Airway and lung tissue mechanics in asthma. Effects of albuterol

Am J Respir Crit Care Med. 1999 Jan;159(1):169-78. doi: 10.1164/ajrccm.159.1.9709109.


We examined the partitioning of total lung resistance (RL) into airway resistance (Raw) and tissue resistance (Rti) in patients with mild to moderate asthma (baseline FEV1, 54 to 91% of predicted) before and after albuterol inhalation. An optimal ventilator waveform was used to measure RL and lung elastance (EL) in 21 asthmatics from approximately 0.1 to 8 Hz during tidal excursions. Analysis of the RL and EL provided separate estimates of airway and lung tissue properties. Eleven subjects, classified as Type A asthmatics, displayed slightly elevated RL but normal EL. Their data were well described with a model consisting of homogeneous airways leading to viscoelastic tissues before and after albuterol. The other 10 subjects, classified as Type B asthmatics, demonstrated highly elevated RL and an EL that became highly elevated at frequencies above 2 Hz. These subjects required the inclusion of an airway wall compliance in the model prealbuterol but not postalbuterol. This suggests that the Type B subjects were experiencing pronounced constriction in the periphery of the lung, resulting in shunting of flow into the airway walls. Spirometric data were consistent with higher constriction in Type B subjects. Both groups demonstrated significant (p < 0.05) decreases in Raw and tissue damping after albuterol, but tissue elastance decreased only in the Type B group. The percent contributions of Raw and Rti to RL were similar in both groups and did not change after albuterol. We conclude that in asthma, Raw comprises the majority (> 70%) of RL at breathing frequencies. The relative contributions of Raw and Rti to RL appear to be independent of the degree of smooth muscle constriction.

Publication types

  • Clinical Trial

MeSH terms

  • Administration, Inhalation
  • Adolescent
  • Adult
  • Airway Resistance / drug effects
  • Airway Resistance / physiology*
  • Albuterol / administration & dosage
  • Albuterol / therapeutic use*
  • Asthma / drug therapy*
  • Asthma / physiopathology*
  • Bronchodilator Agents / administration & dosage
  • Bronchodilator Agents / therapeutic use*
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Lung Compliance / drug effects
  • Lung Compliance / physiology*
  • Male
  • Middle Aged
  • Respiratory Mechanics / drug effects
  • Spirometry


  • Bronchodilator Agents
  • Albuterol