title: Upper Airway Collapsibility Assessed by Negative Expiratory Pressure while Awake is Associated with Upper Airway Anatomy.
abstract: There is a growing interest to develop a simple method to characterize the mechanisms leading to upper airway collapse in order to guide treatment options in patients with obstructive sleep apnea (OSA). Critical closing pressure (Pcrit) during sleep is able to predict the anatomical component of OSA. However, Pcrit is a laborious method that is only used for research purposes. The application of negative expiratory pressure (NEP) is a simple method to assess upper airway collapsibility that can be easily performed during wakefulness. We hypothesized that NEP will be, similarly to Pcrit, associated with upper airway anatomy assessed by computed tomography (CT) scan.
  
  
  
  Patients under investigation for OSA underwent polysomnography, CT of the upper airway, NEP while awake, and Pcrit during sleep. NEP was performed with -5 cm H2O in supine position using a nasal mask. Pcrit was measured during sleep induced by low doses of midazolam.
  
  
  
  Twenty-eight male subjects were studied (age 45 ± 13 y, body mass index 29.4 ± 4.9 kg/m2, apnea-hypopnea index (AHI) 30 ± 26, range 2 to 86 events/h). NEP and Pcrit were similarly associated with tongue area (r = 0.646 and r = 0.585), tongue volume (r = 0.565 and r = 0.613) and pharyngeal length (r = 0.580 and r = 0.611), respectively (p < 0.05 for all comparisons). NEP and Pcrit were also significantly correlated with AHI (r = 0.490 and r = 0.531). NEP and Pcrit were significantly higher in patients with severe OSA than the remaining population.
  
  
  
  NEP is a simple and promising method that is associated with the anatomical component of upper airway collapsibility. NEP may be valuable to select patients for noncontinuous positive airway pressure alternative therapies for OSA.
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Raquel P
authors.initials: RP
authors.lastname: Hirata
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Schorr
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Fabiane
authors.initials: F
authors.lastname: Kayamori
authors.affiliation: Biomedical Engineering Laboratory, Escola Politécnica, Universidade de São Paulo, Brazil.
authors.forename: Henrique Takachi
authors.initials: HT
authors.lastname: Moriya
authors.affiliation: Institute of Biomedicine and Molecular Immunology A. Monroy, Italian National Research Council, Palermo, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Romano
authors.affiliation: Institute of Biomedicine and Molecular Immunology A. Monroy, Italian National Research Council, Palermo, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Insalaco
authors.affiliation: Radiology Institute (InRad), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Eloisa M
authors.initials: EM
authors.lastname: Gebrim
authors.affiliation: Rehabilitation Sciences Master and Doctoral Program, Universidade Nove de Julho, São Paulo, Brazil.
authors.forename: Luis Vicente Franco
authors.initials: LV
authors.lastname: de Oliveira
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Pedro R
authors.initials: PR
authors.lastname: Genta
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
authors.forename: Geraldo
authors.initials: G
authors.lastname: Lorenzi-Filho
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000503:physiopathology*; D045853:Exhalation / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017286:Polysomnography; D011312:Pressure; D020181:Sleep Apnea, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D014851:Wakefulness; D055815:Young Adult
keywords: anatomy; computed tomography; obstructive sleep apnea; pathophysiology; pharynx