of breathing showed a corresponding decrease of 55% with both substitutions. As a rule, therefore, the largest tube tolerated should be employed. This generally equates to a size 7 to 9 in men and size 5 to 7 in women.

There is also little evidence suggesting the appropriate frequency with which to change tracheostomy tubes; however, it has been suggested that frequent manipulation of the tracheostomy tube may lead to an increased risk of ventilator-associated pneumonia. Further, tube exchange is not a benign process. It is common practice, therefore, to change the tube only when there is a malfunction (eg, cuff rupture) or a need for a different tube design arises (eg, fenestrated tube). Complications occur and include failure to insert the replacement tube, insertion of the replacement into a false passage, bleeding, and patient discomfort. The risk for these complications decreases with the age of the stomal tract; consequently, it is recommended that changing of the tracheostomy tube be avoided within the first week following tube placement. A clinician experienced in translaryngeal intubation should always be present if a difficult exchange is anticipated (obese patient with a thick neck or anatomical anomaly).

Cuff Management

Tracheostomy tube cuff pressures must be monitored routinely to ensure inflation pressures in the range of 20 to 25 mm Hg (15 to 34 cm H₂O). Cuff pressures below 18 mm Hg may lead to longitudinal folds in the cuff promoting microaspiration of secretions collected above the cuff, thus increasing the risk of nosocomially acquired pneumonia.⁶ Pressures above 25 to 35 mm Hg may exceed capillary perfusion pressure, thus leading to compression of mucosal capillaries and promoting mucosal ischemia and tracheal stenosis.⁷ Many respiratory therapists use 25 mm Hg as the upper limit for acceptable cuff inflation pressures.

Estimation of cuff pressures by palpation of the external inflation bulb is not a reliable substitute for actual cuff pressure measurements. Some authors have recommended checking cuff pressure once every shift and after any manipulation of the tracheostomy tube. Cuff pressures are most accurately measured using a manometer directly connected to the cuff tubing by a stopcock. The stopcock assembly must communicate simultaneously with the inflation syringe, the manometer, and the cuff to achieve real-time pressure monitoring during cuff inflation.

Speech

Tracheostomies have the potential to promote articulated speech in alert and cooperative patients.⁸ Several techniques exist for speech, and selection of the best method should be individualized to each patient's ability cooperate. Patients who are unsuccessful with a particular technique may successfully master that technique later in their clinical course. Speech therapy should be an early and integral part of any strategy to assist chronically ventilated patients in their efforts to communicate.

Patients who remain dependent on the ventilator but have low tidal volumes may achieve whispered speech during periods of partial deflation of the tracheostomy cuff (Fig 4). To accomplish this safely, secretions pooled in the region above the cuff must be suctioned through the patient's mouth prior to cuff deflation. The cuff is then deflated slowly until enough air leaks around the cuff to enable whispered speech during the ventilator's inspiratory cycle. Patients must be observed for signs of respiratory distress or hypoventilation, and the cuff should be reinflated at the conclusion of the speaking session.⁹ Adding a modest amount of PEEP creates a continuous air leak that may enable some patients to speak throughout the ventilator cycle.⁹ Some authors, though, have suggested that this method allows only whispered monosyllabic communication, which can be frustrating for both patients and caregivers. Manzano and colleagues¹⁰ demonstrated that the addition of a one-way valve such as the Passy-Muir valve (Passy-Muir, Inc; Irvine, CA) [Fig 5] enabled chronically ventilator-dependent patients to communicate effectively, participate more in their care, and improve secretion clearance.

Pneumatic speaking tubes offer an additional way for ventilator-dependent patients to communicate. A source of pressurized gas is connected to the a specialized port on the speaking-tracheostomy tube that delivers gas to the trachea above the cuff. This allows airflow through the larynx and promotes articulated speech (Fig 6).⁸ Nearly 75% of properly selected patients can accomplish speech using this method.

