Transcript Egan’s Fundamentals of Respiratory Care

Chapter 16
Interpreting Clinical and
Laboratory Data
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Learning Objectives
• Describe what a critical value is and state its
importance in clinical practice.
• Define the following terms related to clinical
lab tests: leukocytosis, leukopenia, anemia,
polycythemia, and thrombocytopenia.
• Identify which electrolyte disturbances
interfere with normal respiratory function.
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Learning Objectives (cont.)
• Describe clinical tests used to identify cardiac
stress and myocardial infarction.
• Identify the three main tests used to diagnose
coagulation disorders.
• Describe how the sputum Gram stain and
culture are used to diagnose patients with
pulmonary infections.
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Clinical Laboratory Tests
• Evaluates Patients:
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Health status
Identify organ-system dysfunction
Detect presence of infection
Effects of therapy
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Intro to Laboratory Medicine
• Divided into 5 major disciplines
Clinical Biochemistry – analysis of blood, urine &
bodily fluids
 Hematology – analyzes cellular components of
blood
 Microbiology – analysis of blood & other bodily
fluids for presence of infectious agents
 Immunology – focuses on autoimmune & immune
deficiency diseases
 Anatomic Pathology – analysis of tissue for
diagnosing disease

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Reference Range
• Also referred to as Biological Reference
Intervals or Expected Values
• Takes into account variations related to:
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Age
Gender
Race
Ethnicity
• Vary slightly from laboratory to laboratory
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Critical Test Value
• Result significantly outside reference range
• Represents pathophysiologic condition
• May represent potentially life threatening
situation
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The normal or expected boundaries for any
analysis such as electrolytes, blood cells, proteins,
or enzymes that would likely be encountered in
healthy subjects is called a:
A. Reference range
B. Critical value
C. Range level
D. Normal value
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Complete Blood Count (CBC)
• Common test measuring formed elements of
blood
• Counts & examines:
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Leukocytes (white blood cells)
Erythrocytes (red blood cells)
Thrombocytes (platelets)
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Complete Blood Count (CBC) (cont.)
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___________are evaluated for size and
hemoglobin content.
A. White blood cells
B. Red blood cells
C. Platelets
D. Proteins
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Complete Blood Count (cont.)
• White Blood Cell Count
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WBC count above normal is called leukocytosis
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Leukocytosis - common with infection, stress, &
trauma.
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Degree of leukocytosis depends on severity of
infection

