airway dead space
Springer Online Journal Archives 1860-2000
Abstract Objective.An IBM PC-based real-time data acquisition, monitoringand analysis system was developed for the assessment of cardio-respiratoryfunction, i.e. airway dead space, alveolar volume and pulmonary blood flow,using oscillating inert inspired gas forcing signals. Methods.Theforcing gas mixture was generated by an in-house sinusoid gas delivery unit.The system interfaced with a mass spectrometer and an airway flow transducer,and performed real-time tracking of the breath-by-breath end-inspired,end-expired and mixed-expired concentrations. It calculated thecardio-respiratory parameters using two, i.e. continuous and tidal, in-housemathematical models of the lungs. The system's performance was evaluatedusing a mechanical bench lung, laboratory subjects and awake adults breathingspontaneously. Its predictive accuracy was compared with the measured volumesof the bench lung; single breath CO2 test for airway dead space andN2 washout for alveolar volume in laboratory subjects and awakeadults; and thermal dilution technique for pulmonary blood flow in laboratorysubjects. Results.Close agreements were found between the true andpredicted airway dead space, i.e. mean differences of –12.39%, 14.47%and –17.49%, respectively, and that of alveolar volume, i.e.–8.03%, –3.62% and 7.22%, respectively, in the bench lung,laboratory subject and awake adult studies; and that of pulmonary blood flow(–23.81%) in the laboratory subjects using the continuous lung model.Even closer agreements were observed for airway dead space (–5.8%) andalveolar volume (–4.01%) of the bench lung and for pulmonary blood flow(–8.47%) in the laboratory subjects using the tidal lung model.Conclusions.A system was developed to deliver, monitor and analyseon-line, and in real-time, output data from the sinusoid forcing technique.The technique was administered using the system in various subjects, andproduced favourable predictions.
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