Fenestrated tracheostomy tubes offer another way to facilitate patients' communication while weaning from mechanical ventilation. Patients breathing humidified air through a tracheal collar may speak spontaneously with the use of such a fenestrated tracheostomy tube. The inner cannula of the fenestrated tube is removed after mechanical ventilation has been interrupted. Expiratory airflow can then pass through the larynx when the outer portion of the tracheostomy tube is capped or occluded (Fig 7). Deflation of the tracheostomy cuff further enhances phonation by allowing more expired air to pass through the larynx. Capping of the external tube with a one-way valve (eg, the Passy-Muir valve) allows inspired airflow through the tracheostomy tube during inspiration but closes during expiration, promoting airflow through the tube fenestration and around the deflated cuff (Fig 8).¹⁰ Patients using this technique must be observed to ensure that airway resistance during exhalation when breathing through a fenestrated tube does not interfere with weaning.¹¹

Decannulating Tracheostomies

Before consideration can be given to weaning a patient off the tracheostomy, the original problem that warranted a tracheostomy must have resolved. For example, if a tracheostomy was originally inserted for management of epiglottitis, the swelling of the epiglottis must have subsided enough to permit oropharyngeal breathing after removal of the tracheostomy tube. After direct visualization of the glottis, the cuff can be deflated and the patient observed while spontaneously breathing. If the patient breathes comfortably and if intubation was required for only a short period of time, the tube can be removed.

In other instances of upper airway obstruction, the decision to extubate can be more difficult. In patients with residual glottic abnormalities or pharyngeal neoplasms after radiation therapy, direct visualization with endoscopy may be required to confirm patency of the lumen. If the tracheostomy was placed as access for prolonged mechanical ventilation, the patient must be comfortable with spontaneous breathing without becoming fatigued before decannulation can be considered. While breathing through a tracheostomy tube does decrease airway resistance, these benefits in respiratory mechanics must be weighed against the inability to effectively cough or perform pursed-lip breathing and the added difficulty of clearing airway secretions.

Excessive airway secretions must be controlled before removing the tracheostomy tube. Patients with purulent secretions may benefit from a course of appropriate antibiotics and inhaled b-agonists to assist in mucociliary clearance. Patients with clear mucoid secretions may tolerate decannulation if they have a vigorous and effective cough. Removal of the tube may actually enhance clearance as the tracheostomy tube and cuff may themselves be a source of tracheal irritation and thus increase the amount of tracheal secretions. Secretions often diminish after decannulation.¹²

The patient's ability to avoid aspiration after decannulation must also be considered before removing the tracheostomy tube. An intact gag reflex is encouraging, but it is not a reliable method of testing glottic function. Some studies suggest a gag reflex is absent in up to 20% of healthy people. Thus, the presence of a gag reflex is no guarantee that the patient will not aspirate. If aspiration is apparent after cuff deflation, decannulation will likely be more difficult. Most tracheostomized patients acquire some degree of glottic dysfunction, partly because the tube tethers the larynx and prevents normal glottic closure during swallowing. These patients often experience a decrease in aspiration after tracheostomy tube removal.

Heffner¹² proposed the following checklist to determine a patient's readiness for tracheostomy weaning:

• Has the upper airway obstruction resolved?
• Is mechanical ventilation no longer required?
• Are airway secretions controlled?
• Is aspiration nonexistent or minimal and well tolerated?
• Does the patient have an effective cough?

Lastly, Bach and Saporito¹³ prospectively studied four variables as predictors for successful decannulation in patients with chiefly neuromuscular respiratory failure. Of the four variables-age, extent of predecannulation ventilator use, vital capacity, and peak cough flows (PCFs)-only a PCF of >160 L/min was predictive of successful decannulation. While these data are suggestive, Bach and Saporito¹³ studied only 37 patients, most of whom had neuromuscular disease; only five patients underwent tracheostomy for COPD. PCF measurement prior to decannulation has not been globally adopted.

