Clinical chemistry

1. Pulmonary Function Tests
Dr. C. C. Chemonges

2. Arterial Blood Gases (ABGs)
Definition:
Measurement of oxygen and carbon dioxide levels in arterial blood.
Components:
pH, PaO2, PaCO2, HCO3-, SaO2.
Clinical Significance:
Assessment of respiratory and metabolic status.

3. Mixed Venous Blood Gases
Definition:
Measurement of oxygen and carbon dioxide levels in mixed venous blood.
Components:
SvO2 (mixed venous oxygen saturation).
Clinical Significance:
Evaluation of oxygen extraction and utilization.

4. Anion Gap
Definition:
Calculation of the difference between cations and anions in the blood.
Formula:
Anion Gap = (Na+ + K+) - (Cl- + HCO3-).
Clinical Significance:
Diagnostic tool for metabolic acidosis.

5. Angiotensin-Converting Enzyme (ACE)
Function:
Conversion of angiotensin I to angiotensin II.
Clinical Significance:
Used in the diagnosis and monitoring of sarcoidosis.
Other Roles:
Regulation of blood pressure and electrolyte balance.

6. Lactic Acid
Definition:
Measurement of lactic acid levels in the blood.
Types:
L-lactate (Lactic acid) and D-lactate.
Clinical Significance:
Indication of tissue hypoxia and metabolic stress.

7. Indications and Interpretations
When to Perform These Tests:
Clinical scenarios and symptoms.
Interpretation Guidelines:
Normal ranges and values for each test.
Integration into Patient Care:
How results influence diagnosis and treatment decisions.

9. PULMONARY FUNCTION TEST

10. PFT
• Pulmonary function tests (PFTs) are a group of tests that
measure how well your lungs works, how well the lungs take
in and exhale air, and how efficiently they transfer oxygen
into the blood

11. • PFT or LFT are useful in assessing the functional status of
the respiratory system both in physiological and pathological
condition
• It is based on the measurement of volumes of air breathed
in and out in normal breathing and forced breathing
• It is carried out by using a spirometer

14. Lung volume and capacities
• Lung volumes are the static volumes of air breathed by an individual,
i.e volume of air present in lung under specific position of the thorax
• 4 lung volumes
• Depends on age, weight, gender and body position
• 2 or more vol: when combined are capacity

15. Lung volumes
• TV-the vol: of gas exchanged during a relaxed insp:
followed by an exp: 500ml
• IRV-extra vol: of gas that can be inspired above tidal insp:
3000ml
• ERV-extra vol: of gas that can be expired after a normal
tidal exp: 1000ml
• RV-vol: of gas remain in lungs after a forceful exp: 1500ml

16. • IC-max: amount of gas inspired in to the lungs after a
normal tidal exp: [IC=TV+IRV] 3500ml
• FRC-amount of gas remain in the lungs after normal exp:[
FRC=ERV+RV] 2500ml
• VC-max: amount of gas expired from the lungs after a max:
insp: [VC=IRV+TV+ ERV] 4500ml
• TLC-max: amount of gas inspired to expand the lungs to its
max:extend [TLC=TV+IRV +ERV +RV] 6000ml
Lung capacity

17. Graph

18. Mechanics of Breathing
• Inspiration
Active process
• Expiration
Quiet breathing: passive
Can become active
Pulmonary Function Tests Evaluates 1 or more major
aspects of the respiratory system
• Lung volumes
• Airway function
• Gas exchange

19. Indications/purpose
• Detect disease, It serve as a diagnostic tool investigation
role
• Evaluate severity, extent and monitor the course of disease
• Evaluate treatment
• Measure effects and result of treatment exposures

20. PFTs can help diagnose
• Asthma
• Chronic bronchitis
• Respiratory infections
• Lung fibrosis
• Bronchiectasis
• Allergy

21. • Emphysema
• Cystic fibrosis
• Asbestosis which is a condition caused by exposure to
asbestos
• Sarcoidosis, which is an inflammation of the lungs, liver,
lymph nodes, eyes, skin, or other tissues
• Pulmonary tumors

22. Spirometry
• It is an instrument for measuring the air capacity of the
lungs
• Measurement of the pattern of air movement in and out of
the lungs during controlled ventilatory maneuvers.
• spirometer is used to measure the air flow, ventilatory
regulation, ventilatory mechanics and lung volume during a
forced expiratory maneuver from full inspiration.

