We have calculated pulmonary mechanics on six human subjects using a digital computer to least squares fit the equation describing pulmonary mechanics:
for the constants C and R, during both the inspiratory and expiratory cycles. Values for compliance and resistance were found to be statistically identical with those calculated by methods which use isolated points in the breathing cycle. No difference in mechanics was observed between inspiration and expiration. The method's advantages over isolatedpoints methods are that best-fit parameters are better representations; it calculates parameters independently for inspiration and expiration; and it functions in real time.
Electronic computers are being used in monitoring physiologic changes in hospitalized patients (1-3). Use of least squares fitting to calculate resistance and compliance was first reported by Wald and his colleagues (4, 5) who reported the results of analyses of 1000 breaths in one anesthetized subject. Their technique necessitated least squares fitting for three parameters-compliance, resistance, plus a variable voltage offset of their intraesophageal pressure transducer due to temperature unbalance and drift. We wished to know whether similar results could be obtained by least squares fit for two parameters only, compliance and resistance, using an intraesophageal balloon and external pressure transducer, thereby mechanically eliminating any offset caused by temperature and drift.
Theoretically, one would anticipate that digital-computer least squares solution would be the most accurate method of mechanics calculation, since one can utilize a large number of continuous data points (25/set) in the breathing cycle rather than a few isolated points which are conventionally used when calculating mechanics