PT  - JOURNAL ARTICLE
AU  - Winfried Randerath
AU  - Norbert Anduleit
AU  - Marcel Treml
AU  - Christof Goebel
TI  - Impact of leakage on external flow measurement in non-invasive ventilation
DP  - 2012 Sep 01
TA  - European Respiratory Journal
PG  - 2857
VI  - 40
IP  - Suppl 56
4099  - http://erj.ersjournals.com/content/40/Suppl_56/2857.short
4100  - http://erj.ersjournals.com/content/40/Suppl_56/2857.full
SO  - Eur Respir J2012 Sep 01; 40
AB  - BackgroundExternal flow sensors can be helpful to assess parameters such as tidal volume (VT) or minute ventilation in non-invasive ventilation (NIV). The impact of mask leakage on the reliability of those results is in question.MethodsA NIV device (VENTImotion 2, Weinmann) was connected via standard tubing to an exhalation system (SilentFlow 2), followed by flow sensor (Hamilton Medical) and leak valve. At the end of this setup a calibration syringe (Hans Rudolph) set to 500ml VT was connected. In T mode we recorded device and flow sensor parameters. Leak (measured by NIV device) was varied from ca. 20 (leak valve closed) to ca. 70 l/min. Externally measured and device VT were compared.ResultsView this table:1. With growing leak the externally measured (expiratory) VT (VTe) decreased substantially, while standard deviation increased.2. Device VT is less leakage-dependent and more stable.ConclusionsExternally measured VT is only reliable when mask leakage is minimal. Since measurement is based on airflow inside the sensor, other derived parameters are also affected. The corrected VT from the internal sensor of the NIV device is much less susceptible to leakage but tends to overestimate the actual VT in the setup we used. When exact measurements are crucial, beforehand assessment of results under controlled conditions is advisable.