Association of Obstructive Apnea with Thoracic Fluid Shift and Small Airways Narrowing in Asthma During Sleep

Xiaoshu Cao; Cristina de Oliveira Francisco; T Douglas Bradley; Nasim Montazeri Ghahjaverestan; Susan M Tarlo; Matthew B Stanbrook; Kenneth R Chapman; Mark Inman; Azadeh Yadollahi

doi:10.2147/NSS.S359021

Association of Obstructive Apnea with Thoracic Fluid Shift and Small Airways Narrowing in Asthma During Sleep

Nat Sci Sleep. 2022 May 6:14:891-899. doi: 10.2147/NSS.S359021. eCollection 2022.

Authors

Xiaoshu Cao^{1

2}, Cristina de Oliveira Francisco², T Douglas Bradley^{2

3

4}, Nasim Montazeri Ghahjaverestan^{1

2}, Susan M Tarlo^{3

5

6}, Matthew B Stanbrook^{3

5}, Kenneth R Chapman^{3

5}, Mark Inman⁷, Azadeh Yadollahi^{1

2}

Affiliations

¹ Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.
² KITE, Toronto Rehabilitation Institute - University Health Network, Toronto, ON, Canada.
³ Department of Medicine, University of Toronto, Toronto, ON, Canada.
⁴ Department of Medicine, University Health Network Toronto General Hospital, Toronto, ON, Canada.
⁵ Department of Medicine, University Health Network Toronto Western Hospital, Toronto, ON, Canada.
⁶ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
⁷ Faculty of Medicine (Respirology), McMaster University, Hamilton, ON, Canada.

Abstract

Rationale: Obstructive sleep apnea (OSA) is highly prevalent among patients with asthma, suggesting a pathophysiological link between the two, but a mechanism for this has not been identified.

Hypothesis: Among patients with asthma, those with OSA will have greater overnight increases in thoracic fluid volume and small airways narrowing than those without OSA.

Methods: We enrolled 19 participants with asthma: 9 with OSA (apnea-hypopnea index (AHI) ≥10) and 10 without OSA (AHI <10). All participants underwent overnight polysomnography. Before and after sleep, thoracic fluid volume was measured by bioelectrical impedance and small airways narrowing was primarily assessed by respiratory system reactance at 5Hz using oscillometry.

Results: Patients with asthma and OSA (OSA group) had a greater overnight increase in thoracic fluid volume by 120.5 mL than patients without OSA (non-OSA group) (164.4 ± 44.0 vs 43.9 ± 47.3 mL, p=0.006). Compared to the non-OSA group, the OSA group had greater overnight decrease in reactance at 5Hz (-1.08 ± 0.75 vs 0.21 ± 0.27 cmH₂O/L/s, p=0.02), and overnight increase in reactance area (14.81 ± 11.09 vs -1.20 ± 2.46 cmH₂O/L, p=0.04), frequency dependence of resistance (1.02 ± 0.68 vs 0.05 ± 0.18 cmH₂O/L/s, p=0.04), and resonance frequency (2.80 ± 4.14 vs -1.42 ± 2.13 cmH₂O/L/s, p=0.04).

Conclusion: Patients with asthma and co-existing OSA had greater overnight accumulation of fluid in the thorax in association with greater small airways narrowing than those without OSA. This suggests OSA could contribute to worsening of asthma at night by increasing fluid accumulation in the thorax.

Keywords: asthma; obstructive sleep apnea; small airway narrowing; thoracic fluid volume.

Grants and funding

This study was funded by Ontario Lung Association and the Canadian Respiratory Research Network. XC was supported by a scholarship from Ontario Graduate Scholarship (OGS) program from Province of Ontario and the University of Toronto, and the Asthma Canada-Canadian Allergy, Asthma and Immunology Foundation Graduate Student Research Award-Bastable-Potts from Asthma Canada. TDB was supported by the Godfrey S. Pettit Chair in Respiratory Medicine.