Dihanje je homeostatski mehanizem, ki primarno nasprotuje spremembam pO2 in pCO2 v organizmu, ki jih povzroča okolje ali organizem, in vključuje izmenjavo plinov z okoljem (ventilacijo), prenos plinov skozi alveolokapilarno pregrado (difuzija), transport plinov v krvi in celično uporabo pO2 oziroma proizvodnjo pCO2. Dihanje je uravnavano na vseh teh ravneh, čeprav uravnavanje dihanja običajno enačimo z uravnavanjem ventilacije. Ventilacijo uravnava zapleten sistem, ki vključuje generator centralnega dihalnega ritma / vzorca in integrator v podaljšani hrbtenjači in ponsu. Ta avtomatično generira bazalni ritem za krčenje dihalnih mišic, ki ga nato, glede na informacije iz kemoreceptorjev in mehanoreceptorjev ter drugih struktur, prilagaja spreminjajočim se presnovnim potrebam, mehaničnim razmeram ali vedenju. Uravnavanje ventilacije je primarno nezavedno in avtomatično, vendar lahko nanj do neke mere vplivamo tudi z voljo, kar je je mogoče med budnostjo, ko lahko z voljo celo preglasimo avtomatično uravnavanje ventilacije. Med spanjem se dražljaji budnosti in volje umaknejo, tako da je dihanje odvisno predvsem od avtomatskega uravnavanja. Uravnavanje dihanja se razvije zgodaj v fetalnem obdobju in še naprej dozoreva po rojstvu. Sistem za uravnavanje ventilacije pri dojenčkih, zlasti pri nedonošenčkih, je nezrel in sam po sebi nestabilen, kar povzroča nepravilno dihanje, pogoste apneje in periodično dihanje, zaradi česar so dojenčki bolj dovzetni za dihalno odpoved. V tem prispevku obravnavamo fiziološke osnove zrelega uravnavanja ventilacije pri odraslih in razlike pri dojenčkih.
Physiological Principles of Ventilatory Control from Infants to Adults
Breathing is a homeostatic mechanism that primarily counteracts environment- or organism-induced changes in pO2 and pCO2 in the organism, and involves exchange of gases with the environment (ventilation), transfer of gases across the alveolocapillary barrier (diffusion), transport of gases in blood, and cellular utilization or production of pO2 and pCO2, respectively. Breathing is regulated at all these levels, although breathing regulation is usually equated with the ventilatory control. Ventilation is controlled by a complex system involving a central respiratory rhythm/pattern generator and integrator in the medulla oblongata and pons, which automatically generates the basic rhythm for contraction of the respiratory muscles and then adjusts this rhythm according to changing metabolic needs, varying mechanical conditions, and a range of episodic non-ventilatory behaviours, according to the inputs from chemoreceptors, mechanoreceptors, and other structures. It is primarily involuntary and automatic and can be, to some degree, also influenced by voluntary inputs that are prominent during wakefulness and can even override automatic ventilatory control. During sleep, however, wakefulness stimuli and voluntary influences are withdrawn, so that ventilation depends predominantly on automatic control. Breathing regulation develops early in foetal life and continues to mature after birth. The infantile ventilatory control system, especially in preterm infants, is immature and inherently unstable, resulting in irregular breathing, frequent apnoeas, and periodic breathing, making infants more susceptible to respiratory failure. The article aims to review the physiological principles of mature ventilatory control in adults and the differences in infants.