Lecture 11 Flashcards
What are the two categories of lung disease?
- Obstructive
- reduction in flow through airways - Restrictive
- reduction in lung expansion
Both reduce ventilation
If Forced expiratory volume in one second (FEV1) against vital capacity is under 80% …
Obstructive lung disease
When looking at Flow-Volume relationships, what would a linear decline imply?
Rapid increase of flow rate
Obstructive lung disease
What could the narrowing of the airways be due to?
Excessive secretions - mucus narrows airways Bronchoconstriction e.g. asthma - hypersensitivity triggers airways to constrict Inflammation - In tissue around the airways - Swelling constricts airways
What happens to flow rate in obstructive lung disease?
Flow rate drops as there is an increased resistance to the flow of air
How would obstructive lung disease show in Volume-Time curves?
FVC is unaltered but FEV1 drops
Endpoint volume remains the same but the time taken to reach there is longer
How would obstructive lung disease show in Flow-Volume loops?
The initial flow and peak flow can be similar but there is a sharp fall in flow-rate giving a concave shape to the curve
What are examples of obstructive lung diseases?
Chronic bronchitis
- Persistent productive cough and excessive mucus secretion (3 consecutive months in last 2 years)
Asthma
- Inflammatory disease
Chronic obstructive pulmonary disease (COPD)
- Structural changes
- Lower airways swell
Emphysema
- Loss of elastin
- Can be classified as both obstructive and restrictive
What can happen in asthma patients?
The sufferer has hyperactive airways
Genetic mutations of increased ACh is possible
What can be a trigger for asthma patients?
Atropic (extrinsic) - allergies, contact with allergens e.g.hay fever, pollen, dust, particles leads to increased level of IGEs - has hereditary links
Non-atropic (intrinsic)
- respiratory infections, cold air, stress, exercise, inhaled irritants, drugs
- common in cyclists
- irritants
e. g. smoke - drugs
e. g. aspirin
How does the immune system respond to triggers for asthma?
Movement of the inflammatory cells into the airways
Release of inflammatory mediators
such as histamine and subsequent bronchioconstriction
What kind of asthma treatment is there?
Short-acting beta-2 adrenoreceptor agonists
- salbutamol
- causes dilation of airways
Longer acting treatments:
Inhaled steroids
- Glucocorticoids such as beclometasome act to reduce the inflammatory responses
- Long-acting beta-2 adrenoreceptor agonists
What can be seen in restrictive lung disease?
Reduced lung expansion - Chest wall abnormalities - Muscle contraction deficiencies Loss of compliance (fibrosis) - Normal aging process - Increase in collagen - Exposure to environment factors
What happens to the vital capacity in restrictive lung disease?
It decreases
What can be seen in volume-time curves in restrictive lung disease?
Reduction in FVC, but FEV1 remains unaltered (or increases!)
What can be seen in Flow-Volume loops in restrictive lung disease?
The shape of the relationship tends to be normal, but there is a reduction in the volumes of air moved. There can be a reduction in the peak flow
How is breathing regulated?
Automatic, rhythmical process
Basic respiratory rhythm is generated by centers in the medulla
Inputs from where can modify the respiratory pattern?
Pons
Medulla
How can the Pons regulate breathing?
Control changes in breathing pattern
How can the Medulla regulate breathing?
Controls basic breathing
Breathing is typically an involuntary process. But what are examples of it being controlled consciously?
Hyperventilation
Breath holding
Are conscious modifications of breathing long-term?
It is temporary
Will be overridden if required
e.g. CO2 build up triggers breathing
What are the two medullary centers that regulate breathing?
Dorsal Respiratory Group (DRG)
Ventral Respiratory Group (VRG)
How does the DRG regulate inspiration?
Sends signals to the inspiratory muscles Spontaneously active - shows period of activity - shuts off - period of activity
How does VRG regulate inspiration and expiration?
Inactive during quiet respiration
During activation, helps control forceful inspiration and expiration
Which centers affect the Pre-Botzinger complex to control breathing? Where do they belong?
Pneumotaxic center
Apneustic center
Pons
What does the pneumotaxic center do?
Increases the rate of breathing by shortening inspirations
Period of firing goes on for shorter period
Inhibitory effect on inhibitory center
What does the apneustic center do?
Increases the depth and reduces the rate by prolonging stimulations
- Stimulates inhibitory center
What reflex are stretch receptors involved in when controlling respiration?
Hering-Breuer reflex
How does the Hering-Breuer reflex work?
Stretch receptors in the lung send signals back to the medulla to limit inspiration and prevent over-inflation of the lungs
What are the steps in the Hering-Breuer reflex?
- Inspiratory center acts on Phrenic nerve
- Phrenic nerve stimulation contracts diaphram
- Stretch receptor in lung sends signals
- Vagus nerve stimulation
- Inhibits inspiratory center
How are chemoreceptors involved in respiration?
Central chemoreceptors
- Monitors conditions in CSF
- Sensing CO2 and pH
- Buffering on pH is more sensitive in CSF than in
blood (acidification stimulates breathing)
- Indirect response to a rise in CO2
- Stimulation leads to an increase in ventilation
Peripheral chemoreceptors
- Located in the carotid body and aortic arch
- Respond to : Increase in CO2, Decrease in pH,
Decrease in O2
- Stimulation leads to an increase in ventilation
Which gas is the primary driving force for respiration?
CO2
What happens when patients become accustomed to living with elevated CO2?
CO2 loses driving effect / can stop breathing altogether
O2 becomes primary driving force for respiration
