Expiratory flow limitation and intrinsic positive end-expiratory pressure in obesity.
Breathing at very low lung volumes might be affected by decreased expiratory airflow and air trapping. Our purpose was to detect expiratory flow limitation (EFL) and, as a consequence, intrinsic positive end-expiratory pressure (PEEPi) in grossly obese subjects (OS). Eight OS with a mean body mass index (BMI) of 44 +/- 5 kg/m2 and six age-matched normal-weight control subjects (CS) were studied in different body positions. Negative expiratory pressure (NEP) was used to determine EFL. In contrast to CS, EFL was found in two of eight OS in the upright position and in seven of eight OS in the supine position. Dynamic PEEPi and mean transdiaphragmatic pressure (mean Pdi) were measured in all six CS and in six of eight OS. In OS, PEEPi increased from 0.14 +/- 0.06 (SD) kPa in the upright position to 0.41 +/- 0.11 kPa in the supine position (P < 0.05) and decreased to 0.20 +/- 0.08 kPa in the right lateral position (P < 0.05, compared with supine), whereas, in CS, PEEPi was significantly smaller (<0.05 kPa) in each position. In OS, mean Pdi in each position was significantly larger compared with CS. Mean Pdi increased from 1.02 +/- 0.32 kPa in the upright position to 1.26 +/- 0.17 kPa in the supine position (not significant) and decreased to 1. 06 +/- 0.26 kPa in the right lateral position (P < 0.05, compared with supine), whereas there were no significant changes in CS. We conclude that in OS 1) tidal breathing can be affected by EFL and PEEPi; 2) EFL and PEEPi are promoted by the supine posture; and 3) the increased diaphragmatic load in the supine position is, in part, related to PEEPi.
Department of Internal Medicine, Medizinische Poliklinik, Schlafmedizinisches Labor, Philipps-University Marburg, D-32033 Marburg, Germany.
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W
Pankow
T
T
Podszus
T
T
Gutheil
T
T
Penzel
J
J
Peter
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Von Wichert
D000328:Adult; D000403:Airway Resistance; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000097:blood; D005105:Expiratory Reserve Volume / Q000502:physiology; D005260:Female; D005540:Forced Expiratory Flow Rates / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D014797:Vital Capacity
D002245:Carbon Dioxide; D010100:Oxygen