Pulmonary embolism Flashcards
Inhaled objects are more likely to go to the _________ bronchus. Why is this?
This is because the right bronchus is wider, shorter and more vertical
it is less horizontal
The lung rarely extends beyond the _____ rib. Where does the length of the lung usually end (what rib does it extend to)?
rarely extends beyond the 10th rib
usually ends at the 8th rib
What is the pleura?
This is a thin layer that covers the lungs and lines the inside of the chest cavity
The pleura is made up of …
The viseral and parietal pleura
[similar to fibrous and serous (parietal and visceral) membranes of the heart]
The visceral pleura is the closest membrane to the lungs
What is the pleural cavity?
the pleural cavity is the space between the visceral and parietal pleura
What volume of pleural fluid is contained in the pleural cavity?
15 ml
What is the function of the the pleura (membranes + fluid) ?
facilitates movement of the lungs with the chest wall
Where is the apex beat located?
between the 5th and 6th intercostal space
the apex beat is an indication of left ventricular contraction
A radiolucency on a chest x-ray is an indication of …
a significant collapse of that part of the lung
The alveoli is described as …
the basic unit of ventilation
What types of cells make up the alveoli?
Type I cells (epithelial layer)
Type II cells
Alveolar macrophages
What is the function of type II alveolar cells ?
secretion of surfactant
The alveolar sac is made up of multiple alveoli. The sac is surrounded by __________.
capillaries
What is the purpose of surfactant released by type II cells?
surfactant lines each alveolus and gives them enough tension to prevent them from collapsing in their resting state
Alveoli contain __________ and _________ fibres
collagen
elastic fibres
Oxygenated blood is taken back from the alveolar sacs through what blood vesse?
pulmonary venule
Why are premature babies often put on ventilators?
they are not mature enough to make their own surfactant this alveoli can collapse
What is surfactant?
lipoprotein that decreases surface tension and increases pulmonary compliance
Oxygen diffuses into the ___________ whilst carbondioxide diffuses into the ___________
RBCs
CO2 diffuses into the alveolus
Gas exchange is a ___________ process
passive
no ATP/energy is required for gas exchange to take place
Diffusion of gases is facilitated by a ______________.
concentration gradient
gases diffuse down their concentration gradient
The alveoli cover a surface of 140m2. What is the purpose of this large surface area?
allow large amounts of area for gas exchange to take place
The blood-air barrier is ______ thick.
2.2um
the blood-air barrier refers to the respiratory membrane (alveolar and vascular membranes)
What is the venous blood gas tension for oxygen?
6.0kPa
What is the venous blood gas tension for carbondioxide?
6.0kPa
What is the arterial blood gas tension for oxygen?
13kPa
a separate table in the slides shows 18.0kPa?
What is the arterial blood gas tension for carbondioxide?
5.3kPa
A rise in arterial CO2 is detected by _________ and ________ receptors. What is the consequence of a rise in arterial CO2 ?
peripheral and central receptors
a rise in arterial CO2 triggers an increase in the rate and depth of breathing
What acid is produced as a result of rising CO2 levels? What is the effect of this acid
carbonic acid
(increase in H+ ions)
they stimulate the respiratory centre in the brain; ensure that we are taking a breath
What is the partial pressure of oxygen in the air?
21kPa
What is the partial pressure of carbondioxide in the air?
0.04kPa
Inspiration is initiated by the ______________
respiratory centre in the medulla
What occurs during inspiration?
diaphragm and intercostal muscles contract
intrathoracic cavity expands
intrathoracic cavity pressure decreases
air moves into the airways until alveolar pressure equals atmospheric pressure (18-21kPa?)
Unlike gas exchange, inspiration is an active process. What drives the process of inspiration?
it is driven by a change in pH in the respiratory centre (medulla) of the brain
change in pH of the blood is detected by the medulla - cells in the medulla have pH receptors which detect changes in pH in the blood
Expiration is a ________ process. Briefly describe what happens during expiration
passive process
intercostal muscles and diaphragm relax
there is elastic recoil of the lungs
intrathoracic volume decreases
intrathroacic pressure increeases (to prevent collapse without the partial pressure from the gases to prevent collapse)
expiration of air from the alveoli until the intratroracic pressure = atmospheric pressure
What is a pulmonary embolism?
blockage of pulmonary arteries by a clot - a clot in the pulmonary tree
it is a consequence of thrombus formation in distal veins and subsequent migration
A white thrombi is indicative of …
high platelet content
A red thrombi is indicative of …
low platelet content
high fibrin content
What is the most common origin of pulmonary embolisms?
deep venous systems of lower extremeties
(deep vein thrombi)
What percentage of DVT embolise to the pulmonary vasculature?
