Transpleural Ventilation via Spiracles in Severe Emphysema Increases Alveolar Ventilation

Area of Science:

• Pulmonary Medicine
• Thoracic Surgery
• Respiratory Physiology

Background:

• Emphysema is characterized by increased airway resistance and potential for collateral airflow.
• Severe emphysema can lead to significant airway obstruction, impairing alveolar ventilation.
• Transpleural expiration through chest wall openings (spiracles) is a potential, albeit inadvertent, ventilation pathway.

Purpose of the Study:

• To investigate the physiological effects of transpleural expiration via spiracles in patients with emphysema undergoing lung transplant.
• To assess the impact of spiracle ventilation on alveolar ventilation and gas exchange.

Main Methods:

• Observation of three lung transplant patients with inadvertent spiracles.
• Measurement of inspiratory and expiratory tidal volumes during mechanical ventilation.
• Monitoring of arterial carbon dioxide partial pressure (PCO2) before and after the onset of transpleural spiracle ventilation.

Main Results:

• Inspiratory tidal volumes remained unchanged during transpleural spiracle ventilation.
• Expiration was predominantly or entirely transpleural in two patients, with reduced expired tidal volume to the ventilator in one.
• Mean PCO2 decreased significantly from baseline (61 ± 5 mm Hg) to 49 ± 5 mm Hg within minutes and further to 36 ± 4 mm Hg within 1-2 hours.

Conclusions:

• Transpleural expiration through spiracles can enhance alveolar ventilation in emphysema patients.
• This mechanism effectively reduces hypercapnia, indicating potential therapeutic applications.
• Spiracles warrant further investigation as a novel treatment strategy for advanced emphysema.