Session 6 - notes Flashcards
Define chronic bronchitis
It is defined as the presence of cough and excessive mucus production on most
days for at least 3 consecutive months for 2 successive years.
Define Emphysema
It is defined as permanent destructive enlargement of the airspaces distal to the
terminal bronchiole
Give five changes in airways and lungs in COPD
Increase in bronchial wall thickness and mucus
Enlarged airways and airspaces
Reduced elastic recoil
Reduced alveolar surface for gas exchange
Is a significant improvement in the spirometry or flow volume loop likely to be seen following inhaled bronchodilators in COPD?
No, that sign would be found in asthma
Why is diffusion capacity reduced in ephysema?
Destruction of aveolar walls and capillary bed leads to reduction in effectve surface area
What are the typical radiological findings in COPD?
- Hyperinflation of the lungs (more than 6 ribs seen anteriorly)
- flattening of the diaphragm
- The heart may appear elongated and thin
- Ribs may appear to be more horizontal
- What type of Respiratory failure can occur in COPD?
- In early stages type 1 respiratory failure due to ventilation perfusion mismatch due to poor ventilaton of parts of the lung
- In late stages,( when the FEV1 is less than 1 litre) type 2 respiratory failure occurs due to hypoventilation.
What are three main features of chronic type 2 respiratory failure
o compensatory changes for hypoxia such as polycythaemia
o pulmonary hypertension with right heart failure (Cor pulmonale)
o CO2 retention (flapping tremors, warm hands, bounding pulse)
- What are the possible consequences of using oxygen in patients with chronic hypercapnia?
In the face of persistent hypercapnia, the choroid plexus imports HCO3 into the CSF. This restores the CSF pH to normal and results in the central chemoreceptors being “reset‟ to higher CO2 level. In other words the central chemoreceptors become ‘adapted’ to the chronic hypercapnia.
In this situation it is the hypoxia acting via the peripheral chemoreceptors that is driving the respiration.
Oxygen therapy in such patients may improve the hypoxia to the point where the peripheral chemoreceptors are no longer activated, and the respiratory ‘drive’ ceases. This would result in a reduced rate & depth of respiration, which would worsen the hypercapnia.
Therefore low concentration (24% - 28% oxygen) is used in patients with COPD and chronic type 2 resp failure, (most often in the setting of an acute exacerbation of COPD due to infection)
• How do we cough? Which muscles are used in what way, and how is the cough co-ordinated by the CNS? Where in the CNS is coughing controlled, and what factors trigger a cough?
Cough is coordinated by the medulla oblongata.
Cough is initiated by irritation of Cough receptors in upper airway.
The glottis closes, and strong contraction of the expiratory muscles (abdominal muscles and internal intercostals) builds up intrapulmonary pressure, whereupon the glottis suddenly opens causing an explosive discharge of air.
