Mouth-opening increases upper-airway collapsibility without changing resistance during midazolam sedation.
Sedative doses of anesthetic agents affect upper-airway function. Oral-maxillofacial surgery is frequently performed on sedated patients whose mouths must be as open as possible if the procedures are to be accomplished successfully. We examined upper-airway pressure-flow relationships in closed mouths, mouths opened moderately, and mouths opened maximally to test the hypothesis that mouth-opening compromises upper-airway patency during midazolam sedation. From these relationships, upper-airway critical pressure (Pcrit) and upstream resistance (Rua) were derived. Maximal mouth-opening increased Pcrit to -3.6 +/- 2.9 cm H2O compared with -8.7 +/- 2.8 (p = 0.002) for closed mouths and -7.2 +/- 4.1 (p = 0.038) for mouths opened moderately. In contrast, Rua was similar in all three conditions (18.4 +/- 6.6 vs. 17.7 +/- 7.6 vs. 21.5 +/- 11.6 cm H2O/L/sec). Moreover, maximum mouth-opening produced an inspiratory airflow limitation at atmosphere that was eliminated when nasal pressure was adjusted to 4.3 +/- 2.7 cm H2O. We conclude that maximal mouth-opening increases upper-airway collapsibility, which contributes to upper-airway obstruction at atmosphere during midazolam sedation.
Nagasaki University Graduate School of Biomedical Science, Department of Clinical Physiology, 1-7-1 sakamoto Nagasaki-shi, 852-8588, Japan. ayuse@net.nagasaki-u.ac.jp
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Ayuse
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Inazawa
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Kurata
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Okayasu
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Sakamoto
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Oi
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Schneider
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Schwartz
D000328:Adult; D000402:Airway Obstruction / Q000209:etiology; D000403:Airway Resistance / Q000502:physiology*; D016292:Procedural Sedation; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage*; D001239:Inhalation / Q000502:physiology; D008297:Male; D008874:Midazolam / Q000008:administration & dosage*; D009055:Mouth / Q000502:physiology*; D009666:Nose / Q000502:physiology; D010614:Pharynx / Q000502:physiology*; D017286:Polysomnography; D011312:Pressure; D012123:Pulmonary Ventilation / Q000502:physiology
D006993:Hypnotics and Sedatives; D008874:Midazolam