24. • PFT used to evaluate physiological aspect of breathing from
respiratory muscle function to the diffusion of gas at the
alveolar wall.
• PFT helps physiotherapists to distinguish between
obstructive and restrictive lung problem and to select
appropriate treatment
• It also measures the effect of the given treatment.

25. Lung Factors Affecting Spirometry
• Mechanical properties
• Resistive elements

26. Mechanical Properties
• Compliance
• Describes the stiffness of the lungs
• Change in volume over the change in
pressure
• Elastic recoil
• The tendency of the lung to return to it’s
resting state
• A lung that is fully stretched has more
elastic recoil and thus larger/ maximal flows
of gas

27. Resistive Properties
Affected by:
Lung volume
Age
Sex
Height
Weight
Race
Disease
Bronchial smooth muscles

28. PFT procedure
• Forced expiratory maneuver is the common clinical
approach
• Results are found in patients chart/moniter
• Common spirometric values areFEV1 and FVC FEV1/FVC
ratio
• Lung volume and peak expiratory flow rate (PEF or PEFR) are
measured to differentiate obstructive or restrictive
problems
• Forced expiratory flow (FEF)

29. • Sit up straight
• Get a good seal around the mouth piece
• Rapid inhale maximally
• Without any delay blow out as hard as fast as possible (blast
out)
• Continue the exhale until the patient can`t blow no more
• Expiration should continue at least 6sec (in adult) and 3 sec
(children under 10yrs)
• Repeat at least 3 technically acceptable times (without
cough, air leak and false start)
Procedure

30. Normal spirogram

31. How to interpret abnormal PFT
• If FVC & FEV1 is less than 80% (total vol:of air expelling is approx: 80%
within 1sec ie; FEV1), this suggests either an obstructive/ restrictive
lung pathology.

32. Forced expiratory volume in 1 second (FEV1)
• FEV1 is the volume of air that can forcibly be blown out in
one second, after full inspiration.
• Average values for FEV1 in healthy people depend mainly
on sex and age height and mass.
• Values between 80% and 120% are considered normal.

33. Forced vital capacity (FVC)
• Forced vital capacity(FVC) is the volume of air that can forcibly be
blown out after full inspiration

34. FEV1/FVC ratio (FEV1%)
• FEV1/FVC (FEV1%) is the ratio of FEV1 to FVC. In healthy adults this
should be approximately 75–80%.

35. Forced expiratory flow (FEF)
• Forced expiratory flow (FEF) is the flow (or speed) of air
coming out of the lung during the middle portion of a forced
expiration.
• generally defined by fraction, The usual intervals are 25%,
50% and 75% (FEF25, FEF50 and FEF75)

36. Identify an obstructive problem
• Obstructive disorders (asthma, COPD)
- air flow reduces because of narrowing of air ways
-FEV1 is reduced
• Spirogram is continued to 6 sec to empty lung, FVC also reduced
because gas is trapped behind the obstructed bronchi
• Cardinal feature of obstructive defect is reduction in the FEV1/FVC
ratio

37. • In obstructive diseases (asthma, COPD, chronic bronchitis,
emphysema) FEV1 is diminished because of increased airway
resistance to expiratory flow.
• The FVC may be decreased due to the premature closure of
airway in expiration
• This generates a reduced value (<80%, often 45%).
60-80% -mild
40-60% -moderate
<40% -severe obstructions

38. Obstructive spirogram

39. Obstructive Disorders

40. Restrictive problem
• Restrictive disorders can be cause by disease of the lung
parenchyma (lung fibrosis) and chest wall
disease(kyphoscoliosis)
• This prevent the full expansion of the lungs therefore FVC
may be reduced
• FEV1 will increased because of the stiffness of the fibrotic
lungs increases the expiratory pressure
• Hence expired air comes out very quickly resulting with a
high FEV1/FVC ratio

41. Restrictive spirogram

42. Restrictive Lung Disease

43. References
1. Carl A. Burtis, David E. Bruns (2023) Tietz Fundamentals of Clinical
Chemistry, 9th Ed.
2. Lawrence A. Kaplan, Amadeo J. Pesce (2009) Clinical Chemistry:
Theory, Analysis,Correlation, 5 th Ed.
3. Robert L. Sunheimer (2010) Clinical Laboratory Chemistry.