PMID- 9847295
OWN - NLM
STAT- MEDLINE
DCOM- 19990125
LR  - 20081121
IS  - 1073-449X (Print)
IS  - 1073-449X (Linking)
VI  - 158
IP  - 6
DP  - 1998 Dec
TI  - Progressive retropalatal narrowing preceding obstructive apnea.
PG  - 1974-81
AB  - Pharyngeal occlusion during obstructive apnea is thought to be an 
      inspiratory-related event; however, occlusion also occurs in the absence of 
      negative intrathoracic pressure. We hypothesized that inspiratory-related 
      pharyngeal occlusion would be preceded by significant expiratory narrowing. Eight 
      sleeping patients with obstructive apnea were studied. Pharyngeal caliber, 
      airflow, and esophageal pressure (Pes) were simultaneously monitored during three 
      to four consecutive breaths preceding occlusion (between 3 and 22 events were 
      studied per subject). Relative changes in retropalatal airway cross-sectional 
      area (CSA) were determined from fiberoptic images (five frames per second) 
      normalized to the maximum CSA. During inspiration, CSA was significantly reduced 
      only during the breath immediately preceding the apnea (Group mean CSA +/- SEM: 
      51 +/- 8% at the start of inspiration compared with 37 +/- 8% at midinspiration). 
      During expiration, for all breaths there was an initial significant increase in 
      CSA compared with the nadir CSA during the preceding inspiration (CSA: breath-3, 
      57 +/- 10% to 79 +/- 3%; breath-2, 59 +/- 8% to 76 +/- 4%; breath-1, 37 +/- 8% to 
      64 +/- 8%), followed by a significant narrowing at end-expiration compared with 
      the peak CSA during that expiration (CSA: breath-3, 79 +/- 3% to 62 +/- 6%; 
      breath-2, 76 +/- 4% to 50 +/- 10%; breath-1, 64 +/- 8% to 36 +/- 10%). Occlusion 
      occurred at a pressure significantly less than that generated during the previous 
      unoccluded breath (Pes: breath-1, -10.8 +/- 2.9 cm H2O; occlusion, -8.2 +/- 1.9 
      cm H2O). These results show that expiratory narrowing produced a significant 
      reduction of CSA at end-expiration prior to obstructive apnea.
FAU - Morrell, M J
AU  - Morrell MJ
AD  - William S. Middleton Memorial Veterans Hospital, Department of Preventive 
      Medicine, University of Wisconsin Medical School, Madison, Wisconsin, USA.
FAU - Arabi, Y
AU  - Arabi Y
FAU - Zahn, B
AU  - Zahn B
FAU - Badr, M S
AU  - Badr MS
LA  - eng
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PL  - United States
TA  - Am J Respir Crit Care Med
JT  - American journal of respiratory and critical care medicine
JID - 9421642
SB  - IM
MH  - Adult
MH  - Aged
MH  - Aged, 80 and over
MH  - Anatomy, Cross-Sectional
MH  - Endoscopes
MH  - Esophagus/physiopathology
MH  - Female
MH  - Fiber Optic Technology/instrumentation
MH  - Humans
MH  - Inhalation/physiology
MH  - Male
MH  - Middle Aged
MH  - Palate, Soft
MH  - Pharynx/*pathology/physiopathology
MH  - Polysomnography
MH  - Pressure
MH  - Pulmonary Ventilation/physiology
MH  - Respiration
MH  - Sleep Apnea Syndromes/*etiology/physiopathology
MH  - Tidal Volume/physiology
MH  - Time Factors
EDAT- 1998/12/16 00:00
MHDA- 1998/12/16 00:01
CRDT- 1998/12/16 00:00
PHST- 1998/12/16 00:00 [pubmed]
PHST- 1998/12/16 00:01 [medline]
PHST- 1998/12/16 00:00 [entrez]
AID - 10.1164/ajrccm.158.6.9712107 [doi]
PST - ppublish
SO  - Am J Respir Crit Care Med. 1998 Dec;158(6):1974-81. doi: 
      10.1164/ajrccm.158.6.9712107.