Once appropriate candidates for decannulation have been identified, attempts can be made to remove the tracheostomy tube. Scant evidence exists as to which method of tube removal is safest or most successful, but most patients can be successfully weaned if a systematic approach is followed. Tracheostomy stomas can markedly narrow or close within the first 24 to 48 h after decannulation, making tube replacement difficult or impossible if airway compromise occurs. Moreover, anatomic abnormalities such as granulation tissue or tracheal strictures may exist after long-term intubation, further complicating tube removal. These airway lesions can also contribute to the patient's failure to wean from mechanical ventilation. A systematic approach to decannulation should identify these lesions in most cases.¹⁴

Patients may be considered for decannulation after they demonstrate 24 to 48 h of stability after discontinuation of mechanical ventilation. Deflation of the tracheostomy cuff and capping of the external tube enables the clinician to assess the adequacy of the native airway. If a patient is able to breathe around a capped #8 tracheostomy tube with the cuff deflated, it is likely that he or she has a sufficiently intact native airway and pulmonary reserve to tolerate removal of the tracheostomy tube.¹⁵ Patients who have difficulty breathing around a deflated #8 tube can be reassessed using a capped #7 tube. Successful breathing around a #7 tube suggests that a patient will tolerate decannulation well.¹⁶ Patients who cannot tolerate breathing around a #7 tube should be evaluated with endoscopy to inspect for airway patency. If the airway is too narrow to allow air flow around the tube, a fenestrated cannula can be substituted. This approach is most appropriate in patients with normal pulmonary function and minimal secretions who are recovering from upper airway obstruction. These techniques may not be well suited for patients with underlying pulmonary disease who are recovering from prolonged mechanical ventilation. These patients may include those with neuromuscular disease or underlying COPD. Progressively downsizing the caliber of cuffless tracheostomy tubes until the patient can tolerate a small, uncapped tube without distress may work better. Once a small tube is tolerated, it can be occluded with either a cap or a one-way speaking valve. The ability to breathe spontaneously and clear airway secretions around a small, plugged tube suggests the patient will tolerate decannulation.¹⁷

Integral to this method is the occlusion of the external opening of the tracheostomy tube. Le et al¹⁸ attempted to determine if simple capping or occlusion with a one-way valve was superior. They studied patients who were weaned from mechanical ventilation and who had a tracheostomy for more than 30 days. Five patients received standard tracheostomy capping, and five patients received a Passy-Muir valve occluding expiratory airflow through the tracheostomy. All patients had fenestrated tracheostomy tubes, which varied as to the presence of a cuff. The authors concluded that there is no difference in the success or speed of decannulation between the two methods of occluding expiratory airflow. They suggested that patients "appeared" more comfortable with the one-way valve but did not report any different measures between the groups.

Some patients, however, will have adequate pulmonary mechanics but continue to produce a moderate amount of airway secretions. These patients may have difficulty with downsizing because the tracheal aspect of the tube interferes with clearance of secretions through the native airway. Some authors have suggested the use of a stomal obturator or "button."⁸ This simple device acts to preserve the stomal tract yet remove the tracheal obstruction of tube, thus allowing for easier clearance of secretions. The Olympic stomal button (Olympic Medical Corp; Seattle, WA) is an example of an obturator system; it consists of a hollow tube with retention flanges that dilate with the insertion of a solid plug or ventilator adapter (Fig 9).^19,20 When the patient tolerates breathing through the native airway for 24 to 48 h without the need for suctioning through the button's hollow tube, the button may be removed safely.

It is difficult to know which of the methods above is best suited for any particular patient. No comparative data exist. For patients with limited pulmonary reserve, a clinician may be guided at least by the airway resistance produced by each of the modalities discussed. Beard and Monaco²¹ examined the extent to which tracheostomy tube configurations contribute to Raw. They used model tracheas to measure the effects on Raw of four different tube configurations: (1) a cuffed fenestrated tube with cuff inflated, (2) a cuffed fenestrated tube with cuff deflated, (3) an uncuffed fenestrated tracheostomy tube, and (4) a Jackson-type metal tube with neither cuff nor fenestrations. The Raw was greatest for the cuffed fenestrated tube with the cuff inflated and least for the uncuffed fenestrated tube (Fig 10). Raw with the metal Jackson-type tube was similar to that with uncuffed fenestrated tube. The authors suggest that, given the increase in Raw when using cuffed tubes, uncuffed, fenestrated tubes should be used during tracheostomy occlusion.

