Changes in Pulmonary Mechanics with Increasing Disease Severity in Children and Young Adults with Cystic Fibrosis

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Abstract
As forced expiratory volume in 1 second (FEV1) is a major predictor of outcome in patients with cystic fibrosis (CF), we investigated the effect of FEV1 on pulmonary mechanics in children and young adults with CF. We measured respiratory rate; tidal volume; minute ventilation; arterial blood gases; sniff esophageal pressure; dynamic lung compliance; total pulmonary resistance; intrinsic positive end expiratory pressure; and total, elastic, and resistive work of breathing in 32 patients (FEV1 range: 12–49% predicted). We observed correlations between FEV1 and PaO2 (r = 0.76, p < 0.0001) and PaCO2 (r = −0.70, p < 0.0001), FEV1 and respiratory rate/tidal volume (r = −0.41, p = 0.02), FEV1 and dynamic lung compliance (r = 0.64, p < 0.0001), and FEV1 and total work of breathing (r = −0.52, p = 0.002) and elastic work of breathing (r = −0.60. p = 0.0003). No correlations were observed between FEV1 and sniff esophageal pressure (p = 0.5), minute ventilation (p = 0.9), total pulmonary resistance (p = 0.3), intrinsic positive end expiratory pressure (p = 0.3), or resistive work of breathing (p = 0.1). As FEV1 declines in children and young adults with CF, there is an increase in the elastic load and work of breathing, resulting in a rapid shallow breathing pattern, that is associated with further impairment of gas exchange.