Single breath carbon monoxide diffusing capacity (transfer factor)
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Carbon Monoxide↗
Biomedical subjects
H Imberger
Publications and source records attributed to H Imberger.
Plethysmography and the non-uniform lung--the measurement of the instantaneous energy-based airway resistance--a new concept.
The concept of work and energy is defined and the relation between airway resistance and the work required to move the air through the airways, in the case of spatially uniform lung pressure, is described. When the alveolar pressure is spatially non-uniform, the plethysmograph measures an average pressure (volume weighted). This measured average pressure is not zero at zero flow and consequently does not enable the simple determination of an airway resistance as in the case of the uniform lung. The measured mean alveolar pressure has the characteristics of a pressure measured across both a resistive pathway and an elastic membrane. This "elastic" component of the pressure can be simply subtracted (method of Mead and Whittenberger) and the consequently obtained airway resistance can be compared to that resistance which is directly based on the energy requirements. This procedure has been used in 59 individual representative modelled cases. On the whole, good agreement with the energy-based resistances has been obtained.
Airway Resistance↗
Airway conductance (Gaw) and FEV 1 changes with aerosol bronchodilator and underlying mechanics.
Airway conductance and FEV1 were measured in 25 patients before and after bronchodilator: Following bronchodilator, the correlation coefficient, r, between Gaw and FEV1 increased from 0.58 to 0.70 while there was almost negligible correlation (r = 0.1) between the respective Gaw and FEV1 changes. The lack of correlation is explained by the occurrence of saturated flow during a forced expiration, the saturated flow value also depending on the small airway resistance, the lung elastic recoil and the compressibility of the airway walls. It is concluded that the measurements are complementary but that the flow-alveolar pressure curve of a forced expiration or, better still, the measurement of the iso-volume alveolar pressure, flow curves, would contain the most information.
Airway Resistance↗
Elementary complex number analysis of lung models.
Formulae from the complex number method of network analysis are used by respiratory physiologists with increasing frequency. As yet, however, no elementary derivation of these has been found in physiological journals, the reader usually being referred to electronic texts: the derivations in these texts are not directed to respiratory problems and are generally more involved than required for respiratory purposes. The present presentation of the complex number analysis method is elementary, the necessary grounding in the field of complex numbers being given in an Appendix. The analysis is directed first to a one-compartment lung, then to a simple two-compartment lung (effectively the same method applying also to simple multiple-compartment lungs), and finally an indication is given of the analysis of more complex models that include air-compression effects. By gaining an understanding of the underlying principles the respiratory physiologist will improve the extent and depth of application of this powerful method of analysis. In particular, he will be in a position to analyse the body plethysmographic measurement of the non-uniform lung.
Airway Resistance↗
Increased upper airway resistance in patients with airway narrowing.
The mean air flow resistance of the orolaryngeal (upper) airway was significantly increased in 7 of 11 patients with chronic airway obstruction, when compared with 6 controls. All the patients had noisy respiration with harsh breath sounds audible by auscultation over the larynx. The increase in resistance was greater during expiration than during inspiration. Since 4 patients had normal upper airway resistance, the signs were not invariably associated with upper airway narrowing and presumably could arise also in the chest. When increased, upper airway resistance was usually more than half the total airway resistance. It is suggested that this increase could only be due to narrowing of the glottis, probably by muscle activity. This narrowing may have had the same function as expiration through pursed lips. On the other hand, when present, the increased resistance through the upper airway during inspiration is unlikely to have had a useful function.
Adult↗