| Description |
Scientists have long known that the mechanics of normal spontaneous breathing are fundamentally different from those of breathing under other conditions. Due to advances in computer and electronic technology over the past few decades, videoradiodensitometry, which was initially introduced in the 1960s, is once again a feasible technique for studying the mammalian respiratory system under relatively natural (i.e. non-invasive) conditions. To explore the extent to which modern videoradiodensitometric methods may be useful, I have used a combination of radiodensity volumetric (RDV) and radiodensity displacement (RDD) techniques to monitor the dynamics of lung ventilation in spontaneously breathing and artificially ventilated supine, anesthetized dogs. From these data, I report the development of two models of spontaneous breathing. The models document some of the natural variation associated with the mechanics of respiration in anesthetized mammals and provide a preliminary functional interpretation of these different patterns of breathing. To further demonstrate the usefulness of videoradiodensitometry, I also present a description of the regional dynamics of pulmonary gas flow during ventilated and spontaneous breathing. These data provide direct support for the long-held notion that the ventilation of various regions of the lung may be substantially unequal and asynchronous. They also suggest that positive (artificial) and negative (spontaneous) pressure breathing have very different effects on the thoracic organs, particularly the heart and the cranial regions of the apical lobes of the lungs. Finally, I assess the current limitations of videodensitometry techniques, particularly as they pertain to radiodensity displacement (RDD) analyses. |
