impaired gas exchange

Examples of impaired gas exchange in the following topics:

• Respiratory Distress Syndrome

  • It is characterized by inflammation of the lung parenchyma leading to impaired gas exchange with concomitant systemic release of inflammatory mediators causing inflammation, hypoxemia, and frequently resulting in multiple organ failure.
  • This adds up to the impaired oxygenation which is the central problem of ARDS, as well as to respiratory acidosis, which is often caused by ventilation techniques such as permissive hypercapnia which attempt to limit ventilator-induced lung injury in ARDS.
  • The result is a critical illness in which the 'endothelial disease' of severe sepsis/SIRS is worsened by the pulmonary dysfunction, which further impairs oxygen delivery.

• Pulmonary Edema

  • Pulmonary edema is fluid accumulation in the air spaces and parenchyma of the lungs and it leads to impaired gas exchange which may cause respiratory failure.
  • Low oxygen saturation and disturbed arterial blood gas readings support the proposed diagnosis by suggesting a pulmonary shunt.
  • In the case of cardiogenic pulmonary edema, urgent echocardiography may strengthen the diagnosis by demonstrating impaired left ventricular function, high central venous pressures, and high pulmonary artery pressures.

• Factors Affecting Pulmonary Ventilation: Compliance of the Lungs

  • Low lung compliance is commonly seen in people with restrictive lung diseases, such as pulmonary fibrosis, in which scar tissue deposits in the lung making it much more difficult for the lungs to expand and deflate, and gas exchange is impaired.

• Dead Space: V/Q Mismatch

  • Dead spaces can severely impact breathing due to the reduction in surface area available for gas diffusion.
  • Anatomical dead space, or anatomical shunt, arises from an anatomical failure, while physiological dead space, or physiological shunt, arises from a functional impairment of the lung or arteries.
  • As a result, the rate of gas exchange is reduced.
  • This will decrease ventilation but not affect perfusion; therefore, the V/Q ratio changes and gas exchange is affected .

• Basic Principles of Gas Exchange

  • The purpose of the respiratory system is to perform gas exchange.
  • Pulmonary ventilation provides air to the alveoli for this gas exchange process.
  • Two important aspects of gas exchange in the lung are ventilation and perfusion.
  • This illustrates the exchange of gas in humans between a capillary and an alveolus.
  • Discuss how gas pressures influence the exchange of gases into and out of the body

• Adjustments at High Altitude

  • The partial pressure gradients for gas exchange are also decreased, along with the percentage of oxygen saturation in hemoglobin.
  • Humans can survive at high altitudes with impaired short-term functions that eventually adjust in the long term.
  • Additionally, the peripheral chemoreceptors cause sympathetic nervous system stimulation, which causes the heart rate to increase while stroke volume decreases, and digestion is impaired.

• Gas Pressure and Respiration

  • Gas pressures in the atmosphere and body determine gas exchange: both O2 and CO2 will flow from areas of high to low pressure.
  • This collision between gas particles and vessel walls produces gas pressure.
  • Each gas component of that mixture exerts a pressure.
  • The pressure for an individual gas in the mixture is the partial pressure of that gas.
  • These pressures determine the gas exchange, or the flow of gas, in the system.

• Isothermal Processes

  • This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange.
  • In contrast, an adiabatic process is where a system exchanges no heat with its surroundings (Q = 0).
  • The value of the constant is nRT, where n is the number of moles of gas present and R is the ideal gas constant.
  • In other words, the ideal gas law PV = nRT applies.
  • In thermodynamics, the work involved when a gas changes from state A to state B is simply

• Henry's Law

  • Henry's law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas.
  • The main application of Henry's law in respiratory physiology is to predict how gasses will dissolve in the alveoli and bloodstream during gas exchange.
  • Oxygen has a larger partial pressure gradient to diffuse into the bloodstream, so it's lower solubility in blood doesn't hinder it during gas exchange. 
  • Therefore, based on the properties of Henry's law, both the partial pressure and solubility of the oxygen and carbon dioxide determine how they will behave during gas exchange.
  • Explain the way in which Henry's law relates to gas exchange in the respiratory system

• Functional Anatomy of the Respiratory System

  • The primary function of the respiratory system is gas exchange between the external environment and an organism's circulatory system.
  • As gas exchange occurs, the acid-base balance of the body is maintained as part of homeostasis.
  • At the molecular level, gas exchange occurs in the alveoli—tiny sacs which are the basic functional component of the lungs.
  • Alveolar Ventilation (VA):  The amount of gas per unit of time that reaches the alveoli (the functional part of the lungs where gas exchange occurs).
  • It is defined as tidal volume minus dead space (the space in the lungs where gas exchange does not occur) times the respiratory rate.