ATS Pulmonary Function Laboratory Manual

chapter  9

the laboratory should determine whether either Raw,insp or Raw,exp should be included as part of the data in a final report. Measurements of Raw alone are limited, since lung volume does play such an integral role. Therefore, lung vol- ume–adjusted values should be included when assessing the presence or degree of pulmonary dysfunction. Raw is commonly elevated with active asthma, chronic bronchitis, vocal cord stenosis, airway tumors, and small lung size (e.g., short stature individuals). Raw is often normal in emphysema, peripheral airways diseases, and possibly during asymptomatic asthma. sGaw is reduced in the presence of asthma, chronic bronchitis, peripheral airways disease and is normal in the presence of decreased lung size. Indications for Raw measurement are provided in Table 9.1

Table 9.1

Potential Indications for Raw Include

• Further evaluation of airflow limitation beyond spirometry (4) • Determining the response to bronchodilator (5) • Determination of bronchial hyperreactivity in response to methacholine, mannitol or isocapnic hyperventilation (6, 7)

• Differentiating types of obstructive lung diseases having similar spirometric configurations. • Distinguishing respiratory muscle weakness from obstruction as the cause of low flow rates • Following the course of disease and response to treatment (4)

Table 9.2

Equipment and Supplies 1. System description (e.g., XYZ Corp., Model 101 body plethysmograph) 2. Flow and volume measuring device used in the plethysmograph should meet or exceed American Thoracic Society (ATS)/European Respiratory Society (ERS) performance recommendations (8, 9) 3. Either pressure, volume, or flow-type plethysmograph may be used (4) 4. Transducers in the plethysmograph should meet the following specifications (10) • Presence of devices or other conditions, such as continuous intravenous infusions with pumps or other equip- ment that will not fit into the plethysmograph, that should not be disconnected, or that might interfere with pres- sure changes (e.g., chest tubes, transtracheal O 2 catheter, or ruptured eardrum) • Continuous O 2 therapy that should not be temporarily disconnected • Inability to pant in a smoothly coordinated fashion Relative contraindications for Raw Include • Mental confusion, muscular incoordination, body casts, or other conditions that prevent the patient from enter- ing the plethysmograph cabinet or adequately performing the required maneuvers (i.e., panting against a closed shutter). • Claustrophobia that may be aggravated by entering the plethysmograph cabinet

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