Lífeðlisfræði öndunar

Question 1

Skilgreining á dead space í lungum:

Answer 1

Dead space is defined as the volume of inhaled air that does not take part in gas exchange.

Question 2

Í hvaða 3 atriði má skipta dead space í lunganu?

Answer 2

• Anatomical dead space: the portion of the airways that conducts gas to the alveoli. No gas exchange is possible in these spaces.
• Alveolar dead space: the sum of the volumes of those alveoli that have little or no blood flowing through their adjacent capillaries, i.e. the alveoli that are ventilated but not perfused. This is negligible in healthy people but can increase considerably in individuals with lung disease that causes ventilation-perfusion mismatch.
• Physiological dead space: the sum of the anatomical and alveolar dead spaces. The physiological dead space can account for up to 30% of the tidal volume.

Question 3

Hvernig er hægt að mæla anatomical dead space?

Answer 3

The anatomical dead space can be measured by the nitrogen washout test (Fowler’s method). The physiological dead space can be measured by the Bohr equation.

Question 4

Alveolar dead space er mjög lítið í heilbrigðum einstaklingum en í hvaða sjúkdómum eykst það og út af hverju?

Answer 4

The alveolar dead space is negligible in healthy adults but can increase dramatically in the presence of lung disease (e.g. pulmonary embolus, pneumonia) due to ventilation-perfusion mismatch.

Question 5

Nítrógen N2 - prósentuhlutfall og hlutþrýstingur í alveolar lofti:

Answer 5

74.9%

569 mmHg

Question 6

Súrefni - prósentuhlutfall og hlutþrýstingur í alveolar lofti

Answer 6

13.7%

104 mmHg

Question 7

Vatn - prósentuhlutfall og hlutþrýstingur í alveolar lofti:

Answer 7

6.2%

40 mmHg

Question 8

Koltvísýringur (CO2) - prósentuhlutfall og hlutþrýstingur í alveolar lofti:

Answer 8

5.2%

47 mmHg

Question 9

Hvað er Henry´s law og hvað segir það?

Answer 9

The behaviour of gases when then come into contact with liquids (e.g. blood) is described by Henry’s law. Henry’s law states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas.

Therefore, the greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid. Gas molecules establish an equilibrium between those molecules dissolved in liquid and those in air.

Question 10

2 helstu leiðirnar sem líkaminn bregst við hækkuðu eða lækkuðu V/Q mismatch á staðbundnum hluta í lunganu:

Answer 10

• Hypoxic vasoconstriction: In the presence of a low V/Q ratio (i.e. areas of poor ventilation), hypoxic vasoconstriction can occur, which redirects incoming blood to the affected area to other parts of the lung. This decreases the perfusion of the hypoxic region, raising the V/Q ratio.
• Bronchoconstriction: In the presence of a high V/Q ratio (i.e. areas of poor perfusion), the bronchi constrict, increasing the resistance and decreasing the ventilation of affected area that is not well perfused. This reduces the amount of alveolar dead space that occurs and lowers the VQ ratio.

Question 11

Hvernig bregst líkaminn við low V/Q hlutfalli á einum stað í lunganu?

Answer 11

Hypoxic vasoconstriction: In the presence of a low V/Q ratio (i.e. areas of poor ventilation), hypoxic vasoconstriction can occur, which redirects incoming blood to the affected area to other parts of the lung. This decreases the perfusion of the hypoxic region, raising the V/Q ratio.

Question 12

Hvernig bregst líkaminn við high V/Q hlutfalli á einum stað í lunganu?

Answer 12

Bronchoconstriction: In the presence of a high V/Q ratio (i.e. areas of poor perfusion), the bronchi constrict, increasing the resistance and decreasing the ventilation of affected area that is not well perfused. This reduces the amount of alveolar dead space that occurs and lowers the VQ ratio.

Question 13

Hvar eru periferal chemoreceptors fyrir respiratoriska funksjón?

Answer 13

The peripheral chemoreceptors are situated in the aortic and carotid bodies.

Question 14

Hvar eru carotid bodies periferu chemoreceptorarnir staðsettir nákvæmlega og hver er ítaugun þeirra?

Answer 14

The carotid bodies are small distinct structures located at the bifurcation of the common carotid arteries and are innervated by the carotid sinus nerve and subsequently the glossopharyngeal nerve (CN IX).

Question 15

Í hvaða tvær týpur skiptast frumurnar í carotid bodies chemoreceptorunum?

Answer 15

• Type I (glomus) cells – chemoreceptive cell containing transmission-rich dense granules that contact carotid sinus nerve axons
• Type II (sheath) cells – sustentacular supportive cells

Question 16

Hvar eru aortic bodies periferu chemoreceptorarnir staðsettir og hver er ítaugun þeirra?

