فسلجة

• Lung mechanics


  The forces and properties that govern how our lungs function during breathing
• Lungs


  • Two elastic balloons nestled within the rib cage
  • Composed of millions of tiny air sacs called alveoli, offering a vast surface area for gas exchange
• Diaphragm


  • Dome-shaped muscle that sits below the lungs
  • When it contracts, it pulls down, expanding the chest cavity and creating a pressure difference that draws air in
• Chest wall


  • Ribs and intercostal muscles form a flexible cage surrounding the lungs
  • When these muscles contract, they pull the ribs upward and outward, further increasing the chest cavity volume
• Pleura


  • Double-layered membrane lining the lungs and chest wall
  • The space between these layers, filled with a thin fluid, allows the lungs to slide smoothly against the chest wall during breathing
• Inspiration (inhaling)


  1. Diaphragm and intercostal muscles contract, expanding the chest cavity

  2. This decreases air pressure within the lungs compared to the outside, drawing air in through the airways
• Gas exchange


  In the alveoli, oxygen from the inhaled air diffuses into the bloodstream, while carbon dioxide diffuses out from the blood into the alveoli
• Expiration (exhaling)


  1. Diaphragm and intercostal muscles relax, the chest cavity recoils passively due to its natural elasticity, and the lungs naturally collapse slightly

  2. This pushes air out through the airways
• Elasticity


  • The lungs and chest wall have inherent elasticity that tends to pull them inward (lungs) and outward (chest wall)
  • This counterbalance is crucial for maintaining lung volume and generating the force for expiration
• Surface tension


  • A thin film of fluid lines the alveoli, creating surface tension that resists expansion
  • Special cells in the alveoli produce a surfactant to reduce surface tension, allowing easier expansion during inspiration
• Airway resistance


  • The narrower airways offer some resistance to airflow, affecting how easily air moves in and out
• Compliance


  • Respiratory compliance, specifically pulmonary compliance, refers to the ease with which your lungs and chest wall can expand during inhalation
  • It measures how much volume change occurs in your lungs for a given change in pressure
• Compliance of the respiratory system (CRS) is measured as the change in lung volume (∆V) divided by the change in airway pressure (∆P), this represents the difference between alveolar pressure, at a given lung volume, and ambient (atmospheric) pressure. CRS = ∆V/∆P
• Normal breathing: Adequate compliance ensures
• Compliance of the respiratory system (CRS)


  The ease with which your lungs and chest wall can expand during inhalation. It essentially measures how much volume change occurs in your lungs for a given change in pressure
• Compliance


  Refers to the ease with which your lungs and chest wall can expand during inhalation. It essentially measures how much volume change occurs in your lungs for a given change in pressure
• Compliance of the respiratory system (CRS)

  Measured as the change in lung volume (∆V) divided by the change in airway pressure (∆P), this represents the difference between alveolar pressure, at a given lung volume, and ambient (atmospheric) pressure. CRS = ∆V/∆P
• Importance of Compliance


  • Ensures efficient and effortless breathing in normal breathing
  • Can decrease in lung diseases like asthma, COPD, and emphysema due to reduced lung elasticity, increased airway resistance, or fluid buildup, making breathing more difficult and requiring more work
  • Helps doctors assess lung function and diagnose respiratory issues
• Improving Compliance


  1. Using bronchodilators to relax airway muscles, reducing resistance and improving compliance

  2. Doing breathing exercises to strengthen respiratory muscles and improve diaphragmatic function, potentially increasing compliance
• Resistance

  Respiratory system resistance refers to the opposition to airflow during breathing. It's like friction for air trying to move in and out of your lungs
• Components Contributing to Resistance

  • Narrower airways like smaller bronchioles offering more resistance due to limited space
  • Smooth muscle tone around airways constricting in certain situations like asthma, increasing resistance
  • Mucus buildup in airways acting as a barrier, increasing resistance
  • Elasticity and stiffness of lung tissue and chest wall
• Factors Affecting Resistance


  • Age - Airway resistance generally increases with age due to loss of lung elasticity and changes in airway structure
  • Body posture - Lying down can slightly increase resistance compared to standing
  • Exercise - During exercise, resistance may increase due to increased airflow