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Expiratory pharyngeal narrowing during central hypocapnic hypopnea
Abdul Ghani Sankri-Tarbichi1, James A Rowley, M Safwan Badr
1Wayne State University Sleep Research Laboratory, John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan, USA. atarbich@med.wayne.edu
American Journal of Respiratory and Critical Care Medicine
|February 10, 2009
Summary
Central hypocapnic hypopnea causes expiratory pharyngeal narrowing and increased expiratory upper airway resistance. These findings suggest that central hypopneas can be considered obstructive events due to their effect on airway patency.
Area of Science:
- Respiratory Physiology
- Sleep Medicine
- Upper Airway Mechanics
Background:
- Ventilatory motor output is crucial for maintaining upper airway patency during sleep.
- Understanding factors influencing airway resistance during sleep is vital for diagnosing and treating sleep-disordered breathing.
Purpose of the Study:
- To test the hypothesis that central hypocapnic hypopnea increases expiratory upper airway resistance and causes pharyngeal narrowing during non-REM sleep.
- To investigate the relationship between ventilatory drive, airway resistance, and pharyngeal dimensions during induced hypopnea.
Main Methods:
- Noninvasive positive pressure ventilation was used to induce hypocapnic hypopnea in 20 healthy subjects.
- Retropalatal cross-sectional area (CSA) was measured using a nasopharyngoscope to assess pharyngeal narrowing.
- Upper airway resistance (R(UA)) was calculated by measuring supraglottic pressure and airflow.
Main Results:
- Expiratory pharyngeal cross-sectional area (CSA) significantly decreased during hypopneic breaths compared to eupneic breaths.
- Expiratory upper airway resistance (R(UA)) increased during hypopnea, while inspiratory resistance remained unchanged.
- Body mass index was identified as an independent predictor of retropalatal narrowing during hypopnea.
Conclusions:
- Central hypocapnic hypopnea leads to expiratory pharyngeal narrowing.
- Reduced ventilatory drive during central hypopneas increases expiratory, but not inspiratory, upper airway resistance.
- The observed pharyngeal narrowing suggests that central hypopneas can function as obstructive events, impacting airway patency.
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