Familiarization

Allowing time for the child to become familiar with the equipment is a key component of a successful aerodynamic assessment, as the placement of the face mask over the nose and mouth is unfamiliar and may be met with apprehension or even anxiety. This can be especially true among children who have previously undergone surgery, as they may assume similarities between the face masks used to prepare for surgery and that which is used in the current assessment. Children may feel more comfortable if they are able to handle the face mask on their own prior to the assessment. The clinician can encourage them to hold it up to their face or their parent’s face and take time to become comfortable with the equipment. Many children are put at ease with both the freedom to explore the equipment as well as direct explanations and reassurance that nothing will come out of the face mask.

Task

Aerodynamic measures are collected during a single task consisting of a syllable train of /p/ + vowel productions at a comfortable pitch and loudness. Ideally, the vowel produced allows the tongue to remain in a neutral position such that it does not block the oral cavity and encourages oral airflow and promotes good velopharyngeal closure [6, 7]. For adults, the /i/ vowel is often recommended; however, saying /pi pi pi pi pi/ is silly for many children. Therefore, as vowel choice does not have a significant impact on tasks with similar elicitation methods in adults [8], many clinicians choose an alternate vowel for aerodynamic assessment. In our experience, the /æ/ vowel is a good choice to use for children during this task, and, thus, we will use the exemplar /pæ/ for the remainder of this chapter.

Successful completion of an instrumental aerodynamic assessment involves practice of the task with the child prior to data collection. The clinician should coach the child to produce five to seven consecutive /pæ/ syllables in a single breath. Syllable strings should be produced in an easy manner at a rate of 1.5–2 syllables per second [6]. The /pæ/ syllable strings should be produced with the child’s typical pitch and loudness. One method the clinician can use to accomplish consistent productions is to have the child produce a sustained /æ/ sound and then practice closing his or her lips at even intervals to produce the /p/. Alternately, the clinician can use imitation during practice; have the child mimic your production and provide feedback (e.g., give a thumb’s up indicator) at moments when the productions are optimal. Visual cues can also assist the child in producing the string of /pæ/ productions at a consistent rate. These may include a visual metronome, quietly tapping or clapping, or silently mouthing the productions along with the child. Many children benefit from the clinician counting on her fingers during the task such that the child knows when it is time to take a breath.

Observations During the Task

When performing aerodynamic assessment in children, clinicians must carefully observe the child as well as the instrumentation during the task. The face mask must remain flush on the child’s face the entire time. If necessary, help from the parent or the child can be solicited to ensure that the face mask has a tight seal on the face. If this cannot be accomplished, whether due to a facial abnormality or compliance by the child, aerodynamic estimates will be inaccurate. The clinician will also need to observe for any adverse interaction the child has with the oral catheter tube. The optimal placement is such that the tube sits within the intraoral space and does not impact articulation. However, some children may react to the tube adversely: bunching up their tongue to avoid it, pressing their tongue against it, or keeping their lips open to avoid touching it while they speak. It is important that the clinician encourage the child to close their lips fully around the tube, as a seal at the level of the lips is essential for intraoral pressure estimates. Additionally, bunching up or pressing their tongue against the tube may result in abnormal pressure transducer measures due to tongue position or saliva buildup. Aberrant tongue positions can usually be detected perceptually and often remedied with further instruction.

It is important that the clinician observes the child’s natural speech and resonance patterns prior to completing the task in order to identify any speech deviations that would affect the aerodynamic results. First, the clinician should observe whether nasality or nasal emissions are present in the child’s speech. This is important because the face mask is covering the child’s nose and mouth, and, although stimuli are selected to optimize oral airflow, nasal airflow will be captured. If nasality or nasal emissions are noted, the clinician can examine the possibility of using a nose clip. If the child tolerates a nose clip, this will prevent air from escaping through the nose during speech production. However, many children will not tolerate wearing a nose clip [1], and, therefore, the clinician must take this into account when interpreting the results of the aerodynamic assessment. Second, the clinician should listen to the child’s articulation for production of the voiceless bilabial plosive /p/. If the child displays error production of /p/ with respect to place, manner, or voicing during running speech, the clinician must ensure that the child can accurately produce a voiceless sound with full bilabial occlusion during the assessment tasks. Lastly, the clinician should consider if the child’s general respiratory patterns are adequate to support five /pæ/ productions on a single breath. Fewer syllable productions on a single breath may be acceptable, but a minimum of three syllables is needed for analysis, and analysis should only be performed on the middle productions, ignoring the first and last to control for initiation or termination effects [6].

Noninstrumental Measures

When an instrumental aerodynamic assessment is not practical or successful, noninstrumental assessment of maximum phonation durations may provide some information on the efficiency of the laryngeal system. One task used to measure maximum phonation involves asking the child to take a breath and hold out a vowel for as long as she or he can and timing the sustained vowel production. Children often need external cues to achieve phonation durations that accurately reflect their capacity. Cues may be explicit, such as having the child trace a line with his or her finger during phonation, moving a toy down a path, or showing the child a stopwatch. There is some evidence that children will produce longer phonation times if they are given encouragement and/or coaching during the production [9]. Additionally, repetitions may be helpful to elicit the best performance [10], and an average of multiple productions may increase the reliability of the measure [11].

Another informal method of examining maximum phonation durations is the s/z ratio in which the child holds out an /s/ for as long as they can and a /z/ for a long as they can. The clinician should calculate the ratio by dividing the /s/ production time by the /z/ production time. First proposed by Boone [12], this measure provides information on sustaining sounds with and without vocal fold vibration, and the resulting ratio is suggested to yield a measure of laryngeal efficiency. Previous research has shown that vocally healthy children have an s/z ratio of around one [13–15]. However, large within- and between-subject variability across studies suggests that proposed norms should be interpreted with caution [13–17]. While the clinician may use maximum phonation duration measures to provide additional information about the child’s aerodynamic function, conflicting findings suggest these values should not be used in isolation for assessment.