Lung physiology 2 Flashcards
what is haemodynamics
study of blood flow through the cardiovascular system
what is hypoxaemia?
conditon where there is too little oxygen in blood (PaO2 too low), someoe with hypoxaemia is said to be hypoxic
What each means: tidal volume, Inspiration capacity, residual volume, forced expiration volume, forced vital capacity, peak expiratory flow, transfer factor, lung volumes?
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).
what can be calculated from a volume time plot?
FEV1/FVC calculated
volume time plot
flow/volume loop
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
how to measure total lung capacity?
gas dilution,
Body box (total body plethysmography)
how to do gas dilution?
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
how to do total body plethysmography/
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
How woul you do a TLCO lung capacity test?
small amount of carbon monoxide give to patients and used to estimate TLCO, as has high affinity for haemoglobin
what is exhaled nitric oxide?
marker of eosinophillic airway inflammation, FeNO level in adults of 40 parts per billion (ppb) or more is regarded as positive
how does pulse oximetry work? what does it show?
Measures redness of light transmitted through tissue, shows percentage of haemoglobin that bounds to O2 (can only be used if peripherally pulsified)
abnormal values of FEV1, FVC and FEV1/FVC? Whats classed as obstruction vs restriction?
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
spirometer
A basic test that measures how much air you can breathe out in one forced breath. You’ll sit while performing this test
What is a CO single breath gas transfer?
A test that measures how well oxygen moves from your lungs into your blood.
what is asthma?
a long-term condition where the airways become periodically inflamed (swollen) and narrowed
what is emphysema? symptoms? common cause?
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)
chronic obstructive pulmonary disease (COPD)- what is it?
a group of lung conditions where the airways become narrowed
cystic fibrosis
a genetic condition where the lungs and digestive system become clogged with thick, sticky mucus
pulmonary fibrosis
scarring of the lungs
formula for PiO2?
PiO2 = FiO2 x ambient pressure
Pulmonary circulation vs systemic circulation: vessel wall, muscularization, need for redistribution, blood volume, response to hypoxia, regional distribution of blood flow
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
perfusion is stronger at base- gravity
ventilation is also stronger at base of lungs
what is formula for pressure across pulmonary circuit?
Cardiac Output x Resistance
(like ohms law V=IR)
measured by difference in pressure between L and R atrium
combinatio of two formulas for cardiac circuit pressure?
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)
What is Pouiseuille’s law? relavence to circulation
Resistance = (8 x L x viscosity) / (π r4)
small change in radius has a large effect on resistance
how may pulomanry Haemodynamics change during exercise to respod to an increased poulmonary output?
Recruitment (use reserve vessels) and distention (dilation of vessels) in response to increased pulmonary artery pressure
Causes of hypoxaemia:
Hypoventilation
Diffusion Impairment
Shunting
V/Q mismatch
Reduced pressure of inspired oxygen (e.g. high altitude)
things that affect difuion rates? name 2 conditions related to diffusion imparement?
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
what is hypoventilation? examples of conditions that may cause this?
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).
what is a right to left shunt? name the 2 types and some causes of each type?
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)
what is Eisenmenger’s Syndrome? what are effects of the syndrome?
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
what does V/Q mismatch mean?
V=ventilation (air supply)
Q=perfusion (blood supply)
reduction or increase in V/Q
Give an example of what a high V/Q mismatch could be caused by?
Pulmonary Embolism
What can increased Pulmonary vascular resistance cause?
Pulmonary Arterial Hypertension
What can shunt cause?
Pulmonary Arteriovenous Malformation
at a higher altitude what happens to ambient pressure and FiO2?
Ambient pressure falls
FiO2 remains constant
arterial carbon dioxide level is ….. to alveolar ventilation
inversly proportional
Formula for PaCO2?
k VCO2/VA
what is a CO single breath transfer test used to measure?
gas exchange into the alveolar capillary (measures overall integrity of alveoli)
