Incomplete fissures are associated with increased alveolar ventilation via spiracles in severe emphysema

Area of Science:

• Pulmonary Medicine
• Radiology
• Anatomy

Background:

• Emphysema involves air flow through collateral pathways, potentially connecting entire lungs if fissures are incomplete.
• Spiracles, openings in the chest wall to lung parenchyma, have been observed to facilitate increased alveolar ventilation (VA) in severe emphysema patients.
• Previous observations noted improved VA in emphysema patients with spiracles during lung transplant operations.

Purpose of the Study:

• To identify a computed tomography (CT) imaging phenotype associated with improved VA via spiracles in severe emphysema.
• To investigate the relationship between lung fissure integrity and enhanced ventilation in emphysema patients.

Main Methods:

• Retrospective review of 4 severe emphysema patients undergoing lung transplant with significant spiracle ventilation.
• Quantitative CT image analysis using VIDA VISION software to assess emphysema severity, distribution, and lung fissure integrity.
• Analysis of carbon dioxide levels and calculation of VA at baseline and during spiracle ventilation.

Main Results:

• All 4 subjects had severe hyperinflation (TLC 148±24% predicted, RV 296±79% predicted).
• CT revealed severe emphysema (38.7±9% lung parenchyma < -950 HU) and incomplete fissures (average integrity 67±19%).
• Spiracle ventilation significantly reduced PaCO2 (61±4 to 35±4 mmHg) and increased estimated VA (2.1±0.5 to 3.8±0.8 L/min).

Conclusions:

• Incomplete lung fissures, identified through quantitative CT analysis, represent a key imaging phenotype.
• This phenotype is associated with substantial improvements in alveolar ventilation during transpleural ventilation via spiracles in severe emphysema.
• Findings suggest incomplete fissures play a crucial role in facilitating ventilation in emphysema through spiracles.