[Effect of guided ventilation on gas exchange in kypho-scoliotic patients in post-intensive care]

Post-intensive care stabilized kyphoscoliotic patients are characterized by a limited circulation which reduces VCO in relation to VCO2 (specific VCO, Sp VCO) by diminution of the "contact time". This might help in explaining the hypoxaemia observed in these patients concurrently with alveolar hypoventilation and altered ventilation/perfusion ratio. Bradypnoea (Bp) may reduce the last two factors but not the vascular field amputation. In 10 kyphoscoliotic patients examined in spontaneous ventilation (SV), then in Bp, gas exchanges were evaluated under their 2 aspects: gas flow rates and ventilatory efficiency (ERCO2, VA/V). The results obtained in 16 examinations concerning 10 patients were analysed. There were great differences in the amplitude of ventilatory response, a significant increase of VA improving PaCO2 more constantly than PaO2, a slight increase of Sp VCO and a decrease of VCO/VA. In the discussion, ERCO2 and VA/V are compared, the high VA/V and VD/VT values are justified, the uncertain effect of Bp on PaO2 is confirmed, and the relationship of Sp VCO with DuCO and PaO2 is determined. The evaluation of exchanges in SV and Bp provides information on the degree of deterioration of blood perfusion, the physiopathology of each individual subject and the advisability of kinesitherapy with Bp.