Learn: Respiratory Care and Mechanical Ventilation Review

What are the four purposes of laboratory tests?

Evaluate health; identify organ dysfunction; detect infection; determine therapy effects.

Which blood specimen collection sites are highlighted?

Peripheral veins, arteries, capillaries.

Which other specimens are highlighted?

Body fluids, sputum, pleural fluid, CSF, urine, feces, biopsy material, sweat.

Why is specimen integrity important?

It is vital for accurate test results.

What six factors can affect specimen integrity?

Hemolysis, storage time, temperature, transport, inadequate volume, wrong tube.

What four measures evaluate a laboratory test's predictive value?

Sensitivity, specificity, positive predictive value, negative predictive value.

What is clinical sensitivity?

Frequency of positive tests among patients WITH disease.

What does 98% sensitivity mean?

98% true positives and 2% false negatives among patients with disease.

What is clinical specificity?

Frequency of negative tests among patients WITHOUT disease.

What does 98% specificity mean?

98% true negatives and 2% false positives among patients without disease.

What are lab results compared with?

A reference interval or reference range.

What four factors affect reference intervals?

Age, gender, sample population, test method.

What proportion of healthy people is within a reference interval?

95%, or two standard deviations.

What is a critical test value?

A result far outside reference range that may be life-threatening.

What must be done with all critical lab values?

Report immediately.

About what percent of body weight is water?

60%.

What fluid compartments make up body water?

Extracellular (plasma and interstitial) and intracellular fluids.

What is hypervolemia?

Increased total body fluid.

What signs suggest hypervolemia?

Weight gain, pedal edema, dyspnea, wheezing.

What lung complication can hypervolemia cause?

Pulmonary edema: excessive fluid in the lungs.

What is hypovolemia?

Decreased total body fluid.

What signs suggest hypovolemia?

Low urine output, low BP, orthostatic hypotension, low skin turgor, thirst.

What does a CBC measure?

Amounts and appearance of RBCs, hemoglobin, WBCs, platelets.

What does the CBC's WBC differential tell you?

Total WBC per microliter plus each WBC type's number and percentage.

What is hematocrit (packed cell volume)?

Proportion of whole blood made up of RBCs.

What is hemoglobin's primary function?

Transport oxygen from lungs to tissues.

What is normal hemoglobin in men?

14-18 g/dL.

What is normal hemoglobin in women?

12-16 g/dL.

Which highlighted conditions can lower hemoglobin?

Methemoglobinemia and sickle cell disease.

Which highlighted condition can raise hemoglobin?

Chronic hypoxia.

What does MCV measure?

Average volume of a patient's RBCs.

What does MCH measure?

Average weight of hemoglobin inside an RBC.

What does MCHC measure?

Concentration of hemoglobin inside an RBC.

What are the three RBC indices?

MCV, MCH, MCHC.

What is polycythemia?

Increased RBCs.

What are the three types of polycythemia?

Primary, secondary, relative.

What is primary polycythemia?

Neoplasm-related mutation causing uncontrolled bone marrow cell proliferation.

What is secondary polycythemia?

Bone marrow produces more RBCs in response to another condition to improve oxygenation.

What three examples of secondary polycythemia are highlighted?

Chronic hypoxemia (COPD/CAD), high altitude, smokers without COPD diagnosis.

What is anemia?

Hemoglobin below the reference interval for age and gender.

What are three highlighted anemia symptoms?

Fatigue, pallor, dyspnea.

How does the body compensate for anemia?

Increases HR, RR, cardiac output and redirects blood to vital tissues.

What is the most common cause of anemia?

Iron deficiency.

What two other anemia types are highlighted?

Carboxyhemoglobin and methemoglobin anemia.

What is the main job of WBCs (leukocytes)?

Fight infections.

What is the normal WBC count?

4.0-11.0 × 10³/µL.

What is leukocytosis?

Increased WBC count.

What two highlighted causes of leukocytosis are listed?

Infection; elevated glucocorticoids from stress or steroids.

