Radiographic lung disease and response of persistent pulmonary hypertension to mean airway pressure and alkalosis.

Persistent pulmonary hypertension of the newborn (PPHN) is associated with multiple cardiopulmonary diseases. Therapy often includes hyperventilation/alkalosis despite little evidence as to its efficacy in diverse conditions. To determine (1) if part of the improvement of arterial oxygen tension (PaO2) attributed to alkalosis is actually related to increased mean airway pressure (P(aw)) and (2) if the presence of radiographic pulmonary disease predicts the response to alkalosis or mean airway pressure, we reviewed records of 19 newborns with well-documented PPHN. Arterial blood gases and corresponding ventilator settings were recorded during the first day of life. To adjust for lower FiO2, corrected PaO2 (cPaO2) was calculated when the FiO2 < 1.0, such that cPaO2 = calculated arterial/alveolar oxygen ratio x (713 - PaCO2/0.8). Regression equations were obtained and mean slopes of these were compared for P(aw) vs. cPaO2, and pH vs. cPaO2 by one group t-tests (with assumed population slope of zero). There was no correlation between P(aw) and cPaO2 (mean slope +/- SD = -8.4 +/- 30.8, P = 0.25), but there was a moderate correlation between pH and cPaO2 (mean slope = 333.1 +/- 480.5, P = 0.007). Patients were then classified by chest radiographs as having severe or minimal/no lung disease. Relationships of P(aw) and pH to cPaO2 were then re-examined. No correlation was present between P(aw) and cPaO2 in 11 patients with PPHN and severe radiographic disease (mean slope = -7.4 +/- 26.9, P = 0.38) or in eight patients with PPHN and minimal/no lung disease (mean slope = -9.8 +/- 37.5, P = 0.48).(ABSTRACT TRUNCATED AT 250 WORDS)