71 - Basic Lung Physiology Flashcards
Basic functions of the lungs
1)
2)
3)
1) Oxygenate pulmonary arterial blood
2) Remove CO2 from the blood
3) Maintain acid-base balance (CO2 is the most plentiful acid in the body)
O2 supply given by resp system at rest
250mL/minute of O2
CO2 removed from body by resp system at rest
200mL/minute
Maximum O2 able to be supplied by resp system
4000mL/minute
Maximum CO2 able to be removed from the body by resp system
4000mL/minute
Results of inadequate lung function
1)
2)
1) Hypoxaemia (leading to tissue hypoxia)
2) Hypercapnoea and respiratory acidosis
PaO2 aimed to be maintained by resp system
100mmHg
PaCO2 aimed to be maintained by resp system
40mmHg
pH aimed to be maintained by resp system
7.4
Aspects of the upper airway
1) Nasopharynx
2) Oropharynx
3) larynx
Aspects of lower airways
Trachea, bronchi, bronchioles
Aspects of lung parenchyma
Alveoli, capillaries, interstitial spaces
Components of respiratory system anatomy 1) 2) 3) 4) 5) 6)
1) Upper airways
2) Lower airways
3) Lung parenchyma
4) Pulmonary vasculature
5) Chest wall, pleura, respiratory muscles
6) Peripheral chemoreceptors, respiratory centre in the brain
‘Trap door’ structure over the larynx
Epiglottis
Thickness of alveolar membrane
Two cells thick. Shared basal lamina
General rule for relationship between pressure in pulmonary circulation versus systemic circulation
Systemic pressure is ~ 10x that of pulmonary circulation
Three broad physiological concepts for the lungs
Ventilation
Gas exchange
Perfusion of lungs
Only time that lungs are being inflated by positive pressure being pushed into lungs
When sick, on a ventilator
Effect of contracting external intercostals
Increases antero-posterior dimensions of the thorax
Resistances to expansion of thorax
Resistance (friction of air going through airways), elasticity of lung tissue
How should breathing appear under normal circumstances, at rest?
Shouldn’t be visible.
Gas pressure in pulmonary arteries
40mmHg O2
46mmHg CO2
Gas pressures in the athmosphere
150mmHg O2
~0mmHg of CO2 (less than you’d think)
Gas pressures in pulmonary veins
98mmHg O2
40mmHg CO2
Gas pressures in alveoli
PO2 is 100mmHg
PCO2 is 40mmHg
Effect of difference in gas pressures between alveoli and pulmonary arteies
O2 into circulation, CO2 out
Threats to the resp system
1)
2)
3)
1) Inhalation of foreign objects
2) Circulation
3) Flooding of alveoli
Difference between signs of symptoms
Symptoms are what patients are complaining of.
Signs are what are detected in examination.
Are there nociceptors in the lungs?
No
Which lung structure is innervated with nociceptors?
Pleura.
Quality of pleural pain
Sharp, very localised, very painful.
Structures involved if there is coughing, wheezing?
Airways
Structures involved if there is lung pain
Pleura
Peripheral sign of respiratory disease
Nail clubbing (increased nail movement, strange club shape)
Most useful signs in the respiratory exam
1)
2)
1) Percussion of chest
2) Stethoscope breath signs (extra signs: wheezes, crepitations, pleural rub)
