Lung physiology 2

Question 1

what is haemodynamics

Answer 1

study of blood flow through the cardiovascular system

Question 2

what is hypoxaemia?

Answer 2

conditon where there is too little oxygen in blood (PaO2 too low), someoe with hypoxaemia is said to be hypoxic

Question 3

What each means: tidal volume, Inspiration capacity, residual volume, forced expiration volume, forced vital capacity, peak expiratory flow, transfer factor, lung volumes?

Answer 3

TV- tidal volume, passive breathing in and out

IC- inspiratory capacity

Residual volume- amount left in lungs once fully forcefully expired

FEV1: Forced expiratory volume in one second, or the amount of air exhaled in the first second after a maximal inhalation.

FVC: Forced vital capacity, or the total amount of air exhaled in one breath.

PEF: Peak expiratory flow, or the maximum speed of airflow during exhalation.

Transfer factor: Also known as the diffusing capacity, this measures how well the lungs absorb oxygen from the air.

Lung volumes: A complete spirometry exam measures vital capacity (VC), residual lung volume (RV), and total lung capacity (TLC).

Question 4

what can be calculated from a volume time plot?

Answer 4

FEV1/FVC calculated
volume time plot

Question 5

flow/volume loop

Answer 5

flow/volume plot

PEF; peak flow
FEF25; flow at point when 25% of total volume to be exhaled has been exhaled
FVC; forced vital capacity

Question 6

how to measure total lung capacity?

Answer 6

gas dilution,
Body box (total body plethysmography)

Question 7

how to do gas dilution?

Answer 7

closed-circuit helium dilution or open-circuit nitrogen washout

Measurement of all air in the lungs that communicates with the airways

look at reduction of concentration

Question 8

how to do total body plethysmography/

Answer 8

Patient “pants” with an open glottis against a closed shutter to produce changes in the box pressure that are proportionate to the volume of air in the thorax

Question 9

How woul you do a TLCO lung capacity test?

Answer 9

small amount of carbon monoxide give to patients and used to estimate TLCO, as has high affinity for haemoglobin

Question 10

what is exhaled nitric oxide?

Answer 10

marker of eosinophillic airway inflammation, FeNO level in adults of 40 parts per billion (ppb) or more is regarded as positive

Question 11

how does pulse oximetry work? what does it show?

Answer 11

Measures redness of light transmitted through tissue, shows percentage of haemoglobin that bounds to O2 (can only be used if peripherally pulsified)

Question 12

abnormal values of FEV1, FVC and FEV1/FVC? Whats classed as obstruction vs restriction?

Answer 12

FEV1 <80% predicted or Lower limits of normal
FVC <80% predicted or Lower limits of normal
FEV1/FVC <0.7 or Lower limits of normal

[Airflow] obstruction
= FEV1/FVC < 0.7 or LLN

[Airflow] restriction
= FVC <80% predicted or LLN

Question 13

spirometer

Answer 13

A basic test that measures how much air you can breathe out in one forced breath. You’ll sit while performing this test

Question 15

What is a CO single breath gas transfer?

Answer 15

A test that measures how well oxygen moves from your lungs into your blood.

Question 16

what is asthma?

Answer 16

a long-term condition where the airways become periodically inflamed (swollen) and narrowed

Question 17

what is emphysema? symptoms? common cause?

Answer 17

walls of alveoli weaken and break creating large air spaces, reducing SA, making it harder to move oxygen in and carbon dioxide out.

Symptoms include shortness of breath, especially with exertion, and a cough that produces phlegm.

Most common casue is smoking

(It is a type of COPD)

Question 18

chronic obstructive pulmonary disease (COPD)- what is it?

Answer 18

a group of lung conditions where the airways become narrowed

Question 19

cystic fibrosis

Answer 19

a genetic condition where the lungs and digestive system become clogged with thick, sticky mucus

Question 20

pulmonary fibrosis

Answer 20

scarring of the lungs

Question 21

formula for PiO2?