Severe infection with mild leukocytosis may
represent poor prognosis
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Complete Blood Cell Count (cont.)
• White Blood Cell Count
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Below normal represents leukopenia
(leukocytopenia)
 Occurs with overwhelming infections & when
immune system is depressed due to disease or
certain cancer therapies (chemotherapy)
 Diseases of bone marrow (e.g., leukemia) can
cause leukopenia
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Differential of WBC Count
• White blood cells come in 5 varieties
1.
2.
3.
4.
5.
Neutrophils (40-75%)
Eosinophils (0-6%)
Basophils (0-1%)
Monocytes (2-10%)
Lymphocytes (20-45%)
• Leukocytosis is most often due to elevation of
only 1 of 5 types of white blood cells
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Differential of WBC Count (cont.)
• Neutrophilia: Elevation of absolute value of
neutrophils
• Bands: Immature neutrophils
• Segmented neutrophils (segs): mature
neutrophils
• When bands & segs are elevated in CBC,
patient is likely experiencing more severe
bacterial infection
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A significant elevation of the WBC count (more
than 15 x 103/mcL) will occur only when either
neutrophils or __________ are responding to an
abnormality.
A. Basophils
B. Eosinophils
C. Monocytes
D. Lymphocytes
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Red Blood Cell Count
• Reduced RBC count is called anemia
• Anemia is due to either blood loss or reduced
RBC production by bone marrow
• Anemia reduces oxygen-carrying capacity of
blood
• Several types of anemia exist with different
causes (dietary deficiencies, chronic
inflammatory disease, hereditary)
• Severe anemia is treated with transfusion
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Red Blood Cell Count (cont.)
• Abnormal elevation of RBC count is known as
polycythemia
• Secondary polycythemia occurs when bone
marrow is stimulated to produce more RBCs
in response to chronically low blood oxygen
levels
• Common in people who live at an elevated
altitude & in patients with chronic hypoxemic
lung disease
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Red Blood Cell Count (cont.)
• Includes hemoglobin & hematocrit levels
• Hemoglobin (Hb)
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Plays role of bonding with oxygen
Normal hemoglobin concentration is 12-17 g/dL
RBCs with reduced hemoglobin are smaller than
normal (microcytic anemia) & lack normal color
(hypochromic anemia).
• An RBC transfusion depends on cause of
anemia & patient’s overall condition
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Red Blood Cell Count (cont.)
• Hematocrit Levels
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Ratio of RBC volume to that of whole blood
Proportion of sample represented by packed cells
Low levels occur with anemia or over-hydration
High levels occur with polycythemia & dehydration
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A patient’s results on a blood test shows that her
hematocrit percentage is approximately 20%.
What should the clinician recommend for this
patient?
A. nothing, patient’s result is normal
B. patient should receive a blood transfusion
C. repeat test due to erroneous result.
D. patient should undergo plasmaphoresis
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Electrolyte Test
• Basic Concepts
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Normal cellular function depends upon
homeostasis of fluid, electrolytes & acid-base
balance
Electrolytes are charged ions influencing
functioning of enzymes
Enzymes are proteins regulating all chemical
reactions occurring within cells (metabolism,
protein synthesis)
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Electrolyte Tests (cont.)
• Basic Concepts (cont.)

1 points when interpreting blood test
1. Series of blood samples provides insight of severity &
2.
progression of disease & effectiveness of therapy
Intravascular blood compartment (extracellular
environment) is separate from intracellular
environment. Thus, blood samples provide important,
but indirect information of intracellular electrolytes
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The ability of a complex organisms to maintain a
dynamic balance or equilibrium in their internal
environment by making constant adjustments is
called
A. homeostasis
B. electrolytes
C. cellular function
D. polycythemia
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Electrolyte Tests (cont.)
• Basic Chemistry Panel
• Predominant electrolytes measured in lab:
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Sodium (Na+)
Potassium (K+)
Chloride (Cl-)
Total CO2 / bicarbonate (bicarb)
Glucose (GL)
• Excretion of renal-mediated waste products is
included in panel : Creatine (Cr) & blood urea
nitrogen (BUN).
• More comprehensive metabolic panel would include:
Magnesium, Phosphorus, Calcium
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Electrolyte Tests (cont.)
• Glucose
• Formed from breakdown of carbohydrates
• Metabolized by cells for energy
• Requires insulin to be utilized by cells
• Hyperglycemia
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Elevation of blood glucose
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Often result of diabetes
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Electrolyte Tests (cont.)
• Glucose (cont.)
• Hypoglycemia
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Reduced glucose level
May result from inadequate diet or drug induced
• Diabetes
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Diagnosed by fasting blood glucose levels
Indicated by 140 mg/dL on two occasions
• Severe hyperglycemia occurring with
metabolic acidosis is consistent with diabetic
ketoacidosis
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A medical resident asks for your advice in assessing
renal function in a critically ill patient. You would
suggest to test for all of the following:
1. glucose (GL)
2. BUN
3. Creatinine
4. Sodium (Na+)
A.1, 2 and 3only
B.2 and 3 only
C.1 and 4only
D.1, 2, 3 and 4
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Electrolyte Tests (cont.)
• Anion Gap
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Metabolic acidosis is caused by addition of nonvolatile acids or loss of HCO3Determines if decrease in HCO3- is caused by
disruption of normal anion balance or presence of
abnormal acid anion
Normal level is 8-14 mmol/L
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Electrolyte Tests (cont.)
• Lactate
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End product of anaerobic glucose metabolism
Overproduction or insufficient metabolism results
in lactate acidosis
Abnormal levels can be found in anaerobic
metabolism, diabetes mellitus & malignancies
Initial values of serum lactate > 4 mmol/L are
associated with higher mortality in patients with
septic shock
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Enzyme Tests
• Liver Function Test
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Liver damage is assessed by abnormal increases
in hepatic enzymes
Total bilirubin (TBIL) – crucial component of liver
panel
Total protein (TP) & albumin (ALB) used to asses
protein synthesis
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Enzyme Tests (cont.)
• Pancreatic & Muscle Enzyme Tests
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Pancreatitis will have abnormal levels of
pancreatic enzymes lipase & amylase
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Suffering ischemic damage to the heart, brain, &
skeletal muscle tissue will have elevated creatine
phosphokinase (CPK)

