(Chest. 2004;125:1046-1051.)
© 2004
American College of Chest Physicians
Tracheostomy Tube Enabling Speech During Mechanical Ventilation*
Hiroaki Nomori, MD, PhD
* From the Department of Thoracic Surgery, Saiseikai Central Hospital, Tokyo, Japan.
Correspondence to: Hiroaki Nomori, MD, PhD, Department of Thoracic Surgery, Saiseikai Central Hospital, 1-4-17 Mita, Minato-ku, Tokyo 108-0073, Japan; e-mail: hnomori{at}qk9.so-net.ne.jp
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Abstract
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Background: A voice tracheostomy tube (VTT) was developed to enable patients to speak during mechanical ventilation.
Methods: The VTT has slits cut in it and is covered on part of its side with an elastic cuff, enabling the cuff to expand with positive pressure from the ventilator on inspiration and to deflate on expiration. By this mechanism, inspired air from the ventilator goes to the lung with the cuff inflated, and some of the expired air passes out around the deflated cuff and discharges through the glottis, allowing sufficient ventilation and also enabling vocal fold vibration. An experiment using a model lung showed that there was little leakage on inspiration even for low lung compliance and high airway pressure, and that the leakage volume on expiration was approximately 40% of the ventilated volume, ie, the volume discharging through the vocal fold in clinical use.
Results: Sixteen patients who had been managed by ventilation via a conventional tracheostomy tube were switched to the VTT. All patients except one were able to speak after switching to the VTT without change in PaO2 and PaCO2. There were no complications associated with the use of the VTT. Bronchoscopy showed that the cuff of the VTT did not damage the tracheal mucosa.
Conclusion: The VTT enables patients to speak during mechanical ventilation with sufficient ventilation and without aspiration and damage to the tracheal mucosa, even in patients with low lung compliance.
Key Words: lung compliance • mechanical ventilation • tracheostomy tube • speech • voice
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Introduction
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Communicating one’s needs is an essential part of daily life, especially for patients with respiratory failure who require ventilation support via a tracheostomy. Being unable to communicate should downgrade the quality of medical care. For effective ventilation, cuff inflation is required to block the gap between the trachea and tube, preventing patients from speaking. It has been reported that patients with adequate pulmonary compliance, such as those with neuromuscular disease, can be managed by ventilation support with cuffless tracheostomy tube or minitracheostomy tube without losing the ability to speak.1
2
However, this option is not available for patients with low lung compliance, such as those with pneumonia, advanced COPD, or other restrictive pulmonary disease, because air from the ventilator leaks out during inspiration through the gap between the trachea and tracheostomy tube due to the high airway resistance.3
4
To solve this problem, the voice tracheostomy tube (VTT) was developed, in which the cuff expands on inspiration and deflates on expiration. The experimental data and clinical applications of the VTT are presented.
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Materials and Methods
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The structure of the VTT is shown in Figure 1
. The tube part of the VTT is made of polyvinyl chloride. The VTT has two slits 10 mm in length and 2 mm in width down its side, and this part of the tube is covered with an elastic cuff made from polyurethane approximately 0.1 mm in thickness. Both edges of the cuff are bonded on the tube. This structure connects the insides of the cuff and tube with each other. The cuff therefore expands with positive pressure from the ventilator on inspiration and deflates on expiration (Fig 2
). By this mechanism, the cuff can expand and block the gap between the trachea and the VTT on inspiration, sending air from the ventilator to the lung without air leakage. On expiration, because the cuff is deflated, some of the expired air comes out through a gap between the trachea and VTT and discharges via the upper airway, enabling the patient to speak. The internal and external diameters of the VTT are 7 mm or 8 mm and 10 mm or 11 mm, respectively, and the diameter of the expanded cuff is 30 mm.
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Figure 2.. The cuff expands with positive pressure from the ventilator that sends inspired air to the lung without air leakage. On expiration, the cuff deflates and some of the expired air comes out through a gap between the trachea and VTT and discharges via the vocal fold, enabling the patient to speak.
