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Diagnostic Units 3-4


The pattern of how gas is distributed through the lung areas is known as? gas distribution
Most air flows into areas where it can be absorbed through the alveoli into capillaries and then the blood stream. Some air goes into regions where? gas exchange is not possible, deadspace ventilation
Anatomic Dead space? air in the conducting airways (nose, mouth, terminal bronchioles) no gas exchange occurs, usually 150ml
Alveolar dead space? malfunctioning alveoli, gas exchange should occur but does not
Physiologic dead space? combo of both anatomic and alveolar
When there is not enough blood supply to the alveoli for gas to diffuse this called? ventilation in excess of perfusion, partial dead space
What are the two methods of determining dead space? Fowler method and Bohr method
The fowler method ( nitrogen washout ) ? Can be a single or multiple breath test, uses 100% oxygen
The bohr method? includes alveolar dead space, given as a ratio of dead space to tidal volume
The fowler method measures the amount of air in the patients? conducting airways
How to perform a nitrogen washout test? 1. Patient exhales down to RV 2. Takes deep breath to VC of 100% 02 3. Exhales slowly and evenly into mouth piece 4. Analyzers monitor gas exhaled and N2 concentration
Phase 1 of the N2 washout? gas in the upper airway expired, anatomic dead space (100% 02)
Phase 2? middle airways expired, 02 decreases and N2 increases abruptly
Phase 3? alveolar gas is exhaled, 02 and N2 change slowly and evenly
Phase 4? abrupt increase in N2 that continues until RV is reached. This phase indicates the patients closing volume
What is closing volume? point at which the airways in the lungs bases are closed
The portion of the graph that includes the closing volume and residual volume is called the? closing capacity, closing volume and residual volume equal the closing capacity.
Both the closing volume and closing capacity are expressed as a percentage of the TLC, the normal values are? CV/VC= 7.7% (male) 8.7% (female) CC/TLC= 24.8% (male) 25.1% (female)
Closing volumes will be increased in patients with COPD because? their smaller airways collapse earlier in exhalation
Patients with diseases that cause swelling of the smaller airways will also have increased closing volumes? pulm edema, asthma, chronic bronchitis
Closing volume and capacity can both be used to? identify the presence of small airway disorders before spirometry can detect them
Normal deadspace? 20%-40%
The bohr method uses what equation? PaC02-PeC02/PaC02 PaC02- ABG PeC02- Douglas bag and end tidal C02
The effective alveolar ventilation equation? VAeff= frequency (RR) x (vt-vd) Multiply the VT and VD first, then subtract the number from the VT
Normal effective alveolar ventilation? 3-8 lpm >8 lpm= hyperoxia and hypocarbia <3 lpm= hypoxemia and hypercapnea
What is the amount of gas that can be forcibly exhaled after a maximal inspiration? FVC
The amount of air that remains in the lungs after a forced exhalation? RV
Volume exhaled during the first second of an FVC, shows average air flow from the larger airways? FEV1
Diffusion testing is used to measure how well gas is exchanged from the lungs to blood stream, Carbon monoxide is used for these tests because? uses the same diffusion pathway as 02, great affinity for hemoglobin, no CO remains dissolved in plasma during the diffusion process
Disadvantages of using carbon monoxide? correction factor must be used on those pt's who have been exposed outside of the test ( cigarette smokers). ABG must be done to determine CO levels
What are some reasons to order a diffusion test? evaluate pulm disease (asbestosis, sarcoidosis, cystic fibrosis, emphysema), differentiate emphysema, CB, and asthma, determine if systemic disease is affecting lungs, evaluate amniodorone reactions, effects of pulm hypertension, pulm edema, evaluate inte
DLCO measurements are based on? the idea that the difference between the CO inhaled and exhaled is the amount that has diffused into the bloodstream
What are the three DLCO measurement methods? Single breath ( DLCO SB) Steady state (DLCO SS) Re breathing method
What is the gas mixture used for DLCO? 0.3% CO 10% He, (02, N2, room air as the rest) Pre mixed in an H cylinder
What does an increased closing volume indicate? obstruction
What are some disadvantages of the single breath DLCO test? It may be difficult for some pts, very effort dependant
Name 3 things that must happen for a DLCO test to be considered an acceptable test: VC must be> or = to 90% of the pt’s previously measured VC, Inspiration must be performed within 4 secs of the pts max exhalation, Pt must maintain a stable inspiratory breath hold for 9 to 11 secs w/ no evidence of leaks, allow 4 mins between tests
