Respiratory

• What does ventilation (V) refer to?

  Flow of respiratory gases
• What is perfusion (Q)?

  Flow of blood
• What does the VA:Q ratio represent?

  Ratio of alveolar ventilation to perfusion

  
• Is it necessary to calculate the VA:Q ratio?

  No, just know if there is a mismatch
• What does a VAQ of 1 indicate?

  No mismatch in ventilation and perfusion
• What happens when VA:Q = 0?

  No ventilation occurs, leading to a shunt
• What is a physiological shunt?

  Normal perfusion with no alveolar ventilation
• What can a shunt lead to?

  Arterial hypoxaemia and cyanosis
• What is alveolar dead space?

  Ventilation without perfusion

  
• What is the V/Q ratio in alveolar dead space?

  $V/Q =$$\infty$ because Q=0
• How is alveolar ventilation (VA) calculated?

  VA = (tidal volume – dead space) x respiratory rate
• What is PACO2 proportional to?

  Rate of CO2 production by metabolism

  
• What happens during hyperventilation?

  Leads to hypocapnia (↓ PaCO2)
• What happens during hypoventilation?

  Leads to hypercapnia (↑ PaCO2)
• What is Dalton’s Law?

  Pressure of a gas = sum of partial pressures
• How is the partial pressure of oxygen in inhaled air calculated?

  Using Dalton’s law: $PIO2 =$$FIO2 \times [PB - PH2O]$

  
• What is the partial pressure of oxygen in air inhaled into the nasopharynx?

  $20 \text{ kPa}$
• What does the alveolar gas equation predict?

  PAO2 based on oxygen breathed

  
• What is the respiratory exchange ratio (RER)?

  Ratio of CO2 production to O2 uptake
• What is the relationship between PACO2 and PAO2?

  Described by the alveolar gas equation

  
• What is the significance of the oxygen-haemoglobin dissociation curve?

  Describes oxygen loading and unloading

  
• What is the Bohr effect?

  Changes in affinity due to PCO2 and pH

  
• What happens to haemoglobin in carbon monoxide poisoning?

  CO binds with higher affinity than oxygen

  
• What is the Haldane effect?

  Deoxygenated blood carries more CO2
• What is the chloride shift?

  Exchange of HCO3- for Cl- ions
• How can oxygen content be increased therapeutically?

  By giving supplemental oxygen or blood transfusion
• What is the total oxygen content of blood?

  Sum of oxygen bound to haemoglobin and dissolved in plasma
• What is the role of haemoglobin A (HbA)?

  To bind and transport oxygen in blood
• What is the significance of 2,3-DPG in oxygen transport?

  Reduces affinity for oxygen, facilitating unloading

  
• What is the effect of living at high altitude on 2,3-DPG?

  Stimulates production of 2,3-DPG
• What is the effect of temperature on the oxygen-haemoglobin dissociation curve?

  Increased temperature shifts curve to the right

  
• What is the effect of pH on the oxygen-haemoglobin dissociation curve?

  Decreased pH shifts curve to the right

  
• What is the significance of the P50 value?

  PO2 at which 50% saturation is achieved
• How does the oxygen-haemoglobin dissociation curve change with increased PCO2?

  Shifts to the right, decreasing affinity

  
• What is the relationship between oxygen saturation and partial pressure of oxygen?

  Higher PO2 leads to higher saturation

  
• What is the role of pulse oximeters?

  To detect arterial hypoxaemia
• What happens to oxygen saturation in tissues with low PO2?

  Facilitates unloading of oxygen
• What is the effect of increased 2,3-DPG on oxygen affinity?

  Decreases affinity, facilitating unloading

  
• What is the impact of carbon monoxide on oxygen transport?

  Reduces oxygen binding sites on haemoglobin

  
• What is the significance of the carbon dioxide dissociation curve?

  Describes CO2 transport in blood