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Before clinical application, an experimental study was conducted using a model lung (TTL; MI Instruments; Grand Rapids, MI), a model trachea, and a ventilator (CV 5000; International Medical Intelligence; Saitama, Japan) [Fig 3
]. The model trachea was a cylindrical shape, with an internal diameter of 22 mm. For the experimental study, we used the VTT with an internal diameter of 8 mm and an external diameter of 11 mm. As a control, a conventional tracheostomy tube with the same internal and external diameters and a continuously expanded cuff was used. To measure the inspired and expired air volumes and airway pressure, a sensor (Cardiocap 5; Datex-Ohmeda Division Instrumentarium; Helsinki, Finland) was set between the VTT and ventilator. To measure the ventilated volume of the model lung, another sensor was also set between the VTT and model lung. The ventilator was set to volume- or pressure-controlled mode. For the volume-controlled mode, the tidal volume was set at 600 mL and the positive end-expiratory pressure (PEEP) at 0 cm H2O and 5 cm H2O. For the pressure-controlled mode, the pressure was set at 20 cm H2O, the inspiratory time at 1.0 s, and the PEEP at 0 cm H2O and 5 cm H2O. The leakage volume on expiration from the gap between the VTT and model trachea was calculated by subtracting the expired volume from the ventilated volume. The leakage volume on inspiration was calculated by subtracting the ventilated volume from the inspired volume. To model respiratory failure with low lung compliance, the compliance of the model lung was set from 50 mL/cm H2O down to 30 mL/cm H2O and 10 mL/cm H2O.
Patients
Between January 2002 to May 2003, 16 consecutive patients with respiratory failure who were conscious and had been managed with ventilators using conventional tracheostomy tubes with inflated cuffs were switched to respiratory management with the VTT (Table 1
). Seven patients had tuberculosis sequelae, three patients had pneumonia, three patients had COPD, two patients had amyotrophic lateral sclerosis (ALS), and the remaining patient had spinal cord injury causing ventilation insufficiency. Body mass index ranged from 16 to 23 with 19 ± 2 of mean value (± SD). Nine patients were managed by volume-controlled ventilation, and the other seven patients were managed by pressure-controlled ventilation for periods ranging from 3 to 950 days via a tracheostomy tube with inflated cuff. The sizes of the VTTs were matched to those of the previous tracheostomy tubes, ie, internal diameter of 7 mm for nine patients and internal diameter of 8 mm for seven patients. Lung compliance was calculated by dividing the tidal volume by the plateau airway pressure. All patients except three (patients 4, 5, and 7; Table 1
) received additional oxygen via the ventilator circuit. Volume-controlled ventilation was set to a tidal volume of 350 to 500 mL using a Bear 1000 Ventilator (Bear Medical Systems; Riverside, CA) or an Achieva Portable Volume Ventilator (Tyco Healthcare Japan; Tokyo, Japan). Pressure-controlled ventilation was performed by biphasic positive airway pressure (BiPAP S/T-D; Respironics; Pittsburgh, PA). Three of the nine patients receiving volume-controlled ventilation used PEEP of 3 cm H2O or 5 cm H2O. Four of the seven patients receiving pressure-controlled ventilation used expiratory positive airway pressure of 3 cm H2O or 4 cm H2O.
The conventional tracheostomy tubes with inflated cuffs were replaced with VTTs without changing the conditions of ventilation. The VTTs were routinely exchanged with new ones every 2 or 3 weeks as conventional tracheostomy tubes are usually done. Twelve patients who had been eating meals continued to eat after switching their tubes. In six patients, the tracheal mucosa where the cuff expanded was checked by bronchoscopy before and 2 weeks after switching the tube.
All patients and their families were informed about the use of the VTT, including the setting of therapeutic goals, and written consent was obtained from all patients or their families. The differences between blood gas values before and after the procedure were analyzed for significance by the two-tailed Student t test. Differences at p < 0.05 were considered statistically significant. All values in the text and tables are expressed as mean ± SD.
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Results
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In both volume- and pressure-controlled modes for the model lung, the VTT showed some air leakage on inspiration, but the leakage was usually < 10% of the inspired volume from the ventilator, even under conditions of low lung compliance and high airway pressure (Tables 2
,3
). There was no significant difference of ventilated volume, expired volume, airway pressure, and leakage volume between 0 cm H2O and 5 cm H2O of PEEP. On expiration, the air leakage volume via the gap between the VTT and model trachea was approximately 40% of the ventilated volume.
