title: Using helium-oxygen to improve regional deposition of inhaled particles: mechanical principles.
abstract: BACKGROUND
  Helium-oxygen has been used for decades as a respiratory therapy conjointly with aerosols. It has also been shown under some conditions to be a means to provide more peripheral, deeper, particle deposition for inhalation therapies. Furthermore, we can also consider deposition along parallel paths that are quite different, especially in a heterogeneous pathological lung. It is in this context that it is hypothesized that helium-oxygen can improve regional deposition, leading to more homogeneous deposition by increasing deposition in ventilation-deficient lung regions.
  
  
  METHODS
  Analytical models of inertial impaction, sedimentation, and diffusion are examined to illustrate the importance of gas property values on deposition distribution through both fluid mechanics- and particle mechanics-based mechanisms. Also considered are in vitro results from a bench model for a heterogeneously obstructed lung. In vivo results from three-dimensional (3D) imaging techniques provide visual examples of changes in particle deposition patterns in asthmatics that are further analyzed using computational fluid dynamics (CFD).
  
  
  CONCLUSIONS
  Based on analytical modeling, it is shown that deeper particle deposition is expected when breathing helium-oxygen, as compared with breathing air. A bench model has shown that more homogeneous ventilation distribution is possible breathing helium-oxygen in the presence of heterogeneous obstructions representative of central airway obstructions. 3D imaging of asthmatics has confirmed that aerosol delivery with a helium-oxygen carrier gas results in deeper and more homogeneous deposition distributions. CFD results are consistent with the in vivo imaging and suggest that the mechanics of gas particle interaction are the source of the differences seen in deposition patterns. However, intersubject variability in response to breathing helium-oxygen is expected, and an example of a nonresponder is shown where regional deposition is not significantly changed.
authors.affiliation: 1 R&D Medical Gases Group , Air Liquide Santé International, Les-Loges-en-Josas, France .
authors.forename: I
authors.initials: I
authors.lastname: Katz
authors.forename: M
authors.initials: M
authors.lastname: Pichelin
authors.forename: S
authors.initials: S
authors.lastname: Montesantos
authors.forename: C
authors.initials: C
authors.lastname: Majoral
authors.forename: A
authors.initials: A
authors.lastname: Martin
authors.forename: J
authors.initials: J
authors.lastname: Conway
authors.forename: J
authors.initials: J
authors.lastname: Fleming
authors.forename: J
authors.initials: J
authors.lastname: Venegas
authors.forename: E
authors.initials: E
authors.lastname: Greenblatt
authors.forename: G
authors.initials: G
authors.lastname: Caillibotte
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols; D001249:Asthma / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D016022:Case-Control Studies; D018592:Cross-Over Studies; D005740:Gases; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D008954:Models, Biological; D015609:Organotechnetium Compounds / Q000008:administration & dosage* / Q000378:metabolism*; D010102:Oxygen Inhalation Therapy; D010316:Particle Size; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000378:metabolism*; D012709:Serum Albumin / Q000008:administration & dosage* / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000336:Aerosols; D005740:Gases; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D012709:Serum Albumin; C107869:technetium Tc 99m serum albumin; D006371:Helium