What causes alveolar-capillary block?

The alveolar-capillary block syndrome is based upon a wide range of only par- tially known aetiological agents. Generally speaking, any disease which interposes something between air and blood throughout the greater part of the lungs, or gives a decrease of the surface area for diffusion, can produce the syn- drome.

What are the primary pathophysiologic changes that occur in the injury or exudative phase of ARDS?

In the exudative phase, damage to the alveolar epithelium and vascular endothelium produces leakage of water, protein, and inflammatory and red blood cells into the interstitium and alveolar lumen. These changes are induced by a complex interplay of proinflammatory and anti-inflammatory mediators.

What does the alveolar-capillary membrane do?

The alveolar-capillary barrier (or membrane, or blood-air barrier) exists in the gas exchanging region of the lungs. It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli. The barrier is permeable to molecular oxygen, carbon dioxide, carbon monoxide and many other gases.

What are the two main determinants of lung compliance?

Two important factors of lung compliance are elastic fibers and surface tension. More elastic fibers in the tissue lead to ease in expandability and, therefore, compliance. Surface tension within the alveoli is decreased by the production of surfactant to prevent collapse.

What happens when alveolar capillary beds are destroyed?

In patients with COPD, as destruction of the alveolar–capillary bed occurs, areas of ventilation and perfusion mismatch create hypoxic constriction of pulmonary vessels. Furthermore, airway obstruction increases intrathoracic pressure influencing venous return to the right side of the heart.

What’s the difference between ARF and ARDS?

Acute respiratory failure (ARF) is a term often used alongside ARDS, but it is a broader term that refers to the failure of the lungs from any causes, such as chronic obstructive pulmonary disease (COPD).

What is diffuse alveolar disease?

Diffuse alveolar damage (DAD) is considered the histological hallmark for the acute phase of ARDS. DAD is characterized by an acute phase with edema, hyaline membranes, and inflammation, followed by an organizing phase with alveolar septal fibrosis and type II pneumocyte hyperplasia.

What causes alveolar capillary membrane changes?

Conditions that cause changes or collapse of the alveoli (e.g., atelectasis, pneumonia, pulmonary edema, and acute respiratory distress syndrome) impair ventilation. High altitudes, hypoventilation, and altered oxygen-carrying capacity of the blood from reduced hemoglobin are other factors that affect gas exchange.

How does alveolar surface tension affect ventilation?

Because the alveoli of the lungs are highly elastic, they do not resist surface tension on their own, which allows the force of that surface tension to deflate the alveoli as air is forced out during exhalation by the contraction of the pleural cavity.

What inhibits alveolar inflation?

Surfactant Role in Respiration This fluid, called a surfactant, lowers the surface tension of the balloon-like alveoli by about a factor of 15 compared to the normal mucous tissue fluid in which they are immersed.

What is alveolar capillary dysplasia?

Alveolar capillary dysplasia. Alveolar capillary dysplasia (ACD) is a rare, congenital diffuse lung disease characterized by abnormal blood vessels in the lungs that cause highly elevated pulmonary blood pressure and an inability to effectively oxygenate and remove carbon dioxide from the blood.

What is alveolar capillary block syndrome (ACS)?

In 1951, Austrian and his colleagues 1 introduced the term “alveolar-capillary block” syndrome to identify a group of clinical and physiological features found in some patients with diffuse pulmonary disease who had evidence of impaired pulmonary oxygen diffusion.

What is alveolar-capillary stress failure?

Alveolar–capillary stress failure. When the heart is failing, an increase in capillary pressure and/or volume challenges the integrity of lung capillaries and, as a result, the physiology of these processes.

What is the difference between the alveoli and capillaries?

Alveoli in the lungs. Oxygen can pass from the alveoli to the capillaries because the concentration of oxygen is lower in the capillaries than in alveoli. Similarly, CO2 moves the other way because the concentration of carbon dioxide is lower in the alveoli than in the capillaries.