Pulmonary Function Tests Flashcards
What 3 things cause a variation in ventilatory performance?
Height
Age
Sex
What is the standard deviation for vital capacity (VC)?
500ml
What is ventilation?
The process of moving air in and out of the lungs
What is the tidal volume?
The volume of air that enters and leaves the lungs during normal breathing
What is the functional residual capacity?
The volume of gas within the lungs at the end of a normal expiration
What is the total lung capacity?
The volume of gas in the lungs after a full inspiration
What is the residual volume
The volume of gas remaining in the lungs after a full expiration
What is the Vital Capacity
The volume of air expelled by a full expiration from a position of full inspiration
How can we measure VC
Spirometry
How are residual volume and total lung capacity measured?
Using gas dilution or plethysmography mehtods
What is the most commonly used lung function test
Spirometry
What does spirometry measure
The amount and the speed of airflow that can be exhaled
What might reduce the FVC
Any condition that limits the lungs ability to achieve a full inspiration Lung fibrosis Loss of lung volume Kyphoscoliosis Ankylosing spondylitis Muscle weakness (myopathy Myasthenia gravis COPD
What is FEV1
The volume of air expelled in the first second of a maximal forced expiration from a position of full inspiration
What reduces the FEV1
Any condition that reduces VC
How is an obstructive defect detected
When the ratio of FEV1/FVC is less than 0.7
How is a restrictive defect detected
When the ratio is normal but there is a reduced FEV1 and FVC
What is the Peak expiratory flow
The maximum rate of airflow that can be achieved during a sudden forced expiration from a position of full inspiration
How many times is the PEF completed
3 times and and the best score is taken
What causes a reduced TLC
Restrictive lung disease
What causes an increased TLC?
Manifestation of hyperinflation
Changes in PCO2 are termed as what
Respiratory
Changes in HCO3 are termed as what
Metabolic
What does a disturbance in one system tend to promt
A compensatory response in the other
What is a general principle of compensation
Physiological copensatory mechanisms do not overcompensate. They often stop just short of total correction
What is the most likely abnormality with an increased pH
Alkalosis
What is the most likely abnormality with a decreased pH
Acidosis
Describe the changes found in acute respiratory acidosis
Reduced pH
Increase PCO2
Normal bicarbonate level
Describe the changes found in chronic respiratory acidosis
pH normal
Increased PCO2
High Bicarbonate level
What can cause acute respiratory acidosis
Obstruction of the airway
Overdose of sedative drugs
Acute neurological damage
What can cause chronic respiratory acidosis
Any process that results in sustained hypoventilation
COPD
Describe the changes in respiratory alkalosis
pH raised
PCO2 reduced
Normal bicarbonate level
Describe the changes in metabolic acidosis
pH reduced
PCO2 reduced
Bicarbonate reduced
What can cause respiratory alkalosis
Hyperventilation Pulmonary ebp;os, Acute severe asthma Anxiety related hyperventilation Salicylate poisoning
What can cause metabolic acidosis
Vomiting
Hypokalaemia - reabsorption of bicarbonate
What is respiratory failure?
Failure to maintain oxygenation
Describe what type 1 respiratory failure is
Hypoxaemia in the absence of hypercapnia
Ventilation is normal
Distubance of the VQ matching system within the lung
What can cause type 1 respiratory failure?
Intrinsic lung disease
Acute asthma
Lung fibrosis
Pulmonary embolism
Describe what type 2 respiratory failure is
Hypoxaemia with hypercapnia
What might cause type 2 respiratory failure
Sedative overdose
Reduced neuomuscular power
Resetting of the chemoreceptors that drive ventilation in chronic lung disease (COPD
What is the oxyhaemoglobin dissociation curve
The relationship of PO2 to oxygen saturation
What shape is the oxyhaemoglobin dissociation curve
Sigma
