Alveolar-arterial gradients and small airways in kyphoscoliosis.

In 14 patients, kyphoscoliotics, at the time without cardiorespiratory diseases, of average age 28 years +/- 17 (range 12-64), the average values for the vital capacity was 79.6 +/- 21.2% (range 49-125), for the Tiffeneau Index was 77.9% +/- 10.3% (range 56-91), for the RV/TLC ratio was 39.6% +/- 10.8% (range 18-56), for the MEF 25 was 2,192.8 +/- 732.1 ml/s (range 1,300-3,800), for the MEF 50 was 3,689.3 +/- 1,310.9 ml/s (range 1,750-5,500). The average value for the PaO2 was 90.3 +/- 8.3 mm Hg (range 75-109), and for the PaCO2 35.3 +/- 4.66 mm Hg (range 27.8-46). The average value for the alveolar-arterial gradient of O2 was 11.96 +/- 7.37 mm Hg (range 0.74-27.94) and for the arterial-alveolar gradient of CO2 2.30 +/- 2.41 mm Hg (range 0.22-9.98). The average value for the CO transfer was 20.06 +/- 6.84 ml/min/mm Hg (range 8-31.4). As the angle of scoliosis and the age of the subject increase, the vital capacity and the Tiffeneau Index decrease, the RV/TLC ratio and the respiratory rate increase, the MEF 25, the MEF 50, the PaO2, and the transfer of CO decrease, while PaCO2 increases. The alveolar-arterial gradient of O2 and the arterial-alveolar gradient of CO2 increase as the angle of scoliosis increases. The data so obtained show, therefore, that in kyphoscoliosis a restrictive type of respiratory dysfunction appears, along with hypoxemia due to alveolar hypoventilation and disturbances in diffusion and in the ventilation-perfusion ratio.