What are 3 steps that must be taken before a DLCO study to ensure valid results? No smoking at least 24 hrs(smoking increases (CO) levels), No alcohol at least 4 hrs prior to test(alcohol can reduce DLCO), No eating at least 2 hrs prior to test(a full stomach affects the VC maneuver) no supplemental 02 for 5 minuets prior
Pulmonary disease will affect DLCO results? any disease that decreases AC membrane surface area will decrease DLCO, anything that increases blood flow to the AC membrane will increase DLCO (exercise or disease) asthma will be normal or increased DLCO
The DLCO gas mixture also provides values for? Inspired CO(FICO) and He (FIHe)
How would you coach a pt to perform the breathing maneuver for a DLCO single breath test? Mouth piece in mouth, nose clips, blow out as much air as possible (get down to the pt’s RV), take max inspiration (special gas mixture), hold breath for 10 secs, exhale back to RV level
How does a steady state DLCO test differ from a single breath DLCO study? measurements can be made with pt breathing normally, gas mix contains 0.1% CO with the remaining balance air. Inhaled with each breath for 5-6 minutes, during the last two minutes pt exhales in douglas bag. An ABG is also drawn
How is the DLCO rebreathing method performed? Pt re breaths from a reservoir containing the gas mixture for 30 to 60 seconds at RR of 30 bpm. The final CO He and 02 % are measured after this interval. An equation is then used to calculate DLCO
What is the advantage of using the DLCO rebreathing technique? The results are less affected by V/Q abnormalities or by changes in the pt’s lung volumes during the test
what is the order of complexity of the DLCO tests? Single breath is the easiest, Steady state is moderate, Re breathing is the most complex. Single breath is the most common
What disorders can be assessed using a ventilation scan? The severity and extent or pulmonary disorders, especially bronchiectasis and bullous lung disease
What are perfusion scans used for? shows distribution of pulmonary blood flow, will show clots
V/Q scans are used for? They will show both of what ventilation and perfusion scans show. Normally used to find clots (pulm emboli) especially with positive D-Dimer
What effects does emphysema have on a subject’s DLCO? Why? Decreases DLCO due to decreased alveolar-capillary (AC) surface area
How would fibrosis cause a decreased DLCO? It causes an increased thickness of the membrane in the a-c wall
Why would a physician want to measure a subject’s exhaled nitric oxide? To determine the severity of asthma and the success of asthma treatment – it measures the amount of inflammation in the airways – the higher the NO, the greater amount of inflammation
After starting a subject on an inhaled corticosteroid, a repeat FeNO measurement is obtained. The exhaled NO level has decreased significantly. What does this indicate? That the corticosteroid is reducing the amount of airway inflammation
Predicted DLCO values are directly related to height, body surface area, and blood hb. As each of these items increases? The DLCO increases. For each gram of change in the pt's Hb level the DLCO will change 7%. The older the subject the lower their predicted DLCO
Normal resting value for DLCO? 25mlCO/min/mmhg
Predicted DLCO values? 80-120% normal 60-80% mild defect 40-60% moderate defect 20-40% severe <20% very severe
What pulmonary problems can cause a decreased DLCO? emphysema, cystic fibrosis, pulm resection, pulm/fat emboli, anemia, interstitial lung disease(asbestosis, sarcoidosis, fibrosis, pneumonitis) pulm hypertension/edema
What can cause an increased DLCO? supine position, increased pulm blood flow, exercise, pulm hemorrhage, polycythemia with increased Hb, left heart failure, left to right cardiac shunt, high altitudes that increase Hb
Which parameters does a blood gas analyzer measure & which does it calculate? Measures: pH, PO2, PCO2 Calculates: HCO3, base excess, hemoglobin saturation
What does a co-oximeter measure? Directly mesures TOTAL Hemoglobin(hb), Oxyhemoglobin(HbO2), Methhemoglobin(MetHb), Carboxyhemoglobin(COHB), also calculate 02 percent but does not directly measure it
What sites are used for performing ABG's? radial, brachial, femoral, dorsalis pedis
Factors that may alter ABG results? air bubbles, analyzer protein build up, bacteria growth, electrode cracks, loss of electrolyte solution, aging of electrolytes, electrode membrane problems
The effect's of sitting and bubbling depends on how the sample compares to the atmosphere? P02 in room VS P02 in atmosphere
Advantages of POC devices? Small, portable,run multiple tests w/ small samples,
There are two types of analyzer electrodes that measure? Clark electrode measures P02, severinghaus measures C02
How do air bubbles in an ABG sample effect the CO2 & O2 of the sample? Will lower C02, if blood P02 is low it will falsely raise it, if blood P02 is high it will falsely lower it.