51%
Outline the pathophysiology of pulmonary embolisms
pulmonary vascular resistance increases
right ventricle work load increases
this causes distension of the right ventricle
there is frank-starling law failure (this isn when the stroke volume increases if the end diastolic volume also increases if there are no changes to other factors)
there is reduced right ventricular output
there is a decreased end diastolic volume of the left ventricle (less oxygenated blood being received)
cardiac output increases
decrease in mean arterial pressure
hypotension– > shock (body not getting enough blood flow)—> death
[hypovolemic shock]
Give a clinical scenario that classically cause formation of a pulmonary embolus
10 days following a hip replacement
straining often causes clots to form
What are the elements of virchows triad of thrombosis?
hypercoagulability of the blood - cancer, thrombophilia , inflammatory disease - situations that encourage blood to clot
Stasis of the blood- immobility, varicose veins, venous obstruction; slower moving blood encourages clots to form
Vessel wall injury- surgery, chemical irritation, inflammation. Exposure of collagen can trigger clot formation
[remember static fluid- increased likelihood of infection/clot]
What are the patient risk factors of pulmonary embolism?
increasing age
obesity
bed rest > 5 days
What past medical history/events are risk factors for pulmonary embolism?
previous DVT or PE
surgery in the last 2 months
malignancy (encourages hypercoaguability)
lower limb paralysis (slow moving blood?)
pregnancy
trauma
COPD
varicose veins
sepsis (inflammation and hypercoaguability)
What drugs can increase the risk of pulmonary embolism?
oral contraceptive pill
When taking a social history, what are some important factors to not that increase the risk of a pulmonary embolism?
smoking
recent air travel
What is the presentation of a pulmonary embolism ?
pleuritic chest pain
dyspnoea (subjective shortness of breath)
tachypnoea > 20 per minutes
collapse
hypotension
tachycardia
+/- cough
low grade fever
What can a pulmonary embolism lead to a low grade fever?
inflammatory response as the body tries to attack the clot
inflammatory response leads to low grade pyrexia (fever)
How is pleuritic chest pain characterised?
S- localised
O- sudden
C- sharp
R- nil
A- increased heart rate and increased resporatory rate
T- constant
E- worse on inspiration
S- severe/moderate
What are the complications of a pulmonary embolism?
treatment related bleeding - in order to break clot; anticoagulants given; can cause bleeding
pulmonary infarction (dead pulmonary tissue)
cardiac arrest- no breathing, no response from patient
chronic pulmonary hypertension
recurrent DVT
Briefly explain why chronic pulmonary hypertension is caused by pulmonary embolus
multiple fibrous scarring located where the clots are present
this causes a narrowing of the vessels and thus hypertension of pulmonary vessels
What investigations can be carried out to identify a pulmonary embolus ?
ECG
chest x-ray
ABG- arterial blood gas
INR (international normalised ratio)
D-dimer
ventilation perfusion (V/Q) scan - infusion of radiolabelled white cells to see where blood/air is going
computed tomographic pulmonary angiogram (CTPA)
How is a D-dimer test useful in identifying a pulmonary embolus?
d-dimers are fibrinogen break down products
they are usually an indication that there is a clot somewhere
How is a pulmonary embolus managed?
ABCD resuscitation
anticoagulation (low molecular weight heparin then warfarin)
Give examples of new anticoagulants that can be used to treat a pulmonary embolus
Thrombin inhibitor- dabigatran
Factor Xa inhibitors- apixiban, rivaroxiban
What are some dental considerations for a patient with a pulmonary embolus?
patients on anti-coagulants bleed
Check INR
consult haematologist prior to reversal
delay non urgent procedures until completed anticoagulation course
patients on anticoagulants will carry anticoagulation books
Do NOT stop their anticoagulants