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Table 2.. Ventilated Volume, Expired Volume, Airway Pressure, and Leakage Volume on Expiration: Model Lung on Volume-Controlled Ventilation With 600 mL in Inspiratory Volume
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Table 3.. Ventilated Volume, Expired Volume, Airway Pressure, and Leakage Volume on Expiration: Model Lung on Pressure-Controlled Ventilation With 20 cm H2O in Inspiratory Pressure
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Although the study of model lung showed a little leakage on inspiration with VTT, clinical applications did not show air leakage on inspiration and could take sufficient ventilation via the VTT despite low lung compliances. After switching to the VTT, all patients except one (patient 16; Table 1
) were able to speak by air leakage through the vocal fold on expiration. Patient 16, who could not speak well after switching, had a conspicuously bent trachea due to long-standing tuberculosis, which had an angle of approximately 100°, causing occlusion of the gap between the VTT and trachea and less air leakage on expiration, resulting in insufficient speech. Two patients whose voices were weak (patients 1 and 4; Table 1
) used an in-line, one-way speaking valve (Passy-Muir Valve; Passy-Muir; Irvine, CA)5
between the VTT and the end of ventilator circuit, enabling them to speak with a voice as loud as that of a healthy person, because with the valve all of the expired air was directed through the larynx. They could use the in-line, one-way valve for > 1 h without any changes of PaO2 and PaCO2. The other patients did not require the one-way speaking valve because their voices were loud enough for listeners > 2 m away. Both a PEEP up to 5 cm H2O and expiratory air pressure up to 4 cm H2O were maintained on the pressure gauge of the ventilator.
The mean values of PaCO2 before and 7 days after switching the tube in all patients were 50 ± 11 mm Hg and 51 ± 10 mm Hg, respectively, and the difference between the two was not significant (p = 0.61). The mean values of the PaO2 before and 7 days after switching the tube were 90 ± 13 mm Hg and 93 ± 11 mm Hg, respectively, and the difference between the two was not significant (p = 0.52). Lung compliances ranged from 12 to 35 mL/cm H2O (mean ± SD, 23 ± 5 mL/cm H2O). Nine patients (patients 1 to 9; Table 1
) continued to use the VTT for the periods ranged from 25 to 386 days. Six patients (patients 10 to 15) were weaned from the ventilator 7 to 50 days after switching to the VTT. The one patient (patient 16) who failed to speak when using the VTT because of a bent trachea returned to using the conventional tracheostomy tube.
Two weeks after switching to the VTT, bronchoscopy showed no damage to the tracheal mucosa where the cuff of the VTT expanded. Further, in one patient (patient 11), who had shown a whitish color change of tracheal mucosa caused by the inflated cuff of the conventional tracheostomy tube, the color of the mucosa returned to pink within 2 weeks after switching to the VTT.
There were no complications with the VTT. The 12 patients who had been eating prior to the use of the VTT continued to eat successfully with the VTT. The VTT did not appear to result in any clinically appreciable swallowing complications beyond what was demonstrated with conventional tracheostomy tubes. While we routinely exchange the VTT every 2 or 3 weeks according to the general practice of conventional tubes, the slits of the VTT were never occluded with secretions. There were no cuff problems such as infection, bursting, or insufficient expansion.
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Discussion
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Our study using a model lung showed that the VTT could be used in both pressure-controlled and volume-controlled ventilation. The leakage volume on inspiration was < 10% of the inspired volume from the ventilator, even under conditions of low lung compliance. The leakage volume on expiration was approximately 40% of the ventilated volume; this volume refers to the air expired via the vocal fold in clinical use, which could be enough for speech. The VTT could be useful for low lung compliance, even as low as 10 mL/cm H2O.
Clinically, the VTT enabled patients to speak sufficiently without worsening the ventilation conditions, despite low lung compliances. Neither the PaCO2 nor the PaO2 changed after switching from the conventional tracheostomy tube to the VTT.
Before clinical application of the VTT, we were concerned that aspiration might occur because of deflation of the cuff on expiration, causing an increase in tracheal secretions or aspiration pneumonia. However, this never happened. An inflated cuff is sometimes misunderstood to prevent aspiration of food, gastric contents, and upper airway secretions. However, patients with conventional tracheostomy tubes often aspirate some food or secretion despite full cuff inflation, thus requiring tracheal suctioning. Bach and Alba1
reported that 91 patients with neuromuscular ventilatory insufficiency could be managed with deflated cuffs or cuffless tracheostomy tubes during mechanical ventilation, without any problems including aspiration. While their patients had both sufficient oropharyngeal muscle strength and adequate pulmonary compliance, our patients had the former but did not have the latter, requiring the VTT cuff that expanded during inspiration. We believe that patients with sufficient oropharyngeal function can be managed by the VTT during mechanical ventilation without the problem of aspiration.