Answer 16

The aortic bodies are located in the aortic arch and receive their innervation from the vagus nerve (CN X). They are structurally similar to the carotid bodies but functionally less important.

Question 17

Hvað skynja periferu chemoreceptorarnir nákvæmlega?

Answer 17

The peripheral chemoreceptors detect large changes in pO2 as the arterial blood supply leaves the heart. They are relatively insensitive, but their effects occur almost instantaneous. Following the detection of an abnormally low pO2, afferent impulses travel to the respiratory centres in the brainstem, and several responses are then coordinated, which aim to increase the pO2 again.

Question 18

Hvernig lítur oxygen dissociation kúrvan út? Hvaða þýðingu hefur “right vs. left shift” á kúrvunni?

Answer 18

A right shift indicates decreased oxygen affinity of haemoglobin allowing more oxygen to be available to the tissues. A left shift indicates increased oxygen affinity of haemoglobin allowing less oxygen to be available to the tissues.

Question 19

Hvaða áhrif hefur methemoglobulin á oxygen dissocation kúrvuna?

Answer 19

Methaemoglobin is an abnormal form of haemoglobin in which the normal ferrous form is converted to the ferric state. Methaemoglobinaemia causes a left shift in the curve as methaemoglobin does not unload oxygen from haemoglobin.

Question 20

Hvaða áhrif hafa organisk fosföt (t.d. 2,3-DPG) á súrefnis dissocation kúrvuna?

Answer 20

2,3-Diphosphoglycerate (2,3-DPG) is the main primary organic phosphate. An increase in 2,3-DPG shifts the curve to the right, whilst a decrease in 2,3-DPG shifts the curve to the left. 2,3-DPG binds to haemoglobin and rearranges it into the T state, which decreases its affinity for oxygen.

Question 21

Hvað áhrif hefur pH á oxygen dissociation kúrvuna? Af hverju?

Answer 21

A decrease in the pH shifts the curve to the right, while an increase in pH shifts the curve to the left.

This occurs because a higher hydrogen ion concentration causes an alteration in amino acid residues that stabilises deoxyhaemoglobin in a state (the T state) that has a lower affinity for oxygen. This rightwards shift is referred to as the Bohr effect.

Question 22

Hvaða áhrif hefur CO2 á oxygen dissociation kúrvuna? Af hverju?

Answer 22

A decrease in CO2 shifts the curve to the left, while an increase in CO2 shifts the curve to the right.

CO2 affects the curve in two ways. Firstly, accumulation of CO2 causes carbamino compounds to be generated, which bind to oxygen and form carbaminohaemoglobin. Carbaminohaemoglobin stabilizes deoxyhaemoglobin in the T state. Secondly, accumulation of CO2 causes an increase in H+ ion concentrations and a decrease in the pH, which will shift the curve to the right as explained above.

Question 23

Hvaða áhrif hefur hitastig á oxygen dissociation kúrvuna?

Answer 23

An increase in temperature shifts the curve to the right, whilst a decrease in temperature shifts the curve to the left. Increasing the temperature denatures the bond between oxygen and haemoglobin, which increases the amount of oxygen and haemoglobin and decreases the concentration of oxyhaemoglobin. Temperature does not have a dramatic effect but the effects are noticeable in cases of hypothermia and hyperthermia.

Question 24

The conducting passageways of the respiratory tract (the nasal cavity, trachea, bronchi and bronchioles) are lined by the respiratory epithelium, which is ciliated pseudostratified columnar epithelium. This epithelium serves to moisten and protect the airways as well as providing a barrier to potential pathogens, preventing tissue injury and infection via the secretion of mucous and the action of mucociliary clearance.
Hvar í öndunarveginum er EKKI slíkur vefur og hvaða vefur er þar í staðinn (3 staðir)?

Answer 24

• the vocal cords of the larynx
• the oropharynx
• the laryngopharynx

These areas are lined instead by stratified squamous epithelium.

Question 25

Hvað er átt við með ventilation og perfusion?

Answer 25

Ventilation (V) refers to the flow of air into and out of the alveoli, while perfusion (Q) refers to the flow of blood that reaches the alveoli via the capillaries.

Question 26

Hvað er meðal ventilation og perfusion í L/mín. hjá 70kg heilbrigðum kk?

Answer 26

V is approximately 5 L/min
Q is approximately 5 L/min
The V/Q ratio is, therefore, ideally 1.

Question 27

Hvernig er airflow obstruction flokkuð skv. NICE leiðbeiningunum? (í FEV1)

Answer 27

• Mild airflow obstruction = an FEV1 of >80% in the presence of symptoms
• Moderate airflow obstruction = FEV1 of 50-79%
• Severe airflow obstruction = FEV1 of 30-49%
• Very severe airflow obstruction = FEV1 <30%.

