Pulmonary Pathophysiology - Pulmonary function tests Flashcards
Examples of pulmonary function tests
Forced expiration (spirometry)
Blood gases
Single breath CO diffusing capacity
Single breath Nitrogen test of uneven ventilation
Other pulmonary function tests - see later flashcard
Patterns of forced expirations
FEV1 = Forced expiratory volume in 1 second
FVC = Forced vital capacity
Forced expiratory flows
Volume / time
Expiratory and inspiratory flow-volume curves for healthy lung and obstruction
O2 haemoglobin dissociation curve with P100, P75 and P50
Factors which shift oxygen haemoglobin dissociation curve
Causes of hypoxaemia
Hypoventilation
Diffusion impairment
Shunt
Ventilation perfusion inequality
Alveolar ventilation equation
Alveolar gas equation
Use of alveolar ventilation equation and alveolar gas equation
To predict alveolar PO2 and PCO2 with changes in ventilation
Can also be used to calculate inspired FiO2 required to return alveolar PO2 to normal values
Time course of PO2 in pulmonary capillary normally and with diffusion limitation
Shunt definition
Blood that reaches the arterial system without passing through ventilated areas of lung
How to tell if patient has shunt
Giving patient FiO2 1.0 does not increase arterial PaO2 to expected value
Henderson-Hasselbalch equation
Single breath CO diffusing capacity
Causes of reduced diffusing capacity
Thickened blood gas barrier
Reduced area of blood gas barrier
Reduced capillary blood volume
Inequality of ventilation and diffusion properties
Single breath Nitrogen test of uneven ventilation
Slope 3 should be plateau and degree of slope represents uneven ventilation
Slope 4 represents closing capacity
Overall a useful test of small airway changes
Lung volumes measurements with spirometry
Cannot measure RV, FRC or TLC with spirometry
How to measure functional residual capacity
Body box and Boyle’s Law
Other pulmonary function tests
Airway resistance - with body box
Lung compliance - with oesophageal balloon
Ventilatory response to CO2 and hypoxia
Exercise tests
Uses of pulmonary function tests
Supporting information for diagnosis
Efficacy of bronchodilator drug use
Assessment of patients for surgery
Worker’s compensation
Epidemiological studies
