Acute Pulmonary Oedema (APO) Flashcards
what is pulmonary oedema?
it refers to the accumulation of excessive fluid in the alveolar walls and alveolar spaces of the lungs
what are some causes of APO?
- most often related to heart failure - known as cariogenic pulmonary oedema
- acute respiratory distress syndrome (ARDS)
- kidney failure
- high altitude
- brain trauma
- severe seizures
- brain surgery
- rapid expansion of the lungs
- aspirin overdose
- pulmonary embolism
- viral infections
- eclampsia in pregnancy
why is shortness of breath a common symptom in APO?
fluid in the alveolar space make gas exchange more difficult as O2 and CO2 have to diffuse through a wide layer of interstitial fluid, resulting in poor oxygenation of the blood
what are the symptoms of pulmonary oedema?
- shortened of breath
- easy fatigue
- dyspnoea on exertion
- tachypnoea
- dizziness
- weakness
- hypoxia
- crackles on auscultation of the lungs
what sounds would you likely hear when auscultating the lungs of a patient with APO?
crackles
How would you treat a patient with severe APO?
- high flow oxygen
- GTN administration
- positioning (NOT flat on back, head definitely raised)
- CPAP
what are the starling forces?
describe the movement of fluids between vasculature and interstitial spaces, fluid movement is determined by hydrostatic and osmotic pressure gradients
hydrostatic = pushing fluid out of capillary osmotic = keeping fluid in capillary
explain the pathophysiology of APO caused by left sided heart failure
left ventricle (LV) becomes unhealthy > LV can’t pump effectively > blood backs up from LV into left atrium (LA) > blood continues backing up from LA to pulmonary veins > blood continues to become backed up into the pulmonary capillaries > the excess blood in the pulmonary capillaries as a result of this back up causes pulmonary hypertension (an increase in hydrostatic pressure) > oncotic pressure is unable to oppose this pressure > fluid gets pushed into the interstitial space > fluid gets pushed into the alveoli
how do non-cardiogenic conditions or conditions not related to high systemic blood pressure cause oedema in the lungs?
non-cardiogenic causes can include things like pulmonary infections, trauma to the chest, and inhalation of toxins. These things can cause direct injury to the alveoli. This injury causes an inflammatory process which increases the permeability of the capillaries, meaning fluid is able to cross much more easily.
Another non-cardiogenic cause may be sepsis, this also causes APO through increased membrane permeability but it is not a result of an inflammatory process occuring in the alveoli but rather systemically.
Another cause could be related to not creating enough of the proteins resposible for maintaining oncotic pressure (keeping fluid in the capillaries), this can occur in things like liver disease
what is a common patient presentation that is seen when called to someone with APO?
oftentimes early in the morning or someone sitting up in bed. This is because people with APO often find it harder to breathe when laying down as fluid covers more surface area of the lung and therefore has a greater impact on gsas exchange.
how is APO diagnosed?
chest x-ray or CT scan as these can show fluid in the interstitial space
how many litres of O2 need to be running when using CPAP?
8L