Answer 21

PiO2 = FiO2 x ambient pressure

Question 22

Pulmonary circulation vs systemic circulation: vessel wall, muscularization, need for redistribution, blood volume, response to hypoxia, regional distribution of blood flow

Answer 22

Pulmonary:
thin, minor
not in normal state, 500ml, vasoconstriction, Blood flow is affected by
(i) gravity
(ii) alveolar recruitment
(iii) hypoxic vasoconstriction
Little active regulation occurs

Systemic:
thick, significant, yes, 4500ml, vasodilation, Significant variation of organ-specific regional blood flow, depending on organ demand

Blood flow is less affected by gravity

Answer 23

perfusion is stronger at base- gravity
ventilation is also stronger at base of lungs

Question 24

what is formula for pressure across pulmonary circuit?

Answer 24

Cardiac Output x Resistance
(like ohms law V=IR)

measured by difference in pressure between L and R atrium

Question 25

combinatio of two formulas for cardiac circuit pressure?

Answer 25

mPAP – PAWP = CO x PVR

mPAP (mean pulmonary arterial pressure),
PAWP (pulmonary arterial wedge pressure),

pressure within the pulmonary arterial system when catheter tip ‘wedged’ in the tapering branch of one of the pulmonary arteries.

CO (cardiac output)
PVR (pulmonary vascular resistance)

Question 26

What is Pouiseuille’s law? relavence to circulation

Answer 26

Resistance = (8 x L x viscosity) / (π r4)

small change in radius has a large effect on resistance

Question 27

how may pulomanry Haemodynamics change during exercise to respod to an increased poulmonary output?

Answer 27

Recruitment (use reserve vessels) and distention (dilation of vessels) in response to increased pulmonary artery pressure

Question 28

Causes of hypoxaemia:

Answer 28

Hypoventilation
Diffusion Impairment
Shunting
V/Q mismatch
Reduced pressure of inspired oxygen (e.g. high altitude)

Question 29

things that affect difuion rates? name 2 conditions related to diffusion imparement?

Answer 29

membrane thickness alveolar pressure difernec
solubility of gas, SA of membrane

Lung fibrosis; the thickening of lung tissue increases the alveolar wall thickness

Emphysema; destruction of alveoli decreases the area for gas exchange

Question 30

what is hypoventilation? examples of conditions that may cause this?

Answer 30

decrease oxygen percentage in alveoli, either through airway obstruction or other gases competing in alveolus e.g. CO2

Airway narrowing (proximal and distal)
Impaired respiratory drive (sedation, coma)
Restricted chest wall movement (e.g. obesity hypoventilation syndrome, ankylosing spondylitis)
Neuromuscular diseases (e.g. myasthenia gravis, muscular dystrophy, amyotrophic lateral sclerosis, or phrenic nerve injuries).

Question 31

what is a right to left shunt? name the 2 types and some causes of each type?

Answer 31

when blood bypasses the lungs without oxygenation, V/Q=0

Anatomic shunts: Blood bypasses the alveoli, as seen in intracardiac shunts such as:
Atrial septal defect (ASD), a ventricular septal defect (VSD), or a patent ductus arteriosus (PDA), pulmonary arteriovenous malformations (AVMs), fistulas, and hepato-pulmonary syndrome

Physiologic shunts: Blood passes through non-ventilated alveoli, such as;
Pneumonia, lung collapse (atelectasis)

Question 32

what is Eisenmenger’s Syndrome? what are effects of the syndrome?

Answer 32

Long-standing left-to-rightcardiac shunts(typically caused by septal defect/patent ductus arteriosus)

Can cause pulmonary hypertension, which can lead to an eventual reversal of the shunt; becoming right-to-left, causing hypoxaemia

Question 33

what does V/Q mismatch mean?

Answer 33

V=ventilation (air supply)
Q=perfusion (blood supply)

reduction or increase in V/Q

Question 34

Give an example of what a high V/Q mismatch could be caused by?

Answer 34

Pulmonary Embolism

Question 35

What can increased Pulmonary vascular resistance cause?

Answer 35

Pulmonary Arterial Hypertension

Question 36

What can shunt cause?

Answer 36

Pulmonary Arteriovenous Malformation

Question 37

at a higher altitude what happens to ambient pressure and FiO2?

Answer 37

Ambient pressure falls
FiO2 remains constant

Question 38

arterial carbon dioxide level is ….. to alveolar ventilation

Answer 38

inversly proportional

Question 39

Formula for PaCO2?

Answer 39

k VCO2/VA

Question 40

what is a CO single breath transfer test used to measure?

Answer 40

gas exchange into the alveolar capillary (measures overall integrity of alveoli)