Respiratory Physiology Quiz

Work of Breathing and the Role of Surfactant

• Work of breathing is the energy required to move the lung and chest wall, with elastic work representing about 70% of total work and non-elastic work representing about 30%.
• Oxygen cost of breathing in healthy individuals is low, with respiratory muscles consuming only 2-5% of total oxygen consumption for minute volumes of about 50 L/min.
• Compliance is a measure of the ease with which the lungs can be stretched or inflated, with normal adult lung compliance being 0.1-0.4 L/cmH2O.
• Compliance work has two main contributors: tissue elasticity and surface tension, with energy required to deform elastic tissues and stretch elastin fibers and overcome surface tension.
• Surfactant is a complex mixture of proteins and lipids, synthesized by type II pneumocytes (alveolar cells) and stored in cytoplasmic lamellar bodies until released to the surface of the alveolus and made available at the air-liquid interface.
• The function of surfactant is to reduce surface tension by interfering with water molecule interactions, thereby increasing lung compliance and stabilizing alveoli of different sizes.
• Newborn Respiratory Distress Syndrome is a condition where developing fetal lungs do not normally synthesize surfactant until late in pregnancy, leading to difficulty in breathing in premature infants.
• Surfactant treatment involves the administration of corticosteroids to the mother prior to the delivery of the premature infant, oxygen through continuous positive airway pressure, and surfactant.
• Increased compliance can be due to loss of elastin fibers/elastic tissue in early emphysema or aging, while decreased compliance can be due to chest wall compliance (scoliosis, ankylosing spondylitis) or pulmonary fibrosis.
• Alveoli interdependence has an additional stabilizing function, where when an alveolus in a group of interconnected alveoli begins to collapse, the surrounding alveoli are stretched, pulling outwards on the collapsing alveoli and keeping it open.
• Room air has a pO2 of 21 kPa, exhaled air has a pO2 of 15.9 kPa and alveolar air has a pO2 of 14.7 kPa, while room air has a pCO2 of 0 kPa, exhaled air has a pCO2 of 4.2 kPa and alveolar air has a pCO2 of 5.3 kPa.
• Disease can alter the optimal respiratory rate/tidal volume for minimizing work, with figures 14.10 A and B in Nettler's Essential Physiology providing visual representations of these changes.

Work of Breathing and the Role of Surfactant

• Work of breathing is the energy required to move the lung and chest wall, with elastic work representing about 70% of total work and non-elastic work representing about 30%.
• Oxygen cost of breathing in healthy individuals is low, with respiratory muscles consuming only 2-5% of total oxygen consumption for minute volumes of about 50 L/min.
• Compliance is a measure of the ease with which the lungs can be stretched or inflated, with normal adult lung compliance being 0.1-0.4 L/cmH2O.
• Compliance work has two main contributors: tissue elasticity and surface tension, with energy required to deform elastic tissues and stretch elastin fibers and overcome surface tension.
• Surfactant is a complex mixture of proteins and lipids, synthesized by type II pneumocytes (alveolar cells) and stored in cytoplasmic lamellar bodies until released to the surface of the alveolus and made available at the air-liquid interface.
• The function of surfactant is to reduce surface tension by interfering with water molecule interactions, thereby increasing lung compliance and stabilizing alveoli of different sizes.
• Newborn Respiratory Distress Syndrome is a condition where developing fetal lungs do not normally synthesize surfactant until late in pregnancy, leading to difficulty in breathing in premature infants.
• Surfactant treatment involves the administration of corticosteroids to the mother prior to the delivery of the premature infant, oxygen through continuous positive airway pressure, and surfactant.
• Increased compliance can be due to loss of elastin fibers/elastic tissue in early emphysema or aging, while decreased compliance can be due to chest wall compliance (scoliosis, ankylosing spondylitis) or pulmonary fibrosis.
• Alveoli interdependence has an additional stabilizing function, where when an alveolus in a group of interconnected alveoli begins to collapse, the surrounding alveoli are stretched, pulling outwards on the collapsing alveoli and keeping it open.
• Room air has a pO2 of 21 kPa, exhaled air has a pO2 of 15.9 kPa and alveolar air has a pO2 of 14.7 kPa, while room air has a pCO2 of 0 kPa, exhaled air has a pCO2 of 4.2 kPa and alveolar air has a pCO2 of 5.3 kPa.
• Disease can alter the optimal respiratory rate/tidal volume for minimizing work, with figures 14.10 A and B in Nettler's Essential Physiology providing visual representations of these changes.