Influence of rapid fluid loading on airway structure and function in healthy humans

Abstract

The causes of reduced pulmonary function (PF) in heart failure (HF) patients remain unclear, but may be due to increased pulmonary congestion. Rapid fluid loading (RFL) in healthy adults has been used to simulate intra‐thoracic fluid overload common in HF. This study examined PF using plethysmography, and airway lumen cross sectional area (Alumen), airway wall thickness (taw), and vascular volume using non‐contrast CT imaging before and after RFL in 22 healthy adults. Average infusion volume was 2190 ± 412 ml over 20 ± 3 min. Vascular volume, heart rate, and cardiac output increased (p<0.001). O2 saturation and mean arterial pressure were unchanged. Forced vital capacity (FVC) and expiratory flow measures decreased post RFL (ΔFVC=−13±9%, ΔFEV1=−15±10%, ΔFEF25‐75=−17±19%, p<0.001). Alumen was unchanged from the trachea through airway generation 3; taw decreased in the trachea (p<0.05) but remained unchanged in airway generations 1–3. Both measures increased at airway generation 4 (p<0.01). Changes in taw and Alumen were unrelated and were also independent of any changes in vascular volume or PF. This data suggests that RFL in healthy adults results in decreases in PF, however these decreases are not due to changes in Alumen, taw, or pulmonary blood volume of the larger airways and vessels that can be easily imaged without contrast. Further studies will be needed to assess bronchial changes in the mid to smaller airways.