Question 28

Hvernig breytast FEV1, FVC og FEV1/FVC hlutföllin í obstructivum lungnasjúkdómum?

Answer 28

In obstructive lung disease, FEV1 is reduced to <80% of normal and FVC is usually reduced but to a lesser extent than FEV1. The FEV1/FVC ratio is reduced to < 0.7.

Question 29

4 mælingar í spirometriu sem hækka í obstructivum lungnasjúk´domum:

Answer 29

Total lung capacity (TLC)
Residual volume (RV)
Functional residual capacity (FRC)
Residual volume/total lung capacity (RV/TLC) ratio

Question 30

4 spirometriumælingar sem lækka í obstructivum lungnasjúkdómum:

Answer 30

Vital capacity (VC)
Inspiratory capacity (IC)
Inspiratory reserve volume (IRV)
Expiratory reserve volume (ERV)

Question 31

Hvað er “the gas transfer factor”? Hvernig er hann mældur?

Answer 31

The gas transfer factor is a measure of gas diffusion across the alveolar membrane into capillaries. It is dependent upon blood volume, blood flow, the surface area of the membrane and the distribution of ventilation.

It is measured by the diffusion of carbon monoxide (TLCO). The transfer coefficient (KCO) is the TLCO corrected for lung volume.

Question 32

Dæmi um 9 atriði sem valda lækkun á gas transfer factor:

Answer 32

• COPD
• Acute asthma
• Interstitial lung disease
• Pulmonary oedema
• Pneumonia
• Pneumothorax
• Pulmonary vascular disease
• Pneumonectomy
• Anaemia

Question 33

Hvernig lítur restrictive lung disease pattern út?

Answer 33

FEV1/FVC er hátt
FVC lækkað

In restrictive lung disease, the FVC is reduced to <80% predicted normal, and the FEV1/FVC ratio is usually normal, i.e. >0.7. The FEV1 is also reduced. This occurs in conditions when there is a reduced lung volume, such as scoliosis and fibrosing alveolitis.

Question 34

Hvenær er V/Q hlutfallið óendanlegt?

Answer 34

If the alveoli were ventilated but not perfused at all, then the V/Q ratio would be infinity. A clinical example of this would be a pulmonary embolus that has blocked a pulmonary artery. Perfusion in the region supplied by that artery would be reduced to zero, rising the V/Q ratio to infinity. As no gas exchange is occurring in this area because of the lack of perfusion, this is referred to as alveolar dead space.

Question 35

Hvenær er V/Q hlutfallið núll?

Answer 35

If the alveoli were perfused but not ventilated at all, then the V/Q ratio would be zero. A clinical example of this would be the inhalation of a foreign body that prevented all ventilation to an area of the lung. Ventilation in that region would be reduced to zero, lowering the V/Q ratio to zero. Because this area is being adequately perfused, but no oxygen is being transferred to the blood arriving there, a physiological right-to-left shunt has been created.

Question 36

Hvaða þýðingu hefur PEEP og hvað gerist á lower inflection point vs. upper inflection point á þessu grafi?

Answer 36

The inspiratory curve is a sigmoid shape, reflecting the difference in compliance at different degrees of lung expansion. When the lungs are fully emptied to residual volume, a large proportion of alveoli are collapsed. This is the “zone of atelectasis”. It takes a significant increase in pressure to overcome surface tension, open the alveoli and increase lung volume.

Once a critical point is reached (the lower inflection point; LIP), sufficient alveoli are recruited and compliance increases. The same change in pressure now gives a larger increase in lung volume. The inspiratory curve then flattens out again at the upper inflection point (UIP). This marks “the zone of distension”, where alveoli are maximally expanded and elastic recoil pressure is exerting a significant force so compliance decreases.

The addition of PEEP holds alveoli open at the end of expiration. Inspiration starts further along the curve, closer to the LIP and the steeper part of the curve reflecting increased compliance.

Question 37

Skilgreiningin á tidal volume, TV:

Answer 37

The tidal volume (TV) is the volume of air drawn in and out of the lungs during normal breathing. The usual volume in a healthy male is 0.5 L.

Question 38

Skilgreiningin á vital capacity, VC:

Answer 38

The vital capacity (VC) is the maximum volume of air that can be breathed out following a maximal inspiration. The usual volume in a healthy male is 4.5 L.

Question 39

Skilgreiningin á residual volume:

Answer 39

The residual volume (RV) is the volume of air in the lungs after a maximum expiration. The usual volume in a healthy male is 1.0 L.

