L 06 Lab test of Asthma Flashcards
Define breathing, inspiration and expiration
Respiration is the act of breathing (gas exchange between an organism and its environment)
Inhaling is taking in oxygen
Exhaling is giving off carbon dioxide
What are the 4 functions of gas exchange?
Ventilation, capillary blood flow, diffusion of gases, of gases by blood.
Define ventilation and explain how it occurs
Ventilation is cyclical movement of air into and out of the lungs.
Occurs via contraction and relaxation of respiratory muscles using the elastic recoil of connective tissue in the lungs.
Define the diffusion of gases and explain how it occurs
The movement of O2 and CO2 from the alveolar space across into the blood. Occurs via a concentration gradient
Explain the importance of capillary flow
An adequate capillary flow to the lungs is required for adequate gas exchange, to maintain the concentration gradient.
How are gases carried in the blood? How are they released?
CO2 and O2 are bound to Hb and released by a pressure gradient.
Define alveolar ventilation
The movement of gas from the lungs to the blood (basically diffusion)
What factors can affect ventilation?
Any disease that inhibits elastic recoil can affect ventilation
- e.g obstructive diseases (asthma, COPD) affect inspiratory rate
- e.g restrictive diseases (pulmonary fibrosis) affect inspiratory capacity
Examples of obstructive diseases
Asthma, COPD, bronchitis, (emphysema)
Examples of restrictive diseases
Pulmonary fibrosis, interstitial lung disease
Diseases that affect gas diffusion
Pneumonia (difficulty reaching alveolar space) A tumour (cannot diffuse as easily across the alveolar space)
Diseases that affect pulmonary capillary flow
Pulmonary embolism
Right ventricular dysfunction.
What are the Factors that affect Hb?
AWhat affect O2 binding to Hb?
Anemia and blood loss affect hemoglobin
Arterial pH and carBon moNoxide affect O2 binding to Hb
What are hypoxia and anoxia. When may these happen?
Hypoxia- Low Oxygen in tissues.
Anoxia- No Oxygen in tissues.
May happen if any of the 4 respiratory elements are affected.
What effect will giving an oxygen mask to someone with respiratory problems have?
It will only help if ventilation is the problem (pure O2 vs air). Excess oxygen will not help diffusion occur.
Changes in which two measures cause a change in respiratory rate?
PaCO2 and PaO2 (pressure of arterial CO2 and O2)
What respiratory functions can we measure (x7)? Which can we calculate?
- Respiratory rate, pH, SaO2 (%), PaO2, PaCO2, Hb, Inspired O2
- CaO2 (arterial Oxygen content) can be calculated
Rapid breathing is due to…
Low CaO2 (arterial oxygen content) High PaCO2 (partial pressure of CO2)
What is FEV1 and what is it’s unit? What is it dependent on? Usual value?
FEV1: measure of the Forced expiratory volume in 1 second from the lungs.
Unit: L/s
Dependencies: size, age, sex
Usual value: 80%
What is FVC and what is it’s unit? What is it dependent on? Usual value? What needs to be
FVC: measure of the vital capacity of the lungs. Is a fraction of the total lung volume.
Unit: L
Dependencies: size, age, sex
If lung elasticity is normal then FVC is close to the true vital capacity.
What is the normal FEV1:FVC ratio? and what does this mean?
80% of the capacity of my lungs can be eliminated in a single second.
Within 5% of the predicted ratio
Unit for PEFR(Peak expiratory flow rate)?
What are the normal values dependent on?
What can affect PEFR?
(L/min)
Age, height and weight are the main factors which affect the Peak Expiratory Flow Rate (PEFR),
Forced Expiratory Volume in the first second (FEV1) and Forced Vital Capacity (FVC) also affect the Rate of (PEFR),
Scores range between around 400 and 700 liters per minute, although scores in older women can be lower and still be normal.
What are the normal values dependent on for PEFR?
Peak expiratory flow rate = L/min
More sensitive to large airway diseases (narrowing = more significant)
Dependencies: size, age, sex
How do obstructive diseases affect spirometry? And which part of FEV1:FVC do they affect? What happens therefore to the overall ratio?
Obstructive diseases reduce expiration ability (therefore affect FEV1)
By reducing one part of the ratio, the whole ratio decreases.
