Abstract
Preoperative respiratory function tests are important for evaluating the preoperative condition. To obtain an accurate measurement of respiratory function using spirometry, maximum expiratory effort by patients is necessary. However, under normal breathing and within a few minutes, the impulse oscillation system (IOS) can evaluate total airway resistance (R5), large airway resistance (R20), small airway resistance (R5-R20), and reactance (X5). Preoperative respiratory function assessments (IOS and spirometry) were done on 120 patients scheduled for elective surgery. The subjects were divided into three groups: normal respiratory function (%VC ≥ 80%, %FEV1.0 ≥ 70%), obstructive impairment (%VC ≥ 80%, %FEV1.0 ≥ 70%), and restrictive impairment (%VC ≥ 80%, %FEV1.0 ≥ 70%). Subjects were also divided into two age groups, 30-64 and 65-85 years. Spectrum pattern IOS results show that there was one abnormal pattern in the normal respiratory function group; and a significantly larger number of normal spectrum patterns, as well as a significantly larger number of peripheral airway obstructive spectrum patterns, in the obstructive and restrictive groups than in the normal respiratory function group. Because a conventional respiratory function test requires maximum expiratory efforts by the subject, reproducible and reliable evaluations are often difficult to obtain particularly with the aged. IOS, however, is a useful preoperative respiratory function tool that can be used for accurate measurements under normal breathing.
