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Purpose <p> The recumbent posture during sleep increases small airway narrowing and nocturnal asthma despite optimal asthma treatment. Fluid accumulation in the chest can narrow the airway lumen, contributing to small airway narrowing. We hypothesized that in people with asthma, treatment with a short-acting bronchodilator cannot fully prevent airway narrowing attributable to rostral fluid shift.</p> Methods <p> Using a cross-over design, participants laid supine for 30 minutes and received lower body positive pressure (LBPP) to reproduce overnight fluid shift out of the legs. They either inhaled salbutamol before lying down (bronchodilator arm) or received no bronchodilator (control arm). Airway narrowing was evaluated while participants were supine at 0 and 30 minutes. Oscillometry was used to estimate reactance at 5 Hz (X5), reactance area (AX), overall resistance of the respiratory system at 5 Hz (R5), and the difference in resistance between frequencies of 5 and 19 Hz (R5–19). Thoracic fluid volumes (TFV) were measured using bioelectrical impedance.</p> Results <p> We enrolled 21 people with asthma. TFV increased similarly in both study arms (58.6±57.5 ml vs 73.8±84.2 ml, p=0.37). In both control and intervention arms, small airway narrowing was observed, with significant decreases in X5 (–0.18±0.34 vs –0.26±0.40 cmH₂O/L/s, p=0.21) and increases in Ax (2.82±4.01 vs 2.23±4.46 cmH₂O/L/s, p=0.61), R5 (0.45±0.49 vs 0.64±0.58 cmH₂O/L/s, p=0.26), and R5–19 (0.20±0.26 vs 0.16±0.37 cmH₂O/L/s, p=0.59). The changes were similar between the two study arms.</p> Conclusion <p> Bronchodilator treatment did not prevent the airway narrowing related to rostral fluid shift. These results support a role for rostral fluid shift in the pathophysiology of nocturnal asthma even among appropriately treated patients.</p>

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Effects of rostral fluid shift on small airway narrowing in asthma before and after bronchodilation

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Xiaoshu Cao,
  • Cristina O. Francisco,
  • Behrad TaghiBeyglou,
  • Sania Aftab,
  • Matthew B. Stanbrook,
  • Susan M. Tarlo,
  • Kenneth R. Chapman,
  • T. Douglas Bradley,
  • Mark D. Inman,
  • Azadeh Yadollahi

摘要

Purpose

The recumbent posture during sleep increases small airway narrowing and nocturnal asthma despite optimal asthma treatment. Fluid accumulation in the chest can narrow the airway lumen, contributing to small airway narrowing. We hypothesized that in people with asthma, treatment with a short-acting bronchodilator cannot fully prevent airway narrowing attributable to rostral fluid shift.

Methods

Using a cross-over design, participants laid supine for 30 minutes and received lower body positive pressure (LBPP) to reproduce overnight fluid shift out of the legs. They either inhaled salbutamol before lying down (bronchodilator arm) or received no bronchodilator (control arm). Airway narrowing was evaluated while participants were supine at 0 and 30 minutes. Oscillometry was used to estimate reactance at 5 Hz (X5), reactance area (AX), overall resistance of the respiratory system at 5 Hz (R5), and the difference in resistance between frequencies of 5 and 19 Hz (R5–19). Thoracic fluid volumes (TFV) were measured using bioelectrical impedance.

Results

We enrolled 21 people with asthma. TFV increased similarly in both study arms (58.6±57.5 ml vs 73.8±84.2 ml, p=0.37). In both control and intervention arms, small airway narrowing was observed, with significant decreases in X5 (–0.18±0.34 vs –0.26±0.40 cmH₂O/L/s, p=0.21) and increases in Ax (2.82±4.01 vs 2.23±4.46 cmH₂O/L/s, p=0.61), R5 (0.45±0.49 vs 0.64±0.58 cmH₂O/L/s, p=0.26), and R5–19 (0.20±0.26 vs 0.16±0.37 cmH₂O/L/s, p=0.59). The changes were similar between the two study arms.

Conclusion

Bronchodilator treatment did not prevent the airway narrowing related to rostral fluid shift. These results support a role for rostral fluid shift in the pathophysiology of nocturnal asthma even among appropriately treated patients.