Before using PEEP in clinical application, we had the following concerns: (1) would PEEP work even with air leakage on expiration, and (2) could a patient speak sufficiently when using PEEP, which would make the cuff expand and decrease air leakage on expiration? However, none of these problems occurred in our patients using PEEP up to 5 cm H2O or expiratory positive airway pressure up to 4 cm H2O, which were maintained even after switching to the VTT. This is because the VTT balloon can expand a little with PEEP or expiratory positive airway pressure, which is enough to make those pressures by blocking the gap between the trachea and the VTT. In terms of the second concern, we think the that the patients could speak even when using PEEP because an expiratory airway pressure was increased by expiratory respiratory muscle when speaking, which deflated the cuff and kept air leakage when speaking.
It has been reported that an inflated cuff of a tracheostomy tube during mechanical ventilation could cause tracheomalacia, tracheoesophageal fistulas, erosion of the subclavian artery, and tracheal stenosis.6
7
Bronchoscopy in the present study showed that the VTT had little damage on the trachea mucosa. In one patient, bronchoscopy revealed that the whitish trachea mucosa became pinkish after switching to the VTT, suggesting improvement of tracheal mucosal blood flow. Because the cuff of the VTT expands only during inspiration, trachea mucosal blood flow is not obstructed continuously. It is reasonable that the cuff of VTT could decrease tracheal mucosal damage and subsequent complications, compared with the continuously expanded cuff of the conventional tracheostomy tube.
The possible contraindication for use of the VTT might be ARDS. While we did not experience any air leakage during inspiration in our patients, the maximum airway pressure and PEEP were < 26 cm H2O and 5 cm H2O, respectively. However, patients with ARDS often require higher airway pressure and PEEP to maintain an enough tidal volume and PaO2, which could cause a little air leakage during inspiration around the cuff of the VTT, resulting in insufficient ventilation. Besides, the recent sophisticated ventilators for use in patients with ARDS have an alarm system to check the expiratory volume, which must be decreased with the use of VTT. However, patients with ARDS have to be managed with deep sedation and would not be required to speak. In conclusion, the VTT enabled tracheostomy patients to speak during mechanical ventilation with sufficient ventilation and without aspiration and damage to the tracheal mucosa.
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Footnotes
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Abbreviations: ALS = amyotrophic lateral sclerosis; PEEP = positive end-expiratory pressure; VTT = voice tracheostomy tube
Received for publication March 13, 2003.
Accepted for publication September 1, 2003.
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References
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- Bach, JR, Alba, AS (1990) Tracheostomy ventilation: a study of efficacy with deflated cuffs and cuffless tubes. Chest 97,679-683[Abstract/Free Full Text]
- Nomori, H, Ishihara, T Pressure-controlled ventilation via a mini-tracheostomy tube for patients with neuromuscular disease. Neurology 2000;55,698-702[Abstract/Free Full Text]
- Nomori, H, Horio, H, Suemasu, K Pressure-controlled ventilation via a minitracheostomy tube: experimental study using a mechanical lung model. Surg Today 2001;31,780-784[CrossRef][ISI][Medline]
- Nomori, H, Horio, H, Suemasu, K Assisted pressure control ventilation via a mini-tracheostomy tube for postoperative respiratory management of lung cancer patients. Respir Med 2000;94,214-220[CrossRef][ISI][Medline]
- Passy, V Passy-Muir tracheostomy speaking valve. Otolaryngol Head Neck Surg 1986;95,247-248[ISI][Medline]
- Hedden, M, Ersoz, C, Safar, P Tracheoesophageal fistulas following prolonged artificial ventilation via cuffed tracheostomy tubes. Anesthesiology 1969;31,281-289[ISI][Medline]
- Pingleton, SK Complications of acute respiratory failure. Am Rev Respir Dis 1988;137,1463-1493[ISI][Medline]
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[Abstract]
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Abstract
Introduction
