Mastering Lung Function and Volume Measurements

Methods for Lung Function and Volume Measurements, and Understanding Dead Space and Pulmonary Ventilation

• Spirometers and spirometry are composed of two vessels, with one containing water and the other floating upside down in the first.
• PC spirometers can turn a desktop or laptop into a spirometer when running the software application provided with the device, and Spirotrac is the most widely used spirometry software.
• The functional residual capacity (FRC) can be measured by the helium dilution technique, which involves adding helium to an oxygen mixture in a spirometer.
• Body plethysmography involves a patient sitting in an airtight chamber and breathing through a mouthpiece, and FRC can be calculated using Boyle's law.
• Lung volumes vary based on body size, age, sex, muscular training, posture, race, and respiratory diseases, with vital capacity (VC) being a useful measurement clinically.
• Dead space is the volume occupied by gas in the lungs that does not participate in gas exchange, and there are different types, including anatomical, physiological, and alveolar dead space.
• Anatomical dead space is the volume of air that does not enter the alveoli during normal respiration, with 150 ml of air in anatomical dead space being unable to contribute to gas exchange.
• Alveolar dead space is the air in alveoli surrounded by pulmonary capillaries without blood flow, usually negligible in healthy people but can increase in disease.
• Physiological dead space is the total dead space, and it is calculated by measuring partial pressures or fractional concentration of CO2 in alveoli and expired air.
• Pulmonary or minute ventilation is the total volume of air breathed per minute, and alveolar ventilation is the portion that contributes to gas exchange.
• The normal minute ventilation is 6 L/min, with normal alveolar ventilation being (500 ml - 150 ml) x 12 min-1 = 4200 ml/min.
• Practice questions include comparing the compositions of alveolar air, expired air, and room air and calculating how much inspired air ventilates the alveoli during one minute.

Methods for Lung Function and Volume Measurements, and Understanding Dead Space and Pulmonary Ventilation

• Spirometers and spirometry are composed of two vessels, with one containing water and the other floating upside down in the first.
• PC spirometers can turn a desktop or laptop into a spirometer when running the software application provided with the device, and Spirotrac is the most widely used spirometry software.
• The functional residual capacity (FRC) can be measured by the helium dilution technique, which involves adding helium to an oxygen mixture in a spirometer.
• Body plethysmography involves a patient sitting in an airtight chamber and breathing through a mouthpiece, and FRC can be calculated using Boyle's law.
• Lung volumes vary based on body size, age, sex, muscular training, posture, race, and respiratory diseases, with vital capacity (VC) being a useful measurement clinically.
• Dead space is the volume occupied by gas in the lungs that does not participate in gas exchange, and there are different types, including anatomical, physiological, and alveolar dead space.
• Anatomical dead space is the volume of air that does not enter the alveoli during normal respiration, with 150 ml of air in anatomical dead space being unable to contribute to gas exchange.
• Alveolar dead space is the air in alveoli surrounded by pulmonary capillaries without blood flow, usually negligible in healthy people but can increase in disease.
• Physiological dead space is the total dead space, and it is calculated by measuring partial pressures or fractional concentration of CO2 in alveoli and expired air.
• Pulmonary or minute ventilation is the total volume of air breathed per minute, and alveolar ventilation is the portion that contributes to gas exchange.
• The normal minute ventilation is 6 L/min, with normal alveolar ventilation being (500 ml - 150 ml) x 12 min-1 = 4200 ml/min.
• Practice questions include comparing the compositions of alveolar air, expired air, and room air and calculating how much inspired air ventilates the alveoli during one minute.