title: Modification and testing of a pneumatic dispensing device for controlled delivery of injectable materials.
abstract: OBJECTIVE
  Vocal fold (VF) injections of viscous materials are typically performed using hand-operated syringes or injection guns; however, these methods can be imprecise due to accumulation of pressure, effort-related tremor, and poor feedback regarding injection volume and rate.
  
  
  METHODS
  Apparatus development with laboratory bench-top and animal model testing.
  
  
  METHODS
  A foot pedal-triggered device for dispensing viscous materials was modified by adding a linear transducer and display for monitoring dispensed volume. In bench tests, bovine VFs were injected with fluids/materials of different viscosities (saline, glycerol, hydrogel, and liposuctioned fat) through narrow-bore needles using a range of driving pressures and air pulse durations. The device was further evaluated in >50 in vivo VF injection experiments.
  
  
  RESULTS
  Device function was repeatable, with high correlations (typically R(2) > 0.98) between the readout and direct measures of volume, even for small volumes (<5 μL/pulse). Foot pedal control enabled surgeons to make steady, accurate injections into ferret and dog VFs during phonosurgery, and, because the dispenser released all driving pressure between pulses, there were no instances of clog-related overinjection when the obstruction cleared.
  
  
  CONCLUSIONS
  This VF injection system shows promise for development to enhance human phonosurgery by increasing injection control and precision.
authors.affiliation: Center for Laryngeal Surgery and Voice Rehabilitation, Massachusetts General Hospital, Boston, Massachusetts, USA. james.heaton@mgh.harvard.edu
authors.forename: James T
authors.initials: JT
authors.lastname: Heaton
authors.forename: James B
authors.initials: JB
authors.lastname: Kobler
authors.forename: Mark P
authors.initials: MP
authors.lastname: Ottensmeyer
authors.forename: Gerardo
authors.initials: G
authors.lastname: Lopez-Guerra
authors.forename: Sandeep S
authors.initials: SS
authors.lastname: Karajanagi
authors.forename: James A
authors.initials: JA
authors.lastname: Burns
authors.forename: Steven M
authors.initials: SM
authors.lastname: Zeitels
mesh_terms: D000273:Adipose Tissue / Q000637:transplantation; D000818:Animals; D002417:Cattle; D004285:Dogs; D016503:Drug Delivery Systems / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D005990:Glycerol / Q000494:pharmacology*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D066298:In Vitro Techniques; D015552:Injections, Intralesional; D023421:Models, Animal; D011312:Pressure; D012680:Sensitivity and Specificity; D013552:Swine; D020858:Tissue and Organ Harvesting; D014827:Vocal Cords / Q000187:drug effects* / Q000601:surgery
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D005990:Glycerol