title: Chest vibration redistributes intra-airway CO2 during tracheal insufflation in ventilatory failure.
abstract: OBJECTIVE
  To determine if high-frequency external chest wall vibration added to low flow intratracheal fresh gas insufflation alters the intra-airway CO2 distribution and the resistance to CO2 transport from the lungs.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Experimental laboratory.
  
  
  METHODS
  Six adult anesthesized and paralyzed mongrel dogs (mean weight 24.3+/- 4.4 kg).
  
  
  METHODS
  Dogs were ventilated by three methods: a) intermittent positive pressure ventilation; b) intermittent positive pressure ventilation with tracheal insufflation of fresh gas (FIO2 of 0.4) flowing at 0.15 L/kg/min through a catheter positioned at the carina; and c) intermittent positive pressure ventilation with tracheal insufflation and with external high-frequency chest wall vibration of the dependent hemithorax.
  
  
  RESULTS
  We measured arterial blood gas values as an index of global gas exchange, and intrapulmonary airway CO2 concentrations as an index of local gas exchange. Intra-airway CO2 concentrations along the axis of the airways were measured via a sampling catheter. Airway axial concentration profiles were constructed and resistances to gas transport were calculated from the measured data. Vibration increased intraluminal CO2 concentrations from 1.1% to 2.5% mouthward of the insufflation catheter tip. Peak resistance to CO2 transport decreased by 65% during vibration relative to the insufflation-only value. Vibration displaced peak transport resistance from second- to fourth-generation airways.
  
  
  CONCLUSIONS
  Global gas exchange improves during ventilation by chest wall vibration with low flow insufflation. Local gas exchange in the central airways is also improved due to increased intraluminal mixing and CO2 elimination. This ventilation technique may confer therapeutic advantages over conventional mechanical ventilation in the treatment of ventilatory failure.
authors.affiliation: Department of Anesthesia, Northwestern University Medical School, Evanston, Illinois, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Eckmann
authors.forename: N
authors.initials: N
authors.lastname: Gavriely
mesh_terms: D000403:Airway Resistance; D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000502:physiology*; D004195:Disease Models, Animal; D004285:Dogs; D007327:Insufflation; D008168:Lung / Q000503:physiopathology*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D013909:Thorax; D014132:Trachea; D014732:Vibration / Q000627:therapeutic use*
chemical_list: D002245:Carbon Dioxide