Speech Development in Infants and Young Children with a Tracheostomy

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A tracheostomy is a permanent opening of the trachea to outside air. It most often requires a surgical procedure for closure. The primary reason for performing a surgical tracheostomy is for long-term airway management in cases of chronic upper airway obstruction or central or obstructive sleep apnea, or to provide long-term mechanical ventilatory support. The use of assisted ventilation for more than 1 month in the first year of life has been considered to constitute a chronic tracheostomy (Bleile, 1993). Most of the estimated 900-2,000 infants and children per year who need a tracheostomy, a ventilator, or both for a month or more are, in fact, less than a year old (Singer et al., 1989). Although the mortality associated with a chronic tracheostomy in young children is twice that in adults, the procedure is invaluable for acute and long-term airway management (Fry et al., 1985).

When a tracheostomy or mechanical ventilation is used over a long period, the impact on communication and feeding behavior can be significant. Oral communication in children occurs in tandem with growth and maturation of the structures of the speech apparatus. Neuromuscular or biomechanical difficulties resulting from altered patterns of growth or structural problems can negatively affect the development of oral communication. In particular, the respiratory, laryngeal, and articulatory subsystems of the speech apparatus are at risk for pathological changes affecting the development of speech.

The respiratory subsystem of the speech apparatus comprises the lower airways, rib cage, diaphragm, and abdominal structures. The lower airways consist of the trachea, the right and left mainstem bronchi, and the lungs. The tracheobronchial tree is much smaller in children than in adults, and differs in shape and bio-

mechanics as well. The trachea in young children has been described as the size of a soda straw, and is highly malleable (Fry et al., 1985). The infant tracheal diameter is approximately 0.5 cm, whereas adult tracheal diameters are 1.5-2.5 cm. C-shaped cartilage rings joined by connective tissue help to keep the trachea from collapsing against the flow of air during breathing. Because the membranes of the infant trachea are soft and fragile, there is a risk of tracheal compromise secondary to a tracheostomy. Complications may include reactive granulation at the site of cannula, edema and scaring, chronic irritation of the tracheal lumen, and tracheal collapse as a result of increased negative pressure pulling air through a compromised structure (Fry et al., 1985).

During the first several years of life, significant changes occur in the structure and mechanics of the respiratory system. The airways increase in radius and length and the lungs increase in size and weight. The thoracic cavity enlarges and changes in shape, and overall chest wall compliance decreases with upright posture. Airway resistance decreases, and pleural pressure becomes more subatmospheric (Beckerman, Brouillette, and Hunt, 1992). Tidal volume, inspiratory capacity, vital capacity, and minute ventilation increase with age.

Besides providing phonation, the larynx, along with the epiglottis and soft palate, protects the lower airway. The infant larynx is located high in the neck, close to the base of the tongue. The thyroid cartilage is located directly below the hyoid bone, whereas the cricoid cartilage is the lowest part of the laryngeal structure. Because of its location and size, the infant larynx, like the trachea, is susceptible to trauma during airway management procedures. The laryngeal structures become less susceptible to injury as they change shape and descend during the first year of life.

The articulatory subsystem, composed of the pharynx, mouth, and nose, also undergoes significant changes in growth and function during infancy and early childhood. The pharynx plays a critical role in both respiration and swallowing. The infant pharynx lacks a rigid framework and can collapse if external suction is applied within the airway. If the airway-maintaining muscles are weak or paralyzed, normal negative pressures associated with inspiratory efforts also can cause airway collapse at the level of the pharynx (Thach, 1992). Movement of the pharyngeal walls, elevation of the soft palate, and elevation of posterior portion of the tongue are important maneuvers for achieving velo-pharyngeal closure. The infant tongue is proportionately larger in relation to mouth size than the adult's; thus, tongue retraction can cause upper airway blockage and respiratory distress. Various craniofacial abnormalities may result in structural or neurological situations that require airway management interventions, including tracheostomy.

