Description about FVC test, MVV test, DLCO, nitrogen washout, plethysmography to check pulmonary functions.

1. PULMONARY FUNCTION
TESTS
By: Maitri Parmar(MPT cardiopulmonary)
Guided by: Dr. Boskey Panchal

2. LUNG VOLUMES AND
CAPACITIES
• Volumes:
1. TV
2. IRV
3. ERV
4. RV
• Capacities:
1. IC
2. FRC
3. VC
4. TLC
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3. INDICATIONS
 classify the type of disease as either obstructive,
restrictive, or both (mixed).
 To quantify the severity of pulmonary impairment as
mild, moderate, severe, or very severe.
 To check the treatment effect.
 To evaluate pre and post operative status.

4. CONTRAINDICATIONS
× Haemoptysis
× Pneumothorax
× Acute myocardial infarction or ischemia
× Acute pulmonary embolism
× Acute chest or abdominal pain
× Recent cataract surgery
× Inability to follow instructions

5. SPIROMETRY
• It is the measurement of air entering and leaving the lungs—includes
measurement of several values of forced airflow and volume during
inspiration and expiration.
• Can’t be measured:
RV Measured using…
FRC N2 washout method, He dilution method and
TLC Body Plethysmograph.
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6. Forced Vital Capacity (FVC) Test
• Measures many variables.
• Most commonly performed test.
 For baseline measurement:
• Avoid short acting bronchodilators before 4 hours (e.g. β-agonist: albuterol;
anticholinergic agent: ipratropium bromide. )
• Avoid long-acting β-agonist bronchodilators and oral therapy with
aminophylline before12 hours.
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7.  PROCEDURE:
• Deep inspiration up to TLC
• Rapid forced expiration
• Continue expiration for at least 6 sec.
• Again forced deep inspiration
• For children <10 years expiration time of
3sec. is sufficient.
• Cough, sneeze, air leak, improper mouthpiece
placement disqualifies the test.
• 3 trails should be done.
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8.  Forced Expiratory Volume in 1 Second (
FEV1)
• FEV1 is a measurement of the volume exhaled
in the first second of FVC test.
 FEV1/FVC
• The forced expiratory volume in 1 second-to-
vital capacity ratio (FEV1/FVC) is calculated
by dividing the patient’s largest FEV1 by the
patients FVC.
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OBSTRUCTIVE DISEASE
• FEV1=low,
FVC=normal,
FEV1/FVC= low
• air trapping,
FVC= low
• Small airway
obstruction,
FEV1/FVC= normal
RESTRICTIVE DISEASE
• FEV1=normal,
FVC=low
FEV1/FVC=normal-
high
 Check DLCO
• Low=interstitial
lung disease
• normal= chest wall
or neuromuscular
disease

10.  Flow-volume loop:
• Graphically representing the events
that occur during forced inspiration
and expiration.
 Peak expiratory flow rate:
• The highest point on the expiratory
curves denotes the peak expiratory
flow rate.
 Forced expiratory flow(FEF25-75):
• Forced expiratory flow at mid half of
FVC.
• Represent small airway status
• <60% small airway obstruction
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11. MAXIMAL VOLUNTARY VENTILATION(MVV)
• Amount of air moves in and out during in 12 sec.
• It is an effort-dependent test for which the patient is asked to breathe as deeply
and as rapidly as possible for at least 12 seconds.
• normal values of MVV are based on gender,
age, and height.
• Men: Approximately 150-175 L/min. ,
Slightly less in women.
• Represent respiratory muscle strength.
• Restrictive disease – normal /slightly reduced.
• Obstructive disease- more reduced.
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12. DIFFUSING CAPACITY OF LUNG FOR CARBON
MONOXIDE (DLCO)
• It measures the ability of the lungs to transfer gases across the alveolar-capillary
membrane.
• Single-breath method:
• The patient exhales completely to RV, rapidly inspires to TLC a volume of air
containing small concentration of CO, maintains breath holding for 10 seconds, and
then exhales rapidly.
• CO has a very high affinity for Hb and diffuses rapidly into the pulmonary blood,
keeping the pulmonary capillary partial pressure of CO near zero.
• DLco=Vco/PaCO ( Vco=amount CO taken by lung, PaCO=alveolar partial pressure CO)
• Low= emphysema, interstitial lung disease
• High = elevated cardiac output
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13. BODY PLETHYSMOGRAPHY
• It is an air tight chamber in which the patient sits,
connected to the mouthpiece,
and asked to breathe normally.
• Various volume and pressure values are
measured during phases of respiration.
• It measures FRC, RV and TLC.
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14. HELIUM DILUTION TECHNIQUE
• The helium dilution technique for measuring lung volumes uses a closed,
rebreathing circuit.
• Wearing nose clips, the patient breathes normally in the closed circuit.
• Exhaled CO2 is absorbed with soda lime, and O2 is added at a rate equal to the
patient’s O2 consumption.
• The patient is connected to the He-air mixture, and the concentration of He is
diluted slowly by the patient’s lung volume.
• The patient rebreathes the gas in the system until equilibrium of He
concentration is established.
• Normal= equilibrium occurs in 2 to 5 min.
• Obstruction= 20 min.
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15. • FRC is calculated as:
C1 x V1= C2 x V2
C1 x V1 = C2 (V1 +FRC)
• V1= Volume the beginning
of the test
• V2= Volume at the end of the test
• C1= Concentration of He at the
beginning of the test
• C2= Concentration of He at the
end of the test
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16. NITROGEN WASHOUT
• It is an open circuit technique.
• Wearing nose clips, the patient breathes 100% O2 until nearly all of the N2
has been washed out of the lungs, leaving less than 1.5% N2 in the lungs
• The patient’s exhaled gas is monitored, and its volume and N2 percentage are
measured.
• Normal time for washout= 2 to 5 min.
• Obstructive disease=longer
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17. • FRC is calculated by:
FRC= VE x F2N2
0.78- FAN2
 total volume of gas exhaled during the test (VE)
 the fractional concentration of exhaled N2 in the total gas volume (F2N2)
 the fractional concentration of N2 in the alveoli at the end of the test
(FAN2)
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19. RECENT ADVANCES
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• Capaccione KM, Wang A, Lee SM, Patel N, Austin JHM, Maino P, et al. Quantifying
normal lung in pulmonary fibrosis: CT analysis and correlation with %DLCO. Clin
Imaging [Internet]. 2021;77:287–90. Available from:
http://dx.doi.org/10.1016/j.clinimag.2021.06.021

20. REFERENCES
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1. Kacmarek RM, Stoller JK, Heuer AJ. Egan’s fundamentals of
respiratory care. 12th ed. St. Louis, MO: Mosby; 2020.
2. Study guide for essentials of cardiopulmonary physical therapy
by Hillegass, Ellen. 3
rd
ed. La Vergne, TN: Cram101; 2011.

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