Ventilation and Oxygenation Quiz

In a patient with a shunt fraction of 30%, what is the expected effect on arterial oxygenation when increasing FiO2 from 0.5 to 1.0?

• Significant improvement in PaO2

• Minimal change in PaO2

• Complete normalization of PaO2

• Worsening hypoxemia due to absorption atelectasis

According to the alveolar gas equation, what is the primary reason for a decreased PAO2 in a patient with hypercapnic respiratory failure?

• Increased alveolar CO2 reducing oxygen partial pressure

• Decreased atmospheric pressure

• Increased dead space ventilation

• Reduced tidal volume

In a patient with a high airway resistance, how does the time constant of the respiratory system affect ventilation?

• Shortened time constant requires higher inspiratory flow

• Prolonged time constant delays complete exhalation

• Time constant has no impact on ventilation

• Prolonged time constant reduces tidal volume only

What is the primary mechanism by which positive end-expiratory pressure (PEEP) improves oxygenation in acute respiratory distress syndrome (ARDS)?

• Increased tidal volume delivery

• Recruitment of collapsed alveoli

• Decreased airway resistance

• Enhanced CO2 elimination

A patient on a high-flow nasal cannula (HFNC) at 60 L/min and FiO2 of 0.6 still has refractory hypoxemia. What is the most likely limitation of HFNC in this scenario?

• Inability to deliver precise FiO2

• Lack of positive airway pressure to recruit alveoli

• Excessive dead space ventilation

• Inadequate humidification

When using a Venturi mask at 12 L/min with an FiO2 of 0.4, what happens if the oxygen flow rate is decreased to 8 L/min without changing the entrainment ports?

• FiO2 increases due to reduced air entrainment

• FiO2 decreases due to increased air entrainment

• FiO2 remains constant

• Total flow increases, improving oxygenation

In a patient with a non-rebreather mask at 15 L/min, persistent hypoxemia is noted. What is the most likely cause?

• Insufficient oxygen flow to prevent CO2 rebreathing

• Excessive oxygen flow causing atelectasis

• Inadequate mask seal allowing air entrainment

• Low reservoir bag capacity

In a patient with obesity hypoventilation syndrome on BiPAP, what is the most critical parameter to adjust to improve alveolar ventilation?

• Increase EPAP to improve oxygenation

• Increase IPAP-EPAP difference to enhance tidal volume

• Decrease inspiratory time to reduce auto-PEEP

• Increase backup rate to ensure minute ventilation

What is the most significant risk of using NIV in a patient with severe ARDS (PaO2/FiO2 < 100)?

• Barotrauma from high inspiratory pressures

• Delayed intubation leading to worsening hypoxemia

• Excessive CO2 retention due to low tidal volumes

• Aspiration pneumonia from gastric insufflation

A patient on NIV develops gastric distension and vomiting. What adjustment is most likely to mitigate this complication?

• Increase EPAP

• Decrease IPAP

• Switch to a nasal mask

• Increase inspiratory time