• Resp Care · Sep 2004

    Comparative Study

    Correction of error in respiratory resistance measurements made with the flow-interruption technique during mechanical ventilation: evaluation of the puritan bennett 7200 and 840 ventilators.

    • Louis M Lit, Peter Doelken, and Paul H Mayo.
    • Department of Pulmonary and Critical Care Medicine, Beth Israel Medical Center, New York, NY, USA. lou_lit@hotmail.com.
    • Resp Care. 2004 Sep 1;49(9):1022-8.

    BackgroundCalculation of total inspiratory resistance (Rtot) for patients on ventilatory support is typically based on measurement of airflow velocity and airway opening pressure during end-inspiratory occlusion by the inspiratory valve in the ventilator. Systematic error is introduced into Rtot measurements because the inspiratory valve closes over a period of time (not instantaneously, so gas continues to flow into the circuit while the valve is shutting) and because the circuit tubing is a distensible compartment between the occluding valve and the respiratory system. The Rtot-measurement error can be minimized with a rapidly-shutting occlusion valve positioned at the airway opening, or, alternatively, by mathematical correction that accounts for the valve-closure period and circuit tubing characteristics.MethodsIn a bench study we measured Rtot with the Puritan Bennett 7200 and 840 ventilators (using the inspiratory valves that are built into those ventilators) and compared those measurements to measurements made with a rapidly-shutting valve at the airway opening. We deemed the rapid-occlusion-valve measurements the best available (benchmark) values. We also studied the closure characteristics of the ventilators' inspiratory occlusion valves and created equations for mathematical correction of Rtot values measured with those valves.ResultsCompared to the benchmark measurements, the measurements from the Puritan Bennett 7200 averaged 23.2% relative error and 2.6 cm H2O/L/s absolute error. Measurements from the Puritan Bennett 840 averaged 7.3% relative error and 1.0 cm H2O/L/s absolute error. Mathematical correction for the circuit tubing and valve-closure time reduced the average relative and absolute error to 3.0% and 0.4 cm H2O/L/s, respectively, for the Puritan Bennett 7200, and to 4.5% and 0.3 cm H2O/L/s, respectively, for the Puritan Bennett 840.ConclusionsThe Puritan Bennett 840 measures Rtot more accurately than the Puritan Bennett 7200. Our equations to mathematically correct Rtot measurements made with the PB7200 and PB840 are useful in settings where very accurate Rtot measurements are necessary.Copyright 2004 Daedalus Enterprises

      Pubmed     Free full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…