title: Interrupter mechanics of patients admitted to a chronic ventilator dependency unit.
abstract: We analyzed the results of interrupter mechanics tests of 73 consecutive patients who were admitted to a chronic ventilator dependency unit. The purposes of this study were (1) to establish guidelines for grading the severity of airway obstruction based on interrupter mechanics measurements; (2) to estimate the prevalence of airway obstruction in this population; (3) to compare interrupter test results with the clinical assessment of airway function; and (4) to characterize the distribution of bronchodilator-induced changes in isorecoil flow. Measurements from 65 of 73 patients (89%) were considered technically adequate. Of 65 patients, 29 (45%) showed signs of flow limitation during passive expiration. All patients with severe obstruction documented with spirometry during clinical stability were flow-limited and achieved maximal flows < or = 0.45 L/s at recoil pressures of 10 cm H2O. In contrast to measures of expiratory dynamics, the inspiratory resistance of the respiratory system was a poor index of severity of obstruction. In seven of 12 patients, interrupter testing failed to substantiate a clinical diagnosis of severe obstruction while revealing unsuspected obstruction in six of 25 (24%) patients. The administration of 270 micrograms of albuterol increased flows at comparable recoil pressures by > or = 0.1 L/s in 29% of 41 patients. Changes in flow were unimodally distributed and were not correlated with severity of obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Thoracic Disease and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: M A
authors.initials: MA
authors.lastname: Reinoso
authors.forename: D R
authors.initials: DR
authors.lastname: Gracey
authors.forename: R D
authors.initials: RD
authors.lastname: Hubmayr
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000420:Albuterol / Q000008:administration & dosage; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012121:Respiration, Artificial / Q000379:methods / Q000706:statistics & numerical data; D012129:Respiratory Function Tests / Q000379:methods / Q000706:statistics & numerical data; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology / Q000628:therapy; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D000420:Albuterol