title: Inspiratory Capacity as an Indirect Measure of Immediate Effects of Positive Expiratory Pressure and CPAP Breathing on Functional Residual Capacity in Healthy Subjects.
abstract: BACKGROUND
  Positive expiratory pressure (PEP) and CPAP are used to enhance breathing parameters such as functional residual capacity (FRC) in patients. Studies comparing effects of PEP and CPAP on FRC are few and variable. One reason for this may be that sophisticated equipment, not suitable in the clinical setting, is required. Because total lung capacity (TLC) consists of inspiratory capacity (IC) and FRC, a change in IC should result in a corresponding change in FRC given constant TLC. We aimed to evaluate the effects of different PEP and CPAP devices on IC as an indirect measure of induced changes in FRC from these devices in healthy subjects.
  
  
  METHODS
  Twenty healthy subjects breathed with 2 PEP devices, a PEP mask (flow resistor) and a PEP bottle (threshold resistor), and 2 CPAP devices, a flow resistor and a threshold resistor, in a randomized order. The measurement sequence consisted of 30 breaths with an IC measurement performed before and immediately after the 30th breath while the subjects were still connected to the breathing device. Perceived exertion of the 30 breaths was measured with the Borg category ratio 10 scale.
  
  
  RESULTS
  Three of the 4 breathing devices, the PEP mask and the 2 CPAP devices, significantly decreased IC (P < .001). Median perceived exertion was quite low for all 4 breathing devices, but the difference in perceived exertion among the different breathing devices was large.
  
  
  CONCLUSIONS
  Provided that TLC is constant, we found that measurements of changes in IC could be used as an indirect measure of changes in FRC in healthy subjects. All investigated breathing devices except the PEP bottle decreased IC, as an indirect measure of increased FRC.
authors.affiliation: Department of Surgical and Perioperative Sciences, Anesthesiology and Intensive Care Medicine Department of Community Medicine and Rehabilitation, Physiotherapy Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden. maria.sehlin@umu.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Sehlin
authors.affiliation: Department of Surgical and Perioperative Sciences, Anesthesiology and Intensive Care Medicine.
authors.forename: Ola
authors.initials: O
authors.lastname: Winsö
authors.affiliation: Department of Community Medicine and Rehabilitation, Physiotherapy.
authors.forename: Karin
authors.initials: K
authors.lastname: Wadell
authors.affiliation: Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Öhberg
mesh_terms: D000328:Adult; D045422:Continuous Positive Airway Pressure; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012119:Respiration; D012129:Respiratory Function Tests; D014109:Total Lung Capacity / Q000502:physiology
keywords: Borg CR10 scale; CPAP; PEP; flow resistor; inspiratory capacity; threshold resistor