What does airway resistance tell us about lung function?
Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. Airway  resistance is traditionally measured by relating air flow and driving pressure using body plethysmography, thus deriving airway resistance (R(aw)), specific airway resistance (sR(aw)), and specific airway conductance (sG(aw)). Other methods to measure airway resistance  include the forced oscillation technique (FOT), which allows calculation of respiratory system resistance (R(RS)) and reactance (X(RS)), and the interrupter technique, which allows calculation of interrupter resistance (R(int)). An advantage of these other methods  is that they may be easier to perform than spirometry, making them particularly suited to patients who cannot perform spirometry, such as young children, patients with neuromuscular disorders, or patients on mechanical ventilation. Since spirometry also requires a deep inhalation, which can  alter airway resistance, these alternative methods may provide more sensitive measures of airway resistance. Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique. However,  it is unclear whether any of these measures of airway resistance contribute clinically important information to the traditional measures derived from spirometry (FEV(1), FVC, and FEV(1)/FVC). The purpose of this paper is to review the physiology and methodology of these measures  of airway resistance, and then focus on their clinical utility in relation to each other and to spirometry.
Department of Pulmonary Disease and Critical Care Medicine, University of Vermont College of Medicine, Burlington, USA. david.kaminsky@uvm.edu
David A
DA
Kaminsky
D000403:Airway Resistance / Q000502:physiology; D001249:Asthma / Q000503:physiopathology; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000502:physiology* / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D012129:Respiratory Function Tests / Q000379:methods / Q000592:standards; D013147:Spirometry