Diagnostics Flashcards
Bicarbonate Buffer System/Equation..
CO2 + H2O H2CO3 H^+ + HCO3
CO2 = acid H2O = base
H+ = acid HCO3 = base
H2CO3 = carbonic anhydrase
Respiration Goals?
- Air in/out; blood round and round.
- Diffusion depends on distance, surface area and pressure differences.
- O2 depends on diffusion, CO2 depends on ventilation.
3 ways the body compensates for Acid-Base Changes?
- Bicarb-Buffer System.
- Respiration (Lungs).
- Metabolic (Kidneys).
ABG Format and ABG Normal values?
pH/CO2/PaO2/HCO3
7.4/40/80-100/24
LUNGS —> What? aka? Speed? Control? How?
What: CO2 Aka: acid Speed: Fast Control: involuntary and voluntary inspiration/expiration How: MV = RR x VT
KIDNEYS —> What? Aka? Speed? Control? How?
What: HCO3 aka: base Speed: very slow Control: Involuntary How: make and manage HCO3
What is the 5 step ABG Interpretation Process?
- pH
- Primary RESPIRATORY or METABOLIC Process (look at the PCO2 and HCO3).
- If Respiratory…
3Ra. Acute or Chronic?
3Rb. pH within normal range (compensation from the kidneys).
3M. If a metabolic process, is there respiratory compensation and is it adequate? (EpCO2) - Calculate the Anion Gap (AG).
- Delta Gap (DG) —> if anion gap is high, what is the delta gap?
Superior detail (better than CXR) of internal organs and structures?
CT Chest
Air < fat < bone…
Air is less dense than fat and bone; so black.
Fat is more dense than air but less dense than bone; so gray.
Bone is the most dense; so white.
Type of CT scan that uses a step and shoot process - better for high resolution images, less radiation, slower.
Axial CT
Type of CT that is more common, faster, higher radiation dose, minimizes motion artifact?
Helical CT.
Most effective radiation dose for CT Chest?
Between 5-10 mSv.
Always use lowest dose radiology exam available to achieve your Dx.
A consistent and thorough technique for reviewing images?
Read from the outside in!
- Assess type of scan.
- Review pt H/P findings.
- Pt. Positioning (prone, supine).
- Review all windows (lungs, soft tissue, bone).
- Review prior imaging.
Specific types of CT Chest scans?
Standard
High Resolution (HCRT)
CT Pulmonary Angiogram (CTA)
Low Dose CT Chest (LDCT)
Standard CT Chest scan?
- 3-10 mm Slices or Cuts
- Maximal inspiration
- +/- contrast
- Indications:
- further eval CXR abnormality.
- Empyema/abscess.
- Lung cancer staging.
- Pleural/mediastinal abnormalities.
High Resolution CT (HRCT)?
- 0.625 mm - 1.5 mm every 10 mm
- Highly detailed images of lung parenchyma, vessels, airways.
- Typically w/o contrast
- Indications:
- abnormal PFTs w/normal CXR.
- Diffuse interstitial changes on CXR.
- Known ILD, need to assess progression, response to treatment.
Why is contrast used in CT?
Contrast will make organs more apparent.
CT Pulmonary Angiogram (CTA)?
- Contrast bolus required, timing of bolus is key.
- Allows for optimal vascular enhancement.
- must have adequate venous access.
- Indications:
- concern for PE, Aortic Aneurysm, Aortic dissection.
Low Dose CT Chest (LDCT)?
- Now approved for lung cancer screening in certain pt. Populations.
- Specific for nodules and masses.
- CMS guidelines for LDCT:
- Age 55-77.
- Asymptomatic.
- Tobacco use Hx >30 pack years.
- Active tobacco use or quit within past 15 years.
CT Chest views?
Coronal, Sagittal, Transverse
CT Chest windows?
Lung Windows - lung parenchyma.
Soft Tissue - mediastinum, blood vessels, muscles, heart, LN.
Bone Windows - rib cage, spine.
2 disorders that make up COPD?
Emphysema and Chronic Bronchitis
What do you need to diagnose Emphysema or Chronic Bronchitis as COPD?
Need to prove an obstruction.
On PFT, an FEV1/FVC < 70%.
- Permanent enlargement of air spaces distal to bronchioles in the alveoli.
- Destruction of elastin walls of alveoli.
- 3 Types:
- Centriacinar/lobular.
- Panacinar.
- Distal acinar/paraseptal
EMPHYSEMA
Centriacinar/Lobular - upper lobes of lungs at proximal alveolus.
Panacinar - entire alveolus.
Distal acinar/paraseptal - distal end of alveolus near septum.
What does Bullae on CT mean?
Full extent emphysema
- Dilation of the bronchioles
- airway has larger diameter than corresponding blood vessel.
- leads to impaired secretion clearance and recurrent infection.
- Lower lobes, chronic aspiration, immunodeficiency, IPF.
- Upper lobes: CF, TB, Sarcoidosis, ABPA.
- Central: ABPA
Bronchiectasis