A British Medical Association Lecture ON THE CAUSE AND SIGNIFICANCE OF DYSPNOEA IN PULMONARY DISEASE
Authors: J. Meakins
Journal: BMJ (1924)

THE occurrenice of respiratory distress is onie of the most common and important symptoms in diseases of the lungs.This symptom miiay be described by the p:atient in maniy ways.Ildeed it may vary from an urgent colIj)plaint witlhout any conspicuous or eveni obvious change of rate to a v-ery pro- nounced objective disturbance with or-without the patient inhdicating an} inconvenience.It mray usut.llbe stated that ' dyspnoea "is the conlscious desire fo; ilncreased pulmonary ventilationi.But this is not absolutely correct, as there are: certain pathological conditions in w-hich increased pulinonary ventilation occurs without conlscious distress on the part of the patient.Nevertheless, in cases which exhibit such an increased respiratory function its significance is nione the less important.In fact its diagnostic and prognostic import is frequently in inverse ratio to the dis- tress or discomfort it gives the subject.Therefore the dis- turbances of function and structur e which give rise to respiratory abnor mality in pulmoniary diseases should be .plearlyuinderstood.THE POWER OF ADAPTATION.The underlying causes of dyspnoea are numerous and frequently are to be found in structures far removed from the lungs.Consequently those causes w-hich result from pulmonary diseases may be looked upon as local, in spite of the fact that their effects may in'fluence many other remote and important functions.Buit beinig localized there is a definiite and concrete opportunity for their investigation and inter-pretation.In order that this may be accomplished, certaiin biological phenomena must first be considered.These are concerned mainly with the power of adaptation wlhich the aniimal body seems iliherently to -possess.It is a well knowni fact that an organism if suddenly plunged into a radically new environiment vill rapidly succumb.If, how- ever, the change of environment be brought about slowly it will graduially acquire in the same or succeeding genera- tions ali unexpected tolerance or even a relish for an ordinarily impossible situation.Adaptation occurring ini one generation is amply illustrated by the acquired capacity of aviators and mountaineers to attain altitudes and even accomplish severe physical exertion in such a rarefied atmo- splhere as some authorities had predicted was theoreticall- impossible without certain artificial aids.These prediction's .mustsurely have been niade without knowledge of the powrers of adaptation of the animal organism.Examples might be cited of an almost similar power of adaptation of unicellular organisms to gross changes in their enviionment.Dallingerl showed how successive generations of flagellates gradually accommodated themselves to changes in the tem- perature of theii' environment.This wras increased from 600 to 158°F.byslow graduations over a period of seven Years.In view of these facts due allowance miust be made for the different responses, both local and general, which may result from disturbances of respiration in pulmonai'v diseases.It .rouldobviouslv be illogical to compare the effects of inter- *erence with-respiratory function in bronchllo!neumooniaani'd emphysemia or those resulting -from laryngeal obstruction due to diphtlheria and tracheal obstruction due to a slowly gr'owinig mediastinal tumnour.RESPIRATORY FUINCTION AND THE CONSEQEIENCES OF ITS DISTURBANCE.DYBPNO]A IN PULMONARY DISASE.supply proportionate to the inierease of rate anid decrease of the depth, so in the enld the rate reaches a relative infinity And the depth zero, and respiration ceases.