The need for ethnic-specific reference values of lung function variables (LFs) is acknowledged. Their estimation requires expensive and laborious examinations, and therefore additional use of results in physiology and epidemiology would be profitable. To this end, we proposed a form of prediction equations with physiologically interpretable coefficients: a baseline, the onset age (A0) and rate (S) of LF decline, and a height coefficient. The form was tested with data from healthy, nonsmoking Poles aged 18-85 yr (1,120 men, 1,625 women) who performed spirometry maneuvers according to American Thoracic Society criteria. The values of all the coefficients (also A0) for several LFs were determined with regression of LF on patient's age and deviation of patient's height from the mean height in the year group of this patient. S values for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow, and maximal expiratory flow at 75% of FVC (MEF75) were very similar in both sexes (1.03+/-0.07%/yr). FEV1/FVC declines four to five times slower. S for MEF25 appeared age dependent. A0 was smallest (28-32 yr) for MEF25 and FEV1. About 50% of each age subgroup (18-40, 41-60, 61-85 yr) exhibited LFs below the mean, and 4-6% were below the 5th percentile lower limits of normal, and thus the form of equations proposed in the paper appeared appropriate for spirometry. Additionally, if this form is accepted, epidemiological and physiological comparison of different LFs and populations will be possible by means of direct comparison of the equation coefficients.
Background Due to economic and ethical problems, virtual organs may appear more convenient than experiments on animals or limited investigations on patients. In particular, a virtual respiratory system (VRS) may be useful for tasks such as respirators and support methods testing, education, staff (medical and technical) training, (initial) testing of scientific hypotheses. Methods A comparative study of simulated and real spirometric results for different patient states (healthy lungs, restrictive lung disease, and obstructive lung disease of different localization and degree) was performed. The volume-flow curve and such standard parameters as FEV1, FEV1%VC, MEF75 etc. were analyzed. Results A mathematical description of collapsing bronchi was proposed. All fundamental phenomena present during spirometry also appeared in VRS, especially characteristic dependence between lung volume and air flow for forced expiration. In particular, both airway resistance and the flow limitation were described with one formula derived from commonly known dependence of the resistance on lung volume. Generally there were no significant differences between simulated results and those seen in clinical practice. Only simulation of obstruction in upper airways gave incorrect results, which suggested a different flow limitation mechanism (perhaps wave-speed limitation). Conclusions Our VRS can already be used in medical education, e.g. courses of spirometry, and in some other applications. It seems that the significance of the wave-speed criterion has been overestimated.
Background: Measurement of intrapleural pressure is useful during various pleural procedures. However, a pleural manometer is rarely available. Objectives: The aim of this study was to (1) construct an electronic pleural manometer, (2) assess the accuracy of the measurements done with the new device, (3) calculate the costs of the manometer construction and (4) perform an initial evaluation of the device in a clinical setting. Methods: Only widely accessible elements were used to construct the device. A vascular pressure transducer was used to transform pressure into an electronic signal. Reliability of the measurements was evaluated in a laboratory setting in a prospective, single-blind manner by comparing the results with those measured by a water manometer. Functionality of the device was assessed during therapeutic thoracentesis. The cost of the new pleural manometer was calculated. Results: We built a small, portable device which can precisely measure intrapleural pressure. The measurement results showed very high agreement with those registered with a water manometer (r = 0.999; p < 0.001). The initial evaluation of the electronic manometer during therapeutic thoracentesis showed it was easy to use. The total time needed for 6 measurements after withdrawal of different volumes of pleural fluid in 1 patient did not exceed 6 min. The total cost of the device was calculated to be <2,000 EUR. Conclusions: In the face of very limited offer of commercially available pleural manometers, it is possible to successfully construct a self-made, reliable, electronic pleural manometer at modest costs. The device is easy to use and enables data display and storage in the personal computer.
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