How do restrictive diseases affect spirometry? And which part of FEV1:FVC do they affect? What happens therefore to the overall ratio?
Restrictive diseases reduce the usable capacity of the lungs, therefore decreasing FVC.
As vital capacity is reduced, so is total capacity. Both FEV1 and FVC will therefore decrease,
What is the difference between an obstructive and restrictive lung disease?
Obstructive: conditions that make it hard to exhale all the air in the lungs.
Restrictive: make it difficult to fully expand lungs with air
What does spirometry measure?
(Spirometry:(spy-ROM-uh-tree) is a common office test used to assess how well your lungs work by measuring how much air you inhale, how much you exhale and how quickly you exhale)
Alveolar ventilation
Does the carriage Hb of gases affect PaO2 or PaCO2?
Do changes in ventilation?
No, changes in Hb do not affect PaO2 and PaCO2
Changes in ventilation affect both PaCO2 and PaO2
PaO2 definition and normal value.
Values less than …. typically cause symptoms.
Dependencies?
The pressure of O2 in the arterial circulation.
Normal value: 100mmHg
Values less than 60mmHg typically cause symptoms
Dependent on O2 inspired and atmospheric pressure
PaCO2 definition and normal value.
Values less than … typically cause symptoms.
How is PaCO2 produced?
The pressure of CO2 in the arterial circulation.
Normal values: 40mmHg
Values less than 38- 42mmHg typically cause symptoms. A higher PaCO2 level indicates acidosis while a lower PaCO2 level indicates alkalosis.
CO2 is produced by tissues during the internal respiration
What do arterial gases measure?
The influence of ventilation and diffusion at the alveolar space and capillary flow
What 2 systems tightly control the blood pH?
pH governed by the balance between….?
Renal and respiratory systems.
pH governed by the balance between HCO3(Bicarbonate) and PaCO2
An increase in PaCO2 causes a …. in pH and therefore…..
An increase in PaCO2 causes a decrease in pH and therefore O2 dissociates from Hb
Normal pH value, acidosis value and high-risk pH value of the blood
Normal = 7.4
Acidosis = < 7.35
High risk = < 7.0
What is hypercapnia?
excess carbon dioxide in the blood (increased PaCO2)
O2 binding is affected if there is a … in RBCs. + examples (x4)
O2 binding is affected if there is a decrease in RBCs
e.g: anaemia, blood loss, chronic renal failure, CO poisoning
A decrease in RBCs …. affects the pressure and conc of arterial O2. RBC values less than …
typically cause symptoms
A decrease in RBCs DOES NOT affect the pressure and conc of arterial O2.
RBC values less than 80g/L typically cause symptoms
What is Sa02? Normal value? Symptomatic value? What is SaO2 affected by? A reduction in pH causes…
SaO2 represents the % of Hb that is saturated with O2
Normal values: >95-98% on room air. <90% = symptoms
SaO2 is affected by anything that affects PaO2 and pH
(i.e O2 to Hb binding is dependent on pH, so a reduction in pH will reduce O2 bound)
What is CaO2? What does it represent? Normal values? How is it measured?
CaO2 = arterial concentration of O2
CaO2 provides a measure of the arterial O2 concentration which drives tissue oxygenation.
Normal values: 16-20 (mL/100mL)
Is not measured, is calculated
What happens to PaO2 during ventilation disorder, pH imbalance, and anemia?
Ventilation disorder: PaO2 decreases (less inspired = decreases)
pH imbalance: PaO2 stays the same
Anemia: PaO2 stays the same
What happens to SaO2 during ventilation disorder, pH imbalance, and anemia?
Ventilation disorder: decreases (as PaO2 is decreased)
pH imbalance: decreases (less binding)
Anaemia: SaO2 stays same
What happens to CaO2 during: a ventilation disorder, pH imbalance, and anaemia?
Ventilation disorder: decreases (less present)
pH imbalance: decreases (less bound)
Anemia: decreases (less produced)
What is the body’s goal in terms of respiration?
To maintain tissue oxygenation
What affect does asthma have on the body and what does the body do to respond to this?
Asthma = ventilation decrease = reduces arterial and therefore tissue oxygenation.
Body’s response: Short term = increases HR to increase cardiac output.