The decision to use long-term airway maintenance in the form of a tracheostomy requires consideration of many factors. Even the type of incision can make a difference in overall outcome for the infant or young child (Fry et al., 1985). Other information is needed to select the appropriate tracheostomy tube. Driver (2000) has compiled a list of the critical factors in tracheostomy tube selection. These factors include the child's respiratory requirements, age and weight, tracheal diameter, distance from the tracheal opening to the carina, and anatomical features of the neck for selection of a neck plate or flange. In addition, decisions must be made regarding whether or not there should be an inner cannula, the flexibility of the cannula, whether or not there should be a cuff (an air-inflatable outer bladder used to create a seal against the outer wall of the tracheal tube and trachea), and what external adapters might be used (Driver, 2000).

Tracheostomy tubes are selected primarily on the basis of the ventilatory needs of the infant or young child. Tracheostomy tubes will be larger in diameter and may have a cuff in the event the child needs high ventilator pressures with frequent suctioning. However, because of a young child's susceptibility to trauma of the speech apparatus, it is optimal to have a smaller-diameter, flexible tube without a cuff. When a smaller tube is selected, air leakage around the tube and through the upper airway will be available to the infant for voicing.

Many pediatric upper airway management problems can be successfully addressed with a tracheostomy alone. However, chronic respiratory failure will require some form of mechanical ventilation. The type of mechanical ventilation support required will depend on the type of disorder, the degree of respiratory dependence, and whether the child will ultimately be weaned from ven-tilatory support. There are two types of mechanical ventilation systems commonly used with children. Negative pressure ventilation is noninvasive and uses negative (below atmospheric) pressure by exerting suction on the outside of the chest and abdomen. As a result, intra-thoracic pressure is reduced and induces airflow into the lungs. Expiration is accomplished by passive recoil of the lungs. Negative pressure ventilators work well with children who have relatively normal airways and compliant chest walls. Negative pressure ventilators are associated with fewer complications than positive pressure ventilators and do not require a tracheostomy (Splaingard et al., 1983). However, they are cumbersome and are not adequate for children with severe respiratory disease or rigid chest walls (Driver, 2000). Positive pressure ventilation is invasive and applies positive (above atmospheric) pressure to force air into the lungs via a ventilator connected to a tracheostomy tube (for long-term use). Expiration is accomplished by passive recoil of the lungs. The primary advantages are the flexibility to individualize respiratory support and to deliver various concentrations of oxygen (Metz, 1993). There are two major types of positive pressure ventilators, volume ventilators and pressure ventilators. In addition, ventilators are set in a mode (e.g., assist-control, synchronized intermittent mandatory ventilation) to deliver a certain number of breaths per minute, based on the tidal volume and minute ventilation.

Infants and young children with tracheostomies can become oral communicators if oral motor control is sufficient, the velopharynx is competent, the upper airway is in reasonably good condition (i.e., there is no significant vocal fold paresis or paralysis and no significant airway obstruction), the ability to deliver airflow and pressure to the vocal folds and supporting larngeal structures is sufficient, and chest wall muscular support for speech breathing is sufficient (not a prerequisite for ventilator-supported speech). If oral communication is possible, then the type of tracheostomy tube and the various valve configurations must be selected on the basis of both effective airway management and oral communication criteria. Driver (2000) suggests that the best results for oral communication are achieved if the smallest, simplest tracheostomy tube is selected. The size and nature (fenestrated vs. non-fenestrated) of the tra-cheostomy tube also will affect the effort required to move gas across the airway (Hussey and Bishop, 1996). Respiratory effort to breathe will impact on the additional effort required to vocalize and speak. The most efficient tracheostomy tube is one that has flow characteristics similar to those of the upper respiratory system for the maintenance of respiratory homeostasis, but with some trade-off for air leakage necessary for vocalization (Mullins et al., 1993). When tracheostomy tubes have a cuff, extreme caution should be taken to ensure that cuff deflation is accomplished prior to any attempts to support oral communication. Tracheostomy tubes with cuffs are not recommended for infants and very young children because of increased risk of tracheal wall trauma.

When a sufficient air leak around the tracheostomy tube exists, then a unidirectional speaking valve can be attached to the hub of the tube. When the child inspires, air enters through a diaphragm that closes on expiration, thus forcing air to exit through the upper airway. The same effect can be accomplished by manually occluding the hub of the tracheostomy tube. Speaking valves can be used with ventilator-assisted breathing as well.

