Purpose: Alveolar hypoxia and hypoxic vasoconstriction lead to trapping of sickle cells within the pulmonary vasculature. Improving alveolar ventilation and oxygenation may improve the outcome of acute chest syndrome (ACS).
Methods: Prospective randomized single-center open study from November 1998 to February 2002 to test whether noninvasive ventilation (NIV) was more effective than oxygen alone in improving oxygenation on day 3 in adults with ACS and to evaluate the effects on pain, transfusion requirements, and length of stay.
Results: Seventy-one consecutive ACS episodes in 67 patients were randomly allocated to oxygen (n = 36) or NIV (n = 35) for 3 days in a medical step-down unit. Baseline respiratory rate and pain score were higher in the NIV group. NIV promptly lowered the respiratory rate, raised PaO2, and decreased alveolar-arterial oxygen gradient ((A- a)O2), which remained unchanged with oxygen alone. PaCO2significantly worsened only in the oxygen group. On day 3, the groups did not differ regarding the proportion of episodes with normal PaO2 (35% with NIV and 25% with oxygen; P = 0.5) or A - a). Patient satisfaction and compliance were lower with NIV. No differences were noted in pain relief, transfusions, or length of stay. In the subgroup of patients with severe hypoxemia PaO2 <or=, physiological variables also improved faster with NIV, the differences being slightly more pronounced.
Conclusions: Respiratory rate and gas exchange improved faster with NIV. However, NIV failed to significantly reduce the number of patients remaining hypoxemic at day 3, and was associated with greater patient discomfort.