title: Assessment of gas compression and lung volume during air stacking maneuver.
abstract: OBJECTIVE
  We reasoned that the application of positive pressure through air stacking (AS) technique could cause gas compression and the absolute lung volumes could be estimated. The aim of this study was to estimate the amount of gas compression (ΔVcomp) during AS in healthy subjects positioned at 45° trunk inclination and verify if the simultaneous measurements of chest wall volume changes (ΔVCW), by optoelectronic plethysmography, and changes in lung volume (ΔVao), by pneumotachograph, combined with pressure variation at the airways opening (ΔPao) during AS are able to provide reliable data on absolute lung volumes.
  
  
  METHODS
  Twenty healthy subjects (mean age 23.5 ± 3.8 years) were studied during a protocol that included slow vital capacity and AS maneuvers. Vcompwas calculated by subtracting ΔVaoand ΔVCWoccurring during AS and total lung capacity (TLC) was estimated by applying Boyle-Mariote's law using Vcompand ΔPao.
  
  
  RESULTS
  During AS, 0.140 ± 0.050 L of gas was compressed with an average ΔPaoof 21.78 ± 6.18 cmH2O. No significant differences between the estimated TLC (-0.03 ± 3.0% difference, p = 0.6020), estimated FRC (-2.0 ± 12.4% difference, p = 0.5172), measured IC (1.2 ± 11.2% difference, p = 0.7627) and predicted values were found.
  
  
  CONCLUSIONS
  During AS, a significant gas compression occurs and absolute lung volumes can be estimated by simultaneous measurements of ΔVCW, ΔVaoand ΔPao.
authors.affiliation: Laboratório de Desempenho PneumoCardioVascular e Músculos Respiratórios, Departamento de Fisioterapia, Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil.|PneumoCardioVascular Lab, Hospital Universitário Onofre Lopes, Empresa Brasileira de Serviços Hospitalares (EBSERH), UFRN, Natal, RN, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Sarmento
authors.affiliation: Laboratório de Desempenho PneumoCardioVascular e Músculos Respiratórios, Departamento de Fisioterapia, Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil.|PneumoCardioVascular Lab, Hospital Universitário Onofre Lopes, Empresa Brasileira de Serviços Hospitalares (EBSERH), UFRN, Natal, RN, Brazil.
authors.forename: V R
authors.initials: VR
authors.lastname: Resqueti
authors.affiliation: Laboratório de Desempenho PneumoCardioVascular e Músculos Respiratórios, Departamento de Fisioterapia, Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil.|PneumoCardioVascular Lab, Hospital Universitário Onofre Lopes, Empresa Brasileira de Serviços Hospitalares (EBSERH), UFRN, Natal, RN, Brazil.
authors.forename: G A F
authors.initials: GA
authors.lastname: Fregonezi
authors.affiliation: TBMLab, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milan, Italy. andrea.aliverti@polimi.it.
authors.forename: A
authors.initials: A
authors.lastname: Aliverti
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D010993:Plethysmography, Whole Body / Q000295:instrumentation / Q000379:methods; D012123:Pulmonary Ventilation; D014797:Vital Capacity
keywords: Absolute lung volumes; Air stacking; Boyle–Mariote’s law; Gas compression; Optoelectronic plethysmography