Effect of altering smooth muscle tone on maximal expiratory flows in patients with tracheomalacia

Pediatr Pulmonol. 1990;9(3):170-6. doi: 10.1002/ppul.1950090309.


We obtained maximal partial expiratory flow-volume (PEFV) curves using the rapid compression technique in three infants with intrathoracic tracheomalacia. Maximum flows were quantitated at functional residual capacity (VmaxFRC). Studies were performed at baseline, after inhalation of methacholine (MCh) and after inhalation of albuterol. At baseline, all three patients had significantly lower than normal VmaxFRC values, and two patients displayed expiratory flow limitation during tidal breathing. VmaxFRC improved significantly after MCh administration, but fell back toward or below baseline after albuterol. Additionally, the ratio of forced to tidal flows at mid-tidal volume (Vmid(forced/tidal), a reflection of expiratory flow reserve, increased after MCh administration and decreased after albuterol. Two patients also received oral bethanechol: 2.9 mg/M2, q 8 hr for 10 days, after which PEFV curves were repeated. Both Vmax FRC and Vmid(forced/tidal) were increased over baseline after bethanechol administration, but decreased after albuterol. These results suggest that in patients with abnormally collapsible tracheae, stimulation of tracheal smooth muscle can improve airway stability, thereby increasing forced expiratory flows. Additionally, relaxation of airway smooth muscle by bronchodilators can have the opposite effect and exacerbate obstruction.

Publication types

  • Case Reports

MeSH terms

  • Albuterol / pharmacology
  • Albuterol / therapeutic use
  • Bethanechol
  • Bethanechol Compounds / pharmacology
  • Bethanechol Compounds / therapeutic use
  • Bronchoconstrictor Agents / pharmacology*
  • Bronchoconstrictor Agents / therapeutic use
  • Bronchodilator Agents / pharmacology*
  • Bronchodilator Agents / therapeutic use
  • Female
  • Functional Residual Capacity / drug effects
  • Humans
  • Infant
  • Male
  • Methacholine Chloride / pharmacology
  • Methacholine Chloride / therapeutic use
  • Muscle Tonus / drug effects
  • Muscle, Smooth / drug effects
  • Pulmonary Ventilation / drug effects*
  • Trachea / abnormalities*
  • Trachea / drug effects
  • Tracheal Stenosis / drug therapy


  • Bethanechol Compounds
  • Bronchoconstrictor Agents
  • Bronchodilator Agents
  • Bethanechol
  • Methacholine Chloride
  • Albuterol