Compliance

Definition

Compliance refers to the ability of the lungs and thoracic cavity to expand during inhalation. It is a measure of the lung's distensibility, indicating how easily the lungs can stretch and accommodate changes in volume. Understanding compliance is essential because it directly impacts ventilation efficiency and the overall mechanics of breathing.

5 Must Know Facts For Your Next Test

1. Compliance is measured as the change in lung volume per unit change in pressure, often expressed in liters per centimeter of water (L/cm H2O).
2. Higher compliance indicates that the lungs can easily expand, while lower compliance suggests stiffer lungs, which require more effort to inflate.
3. In conditions like pulmonary fibrosis, compliance decreases, leading to restrictive lung disease where breathing becomes more difficult.
4. Surfactant, a substance produced by the alveoli, plays a critical role in maintaining compliance by reducing surface tension in the lungs.
5. In healthy individuals, the normal compliance value for adult lungs is about 0.1 L/cm H2O, but this can vary based on age, health status, and body position.

Review Questions

• How does compliance affect the mechanics of breathing?
  • Compliance significantly impacts how easily air can enter and exit the lungs. When compliance is high, the lungs can expand effortlessly during inhalation, allowing for efficient gas exchange. Conversely, low compliance means more effort is required to inflate the lungs, leading to potential respiratory distress and reduced oxygen intake.
• What are some clinical conditions associated with decreased lung compliance, and what are their implications for respiratory function?
  • Conditions like pulmonary fibrosis and acute respiratory distress syndrome (ARDS) are linked to decreased lung compliance. These conditions result in stiffened lungs that require more pressure to achieve the same volume during breathing. This impairment can lead to inadequate ventilation and lower oxygen levels in the bloodstream, ultimately compromising respiratory function.
• Evaluate how surfactant deficiency impacts lung compliance and overall respiratory health.
  • Surfactant deficiency leads to increased surface tension within the alveoli, which results in decreased lung compliance. This makes it harder for the lungs to inflate fully during inspiration, causing difficulty in breathing and reduced oxygen exchange. In premature infants, surfactant deficiency can cause neonatal respiratory distress syndrome, highlighting the crucial role surfactant plays in maintaining optimal lung function and compliance.

Related terms

Tidal Volume: The amount of air that is inhaled or exhaled during normal breathing.

Elastance: The ability of the lung or thoracic structure to return to its original shape after being stretched or deformed.

Pulmonary Fibrosis: A lung disease that occurs when lung tissue becomes damaged and scarred, leading to decreased compliance and difficulty in breathing.