EFFECTS OF PRETERM BIRTH ON EXERCISE CAPACITY IN HYPOXIA IN CHILDREN

Predčasno rojstvo lahko na respiratornem sistemu pusti anatomske in funkcionalne posledice za celo življenje. Težave z nepopolno razvitim dihalnim sistemom in ventilatornim odzivom na hipoksijo so pri novorojenčkih že dobro raziskane, ostaja pa vprašanje, ali se posledice ohranijo tudi z odraščanjem ter ali te posledice vplivajo na sposobnost premagovanja napora v hipoksiji. Nekaj raziskav je že preučevalo športno sposobnost in ventilatorni odziv v hipoksiji pri odraslih osebah, namen pričujoče raziskave pa je bil ugotoviti sposobnost premagovanja napora v hipoksiji pri predčasno rojenih in donošenih otrocih, starih med 8 in 10 let. V raziskavi je sodelovalo petnajst predčasno rojenih otrok (gestacijska starost = 29 2 tednovtelesna masa ob rojstvu = 1202 184 g) in štirinajst donošenih vrstnikov (gestacijska starost = 39 1 tednovtelesna masa ob rojstvu = 3270 307 g). Vsi otroci so izvedli dve obremenitveni testiranji v naključnem vrstnem redu: (1) Stopnjevan obremenitveni test v normoksiji (procent O2 v vdihanem zraku (FiO2) = 0,21) in (2) Stopnjevan obremenitveni test v normobarični hipoksiji (FiO2 = 0,13). Na podlagi obremenitvenih testiranj smo primerjali rezultate največje proizvedene moči v hipoksiji pri nedonošenih otrocih in njihovih donošenih vrstnikih ter izmerili spremembe v izbranih kardio-vaskularnih parametrih med obema skupinama in med obema pogojema. Znižanje maksimalne aerobne moči (predčasno rojeni -23 %donošeni -26 %p 0,05donošeni -12 %p < 0,05) v hipoksiji je bilo med skupinama primerljivo. Prav tako nismo ugotovili značilnih razlik v ventilatornem odzivu med naporom v hipoksiji. Edina značilna razlika je bila v dihalnem volumnu, ki je bil pri 75 % maksimalne obremenitve nižji pri predčasno rojenih otrocih (p=0,03). V normoksiji pa so se razlike pokazale pri 75 % in 100 % maksimalne obremenitve tako pri dihalnem volumnu kot pri pljučni ventilaciji, porabi kisika in količini izdihanega CO2 (p < 0,05). Modulacija frekvence srca pri naporu v hipoksiji se med skupinama ni razlikovala. Pridobljeni rezultati kažejo, da zdravi predčasno rojeni otroci nimajo posebnih omejitev glede telesnega napora ob akutni izpostavitvi hipoksiji, potrebne pa so nadaljnje raziskave, ki bi preučevale odziv na napor na dejanski nadmorski višini ter v obdobju daljše aklimatizacije.Pre-term birth might result in life-long anatomical and functional respiratory system sequalae. Reduced hypoxic ventilatory response, most probably related to insufficiently developed lungs and respiratory system control, is consistently observed in pre-term infants, whereas subsistence of respiratory system sequalae with ageing remains unclear. Moreover, the effects of prematurity on hypoxic exercise capacity remains poorly investigated. While some recent studies have investigated the effects of hypoxia on exercise capacity and ventilatory response in adults but not in children. Accordingly, the aim of the present study was to assess maximal aerobic power as well as exercise cardiorespiratory responses in prematurely born children (aged 8 to 10 years) and their full term born matched counterparts. Fifteen prematurely born children (gestational age = 29 2 weeksgestation weight = 1202 184 g) and fourteen age matched controls born at full term (gestational age = 39 1 weeksgestation weight = 3270 307 g) participated in the study. All children underwent two graded exercise tests to volitional exhaustion in randomised manner, one in (1) normoxia (FiO2 = 0,21) and the other in (2) normobaric hypoxia (FiO2 = 0,13) to compare the hypoxia-related effects on maximal aerobic power and selected cardio-respiratory parameters between the groups and the two conditions. Hypoxia-related reduction in maximal aerobic power (pre-term group -23%full-term group -26%p 0,05full-term -12%p < 0,05) was comparable between the pre-term and full-term born children. No differences were also noted in the ventilatory response to hypoxia during the exercise test. The only exception being tidal volume, which was lower in pre-term group at 75% of maximal aerobic power (p=0,03). In normoxia, differences between the groups were noted in tidal volume, ventilation and consequently also oxygen uptake aa well as CO2 output (p < 0,05). No between-group differences were noted in heart rate modulation during hypoxic exercise. Present results do not indicate that healthy, prematurely born children should not engage in acute hypoxic exercise. Nevertheless, the potential negative effects of terrestrial (real) altitude exposure as well as prolonged altitude exposure warrant further investigation