2. Ventilation And Lung Mechanics Flashcards
(30 cards)
What is the range of normal pO2?
9.3-13.3 kPa
What is the normal range of pCO2?
4.7-6 kPa
What is lung parenchyma?
The portion of the lungs involved in gas exchange.
What is the definition of resting end-respiratory level/functional residual capacity?
The volume of air in the lungs at the end of a passive exhalation.
What is the resting end-respiratory level/functional residual capacity determined by?
The balance of elastic forces of the chest wall, favouring outward expansion, and the elasticity and surface tension of the lung, favouring a smaller lung volume.
What is the lung sealed to the chest wall by?
The pleural membranes.
The pressure within the pleural space is always slightly negative. However, when is it more negative - at end-inspiration or end-expiration?
At end-inspiration
What leads to a negative pressure in the pleural space?
The tension between the elastic forces acting to make the ribcage spring out and the elastic recoil of the lung.
Name the 5 accessory muscles of inspiration
Sternocleidomastoid.
Scalene.
Pectoralis major and minor.
Trapezius.
Name the 2 accessory muscles of expiration
Internal intercostals.
Muscles of the abdominal wall.
In an older adult, the resting expiratory level (FRC) is relatively higher than in a younger person. Why is this?
Lungs lose elasticity, so recoils in less on expiration.
What is lung compliance?
The relationship between pressure and volume.
What condition is caused by lowered lung compliance?
Fibrosis.
What condition is caused by increased lung compliance?
Emphysema
What is surfactant?
Mixture of lipids and proteins, secreted by alveolar cells.
What does surfactant do?
Acts to reduce surface tension allowing the lungs to inflate more easily (increased compliance), helps regulate alveolar size, and prevents alveolar collapse.
Production of surfactant begins between what weeks of gestational age? When is it adequate?
25-28 weeks.
Adequate at 35 weeks.
In what disease is surfactant production diminished?
Acute respiratory distress syndrome (ARDS).
Why is the pressure in small and large alveoli the same in the lungs, so that small alveoli do not collapse into the large ones?
Surfactant spreads more thinly across the surface of the large alveoli, so surfactant is less effective and surface tension increases, making inflation harder, and pressure remains the same in both large and small alveoli.
How is minute ventilation calculated?
Respiratory frequency x tidal volume.
Why is not all the respire volume available for gas exchange?
Physiological dead space - combination of:
Anatomical dead space - upper respiratory tract between mouth and respiratory bronchioles.
Alveolar dead space - alveolar that are ventilated but not perfused or very poorly perfused.
What is the rough volume of anatomical dead space? Therefore what is the tidal volume entering the gas-exchange region of the lung?
150ml.
350ml.
How is alveolar ventilation calculated?
Respiratory frequency x volume available for gas exchange (tidal volume - anatomical dead space)
What structures form the conducting airways? What division numbers are these up to?
Trachea, bronchi, bronchioles, terminal bronchial, transitional bronchioles.
Divisions 1-14.
