Physiological strategy of the ventilation in response to spécific constraints in child-divers

Introduction: Intervention in the subaquatic environment was made possible by the self-contained breathing apparatus (SCUBA), which allows breathing in aquatic environment. However, this apparatus imposes to the respiratory function new constraints and a mechanical work The aim of this study was to evaluate the effect of SCUBA on lung function in child divers. SCUBA imposes external inspiratory and expiratory resistances and an increase the dead space. Materials and methods: 22 child divers (11 boys and 11 girls) aged 7 to 13 breathed with a SCUBA or with a no-resistance mouthpiece of the same volume (added dead space) as the SCUBA. We recorded respiratory parameters (tidal volume, ventilation, vital capacity, inspiratory time, expiratory time, total time of a respiratory cycle, inspiratory and expiratory pressure, oxygen consumption) at rest out of the water, (VT, VE, V, Ti, TE, Ttot, Pi, Pe and VO2). They were mesured with a CPX medical graphics device. Inspiratory and expiratory pressures refleced the pressure generated by respiratory muscle in the faces of stress and mechanical work. Results: They showed respiration (VT) with self-contained breathing apparatus in the inspiratory reserve volume (IRV) with an increased expiratory reserve volume (ERV), a variation in respiratory frequency with a decrease in Ttot, Ti and Te, and a increases in Pi, PE, Ptot and VO2. Discussion: To respond to the constraints imposed by a regulator with an increase in respiratory resistance and dead space, the children breathe at their VRI thus increasing the retraction response of the still immature pulmonary elastic fibers, with an acceleration of the rhythm at the détriment of Ti and Te. This adaptation has an energy cost with an increase in oxygen consomption due to both the work of the inhalation and exhalation muscles. This reflex adaptation is the response to information of an increase in pressure via pulmonary mechanoreceptors, and pathways of phrenic nerves sensitivity. The information is taken into account by the bulbo-protuberant respiratory centers (Central Respiratory Generator, GCResp), and Pre-Bötzinger Complex. The vagus nerve (10th cranial pair) will also modify the kinetics of the diaphragm muscle. Conclusion: These adaptations are different from those of adults under the same conditions, who promote a decrease in respiratory rate, with an increase in Ti, TE and Ttot. They also have a smaller increase in VO2 than children (35.5% versus 45.1%). The adaptation strategy of child divers corresponds to their immaturity of the lung tissue and in particular to the state of development of elastin fibers and the elastic retraction of the lung at the end of inspiration. ADMS 9 rue Bochart de Saron, 75009 Paris France Service de médecine de l’exercice et du sport, Hôpital Jean Verdier, Bondy France This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.