ICM - OSCE - Equipment Flashcards
Describe the Capnography wave form
Phase 1 - (flat line) - inspiratory baseline. This is insp gas with no CO2
Phase 2 (vertical upward line) - exp upstroke - transition between dead space and alveolar gas
Phase 3 - exp plateau with the end point being the etCO2
Phase 0 - inspiratory downstroke, beginning of next breath
Which is higher, arterial CO2 or etCO2
Arterial
Wavelength of CO2 monitoring
IR - 4.3um
How does capnograph work
CO2 absorbs infra red.
Beam of IR is passed across gas sample to a sensor.
CO2 will reduce amount of light to the sensor - changes the voltage in a circuit
Amount of CO2 absorbed is proportional to infra red absorbing substance (Lambert Law)
Capnography measures the partial pressure of expired CO2, which reflect artieral conc.
Systems of Capnogaphy
Mainstream and sidestream
Main - bulky on catheter mount, may pull on circuit
Sidestream - need a pump and sample gas, delay in detection of CO2
Difference between arterial and etCO2
Health - small
In lung disease or cyanatic lung disease - can exceed 1kPa
Describe collision broadening
Other gases in mix alter the IR absorption of CO2 as molecule collide with each other.
This widens the spectrum over which IR is absorbed
Nitrous oxide absorbs IR at a similar wavelength to CO2.
Fix it - specific frequencies/filtering, or by measuring the other gases
Causes of Waveform - flat line
Ventilator disconnection Capnograph not connected Airway misplaced Complete obstruction Apnoea Cardiac arrest
Wave form - sloping phase 3
Partial Obstruction - bronchospasm
COPD
Kinked tube
Waveform - steadily decreasing
Decreased CO - arrest, hypotension, cardiogenic shock
VQ - massive PE
Sample line issue
What is the use for a CO2 volume trace (volumetric capnography)
Gives VQ measurement
Measures dead space
Provides data on CO2 elimination
Mixed expired CO2 concentration
When should we use continuous capnography
Any airway manipulation
Tracheostomy
Transfers with an airway
All vented patients, even if on CPAP
Management of an STEMI
Assess patient and resuscitate using and ABCDE approach
Give oxygen, morphine, 300mg aspirin and nitrates (GTN)
Revascularise (primary PCI - if available within 120 minutes of time fibrinolytic could be given)
Thrombolysis - were a pPCI is not available within 120 minutes. Alteplase.
Post PCI still hypotensivewhat ix can you do and why
TTE (ideally TOE)
Left and right ventricle function
Post MI complications, LV aneurysm, interseptal haemorrhage
Vasopressors/inotropes
IABP
How does an IABP work
Balloon placed fluoroscopically distal to left subclavian artery from femoral artery, proximal to renal arteries
Relies on counterpulsation
Inflates in diastole —> increases coronary perfusion in diastole, increases myocardial oxygenation
Deflates at end of diastole just before systole, reducing aortic end diastolic pressure, lowers after load, less work
