1. Esophageal Pressure Estimates of Subglottal Air Pressure
Ron Netsell, Megan Hargens, Nancy Dion
Missouri State University
Springfield, MO
Purposes of Present Study
To develop a relatively non-invasive procedure to estimate subglottal air pressure using esophageal pressure during continuous speech.
To look for any effects of balloon position in the esophagus.
Maintaining a steady subglottal air pressure over time is essential for speech production. During the stop phase of voiceless consonants, intraoral air pressure (Po) equals subglottal air pressure (Ps). See [k] and [p] below (Netsell, 1973).
Results and Discussion
Linearity: Long periods of linearity were evident in esophageal pressure (shown between cursors below).
Top trace: intraoral air pressure. Middle trace: esophageal pressure. Bottom trace: lung volume level.
Estimates of Subglottal Air Pressure: Pe gave valid estimates of Ps, especially in the mid-range of lung volume (where speech typically is produced).
Top trace: esophageal pressure. Bottom trace: Ps
Balloon Placement: With one exception, the esophageal pressure curves were identical for the balloon positions tested. The exception may have been a postural shift by the participant.
Methods
Participant: One adult male.
Tasks: The participant repeated the syllable [pa] at about 4 syllables per second throughout his vital capacity. NOTE: The pressure behind the lips during [p] production is equal to subglottal air pressure. Three balloon depths were used: 34cm-37cm-40cm. The task was performed twice at each balloon depth.
Instrumentation: Recordings of intraoral air pressure, esophageal pressure, and lung volume level were digitized and analyzed with commercially available software (EGAA, RC Electronics, Santa Barbara, CA). A SmartCath esophageal catheter (8 FR adult) from VIASYS was used.
Balloon Placement: The balloon was inserted through
a nostril and placed approximately mid-level in the
esophagus. After the balloon was inserted, the
participant completed a Valsalva maneuver to empty
any air that may have been in the balloon. Then, the
Balloon was inflated with 0.5 mL of air.
Presented to the annual meeting of the Missouri Speech-Language-Hearing Association. Osage Beach, MO (2007).
Background
Invasive methods to record Ps require a needle or transducer be inserted into the trachea, beneath the vocal folds. Less invasive measures of esophageal pressure (Pe) have been used to estimate Ps; but, the validity of this method has been questioned (Kunze, 1964). Kunze (1964) used a balloon inserted into the esophagus to measure esophageal pressure and a hypodermic needle inserted into the trachea to measure subglottal air pressure. Kunze concluded that Pe does not accurately estimate Ps, and stated, “intra-esophageal pressure measures do not provide adequate estimates of sub-glottal pressures regardless of the size of the balloon or its position in the esophagus.” Kunze’s 1964 data may have led a hiatus Pe use in speech research. Also, see Lieberman (1968).
It appears 35 years elapsed before another report of Pe use was published (Slifka, 2003). She used a commercially available catheter-balloon system. These systems may have resulted in better estimates of Ps. Slifka (1993) demonstrated that the peaks of intraoral air pressure (Po) during the [p] stop phase were closely approximated by esophageal pressure, Ps (see figure below). The participant was repeating [pa-pa-pa-pa].
CONCLUSIONS
1. The Pe procedure described here provides valid estimates of subglottal air pressure during continuous speech.
2. Balloon depths tested here do not affect the magnitude or linearity of esophageal pressures.
3. Additional participants are needed, as is a study of postural shifts.
REFERENCES
Kunze, L. (1964). Evaluation of methods of estimating sub-glottal air pressure. Journal of Speech and Hearing Research 7:
Liebermann, P . (1968). Direct comparison of subglottal and esophageal pressure during speech. Journal of the Acoustical Society of America (5):
Netsell, R. (1973). Speech Physiology. In Normal Aspects of Speech, Hearing, and Language (Minifie, Hixon, & Williams, Eds.). Prentice-Hall: Englewood Cliffs, NJ.
Slifka, J. (2003). Respiratory constraints on speech production: starting an utterance. Journal of the Acoustical Society of America (6):
VIASYS Healthcare (2007) Bird Center Drive. Palm Springs, CA.