Respiratory Physiology Flashcards
Rate of gas exchange at rest
250ml/min O2 and CO2
How much air in dead space at rest
150ml
Effect of sympathetic on airways
Airway dilation
Effect of parasympathetic on airways
Airway constriction
What is lung compliance
Measure of lungs ability to change volume in relation to changes in pressure
(How easy it is to inflate lungs)
What is the compliance in emphysema
High compliance (but low elasticity- easy to inflate lungs, hard to get back out)
Surface area of alveoli
80m^2
Total lung capacity
6L
How much air in lung in normal inspiration? Normal tidal volume?
2.8L
Tidal volume = 500mL
What is role of residual volume
Prevent alveolar collapse (reduce breathing work)
What is boyles law
Pressure exerted by gas is inversely proportional to its volume (bigger volume = less pressure)
Which muscles used in inspiration at rest and at increased respiratory effort
Rest: External intercostals and diaphragm (70%)
Increased respiratory effort: scalenes and sternocleidomastoid
Muscles used in expiration
Passive at rest
Increased respiratory effort = internal intercostals and abdominal
What is role of surfactant
Increase compliance and reduce tendency to recoil (law of laplace describes pressure required to keep alveoli open)
What is the main breathing force in normal circumstances
CO2
What is the pulmonary circulation pressure
Low pressure high flow
25/10
Why does CO2 diffuse into alveoli so rapidly?
Very soluble in water (compared to O2)
Where is ventilation and perfusion matched
Rib 3
What causes decreased affinity/rightward curve shift
Acidosis, increased temperature, increased PCO2, increased DPG (diastolic pulmonary gradient)
Aids oxygen unloading in periphery (Bohr effect)
What causes leftward shift
(Opposite to right shift)
+
Foetal haemoglobin
Leads to increased affinity
Signs of carbon monoxide poisoning
Cherry red skin and mucous membrane
Brain damage
What does dorsal respiratory group stimulate?
Inspiratory muscles
What does ventral respiratory group stimulate
Tongue, pharynx and expiratory muscles
What do central chemoreceptors respond to (where are they located)
Located in medulla
Respond to H+ concentration (CO2
What do peripheral chemoreceptors respond to (where are they located)
Carotid and aortic bodies
Respond to H+ concentration and O2 (secondary Ventilatory drive)
What is the effect of barbiturates and opioids on respiratory centres
Depress respiratory centres —> overdose can lead to respiratory failure
Is nitrous oxide a safe sedative to use? When might it not be?
Safe in most individuals as only blunts peripheral chemoreceptor activity
Not suitable for chronic lung disease patients relying on secondary Ventilatory drive
What is a shunt
Blood shunted from one side of heart to other without participating in gas exchange
Is respiratory acidosis or alkalosis associated with severe lung pathology?
Acidosis
