title: Airway dysfunction in obesity: response to voluntary restoration of end expiratory lung volume.
abstract: BACKGROUND
  Abnormality in distal lung function may occur in obesity due to reduction in resting lung volume; however, airway inflammation, vascular congestion and/or concomitant intrinsic airway disease may also be present. The goal of this study is to 1) describe the phenotype of lung function in obese subjects utilizing spirometry, plethysmography and oscillometry; and 2) evaluate residual abnormality when the effect of mass loading is removed by voluntary elevation of end expiratory lung volume (EELV) to predicted FRC.
  
  
  METHODS
  100 non-smoking obese subjects without cardio-pulmonary disease and with normal airflow on spirometry underwent impulse oscillometry (IOS) at baseline and at the elevated EELV.
  
  
  RESULTS
  FRC and ERV were reduced (44 ± 22, 62 ± 14% predicted) with normal RV/TLC (29 ± 9%). IOS demonstrated elevated resistance at 20 Hz (R20, 4.65 ± 1.07 cmH2O/L/s); however, specific conductance was normal (0.14 ± 0.04). Resistance at 5-20 Hz (R5-20, 1.86 ± 1.11 cmH2O/L/s) and reactance at 5 Hz (X5, -2.70 ± 1.44 cmH2O/L/s) were abnormal. During elevation of EELV, IOS abnormalities reversed to or towards normal. Residual abnormality in R5-20 was observed in some subjects despite elevation of EELV (1.16 ± 0.8 cmH2O/L/s). R5-20 responded to bronchodilator at baseline but not during elevation of EELV.
  
  
  CONCLUSIONS
  This study describes the phenotype of lung dysfunction in obesity as reduction in FRC with airway narrowing, distal respiratory dysfunction and bronchodilator responsiveness. When R5-20 normalized during voluntary inflation, mass loading was considered the predominant mechanism. In contrast, when residual abnormality in R5-20 was demonstrable despite return of EELV to predicted FRC, mechanisms for airway dysfunction in addition to mass loading could be invoked.
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Beno W
authors: BW
authors: Oppenheimer
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Kenneth I
authors: KI
authors: Berger
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Leopoldo N
authors: LN
authors: Segal
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Alexandra
authors: A
authors: Stabile
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Katherine D
authors: KD
authors: Coles
authors: Bellevue Hospital Bariatric Center, Department of Surgery, New York University School of Medicine, New York, New York, United States of America.
authors: Manish
authors: M
authors: Parikh
authors: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Bellevue Hospital/New York University School of Medicine, New York, New York, United States of America.
authors: Roberta M
authors: RM
authors: Goldring
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D012120:Respiration Disorders / Q000503:physiopathology*; D012129:Respiratory Function Tests / Q000379:methods; D012137:Respiratory System / Q000503:physiopathology*; D013990:Tidal Volume / Q000502:physiology