title: Influence of interface and position on upper airway collapsibility assessed by negative expiratory pressure.
abstract: OBJECTIVE
  Negative expiratory pressure (NEP) is a simple technique for the evaluation of upper airway collapsibility in patients with obstructive sleep apnea (OSA). Most studies evaluated NEP using a mouthpiece that may exclude the cephalic portion of the upper airway. We hypothesize that NEP determination is influenced by interface and position.
  
  
  METHODS
  We evaluated patients with suspected OSA using polysomnography, NEP (-5 cmH2O in sitting and supine position with mouthpiece and nasal mask). A subgroup also underwent computed tomography (CT) of the upper airway.
  
  
  RESULTS
  We studied a total of 86 subjects (72 male, age 46 ± 12 yrs, body mass index 30.0 ± 4.4 kg/m2, neck circumference 40.0 ± 3.5 cm, AHI 32.9 ± 26.4, range 0.5 to 122.5 events/hour). NEP was influenced by interface and position (p = 0.007), and upper airway was more collapsible with mouthpiece than with nasal mask in sitting position (p = 0.001). Position influenced NEP and was worse in supine only when evaluated by nasal mask. Expiratory resistance (R0.2) at 0.2 s during NEP was significantly higher and independent of position with mouthpiece than with nasal mask (20.7 versus 8.6 cmH2O/L s-1, respectively, p = 0.018). NEP evaluated with nasal mask in supine position and with mouthpiece in sitting position, but not when evaluated with mouthpiece in supine position, were correlated with upper airway anatomical measurements including tongue dimensions and pharyngeal length.
  
  
  CONCLUSIONS
  Interface and position influence NEP. NEP evaluated with nasal mask in supine position may convey more relevant information for patients under investigation for OSA than when evaluated with mouthpiece.
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Avenida Doutor Eneas de Carvalho Aguiar, 44, 8° Andar, Bloco I, CEP, São Paulo, SP, 05403-900, Brazil.
authors.forename: Raquel Pastrello
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, Avenida Doutor Eneas de Carvalho Aguiar, 44, 8° Andar, Bloco I, CEP, São Paulo, SP, 05403-900, Brazil.
authors.forename: Fabiane
authors.initials: F
authors.lastname: Kayamori
authors.affiliation: Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Avenida Doutor Eneas de Carvalho Aguiar, 44, 8° Andar, Bloco I, CEP, São Paulo, SP, 05403-900, Brazil.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Schorr
authors.affiliation: Biomedical Engineering Laboratory, Escola Politécnica, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Henrique Takachi
authors.initials: HT
authors.lastname: Moriya
authors.affiliation: Italian National Research Council, Institute of Biomedicine and Molecular Immunology A. Monroy, Palermo, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Romano
authors.affiliation: Italian National Research Council, Institute of Biomedicine and Molecular Immunology A. Monroy, Palermo, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Insalaco
authors.affiliation: Radiology Institute (InRad), Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Eloisa
authors.initials: E
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: LVF
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, Avenida Doutor Eneas de Carvalho Aguiar, 44, 8° Andar, Bloco I, CEP, São Paulo, SP, 05403-900, Brazil.
authors.forename: Pedro Rodrigues
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, Avenida Doutor Eneas de Carvalho Aguiar, 44, 8° Andar, Bloco I, CEP, São Paulo, SP, 05403-900, Brazil. geraldo.lorenzi@gmail.com.
authors.forename: Geraldo
authors.initials: G
authors.lastname: Lorenzi-Filho
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008397:Masks; D009666:Nose / Q000503:physiopathology; D010614:Pharynx / Q000503:physiopathology; D017286:Polysomnography; D011175:Positive-Pressure Respiration; D016684:Prone Position; D020181:Sleep Apnea, Obstructive / Q000628:therapy*; D014059:Tongue / Q000503:physiopathology
keywords: Anatomy; Obstructive sleep apnea; Pathophysiology; Pharynx; Supine position