Several factors should be considered when selecting a pediatric speaking valve. These factors include the type of diaphragm construction (bias open or bias closed), the amount of resistance inherent in the valve type, and the amount of air loss during vocalization and speech production. First, speaking valves can be either bias open or bias closed at atmospheric pressure. A biased closed valve remains closed until negative air pressure is applied during inspiration. In this case, the valve will open during inspiration and close during expiration. A bias open valve remains open and only closes during the expiratory phase of the breath cycle. A bias closed valve may require greater effort to achieve airflow (Zajac, Fronataro-Clerici, and Roop, 1999). Differences in resistance have been found among valve types, especially during low flows (.450 liters/sec), however, all valves recently tested have resistances in the range of nasal resistance reported for normal adults. Whereas speaking valves have similar resistances, bias-open valves consistently show air loss during the rise in pressure associated with the /p/ consonant (Zajac, Frontaro-Clerici, and Roop, 1999).

Introducing a speaking valve to a young child can be challenging. The valve changes the sensation of breathing probably due to increases in resistance on both inspiration and expiration. Extra effort from expiratory muscles during phonation also must be generated to force air around the tracheostomy tube to the vocal folds. Finally, young children may not be familiar with coughing up secretions through the oral cavities and show distress until this skill is acquired (McGowan et al., 1993). Initially, the young child may be able to tolerate the speaking valve for only 5 minutes at a time. With encouragement and appropriate reinforcement, the child will likely tolerate the speaking valve for increasing amounts of time. When a speaking valve is placed in line with mechanical ventilation, various volume or pressure adjustments may be made to maximize the timing of phonation and the natural characteristics of the breathing and speaking cycles. Only a few general guidelines on mechanical ventilation and speech in infants and young children have been published (e.g., Lohmeier and Boliek, 1999).

A chronic tracheostomy interferes with the development of oral motor skills and experimentation with sound production by limiting movements of the jaw, tongue, and lips. In addition, long-term intubation may result in a significantly high-vaulted palate and vocal cord injury (Driver, 2000). Adequate breath support for speech also may be affected because of neuromuscular weakness, hypotonia, hypertonia, or paralysis. Consequently, infants and young children may have one or several issues affecting the speech mechanism. Infants and young children who need mechanical ventilation may not vocalize until near the end of the first year of life and may not be able to appropriately time their vocalizations to ventilator cycle until well after 12 months of age (Lohmeier and Boliek, 1999). The speech characteristics of infants and children with tracheos-tomies, using speaking valves or manual occlusion, include a smaller lung volume initiations, terminations, and excursions, fewer syllables per breath group, variable chest wall configurations during vocalization including rib cage or abdomen paradoxical movements, breathy or pressed voice quality that reflects available airflow and tracheal pressures, intermittent voice stoppages, hypernasality, and poor intelligibility (Lohmeier and Boliek, 1999). In addition, experimentation with vocal play, feeding, and oral-motor exploration may be limited during a sensitive period for speech and language acquisition. Therefore, all efforts should be made to support phonation and other communicative opportunities.

Only a handful of group and single case studies have assessed the developmental outcomes of speech and language following the long-term use of a tracheostomy or mechanical ventilation. These studies suffer from problems such as sample heterogeneity and the prelinguistic or linguistic status of the child at the time the intervention is performed, but they do suggest some general trends and outcomes. Fairly obviously, these children are at risk for delay in speech and language development (Simon and Handler, 1981; Simon, Fowler, and Handler, 1983; Kaslon and Stein, 1985; Simon and Mc-

Gowan, 1989; Bleile and Miller, 1994). Major gains in the development of speech and language can sometimes be made during and after decannulation with total communication intervention approaches. However, the data suggest that residual effects of long-term tracheostomy can be measured long after decannulation. Most reported delays seem to be articulatory in nature; voice and respiratory dysfunction are rarely reported in children after decannulation (Singer, Wood, and Lambert, 1985; Singer et al., 1989; Hill and Singer, 1990; Kamen and Watson, 199l; Kertoy et al., 1999). Taken together, these studies indicate possible residual effects of long-term tracheostomy on the speech mechanism. These effects appear unrelated to the time of intervention (i.e., prelinguistic or linguistic) but may be related to length of cannulation and the general constellation of medical conditions associated with long-term tracheostomy use.

—Carol A. Boliek References

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