title: Estimation of Pharyngeal Collapsibility During Sleep by Peak Inspiratory Airflow.
abstract: Pharyngeal critical closing pressure (Pcrit) or collapsibility is a major determinant of obstructive sleep apnea (OSA) and may be used to predict the success/failure of non-continuous positive airway pressure (CPAP) therapies. Since its assessment involves overnight manipulation of CPAP, we sought to validate the peak inspiratory flow during natural sleep (without CPAP) as a simple surrogate measurement of collapsibility.
  
  
  
  Fourteen patients with OSA attended overnight polysomnography with pneumotachograph airflow. The middle third of the night (non-rapid eye movement sleep [NREM]) was dedicated to assessing Pcrit in passive and active states via abrupt and gradual CPAP pressure drops, respectively. Pcrit is the extrapolated CPAP pressure at which flow is zero. Peak and mid-inspiratory flow off CPAP was obtained from all breaths during sleep (excluding arousal) and compared with Pcrit.
  
  
  
  Active Pcrit, measured during NREM sleep, was strongly correlated with both peak and mid-inspiratory flow during NREM sleep (r = -0.71, p < .005 and r = -0.64, p < .05, respectively), indicating that active pharyngeal collapsibility can be reliably estimated from simple airflow measurements during polysomnography. However, there was no significant relationship between passive Pcrit, measured during NREM sleep, and peak or mid-inspiratory flow obtained from NREM sleep. Flow measurements during REM sleep were not significantly associated with active or passive Pcrit.
  
  
  
  Our study demonstrates the feasibility of estimating active Pcrit using flow measurements in patients with OSA. This method may enable clinicians to estimate pharyngeal collapsibility without sophisticated equipment and potentially aid in the selection of patients for non- positive airway pressure therapies.
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Ali
authors.initials: A
authors.lastname: Azarbarzin
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.|Department of Allergy Immunology and Respiratory Medicine and Central Clinical School, The Alfred and Monash University, Melbourne, Australia.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Sands
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Luigi
authors.initials: L
authors.lastname: Taranto-Montemurro
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.|Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas, University of São Paulo School of Medicine, São Paulo, Brazil.
authors.forename: Melania D
authors.initials: MD
authors.lastname: Oliveira Marques
authors.affiliation: Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas, University of São Paulo School of Medicine, São Paulo, Brazil.
authors.forename: Pedro R
authors.initials: PR
authors.lastname: Genta
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.|Sleep and Circadian Medicine Laboratory, Department of Physiology Monash University, Melbourne, Victoria, Australia.|School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne, Victoria, Australia.
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Edwards
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: James
authors.initials: J
authors.lastname: Butler
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: David P
authors.initials: DP
authors.lastname: White
authors.affiliation: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Andrew
authors.initials: A
authors.lastname: Wellman
mesh_terms: D001143:Arousal / Q000502:physiology; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000503:physiopathology*; D017286:Polysomnography; D011312:Pressure; D012119:Respiration; D012890:Sleep / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D012895:Sleep, REM / Q000502:physiology
keywords: active Pcrit; collapsibility; peak inspiratory flow; sleep apnea.