· Air
· Blood
· Homeostasis
· Drugs
|
Reservoir |
· For gas exchange during expiration, between breaths, during apnoea (e.g.heavy lifting) |
|
Humidification |
· Countercurrent heat and moisture exchange · Purpose o Prevent heat loss o Prevent water loss o Prevent crusting of secretions o Maintain mucociliary function o Prevent infection · Mechanism o Cool dry air inhaled § ↑Temp by conduction, convection § Evaporation-> humidification due to ↓ relative humidity o Warm, humidified air exhaled § ↓Temp by conduction, convection § Condensation->drying due to ↑ relative humidity |
|
Filtration |
· Particles e.g. dust, pathogens e.g. viruses, bacteria · >3um: stick to airway -> mucociliary escalator -> swallowed · 1-3um: sediment in alveoli -> phagocytosis by macrophage = dust cell · <1um free in air ± deposit anywhere |
|
Immune |
· Innate: mucociliary escalator, lysozyme, macrophage · Adaptive: IgA, IgG in alveolar lining fluid |
|
Phonation |
· Exhalation against variably closed glottis |
|
Pump |
· Inspiration: ↓ intrathoracic pressure -> ↑ gradient for systemic venous return · Expiration: venous valves prevent flow reversal · Cardiac output higher during spontaneous ventilation than during apnoea |
|
Reservoir |
· 15% blood volume supine (8% arteries, 3% capillaries, 5% veins) · 9% blood volume erect |
|
Filtration |
· Of microemboli to prevent stroke |
|
Acid-base |
· CO2 excretion for homeostasis o 15,000mmol/day by Krebs cycle in mitochondria during aerobic respiration o Alveolar ventilation is coupled to metabolic rate via control of PaCO2 · CO2 excretion for compensation during metabolic acidosis o CO2 + H2O <-> H+ + HCO3- o ↑Alveolar ventilation -> left shift -> ↑pH |
|
Fluid |
· Endothelial angiotensin-converting enzyme: AT1 (inactive) -> AT2 (active) · AT2: Na+/H2O reabsorption, vasoconstriction |
|
Metabolic |
· Inactivate serotonin near 100%, bradykinin 80%, noradrenaline 30% · Inactivate PGE2, PGF2α, leukotrienes |
|
Route |
· Local: e.g. salbutamol · Systemic: e.g. naloxone |
|
Reservoir |
· e.g. first pass uptake of fentanyl up to 75% |
|
Metabolism |
· e.g. ? propofol and CYP450 |
|
Excretion |
· e.g. sevoflurane |