What is leukopenia?

Decreased WBC count.

What two highlighted causes of leukopenia are listed?

Overwhelming infection and malignant bone marrow involvement.

Which WBCs are a major line of defense?

Neutrophils.

Which WBCs respond to allergens?

Eosinophils.

What are platelets also called?

Thrombocytes.

What is the main function of platelets?

Form blood clots after vascular injury.

Where are platelets produced?

Bone marrow.

What size are platelets compared with other peripheral blood cells?

The smallest cells in peripheral blood.

What does aPTT evaluate?

Time for plasma to form a fibrin clot via intrinsic pathway.

What does PT evaluate?

Clotting through the extrinsic pathway.

How is INR calculated?

From PT, adjusting for reagents and instruments used.

What does prolonged aPTT or PT/INR indicate?

Reduced blood-clotting ability.

What is D-dimer?

Product of fibrin clot breakdown in blood vessels.

What does a D-dimer test help investigate?

Blood clotting problems.

What systemic clotting disorder is highlighted for D-dimer?

Disseminated intravascular coagulation (DIC).

Which local thromboses are highlighted for D-dimer?

Pulmonary embolism (PE) and deep vein thrombosis (DVT).

What is the most ordered group of blood chemistry tests?

Basic metabolic panel (BMP).

What is a chemistry panel?

A grouping of chemistry tests.

What four major electrolytes/tests are listed in the BMP?

Sodium, potassium, chloride, total CO₂.

What blood sugar test is included in a BMP?

Fasting glucose.

What two renal function tests are in a BMP?

BUN and creatinine.

What is homeostasis?

Maintaining a dynamic balance or equilibrium.

What does normal cellular function depend on?

Balance of fluids, electrolytes and acid-base status.

What are electrolytes?

Positively or negatively charged ions.

What problems can electrolyte testing help identify?

Irregular heart rhythms and respiratory muscle weakness.

When is electrolyte measurement especially important?

When body fluids are manipulated, e.g., IV therapy, renal disease, diarrhea.

Where is sodium the most common cation?

Extracellular fluid.

What is the normal sodium level?

135-145 mmol/L.

Sodium concentration regulation is tied to what?

Total body water regulation.

What is hyponatremia?

Decreased sodium.

What is hypernatremia?

Increased serum sodium.

What is the normal potassium level?

3.5-5.0 mmol/L.

What is hypokalemia?

Decreased potassium.

What highlighted symptoms can occur with low potassium?

Muscle weakness, arrhythmias, delirium, convulsions.

What is hyperkalemia?

Increased potassium.

What life-threatening complication can high potassium cause?

Cardiac arrhythmias leading to cardiac arrest.

What highlighted symptoms can occur with high potassium?

Muscle weakness, arrhythmias, delirium, convulsions.

What is normal serum chloride?

98-107 mmol/L.

What is hypochloremia?

Low serum chloride.

What is hyperchloremia?

High serum chloride.

What does total CO₂ measure?

Dissolved CO₂ and CO₂ dissociated as bicarbonate (HCO₃⁻).

Why can total CO₂ and HCO₃⁻ be used interchangeably?

About 95% of total CO₂ exists as bicarbonate.

What is calcium important for in the highlighted notes?

Neuromuscular function and cell enzyme processes.

What is normal ionized calcium?

1.2-1.3 mmol/L.

What is hypocalcemia?

Decreased calcium.

What is hypercalcemia?

Increased calcium.

What cellular roles of magnesium are highlighted?

Energy transfer, nutrient metabolism, normal cell membrane function.

What is serum glucose used for?

Energy for cells following carbohydrate breakdown.

What is normal glucose?

70-99 mg/dL.

What three highlighted causes of hypoglycemia are listed?

Severe liver injury, excess insulin treatment, inadequate carbohydrate intake.

What highlighted cause of hyperglycemia is listed?

Pancreatic injury or islet cell dysfunction impairing insulin production.

When insulin is insufficient, what fuels does the body use?

Fats and proteins.