Thorax Inspection in the Respiratory System Medical Examination.

Inspection of the Thorax

Normal Form of Thorax and Normal Respiration

In a well-constructed thorax we expect, first, perfect symmetry (this is departed from almost always normally, in that there is a very slight curvature of the dorsal vertebrae toward the right).  Moreover, the clavicular depressions may only be indicated ; the angulus Ludo- vici [also called the angle of Louis] (the angle formed by the junction of the manubrium and corpus sterni) may just be recognizable; the true ribs should so leave the sternum that from the top downward there is increasing obliquity, making the angle formed by the two opposite bendings of the ribs, " the epigastric angle," almost a right angle ; the thorax should be well developed ; the scapulse should, in the upright position, lie flat upon it ; the intercostal spaces should be visible only at the lower ribs ; finally, the dimensions of the chest and the size of the body should have a certain relation to each other.  Very seldom does the normal thorax correspond to this ideal, and there are many departures from it in persons who are perfectly sound.  Such " physio- logical " departures may be mentioned; a slight asymmetry in a gradually-aquired spinal curvature or a deformity of the ribs self- established ; further, a peculiar form of thorax, where the upper part is somewhat shallow, but the lower of increasing depth, so that the lower aperture of the thorax is very large ; also more marked angle of Louis (Braune) ; again, in a shorter thorax, a more acute epigastric angle may sometimes be observed in healthy persons (hence, also, without signs of emphysema, see below).  The supra-clavicular de- pressions are often both deepened, with the apices of the lung entirely normal (unequal deepening of them is, however, very suspicious of tuberculosis, see below) ; single ribs, more frequently the second, third, also the fourth, sometimes on account of greater curvature, project more in front ; on the other hand, the lower ribs will often be found pressed into the side and from there flattened forward, and other variations.  The boundary between the unsymmetrical and the path- ological form of chest is much confused ; it can only be recognized in the individual case by attention to the location and function of the thoracic organs.

Respiratory Rate Assessment

Normal breathing takes place in this wise : inspiration only is active, that is, is accomplished by muscular action ; expiration, on the contrary, is produced wholly by the elasticity of the lungs, the weight of the chest wall, and the pressure of the abdominal organs upon the diaphragm.  The number of respirations to the minute in the newborn is about 44 ; at five years, about 26 ; from the twentieth year, about 13 to 20. 

It is very easily influenced by a number of conditions : in sitting and standing it is somewhat higher than in lying ; it is increased by bodily activity and psychical impressions.  Therefore, it can only be determined during perfect quiet, with the attention withdrawn from the examiner, or during sleep.  For counting  it is generally most advantageous to lay the hand lightly upon the chest (or upon the epigastrium).

The breathing is generally regular, and the single breaths of equal strength ; but under the influence of the shghtest psychical disturbance it easily becomes irregular and unequal.  Many persons of sound health, as snorers in sleep, often breathe irregularly or unequally deeply.  Breathing is either exactly or very nearly symmetrical, though the left side frequently inclines to breathe a trifle stronger.

The inspiratory enlargement of the thorax is occasioned by the elevation of the ribs and the sternum, and the simultaneous drawing of the former upward and outward (intercostales externi and interni muscles and costal breathing'; moreover, by the contraction of the diaphragm, and, hence, flattening of its dome.  The latter movement, at the same time, draws down the intestines, and so with every inspira- tion the whole anterior wall of the abdomen projects, but especially the epigastrium (diaphragmatic, or abdominal, breathing).  The combination of costal and diaphragmatic breathing varies in the two sexes in that in the male the latter, and in the female the former, preponderates.  But in aged females, with firm thoracic walls, diaphragmatic breathing increases ; While, on the other hand, male as well as female children incline to the costal type of breathing.  From this it seems that the degree of flexibility of the thorax influences the kind of breathing.

In the costal breathing of women, even in quiet respiration, the scaleni muscles (elevators of the first and second ribs) take a part ; while in men these muscles belong to the auxiliary muscles of respiration.

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