Respiratory disease

Question 1

Briefly describe the two types of respiratory failure

Answer 1

1. Low PaO2 but normal/low PaCO2

2. Low PaO2 but high PaCO2

Question 2

What are causes of hypoxaemia?

Answer 2

Hypoventilation eg. Blocked airway
Low P(I)O2 eg. Altitude or asphyxia
Diffusion barrier eg. Fick’s law and fibrosis
ventilation-perfusion mismatch eg. Left-riught shunt

Question 3

What is sleep apnoea?

Answer 3

A cessation of breathing during sleep
Absence if naso-oral airflow for more than 10s
Obstructive origin- respiratory efforts
Central origin- no respiratory efforts

Question 4

Describe type 2 respiratory failure

Answer 4

Low PaO2 with high PaCO2

Hypoventilation with reduced V(A)

Question 5

Describe type 1 respiratory failure

Answer 5

Low PaO2 with normal/low PaCO2
Good and bad parts of lung average saturation to lower
Hypoxia stimulates increases ventilation but this only effects the good parts of the lung with little effect on the total saturation as normal lung function is already 100%
Extra CO2 blown off

Question 6

What are the consequences of systemic hypoxia?

Answer 6

Central hypoxia- drowsiness and confusion, coma, death
Renal hypoxia- EPO production, increased O2 capacity
Pulmonary hypoxia- hypoxic pulmonary vasoconstriction (HPV), pulmonary hypertension
Hypercapnia- respiratory acidiosis

Question 7

What happens in obstructive sleep apnoea?

Answer 7

Smooth muscle tone is lost and the aiurways close more easily- obesity is a risk factor and ius associated with hypertension

Question 8

What happens in central sleep apnoea?

Answer 8

Sleep-onset- removal of wakefulness exposes apneic threshold
Post-arousal/sigh- arousal has them return to wakefulness- hypercapnic response
Phasic REM sleep- pontogenicolo-occipal (PGO) waves bypass medullary centres and inhibit diaphragm
Hypocapnic CSA
Low PaCO2 awake with increased CO2 sensitivity- falls below apneic threshold
Heart failure- no rise in PaCO2 in PaCO2 in sleep as no fall in ventilation
High altitude- by lost ventilation induces hypocapnia
Hypercapnia CSA
Hypoventilation in wakefulness- worsenbs in sleep- arousal
CCHS
Brainstem disorders or opoiod use

Question 9

What is CCHS?

Answer 9

Congenital central hypoventilation syndrome
During sleep the patient “forgets” to breath
CO2 chemoreception?- CO2 provides the drive to breath
PHOX2B mutation- neuronal differentiation and maturation
Treatment- remove hypoventilation, mechganiucak ventilation, phrenic nerve pacing

Question 10

Describe asthma

Answer 10

Chronic airway inflammation- alveolar wall infiltration by immune cells
Increased airway responsiveness
Bronchoconstriction- effective diameter reduced and reusyance increased
Airway obstruction
Wheeze, cough and dyspnoea
Decreased alveolar ventilation- hypoventilation
Decreased partial pressure gradients lead to hypoxia
Reduced- FEV, FEV:FVC, PEFR
Treatment- relievers
Beta-2 agonists- salbutamol, salmeterol
Phosphodiesterase inhibitor- aminophylline
Antimuscarinics- iprateropium bromide
Preventers
Steroids- beclometasone, pregnisolone
Leukotriene receptor antagonist- montelukast

Question 11

Describe chronic obstructive pulmonary disease

Answer 11

Emphysema- loss of elastic recoil and airway traction and reduced surface area for diffussion
Hyperinflation- air trapping
Decreased PEFR, FEV, FEV:FVC
Management- smoking cessation
Bronchi dilators
Oxygen therapy
Reduce exacerbations- vaccinations and corticosteroids to reduce neutrophil infiltration

Question 12

Describe fibrosis

Answer 12

Decreased lung compliance
Dyspnoea
Dry cough
Lung crackles
Hypoxamia with hypocapnia
Increased fibroblast proliferation
Increased secretion of elastin and collagen
Fibro collage nous thickening of alveoli
Decreased lung compliance
Increased thickness of diffusion barrier
Decreases TLC, VC but no change in FEV:FVC