How is a Modified Allen's Test performed? Occlude the radial & ulnar arteries, have pt open/close hand, release ulnar artery, see white hand become pink again w/in 15secs = collateral circulation
ABG indications: Dyspnea, cyanosis, heavy use of accessory muscles, CPR, changes in vent settings, metabolic conditions
ABG contraindications: Negative result on a Modified Allen's Test, do not test through a lesion, scar, sore, distal to a dialysis or surgical shunt, coagulopathy or anticoagulation therapy
ABG complications: Infection, arteriospasm, air or blood clot emboli, hematoma, hemorrhage, vessel trauma, vasovagal response, pain
What is the most important aspect of a Quality Assurance program? Record keeping
Errors when handling blood gas samples? inadequate mixing, air in sample, venous blood, excess anticoagulant (heparin), waiting too long to run sample
What is the Fowler Method used for? determine FRC
What is performance evaluation? testing a new instrument to confirm the manufacturers claim of accuracy, involves running samples in an established analyzer and comparing to new analyzer
What are components of a quality assurance program? record keeping, calibration and verification, quality control, proficiency testing, preventative maintenance, performance validation
What is preventive maintenance? parts of the machine are replaced such as filters, membranes, etc.. The manufacturers provide schedules for maintenance
What are function checks? Manufacturer provides a schedule of routine function checks and parts replacement that must be strictly adhered.
Automated calibrations? insure accuracy, regularly calibrate themselves using calibration gases or solutions, If there is a small difference the machine can correct itself, if it is too big a warning message is given
One point calibrations are run every 30 minuets and two point calibrations are done? every 2 hours
What is calibration verification measurement? a set of 5 fake blood gas samples with unknown values that are developed by the manufacturer, they are run and then compared to acceptable ranges
CVM must be performed when? new analyzer, after major maintenance, overhauled analyzer, analyzer moved outside of building, every 6 months
Correlation studies? A study that compares results of one analyzer to another.Several samples are run on both machines 4x's/year to ensure results from both machines are similar. Results must be w/in 10% of each other.
What is remedial action? process of applying appropriate measures to correct errors
Examples of errors that would need remedial action? calibration errors, internal quality control errors, sample errors, unsatisfactory proficiency results, correlation problems, unsatisfactory CVM
Examples of remedial action? procedural changes, staff training, closer supervision, frequent preventative maintenance. The action should always be appropriate for the problem
Thorough record keeping is required by both? statutory law and the professional associations that accredit blood gas labs
Agencies that accredit blood gas labs: College of American Pathologists, Joint Commission for Healthcare Accreditation, agency for healthcare administration, american thoracic society (ATS)
What are Levey-Jennings plots used for? They provide a visual indicator of the performance of the ABG machine. One can determine whether a QC sample that is out of range is a random error, part of a trend, or systemic error (bias) that is trending out of range
Internal quality control? Uses control (fake) samples every 8 hours with known values
ABG analyzers plot results of all quality control samples on a levy jennings graph. This helps to determine? If the sample has an error that is part of a trend, is in normal range, has a random error ( sporadic, out of range) or a systemic error (bias, abrupt shift outside of limits)
External quality control proficiency testing? Mandated by Federal Gov't. 4-5x's/yr 5 external samples are sent to lab, they are run w/in a 10 day period and the results are returned. All results must be correct.
Created by: juialynn92
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