Conclusion

References

1. Diehl JL, El Atrous S, Touchard D, et al. Changes in the work of breathing induced by tracheotomy in ventilator-dependent patients. Am J Respir Crit Care Med 1999; 159(2):383-388
2. Davis K, Campbell RS, Johannigman JA, et al. Changes in respiratory mechanics after tracheostomy. Arch Surg 1999; 134(1):59-62
3. Ibrahim EH, Tracy L, Hill C, et al. The occurrence of ventilator-associated pneumonia in a community hospital: risk factors and clinical outcomes. Chest 2001; 120(2):555-561
4. Colice GL, Stukel TA, Dain B. Laryngeal complications of prolonged intubation. Chest 1989; 96(4):877-884
5. Mullins JB, Templer JW, Kong J, et al. Airway resistance and work of breathing in tracheostomy tubes. Laryngoscope 1993; 103:1367-1372
6. Bernhard WN, Cottrell JE, Sivakumaran C, et al. Adjustment of intracuff pressure to prevent aspiration. Anesthesiology 1979; 50(4):363-366
7. Seegobin RD, van Hasselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. Br Med J (Clin Res Ed) 1984; 288(6422):965-968
8. Godwin JE, Heffner JE. Special critical care considerations in tracheostomy management. Clin Chest Med 1991; 12(3):573-583
9. Heffner J. Care of the intensive care unit patient with a tracheostomy. Problems in Anesthesia 1988; 2:269-277
10. Manzano JL, Lubillo S, Henriquez D, et al. Verbal communication of ventilator-dependent patients. Crit Care Med 1993; 21(4):512-517
11. Criner G, Make B, Celli B. Respiratory muscle dysfunction secondary to chronic tracheostomy tube placement. Chest 1987; 91(1):139-141
12. Heffner JE. The technique of weaning from tracheostomy: criteria for weaning; practical measures to prevent failure. J Crit Illn 1995; 10(10):729-733
13. Bach JR, Saporito LR. Criteria for extubation and tracheostomy tube removal for patients with ventilatory failure: a different approach to weaning. Chest 1996; 110(6):1566-1571
14. Rumbak MJ, Walsh FW, Anderson WM, et al. Significant tracheal obstruction causing failure to wean in patients requiring prolonged mechanical ventilation: a forgotten complication of long-term mechanical ventilation. Chest 1999; 115(4):1092-1095
15. Heffner JE, Hess D. Tracheostomy management in the chronically ventilated patient. Clin Chest Med 2001; 22(1):55-69
16. Rumbak MJ, Graves AE, Scott MP, et al. Tracheostomy tube occlusion protocol predicts significant tracheal obstruction to air flow in patients requiring prolonged mechanical ventilation. Crit Care Med 1997; 25(3):413-417
17. Reibel J. Decannulation: how and where. Respir Care Clin North Am 1999; 44:856-860
18. Le H, Aten J, Chiang J, et al. Comparison between conventional cap and one-way valve in the decannulation of patients with long-term tracheostomies. Respir Care 1993; 38(11):1161-1167
19. Heffner J, Casey K, Hoffman C. Care of the mechanically ventilated patient with tracheostomy. In: Tobin M, ed. Principles and practice of mechanical ventilation. New York, NY: McGraw-Hill, 1994; 749-774
20. Long J, West G. Evaluation of the Olympic Trach-Button as a precursor to tracheostomy tube removal. Respir Care Clin North Am 1980; 25:1242-1243
21. Beard B, Monaco F. Tracheostomy discontinuation:   impact of tube selection on resistance during tube occlusion. Respir Care 1993; 38:267-270