Lung Physiology 1 Flashcards
what is dead space in alveolar ventilation? what is the anatomic, alveolar and physiological dead space?
volume of air not contributing to ventilation,
In anatomic its 150 mls (in bronchi and trachea)
in alveolar its 25 mls (air in alveoli with no blood supply)
Physiological dead space is 175 mls
static lung
resting (unstressed) volume pulled back by elastic properties of chest wall and lung
Types of nerves that inervate the lungs?
sensory (sensory receptors assess flow and stretch, C fibres, afferents via vagus nerve)
autonomic sympathetic and parasympathetic
ventilation vs perfusion
bulk flow of air in the airways
adequate pulmonary blood supply
pressure profiles of RA, RV, PA, LA, LV, Aorta?
Pressure profiles;
RA 5 mmHg
RV 25/0
Pulmonary Artery 25/8
LA 5
LV 120/0
Aorta 120/80
how many capliaries per alveolus?
1000, by 25percent way throiugh erythrocyte has picked up oxygen and haemoglobin is saturated
What does perfusion of capillaries depend on?
Perfusion of capillaries also depends on;
Pulmonary artery pressure
Pulmonary venous pressure
Alveolar pressure
Matching vetilation and perfusion: how do systemic vessels react to oxygen vs CO2?
how do pulmonary vessels react to oxygen vs CO2?
Systemic vessels deliver oxygen to hypoxic tissues: Hypoxia/acidosis/CO2 are vasodilators
Oxygen is a vasoconstrictor
Pulmonary vessels pick up oxygen from oxygenated lung: Oxygen is a vasodilator
Hypoxia/acidosis/CO2 are vasoconstrictors
(hypoxic pulmonary vasoconstriction)- mechanism to divert blood away from areas of lung that cannot oxygenate
What does PACO2 mean? What does PaCO2 mean?
Alveolar CO2, arterial CO2
what does PiO2 mean?
What does FiO2 mean?
pressure of inspired air, fraction of inspired air
what does V’A and V’CO2 mean?
alveolar ventilation and CO2 production
What is the formula for PaCO2? normal range for it?
relationship betwreen the two?
PaCO2 = KV’CO2/V’A
4-6 Kpa
arteriorly pressure of CO2 is inversly proportional to alveolar vetilation
Three ways of CO2 elimination?
bound to haemoglobin
dissolved in plams
as carbonic acid
physiological causes of high CO2?
alveolar ventilation is reduced:
1. reduce minute ventilation
2. increase dead space ventilation by rapid shallow breathing
3. increase dead space by ventilation/perfusion mismatching
OR
4. increased CO2 production
Formula for PAO2? pressure of alveolar oxygen
PiO2 – PaCO2/R
R= repiratory quotient which is always assumed 0.8 (carb is 1, fat is 0.7)
Causes of low PaO2?
Alveolar hypoventilation
Reduced PiO2
Ventilation/perfusion mismatching (V/Q)
Diffusion abnormality
what may cause a right curve shift?
increased acidity
increased 2,3-DPG
Alveolar arterial O2 difference?
PAO2 – PaO2 = (approx) 1KPa
Normal arterial blood gases values: PaO2, PaCO2, pH, HCO3
PaO2 11-13 KPa
PaCO2 4.7-6.0 KPa
pH 7.35-7.45
HCO3- 22 - 26 mEq/L
Acid base control in blood- normal pH and H+ concentration?
pH normally 7.40 (7.36-7.44)
H+ concentration 40nmol/l [34-44 nmol/l]
How is pH of blood controlled?
Blood and tissue buffers important
Carbonic acid / bicarbonate buffer in particular
CO2 under predominant respiratory control (rapid)
HCO3- under predominant renal control (less rapid)
The respiratory system is able to compensate for increased carbonic acid production,
but elimination of fixed acids requires a functioning renal system
Carbonic acid equilibrium equation?
Carbonic acid equilibrium
CO2 + H2O = H2CO3 = H+ + HCO3
Carbonic anhydrase
What is the Hendersons-Hasselbalch equation?
pH=6.1 + log10[[HCO3-]/[0.03*PCO2]]
6.1- is base level, rest depends upon HCO3 and CO2 levels
Discuss the 4 main acid base disorders:
respiratory acidosis- increased PaCO2, decreased pH, mild increased HCO3-
Respiratory alkalosis; decreased PaCO2, increased pH, mild decreased HCO3-
Metabolic acidosis; reduced bicarbonate and decreased pH
Metabolic alkalosis; increased bicarbonate and increased pH
