Chapter 26
- Pulmonary Function Testing
- Thomas J. Gal
Pulmonary function testing continues to play a role in traditional
preoperative evaluation of patients undergoing major surgery. Although it is simple
and risk free, such testing is often performed in a reflex fashion without real indications
because of limited physiologic and clinical insight on the part of many practicing
physicians. As a result, these practitioners are often uncomfortable interpreting
test data and are unsure about what the data mean or what was actually measured.
Such preoperative screening is aimed at identifying individuals
with abnormal lung function not so much to detect unrecognized disease as to quantitate
its severity in the hope of reducing the risk of postoperative ventilatory impairment
and other respiratory complications. The subjective information provided by the
medical history and the findings on physical examination seldom identify the actual
abnormalities of respiratory function, and the findings are often poor indicators
of the severity of disease. In contrast, pulmonary function testing provides objective,
standardized measurements for assessing the presence and severity of respiratory
dysfunction. These measurements also enable the clinician to monitor the progression
of any impairment and to document the response to therapy (e.g., bronchodilators).
The tests fall into two major groups: those that detect abnormalities of gas exchange
and those related to the mechanical ventilatory function of the lungs and chest wall.
This discussion deals principally with the latter group.
The cornerstone of all pulmonary function testing is clinical
spirometry. There are numerous other tests, including some that purport to indicate
abnormalities of gas exchange. This chapter reviews the measurement techniques and
interprets the physiologic basis and significance of many of these tests. The aim
is to provide a better understanding of the defects identified by each testing scheme.
Such information does not merely serve to impress a board examiner or a colleague;
it also enhances the anesthesiologist's role as a consultant in the rational perioperative
management of the cases evaluated. Management considerations include the risk of
postoperative morbidity, resectability of lung tissue, and management of the anesthetic.
