1. Ventilation Parameters Flashcards
Why is respiratory ventilation in anesthesia important?
normal alveolar respo ventilation is done unconsciously to maintain arterial blood gas tension (particularly CO2)
Anes + drugs can interfere w/ unconscious mechanism. It is responsibility of people monitoring to recog changes and act accordingly
What is the physiology of respiration
takes place in th emedulla oblongata or resp center
2 systems that control breathing are mechanical control and chemical ontrol
What is mechanical control of the resp center?
nerve impulses that respond when the lungs are fully inflated and deflated
These are @ autonomic preset levels that prevent over-inflation and ensure proper amounts of exhalation
this system’s control is to maintain normal, rhythmic, resting breathing pattern
What is chemical control of the resp center?
chemical receptors within blood vessels that monitor physical and chemical characteristics of the blood
What are 3 characteristic that affect breathing processes?
CO2 content
blood pH
O2 content
What happens if Co2 increases in the body?
Blood pH becomes more acidic -> triggers the resp center to inc rate and depths of breaths -> CO2 eliminated
What happens if CO2 decreased in the body?
Blood pH becomes more basic -> triggers resp center to dec create and depth of breaths -> allows CO2 to increase
can also occur while bagging our patients under anes and can take awhile for animal to breath on its own due to low lvls of CO2
What happens if O2 decreased in the body?
triggers resp center to inc rate and depth of breaths
NOTE: severe hypoxia can cause the resp center to fail due to neuron depression and may cause a dec or arrest of breathing
What are 2 respiratory monitors for anesthesia?
- capnography A) side stream sampling, B ) mainstream sampling
- Pulse oximetry
What is capnography?
the measurement of conc CO2 lvls in expired gas
the exp baseline should always be 0
upward slope indicates expiration
the highest value is the end-tidal CO2
Downward slope indicates inspiration
the results are displayed in millimetres of mercury (mmHg) or percent (%) CO2
What are the normal values for a patient for capnography?
btw 35-45 mmHg
>45 mmHg = hypercapnia=hypoventilation
45-45 mmHg = eucapnia = normal
<35 mmHg=hypocapnia=hyperventilation
What should we troubleshoot capnography when we have low ETCO2 for patient issues?
cardia arrest
dec in cardia output
hyperventilation
hypotension
air or pulmonary embolism
tidal volume too sm (collapsed lung/diaphragmatic hernia)
What should we troubleshoot with capnography and low ETCO with monitoring issues?
sampling line disconnected or broken
endotracheal tube cuff deflated or leaking
What do we need to troubleshoot with zero ETCO2 capnography lvls with patients and monitoring issues?
Patient: alive??, airway obstruction
Monitoring: endotracheal tube disconnect, esophageal intubation, obstruction in line or ET tube
What do we need to trouble shoot with high ETCO2 capnography lvls with patient and monitoring issues?
Patient: hypoventilation, pneumothorax/lung Dz, hyperthermia/inc metabolism, pain, shivering
Monitor: pop-off valve closed, improper ventilation, valves sticking in rebreathe system
What do we trouble shoot with baseline high ETCO2 capnography with patient and monitoring issues
Patient: rapid and shallow breaths
Monitor: large dead-space apparatus, exhausted CO2 absorbant, bain system incorrectly assembled
What is side-stream sampling
extracts a sample of the resp gas btw the ET tube and the anes hose and diverts it back to a measuring chamber
PROs: small, lightweight, can be used in remote monitoring (MRI), can be used in non-anes’d patients
CONs: can prod falsely low ETCO2 in sm patients with high oxygen flow, 2-3s delay for results on monitor, sample tubes can be occluded with moisture/condensation build up
attachments can become lost or broken easily
What is mainstream sampling and its pros/cons
Device that locally analyzes the respiratory gases btw the ET tube and anesthetic hoses but prods instant results
PROs: less moisture/condensation build up then side-stream. no disposable supplies to lose or break
CONs: heavy, prone to accidental disconnection, leaks, dropping damage, tendency to kink tubes
What is pulse oximetry?
Measurement of haemoglobin O2 saturation
Non-invasive method of continuous measurement
abbreviated to Sp02 meaning the method of measuring saturated oxygen in bloodstream
Light-emitting diodes (LEDs) in red and infrared wavelengths penetrate the tissue and measure the light absorption spectra of the haemoglobin
will pick up HR
valuable info to detect earl dec oxygen saturation b4 resp or Cardiovasc failure occurs
greatly reduces the odds for anes related deaths
What are Sp02 normal values
Normal % of Sp02 to sustain life and properly perfuse all the internal orgains is over 95%
Some will read lower around 93
Very important to detect hypoxia rather than an exact measurement reading
compare the color of mucous membranes is concerned
Sp)2 placement cont’d
needs to be on an area for 30s b4 it can be assumed accurate
for quality control the HR needs to match the monitor reading
Can be placed on ear, tongue, pawpads, lip, prepuce/vulva
Readings affected by pigment of skin, amount of hair, movement of patient, peripheral vasoconstriction, thickness of tissue