Increased levels of lactate dehydrogenase (LD) is
associated with tissue breakdown
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Enzyme Tests (cont.)
• Cardiac Enzyme & Protein Tests
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Most common CPK enzyme test is for CPK-2 which
is released from heart following MI
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Troponin-I (protein fragment) levels peak 12-16
hours after MI
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B-Type Natriuretic Peptide (BNP) is used to
evaluate patients for heart failure
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A 67-year old female is assessed with abnormal
increases in the enzymes alanine
aminotransferase (ALT), aspartate
aminotransferase (AST), as well as alkaline
phosphatase (ALK). What does this indicate?
A. respiratory problem.
B. kidney damage.
C. pancreas disorder.
D. liver damage.
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Enzyme Tests (cont.)
• Coagulation Studies
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Thrombocytopenia (low platelets) &
thrombasthenia (abnormal platelet functioning)
leads to excessive bleeding
Thrombocytosis (excessive platelets) causes
excessive clotting
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Enzyme Tests (cont.)
• Coagulation Studies
• Measured by
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Prothrombin Time (PT)
Partial Thromboplastin Time (PTT)
• PT is accompanied by an additional
measurement - International Standardized
Ratio (INR)
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Enzyme Tests (cont.)
• Coagulation Studies
• D-Dimer
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•
Found in blood when fibrin clots are dissolving
Help diagnose the presence of deep vein
thrombosis, pulmonary embolism or disseminated
intravascular coagulation (DIC)
Protein C
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Regulates coagulation
Active state (Activated Protein C (APC)) inhibits
coagulation & promotes degradation of clots
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Enzyme Tests (cont.)
• Sweat Chloride
• Cystic Fibrosis (CF)
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CF patient’s have elevated level of sweat Cl40-60 mmol/L is borderline
<40 mmol/L are unlikely to be diagnosed
Must be accompanied by other tests to confirm
diagnosis
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Microbiology
• Sputum Gram Stain

Suspected infection in lungs or airways may
benefit from analysis of sputum sample
 Legitimate sputum sample will have numerous pus
cells & few epithelial cells
 Gram stain can determine if offending organism is
gram positive or gram negative & its shape
 Culture can identify specific organism
 Determine organisms sensitivity to antibiotic
therapy
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Microbiology (cont.)
• Acid-Fast Testing
• Identifies acid-fast bacterium
• Steps:
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Gram stain sputum sample
Acid wash sputum sample
If organism is resistant to decolorization, then it is
classified as an acid-fast bacterium
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Coagulation Disorders
• Must check patient’s clotting levels prior to
performing an arterial blood gas (ABG) or
nasotracheal suctioning
• Abnormally low platelet count or an elevated PT
and INR will need an ABG puncture site
compressed for longer time to prevent bleeding
& hematoma
• Extremely low platelet count should have an
ABG or nasotracheal suctioning done only when
necessary
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Electrolyte Disorders
• Severe levels have profound impact on
pulmonary function
• Causes skeletal muscle weakness that may
limit ambulation - may lead to development of
pneumonia
• Causes respiratory muscle weakness
impairing ability to sustain spontaneous
ventilation & maintain pulmonary hygiene
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