Respiratory responses to increased ventilatory demand and respiratory failure Flashcards
What physiological responses happen with an increased ventilatory demand?
Increase perfusion to match increased ventilation (Pa:Q) - by changing tidal volume or respiratory rate
Minimise resistance
Active expiration
Increased perfusion and ventilation demands are achieved by which nervous system? What receptors trigger this?
Autonomic nervous system
Chemreceptors - detect blood chemistry e.g. hypoxia, hypercapnia, acidaemia
How is resistance minimised?
Increased inspiratory movements cause dilation of extra-alveolar blood vessels and lower conducting airways
Postural changes
What is orthopnea?
Lack of breath due to laying flat
What are the consequences of persistent hyperventilation due to hypoxia?
Hypocapnia
Increased workload and demand on respiratory muscles
Increased production of CO2 and H+ - acidosis
Exhaustion
Respiratory failure
How does hypoxia and hyperventilation lead to hypocapnia (in longterm)?
CO2 more soluble than O2
Diffuses out of blood more easily
Reduces drive for increased ventilation
pH becomes alkalotic
Respiratory failure is the end result of uncontrolled disease. It is classified on blood-gas imbalance. What defines type 1 and type 2 respiratory failure?
Type 1 - hypoxia and normal CO2 or hypocapnia
Type 2 - hypoxia and hypercapnia
Type 1 respiratory failure (hypoxia and hypo/normal CO2) is usually in what portion of the respiratory tract?
Gas exchange portion
Lung parenchyma
Type 2 respiratory failure (hypoxia and hypercapnia) is usually in what portion of the respiratory tract?
Conducting portion
Usually due to obstruction
What pH misbalance can type 1 respiratory failure result in?
Respiratory alkalosis
Do both types of respiratory failure respond well to oxygen supplementation?
Type 1 - yes
Type 2 - no, can worsen by reducing respiratory drive
How can respiratory efficiency be improved?
Mechanical dilation of airways (by bronchovascular bundle)
Reducing resistance e.g. postural changes
Increase RR and tidal volume (increased ventilation)