Question 40

Inspiratory reserve volume skilgreining:

Answer 40

The inspiratory reserve volume (IRV) is the maximum volume of air that can be breathed in at the end of a normal tidal inspiration. The usual volume in a healthy male is 3.0 L.

Question 41

Skilgreining á expiratory reserve volume:

Answer 41

The expiratory reserve volume (ERV) is the maximum volume of air that can be breathed out at the end of a normal tidal expiration. The usual volume in a healthy male is 1.0 L.

Question 42

Skilgreining á total lung capacity:

Answer 42

Total lung capacity (TLC) is the volume of air in the lungs at the end of a maximal inspiration. TLC = RV+VC. The usual volume in a healthy male is 5.5 L.

Question 43

Skilgreining á functional residual capacity:

Answer 43

Functional residual capacity (FRC) is the volume of air present in the lungs at the end of a normal expiration. FRC = ERV + RV. The usual volume in a healthy male is 2.0 L.

Question 44

Hver er formúlan og skilgreiningin fyrir lung compliance?

Answer 44

The compliance of the respiratory system is analogous to the capacitance in the cardiovascular system. It is defined as the change in volume for a given change in pressure {C = ∆ V/∆P}.

Question 45

Compliance lungna - er í öfugu hlutfalli við hvaða tvö atriði, hvernig er hann teiknaður á kúrvu og hvaða þættir spila inn í?

Answer 45

Compliance is inversely related to elastance and stiffness, and is charted as a slope of the pressure volume curve. It is comprised of static (no air flow) and dynamic (during continuous breathing) components. The static compliance is dependent on factors such as age, size and sex of the person, whereas the dynamic lung compliance is dependent on the airway resistance, which is depicted by the area of the curve.

Question 46

Skilgreiningin á inspiratory reserve volume og hvað er normal gildi fyrir heilbrigðan kk?

Answer 46

The inspiratory reserve volume (IRV) is the maximum volume of air that can be breathed in at the end of a normal tidal inspiration. The usual volume in a healthy male is 3.0 L.

Question 47

Functional residual capacity er summan af hvaða 2 öðrum stærðum?

Answer 47

The FRC is the sum of the expiratory reserve volume (ERV) and the residual volume (RV):

FRC = ERV + RV

Question 48

3 leiðir til að meta functional residual capacity:

Answer 48

Nitrogen washout (Fowler’s method)
Helium dilution technique
Body plethysmography

Question 49

2 atriði sem auka functional residual capacity:

Answer 49

• Marked airway obstruction (e.g. severe asthma and COPD)

- Loss of elastic recoil (e.g. advanced age and emphysema)

Question 50

3 atriði sem minnka functional residual capacity:

Answer 50

• Abnormally stiff, non-compliant lungs (e.g. restrictive lung disorders such as pulmonary fibrosis)
• Bilateral paralysis of the diaphragm
• Lying in the supine position

Question 51

Hvernig líta FEV1, FVC og FEV1/FVC út í obstructivum lungnasjúkdómum?

Answer 51

In obstructive lung disease, FEV1 is reduced to <80% of normal and FVC is usually reduced but to a lesser extent than FEV1, with the resulting FEV1/FVC ratio being reduced to <0.7. This occurs in conditions when the airways are narrowed, causing obstruction, such as in asthma, COPD and bronchiectasis.

Question 52

Hver eru áhrif CO (carbon monoxide) eitrunar á flutning súrefnis í blóði og á oxygen dissociation kúrvuna?

Answer 52

Carbon monoxide (CO) interferes with the oxygen transport function of the blood by combining with haemoglobin to form carboxyhaemoglobin (COHb). CO has approximately 240 times the affinity for haemoglobin than oxygen does. For that reason, even small amounts of CO can tie up a large proportion of the haemoglobin in the blood, making it unavailable for oxygen carriage. If this happens, the PO2 of the blood and haemoglobin concentration will be normal, but the oxygen concentration will be grossly reduced. The presence of COHb also causes the oxygen dissociation curve to be shifted to the left, interfering with the unloading of oxygen.

Question 53

Normal PEFR range fyrir heilbrigða kk 20-70 ára?

Answer 53

Age 20 540-600 l/min
Age 30 600-660 l/min
Age 40 600-660 l/min
Age 50 570-630 l/min
Age 60 540-590 l/min
Age 70 490-540 l/min

Question 54

Normal PEFR range fyrir heilbrigðar kvk á aldrinum 20-70 ára:

Answer 54

Age 20 410-450 l/min
Age 30 420-460 l/min
Age 40 420-460 l/min
Age 50 400-440 l/min
Age 60 370-410 l/min
Age 70 350-390 l/min