From the Guidelines
Mucolytic therapy is a beneficial treatment for critically ill patients with chronic obstructive pulmonary disease (COPD), as it reduces the likelihood of hospitalization and COPD exacerbations.
Physiology and Pathophysiology of Mucus
- Mucus in COPD is copious and tenacious, properties that promote infection and lung damage 1.
- The production of mucus is a natural defense mechanism, but in COPD, it can become excessive and harmful.
- Mucolytic therapy aims to break down mucoproteins, reducing the viscosity of mucus and improving sputum clearance.
Role of Mucolytic Therapy
- N-acetylcysteine, ambroxol, and carbocisteine are commonly used mucolytic agents, with N-acetylcysteine being the most studied 1.
- High-dose mucolytic therapy (e.g., N-acetylcysteine 600 mg twice daily) has been shown to reduce the rate of COPD exacerbations 1.
- Mucolytic therapy has been found to decrease the likelihood of hospitalization, with a number needed to treat of 25 to prevent one hospitalization 1.
- The effect of mucolytic therapy on mortality is unclear, but it does not appear to increase adverse effects or alter quality of life 1.
From the Research
Physiology of Mucus
- Airway mucus is a highly specialized secretory fluid that functions as a physical and immunological barrier to pathogens, lubricates the airways, and humidifies atmospheric air 2
- The mucus clearance system is the dominant mechanical host defense system of the human lung, with mucus cleared by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms 3
- Mucus transport rates are heavily dependent on mucus concentration and are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers 3
Pathophysiology of Mucus
- Dysfunction of airway mucus is common during critical illness and is characterized by changes in production rate, chemical composition, physical properties, and inflammatory phenotype 2
- Mucociliary clearance is dysfunctional in critical illness via disease-related and iatrogenic mechanisms, leading to potentially devastating consequences, including prolonged ventilator dependency, increased risk of secondary pneumonia, and worsened lung injury 2
- Mucus hypersecretion is a cardinal sign of both acute and chronic pulmonary diseases, and its overproduction leads to airway obstruction and promotes bacterial colonization 4
Role of Mucolytic Therapy
- Mucolytic therapies are designed to decrease viscosity, improve expectoration/suctioning, and promote mucus removal 2
- Mucolytics, including hypertonic saline, dornase alfa/rhDNase, nebulised heparin, carbocisteine/N-Acetyl cysteine, are commonly used in critically ill patients 2
- Mucolytic agents, such as Ambroxol and N-acetylcysteine, can alter the secretion of mucus and its physical properties, resulting in improvement of mucociliary clearance and symptom control in patients with respiratory tract disorders 5, 4
- Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are being reviewed 3