Voluntary changes in breathing pattern and N₂ clearance from lungs

Abstract

Lung N2 clearance curves were recorded in three normal and two symptom-free asthmatic subjects at breathing rates of 10—60/min and tidal volumes of 350—1,950 ml. A change toward more uniform gas distribution at larger tidal volumes was found in one subject. Changes in breathing rate did not affect gas distribution demonstrably. The washout ventilation per liter lung volume (lung clearance index) did not show significant changes with either breathing rate or tidal volume except for an increase at tidal volumes of less than 450 ml. These findings agree with the assumption of a constant dead space volume at tidal volumes within the range studied. The results are of practical importance for the use of the lung clearance index as a measure of the effect of broncho-active substances on the lung ventilation in man. Submitted on April 28, 1961

Validation of a Photoacoustic Gas Analyser for the Measurement of Functional Residual Capacity Using Multiple-Breath Inert Gas Washout

“…In addition, the device can simultaneously measure oxygen uptake and carbon dioxide production. At the heart of the Innocor device is a photoacoustic gas analyser, which is capable of measuring the concentrations of CO 2 , SF 6 and N 2 O at high accuracy and temporal resolution. A separate oxygen analyser is placed in series before the photoacoustic analyser.…”

“…The flow rate of SF 6 through the open circuit was increased sufficiently to allow complete wash-in of SF 6 .…”

“…In vivo Testing Procedure MBW was performed in triplicate at a single visit between the dates of June 15, 2010, and March 2, 2011, using the method initially described by Horsley et al [2] . Participants wore a nose clip and breathed an air mixture containing 0.2% SF 6 , via an opencircuit bypass flow system connected to an Innocor gas analyser, until the concentration in their exhaled breath reached a steady state. For in vivo tests a Douglas bag, fitted with a two-way valve, was utilised as a reservoir for SF 6 .…”

“…The current gold-standard MBW system is the respiratory mass spectrometer [1] , but this is expensive and lacks portability. An alternative system based upon a modified photoacoustic gas analyser (Innocor TM , Innovision A/S, Odense, Denmark) and 0.2% sulphur hexafluoride (SF 6 ) as the tracer gas has been developed, and shown to be both repeatable and practical [2] , but its accuracy has not been formally validated. The functional residual capacity (FRC) may be derived from an MBW by dividing the total volume of inert gas expired by the difference between the inert gas concentrations at the beginning and end of the washout period [3] .…”

“…A number of alternative techniques have recently been described. Objectives: We aimed to validate, using an in vitro lung model, an open-circuit MBW system that utilises a portable photoacoustic gas analyser, with sulphur hexafluoride (SF 6 ) as the inert tracer gas. Methods: An acrylic glass lung model was utilised to assess the accuracy of functional residual capacity (FRC) measurements derived from MBW.…”