pulmonary function tests

PRESENTER- Dr. M.MADHU CHAITANYA 2d year PG
MODERATOR-Dr. KALYAN CHAKRAVARTHY/ Dr. HEMNATH BABU
PULMONARY FUNCTIONTESTS

Pulmonary function tests is a generic term used to indicate a battery of
studies or maneuvers that may be performed using standardized
equipment to measure lung function.
Evaluates one or more aspects of the respiratory system
– Respiratory mechanics
– Lung parenchymal function/ Gas exchange
– Cardiopulmonary interaction
INTRODUCTION

 Includes a wide variety of Objective tests to assess lung function.
 Provides Standardized measurements for assessing the presence and severity
of Respiratory dysfunction.
 Pulmonary function tests have been used traditionally in the preoperative assessment
before any major surgery
PFTs take approximately 15 minutes for adults, 15 to 30 minutes for children,
45 minutes for pre- and postbronchodilator testing, and one hour for full PFTs with
diffusing capacity of the lung for carbon monoxide (DLCO) testing.
Five years is usually the youngest age at which children are able to cooperate with
PFT procedures

PREOPERATIVE TISI GUIDELINES
1. Age > 70
2. Obese patients
3. Thoracic surgery
4. Upper abdominal surgery
5. History of cough/ smoking
6. Any pulmonary disease

American College of Physicians Guidelines
1. Lung resection
2. H/o smoking, dyspnoea
3. Cardiac surgery
4. Upper abdominal surgery
5. Lower abdominal surgery
6. Uncharacterized pulmonary disease(defined as history of Pulmonary
Disease or symptoms and no PFT in last 60 days)

Contraindications
Recent eye surgery
Thoracic , abdominal and cerebral aneurysms
Active hemoptysis
Pneumothorax
Unstable angina/ recent MI within 1 month

INDEX
1. Categorization of PFT’s
2. Bedside pulmonary function tests
3. Static lung volumes and capacities
4. Measurement of FRC, RV
5. Dynamic lung volumes/forced spirometry
6. Physiological determinant of spirometry
7. Flow volume loops and detection of airway obstruction
8. Flow volume loop and lung diseases
9. Tests of gas exchange function
10. Tests for cardiopulmonary reserve
11. Preoperative assessment of thoracotomy patients

CATEGORIZATION OF PFT
MECHANICAL VENTILATORY FUNCTIONS OF LUNG
/ CHEST WALL:
• BED SIDE PULMONARY FUNCTION TESTS
• STATIC LUNG VOLUMES & CAPACITIES – VC, IC, IRV, ERV, RV, FRC.
• DYNAMIC LUNG VOLUMES –FVC, FEV1, FEF 25‐75%, PEFR, MVV,
RESP. MUSCLE STRENGTH

GAS‐ EXCHANGE TESTS :
• A) Alveolar‐arterial po2 gradient
• B) Diffusion capacity
• C) Gas distribution tests‐
1) Single breath N2 test.
2) Multiple Breath N2 test
3) Helium dilution method
4) Radio Xe scinitigram.

CARDIOPULMONARY INTERACTION:
• Qualitative tests:
1) History , examination
2) ABG
• Quantitative tests
1) 6 min walk test
2) Stair climbing test
3) Shuttle walk
4) CPET(cardiopulmonary exercise testing)

Bed side pulmonary function tests
1) RESPIRATORY RATE
‐ Essential yet frequently undervalued component
of PFT
‐ Imp evaluator in weaning & extubation protocols
Increase RR ‐ muscle fatigue ‐ work load ‐ weaning fails

Sabrasez breath holding test:
Ask the patient to take a full but not too deep breath & hold it as long as possible.
>25 SEC.‐NORMAL Cardiopulmonary Reserve (CPR)
15‐25 SEC‐ LIMITED CPR
<15 SEC‐ VERY POOR CPR(Contraindication for elective surgery)
25‐ 30 SEC ‐ 3500 ml VC
20 – 25 SEC ‐ 3000 ml VC
15 ‐ 20 SEC ