CTB3 Flashcards
What is pulmonary ventilation?
The movement of air into and out of the lungs.
What is alveolar ventilation?
The volume of air reaching the alveoli for gas exchange per minute.
How is alveolar ventilation calculated?
Alveolar ventilation = (Tidal Volume - Dead Space) × Respiratory Rate.
What is tidal volume (VT)?
The amount of air inhaled or exhaled during a normal breath.
What is dead space?
Air in the respiratory tract that does not participate in gas exchange.
What are the two types of dead space?
Anatomical dead space (conducting airways) and alveolar dead space (non-perfused alveoli).
What is physiological dead space?
The sum of anatomical and alveolar dead space.
How is oxygen transported in the blood?
Primarily bound to haemoglobin and a small amount dissolved in plasma.
How is carbon dioxide transported in the blood?
As bicarbonate ions (majority), bound to haemoglobin, or dissolved in plasma.
What is the oxygen-haemoglobin dissociation curve?
A graph showing the relationship between haemoglobin saturation and oxygen partial pressure.
What is the Bohr effect?
The reduction in haemoglobin’s oxygen-binding affinity due to increased CO2 or H+ concentration.
How does exercise affect the dissociation curve?
The curve shifts right, facilitating oxygen unloading in tissues.
What is the role of the respiratory muscles during inspiration?
The diaphragm and external intercostal muscles contract, expanding the thoracic cavity.
What drives expiration at rest?
Passive recoil of the lungs and chest wall.
How does forced expiration differ from passive expiration?
It involves active contraction of abdominal and internal intercostal muscles.
What is compliance in the lungs?
The ability of the lungs to expand in response to pressure changes.
How does reduced compliance affect breathing?
It makes lung expansion more difficult, as seen in fibrosis.
What is resistance in the airways?
The opposition to airflow caused by airway diameter and turbulence.
What factors influence airway resistance?
Airway diameter, smooth muscle tone, and mucus presence.
How does asthma affect airway resistance?
It increases resistance due to bronchoconstriction and mucus production.
What is the importance of surfactant?
It reduces alveolar surface tension, preventing alveolar collapse.
How is surfactant produced?
By type II alveolar cells.
What is the role of haemoglobin in oxygen transport?
Haemoglobin binds oxygen in the lungs and releases it in tissues.
What is Fick’s law of diffusion?
Gas diffusion rate is proportional to surface area, concentration gradient, and inversely proportional to membrane thickness.
How does emphysema affect gas exchange?
It reduces alveolar surface area, impairing diffusion.
How does pulmonary fibrosis affect gas exchange?
It thickens the alveolar membrane, reducing diffusion efficiency.
What is ventilation-perfusion matching?
The coordination of airflow (ventilation) and blood flow (perfusion) in the lungs for optimal gas exchange.
What is the significance of the V/Q ratio?
The ventilation-perfusion ratio determines the efficiency of gas exchange.
What causes a low V/Q ratio?
Poor ventilation relative to perfusion, as seen in asthma or pneumonia.
What causes a high V/Q ratio?
Reduced perfusion relative to ventilation, as seen in pulmonary embolism.
What is hypoxic pulmonary vasoconstriction?
Constriction of pulmonary vessels in poorly ventilated areas to redirect blood to better-ventilated regions.
How is breathing rate regulated?
By the respiratory centres in the medulla oblongata and pons.
What are central chemoreceptors?
Receptors in the medulla that detect changes in CO2 and pH levels in cerebrospinal fluid.
What are peripheral chemoreceptors?
Receptors in the carotid and aortic bodies that detect changes in O2, CO2, and pH in arterial blood.
How does hypercapnia affect ventilation?
Increased CO2 stimulates central chemoreceptors, increasing ventilation rate.
What is the role of the diaphragm in ventilation?
Its contraction increases thoracic volume, reducing intrapulmonary pressure to draw air in.
How does altitude affect oxygen transport?
Low partial pressure of oxygen reduces arterial oxygen saturation.
What is hypoxaemia?
Low oxygen levels in arterial blood.
How does chronic obstructive pulmonary disease (COPD) affect ventilation?
COPD increases airway resistance and reduces alveolar ventilation.
What is hyperventilation?
Excessive ventilation leading to decreased arterial CO2 (hypocapnia).
What is hypoventilation?
Reduced ventilation causing elevated arterial CO2 (hypercapnia).
How does haemoglobin saturation change with exercise?
Increased demand causes more oxygen to be released to tissues (rightward curve shift).
How is carbonic acid formed in blood?
CO2 reacts with water, catalysed by carbonic anhydrase.
How is carbonic acid buffered?
It dissociates into bicarbonate and hydrogen ions, maintaining blood pH.
What is respiratory acidosis?
A condition where CO2 retention lowers blood pH.
What is respiratory alkalosis?
A condition where excessive CO2 loss raises blood pH.
How does the body compensate for metabolic acidosis?
By increasing ventilation to expel CO2.
What is the significance of the partial pressure gradient for oxygen?
It drives oxygen diffusion from alveoli to blood.
What is the significance of the partial pressure gradient for CO2?
It drives CO2 diffusion from blood to alveoli.
How does pulmonary oedema affect gas exchange?
Fluid accumulation in alveoli reduces gas diffusion efficiency.
