Reversive Loss of Pulmonary Function Induced by Acute Chest Syndrome: A Report from the National Acute Chest Syndrome Study Group (NACSG).

Acute Chest Syndrome (ACS) remains the leading cause of death and hospitalization in patients (pts) with sickle cell disease (SCD). There is limited data on the effects of ACS on lung function. From 1993 to 1997, 30 centers participated in the NACSG and prospectively analyzed 671 episodes of ACS in 538 pts. Pulmonary function tests (PFTs) included forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), forced expiratory flow during 25% to 75% of FVC (FEF 25–75), peak expiratory flow rate (PEF) and the ratio of FEV1/FVC. Data is reported as percent-predicted of normal values based on age and height. 128 pts (mean 16yrs, 4 to 52 yr range) had PFTs during an ACS episode (within a mean of 2.5 days of diagnosis) and then 12 weeks later. 94% of pts had abnormal lung volumes, defined as either FEV1 or FVC < 80%. Mean lung volumes during ACS and at follow-up are shown below.

Pts with abnormal lung volumes (FEV1 or FVC < 80%) and considered to have an obstructive pattern if the FEV1/FVC ratio was < to 85. Obstructive patterns in pts with abnormal lung volumes and the percent of pts who responded to bronchodilators (15% improvement in either FEV1 or FVC) are shown below.

In summary, ACS resulted in decreased pulmonary function in 94% of pts. It is striking that 49% pts had their PFTs reduced by half (FEV1 52% and FVC 55%). In pts with abnormal PFTs, 48% had evidence of obstruction and 25% of all pts tested improved with a bronchodilator. This is the first description of reversible abnormalities of pulmonary function occurring during ACS compared to baseline. An obstructive pattern is identified in a higher percentage of pts with SCD than in the local Oakland African American population (asthma prevalance 16%). While some pts PFTs improved with time, 45% remained abnormal at 12-week follow-up. ACS results in acute and chronic worsening of lung function. Future studies of ACS may reveal common pathogenic mechanisms with asthma, and lead to improved therapeutic interventions.