025 Understanding Respiratory Illness Flashcards
What is the difference between hypoxaemia and hypoxia?
hypoxaemia is low O2 blood concentration. Hypoxia is the low O2 levels reaching the tissues.
What does the A-a gradient show? what are the axis of the graph?
This shows the alveolar – artery ratio of oxygen. The axis of the graph are PaO2 on the x axis and the PaCO2 on the y axis.
What equations are used to determine the A-a gradient?
PO2A-a = PAO2 – PaO2, PAO2 = PiO2 – (PaCO2/0.8), assuming that PaCO2 and PACO2 are equal because all of the CO2 in the blood system should be expired. 0.8 is the correction factor.
What is the physiological limit for the A-a gradient? What about clinically?
A healthy individual should be less than <2. Although, ideally it should be 1. This value is corrected for inaccuracies. In hospital, it is acceptable to have it <4.
Do physiological shunts cause low or high V/Q ratio?
Low
How does the body respond to a high V/Q ratio caused by alveolar dead space?
Bronchial constriction decreasing amount of ventilation to under perfused area of the lung
How does the body respond to a low V/Q ratio caused by physiological shunts?
Hypoxic vasoconstriction of underventilated area to direct blood flow to other well ventilated parts?
What is the HCO3- concentration for type I and II respiratory disease?
Normal concentrations for both acute respiration type I and II disease. Normal concentrations for chronic type I, however can be high for type II chronic respiratory illnesses due to compensation.
What is the A-a gradient for type I and II respiratory disease?
Type I disease - normal A-a gradient
Type II disease - normal/high A-a gradient
Discuss physiological V/Q mismatches at the apices and bases of the lung
At the apices of the lung, there tends to be lower PCO2 and higher PO2. At the base of the lung, there tends to be higher PCO2 and lower PO2.
What V/Q mismatch does chronic bronchitis cause?
Low
What V/Q mismatch does pneumonia cause?
Low
What V/Q mismatch does fibrosis cause?
High
What V/Q mismatch does asthma cause?
Low
What V/Q mismatch does pulmonary embolism cause?
High
