Intensive Care Medicine

, Volume 27, Issue 12, pp 1887–1891

Mask mechanics and leak dynamics during noninvasive pressure support ventilation: a bench study

  • Guilherme Schettino
  • Mauro Tucci
  • Rogério Sousa
  • Carmen Barbas
  • Marcelo Amato
  • Carlos Carvalho
Original

DOI: 10.1007/s00134-001-1146-9

Cite this article as:
Schettino, G., Tucci, M., Sousa, R. et al. Intensive Care Med (2001) 27: 1887. doi:10.1007/s00134-001-1146-9

Abstract.

Objective: To study the mask mechanics and air leak dynamics during noninvasive pressure support ventilation. Setting: Laboratory of a university hospital. Design: A facial mask was connected to a mannequin head that was part of a mechanical respiratory system model. The mask fit pressure (Pmask-fit) measured inside the mask's pneumatic cushion was adjusted to 25 cmH2O using elastic straps. Pressure support (PS) was set to ensure a maximal tidal volume distal to the mask (VTdistal) but avoiding failure to cycle to exhalation. Measurements: Airway pressure (Paw), Pmask-fit, mask occlusion pressure (Pmask-occl=Pmask-fit–Paw), VT proximal (VTprox), distal to the mask (VTdistal), air leak volume (Leak=VTprox–VTdistal), and inspiratory air leak flow rate (difference between inspiratory flow proximal and distal to the mask) were recorded. Results: PS 15 cmH2O was the highest level that could be used without failure to cycle to exhalation (VTdistal of 585±4 ml, leak of 32±1 ml or 5.2±0.2% of VTprox, and a minimum Pmask-occl of 1.7±0.1 cmH2O). During PS 16 cmH2O the Pmask-occl dropped to 1.1±0.1 cmH2O, and at this point all flow delivered by the ventilator leaked around the mask, preventing the inspiratory flow delivered by the ventilator from reaching the expiratory trigger threshold. Conclusion: Pmask-fit and Pmask-occl can be easily measured in pneumatic cushioned masks and the data obtained may be useful to guide mask fit and inspiratory pressure set during noninvasive positive pressure ventilation.

Noninvasive positive pressure ventilation Facial mask Mask mechanics Air leak 

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Guilherme Schettino
    • 1
  • Mauro Tucci
    • 1
  • Rogério Sousa
    • 1
  • Carmen Barbas
    • 1
  • Marcelo Amato
    • 1
  • Carlos Carvalho
    • 1
  1. 1.Experimental Laboratory of Mechanical Ventilation, Respiratory ICU, Pulmonary Division, Hospital das Clínicas and Heart Institute, University of São Paulo Medical School, São PauloBrazil
  2. 2.Rua Maria Figueiredo 396 Apt. 141, São Paulo, SP, CEP 04002-002Brazil