Pneumograph

PNEUMOGRAPH, a device (and corresponding method) for recording the movements of the chest wall. There are several types of pneumographs. The most common type is the Marey pneumograph, consisting of a steel band 7 cm wide, on which a Marey receiving capsule is mounted vertically. A band made of canvas or other dense material encircles the subject's chest and is attached at one end to the aforementioned steel band, and at the other to a lever articulated with a metal disc on the rubber membrane of the Marey capsule. During inhalation, the volume of the capsule increases; during exhalation, it decreases. Its cavity is connected by a rubber tube to the cavity of a recording capsule, the pen of which writes on a kymograph or polygraph (see). Recently, another type of pneumograph has become widely used, consisting of a non-stretchable band to which a piece of an inner tube from a bicycle tire is glued. Both ends of this piece are blind (sealed). Before the experiment, air is blown into the chamber, and then the pneumograph band is placed on the subject's chest and fastened with a buckle. During inhalation, the chamber is compressed, and part of the air contained within it passes through the connecting rubber tube into the Marey recording capsule (a so-called zero valve is mandatory, allowing for pressure equalization and thus avoiding rupture of the thin rubber of the capsule). In some pneumographs, the chamber is replaced by 2-3 flat rubber balloons. On the kymograph, inhalation corresponds to an upward movement of the curve, not a downward one as in the Marey pneumograph. The second type of pneumograph is more convenient, especially when studying labor processes. Clinical medicine uses pneumography to study and differentiate various forms of dyspnea, as well as to detect certain subtle respiratory disorders (wogende Atmung, see Dyspnea) that are not detectable by simple observation. The pneumogram reflects changes in inspiration (i in Figure 1), expiration (e), and respiratory pauses. Most often, an intensification of inspiration and a change in the duration of respiratory pauses are observed. In cases of severe cardiac decompensation, the pneumogram is characterized by steep descents corresponding to inspiration and steep (expiratory) rises of the curve. Respiratory pauses are shortened or absent. After cardiac therapy, the character of the curve changes—the curve flattens. The predominance of inspiration over expiration characterizes the curve of "large breathing" (Figure 2), in which, in addition, a sharp lengthening of respiratory pauses is observed.

Figure 3. Pneumogram in purulent meningitis.

Complete irregularity of the respiratory rhythm is observed in meningitis. On the pneumogram (Figure 3), both lengthening and shortening of respiratory pauses are visible, as well as irregularity in the amplitude of the curve. Cheyne-Stokes respiration stands apart, in which a regular periodic disturbance of the respiratory rhythm occurs. On the pneumogram, a prolonged respiratory pause (apnea) is visible, followed by a respiratory curve increasing in amplitude, reaching a physiological maximum, and then decreasing until complete disappearance and a new pause (Figure 4).