title: Performance characteristics of upper airway critical collapsing pressure measurements during sleep.
abstract: OBJECTIVE
  The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant of the severity of upper airway obstruction during sleep. We examined the performance characteristics of the passive and active P(CRIT) by examining both within-night and between-night variability in the measurements.
  
  
  METHODS
  We studied 54 sleep apnea patients (39 men, 15 women) and 34 normal subjects (20 men, 14 women) on either 1 or 2 nights during sleep. The P(CRIT) was measured during relative hypotonia ("passive" state) or during periods of sustained upper airway obstruction used to recruit upper airway neuromuscular responses ("active" state) within- and between-nights. In a subgroup of 10 normal subjects, we performed repeated measurements during hypnotic-induced sleep. Bland-Altman analyses were used to determine the within-night and between-night reliability of the P(CRIT) measurements.
  
  
  RESULTS
  There were no significant within-night or between-night differences for the mean passive P(CRIT). The active P(CRIT) was ∼1 cm H(2)O more collapsible on the second night than on the first night. The limits of agreement, which bound the passive and active P(CRIT), was ∼ ± 3 cm H(2)O and was reduced to ∼ ± 1 cm H(2)O for the passive P(CRIT) with hypnotic-induced sleep.
  
  
  CONCLUSIONS
  Passive and active P(CRIT) measurements are reasonably reliable within and between nights. An approximately 3 cm H(2)O change in passive or active P(CRIT) appears to represent the minimally significant change in P(CRIT) necessary to assess the effect of an intervention (e.g., positional therapy, surgical interventions, oral appliance effects, and pharmacotherapy) on upper airway mechanical loads or neuromuscular responses.
authors: Johns Hopkins Sleep Disorders Center, Johns Hopkins School of Medicine, Baltimore, MD 21224, USA. Jason.Kirkness@jhmi.edu
authors: Jason P
authors: JP
authors: Kirkness
authors: Leigh A
authors: LA
authors: Peterson
authors: Samuel B
authors: SB
authors: Squier
authors: Brian M
authors: BM
authors: McGinley
authors: Hartmut
authors: H
authors: Schneider
authors: Adrian
authors: A
authors: Meyer
authors: Alan R
authors: AR
authors: Schwartz
authors: Philip L
authors: PL
authors: Smith
authors: Susheel P
authors: SP
authors: Patil
mesh_terms: D000328:Adult; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012137:Respiratory System / Q000503:physiopathology*; D012890:Sleep / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*