Respiratory Physiology Flashcards
Upper respiratory tract
Larynx and above
Lower respiratory tract
Trachea and below
What level of bronchus division for each bronchial segment?
Tertiary bronchi
In which primary bronchus are aspirated foreign bodies more common and why?
Right. More vertical direction than left, foreign bodies more likely to enter it
Two types of pneumocytes at alveoli and function
Type 1- majority of alveoli, gas exchange
Type 2- produces surfactant
Purpose of surfactant
Reduces surface tension, increases lung compliance
Lung volume
6000ml
Tidal volume
500ml
Expiratory reserve volume
1100ml
Inspiratory reserve volume
3000ml
Residual volume
1200ml
Function of intrapleural fluid
Prevents friction, holds lungs to ribcage and diaphragm so they expand
Muscles of inspiration
External intercostals and diaphragm at rest
+sternocleidomastoids and scalenes on exertion
Muscles of expiration
Passive at rest
internal intercostals and abdominals on exertion
Compliance definition and is high or low good
Change in volume relative to change in pressure
HIGH= good
LOW= bad
Partial pressure of oxygen
100mmHg (13.3kPa)
Partial pressure of CO2
40mmHg (5.3kPa)
How does alveolar ventilation vary throughout the lung
Decreases with height from base to apex due to changes in compliance (highest at base, lowest at apex)
What is value for FEV1/FVC in health?
around 80%
Effect of obstructive disease on FEV1/FVC ratio
reduced
Effect of restrictive disease on FEV1/FVC ratio
stays same, may even increase
Where in lung is blood flow greater than ventilation and vice versa?
Blood flow higher at base
Ventilation higher at apex
(BLOOD FLOW AND VENTILATION BOTH HIGHER AT BASE THAN APEX, THIS IS COMPARATIVE DIFFERENCE)
Autoregulation effects when blood flow is greater than ventilation
Blood vessels around poorly ventilated alveoli constrict
Diverts blood to better ventilated alveoli
Bronchioles dilate to increase ventilation
Autoregulation effects when ventilation is greater than blood flow
Blood vessels dilate to increase perfusion
Bronchioles constrict to reduce ventilation
Shunt definition
Passage of blood through areas of lung that are poorly ventilated
Alveolar dead space
Alveoli that are ventilated but not perfused (opposite of shunt)
Oxygen transport in blood
3ml dissolved per litre in plasma
197ml bound to haemoglobin per litre
CO2 transport in blood
77% transported in solution in plasma
23% within haemoglobin
Why does anaemia not affect PO2
RBCs will still be saturated as partial pressure is normal (still less RBCs)
Types of haemoglobin
HbA (normal)- 92%
HbA2
HbF
glycosylated Hb
Types of hypoxia
Hypoxaemic Anaemic Stagnant Histotoxic Metabolic
Hypoxaemic hypoxia
Most common. Reduction in oxygen diffusion at lungs
Anaemic hypoxia
Reduction in oxygen carrying capacity of blood due to anaemia
Stagnant hypoxia
Heart disease results in inefficient pumping of blood to lungs/around body
Histotoxic hypoxia
Poisoning prevents cells utilising oxygen delivered to them (e.g. carbon monoxide/cyanide)
Metabolic hypoxia
Oxygen delivery to tissues doesn’t meet increased demand by cells
2 classes of chemoreceptors
Central and peripheral
Central chemoreceptors location and function
In medulla Detect changes in [H+] in CSF around brain Increase ventilation (increased [H+] caused by raised PCO2)
Peripheral chemoreceptors location and function
In carotid and aortic bodies
Detect changes in arterial PO2 and [H+]
Cause stimulation of ventilation in response to significant fall in arterial PO2 (not oxygen content) or increased [H+] from any origin
Barbiturates and opioids effect on ventilatory control
Depress respiratory centres in brain
Decreases sensitivity to pH so response to PCO2 decreases
Decreases peripheral chemoreceptor response to changes in PO2
Nitrous Oxide effects on ventilatory control
Blunts peripheral chemoreceptor response to decreased PaO2
What term describes the maximum volume of air that can be voluntarily exhaled following a maximum inspiration?
Vital Capacity
