Background: Right to left shunt and regional hypoventilation (reduced ventilation/perfusion ratio (V A /Q)) have different effects on the curve relating inspired oxygen (P I O 2 ) to oxygen saturation measured by pulse oximetry (SpO 2 ) and can be derived non-invasively from measurements of SpO 2 and inspired oxygen pressure (P I O 2 ) using complex models of gas exchange. We developed a simpler computerised ''slide-rule'' method of making these derivations. Aims: To describe the slide-rule method and determine agreement between measurements derived with this and a more complex algorithm. Methods: Series of P I O 2 versus SpO 2 data points obtained during 43 studies in 16 preterm infants with bronchopulmonary dysplasia were analysed. Percentage shunt and the degree of right shift (kPa) of the P I O 2 versus SpO 2 curve compared with the oxyhaemoglobin dissociation curve (a measure of V A /Q) were determined for each dataset with both methods, and the results were compared using the method of Bland and Altman. Results: The computer slide-rule method produced results for all 43 datasets. The more complex model could derive results for 40/43 datasets. The mean differences (95% limits of agreement) between the two methods for measurements of shunt were 21.7% (26.5 to +3.5%) and for measurements of right shift were 0.3 kPa (22.9 to +3.6 kPa). Conclusion: The slide-rule method was reliable for deriving shunt and right shift (reduced V A /Q) of the P I O 2 versus SpO 2 curve when compared with the more complex algorithm. The new method should enable wider clinical application of these measurements of oxygen exchange.

Background: Hypertensive disorders of pregnancy are the common medical disorders in pregnancy. The present study was conducted to compare oral labetalol and oral nifedipine in hypertensive disorders of pregnancy. Subjects and Methods: The present study was conducted on 60 pregnant women. Preterm or term pregnant women with severe preeclampsia/ eclampsia and BP ≥160/100 mm Hg were included in the study. Patients were divided into 2 groups of 30 each. Group I patients were given oral labetalol and group II were given oral 10 mg Nifedipine. Results: Primi was seen in 18 in group I and 17 in group II, G2 6 in group I and 5 in group II, G3 4 in group I and 5 in group II and G4 2 in group and 3 in group II. The difference was non-significant (P> 0.05). In group I, SBP was 174.2 mm Hg in group I and 166.4 mm Hg in group II, DBP was 112.6 mmHg in group I and 110.8 mm Hg in group II. The difference was significant (P< 0.05). Conclusion: The study concluded that oral Nifedipine better in terms of lowering blood pressure in pregnant ladies, although the difference was nonsignificant.