Risk factors of transient tachypnea of the newborn developing into pulmonary hypertension of the newborn: a case-control study

BACKGROUND: Transient tachypnea of the newborn (TTN) is the consequence of delayed resorption of lung fluid. When TTN develops, the infant may develop severe hypoxemia and progress to persistent pulmonary hypertension of the newborn (PPHN). OBJECTIVES: To examine factors associated with the development of PPHN in TTN infants. METHODS: This retrospective study comprised 23 infants in whom a diagnosis of TTN with PPHN (TTN-PPHN) was confirmed and 59 infants with severe TTN without PPHN who required mechanical ventilation between 2009 and 2018 at Songklanagarind Hospital, Thailand. Logistic regression was used to assess factors associated with TTN and PPHN. RESULTS: The factors identified by univariate analysis that were associated with development of PPHN were oxygen saturation (SpO(2)) <90% and respiratory rate (RR) ≥70 breaths/min at the time of admission, mean airway pressure (MAP) ≥8 cmH(2)O, oxygen index (OI) ≥10, partial pressure of oxygen (PaO(2)) ≤60, partial pressure of carbon dioxide (PCO(2)) ≥45 mmHg, and infants who did not receive positive pressure ventilation (PPV). In multivariate analyses, RR ≥70 breaths/min (adjusted odds ratio [aOR] 9.96, 95% confidence interval [CI] 2.1–47.29, P < 0.001) and OI ≥10 (aOR 29.22, 95% CI 4.46–191.23, P < 0.001) remained statistically significantly associated with PPHN. CONCLUSIONS: High RR and high OI were factors associated with PPHN in TTN infants.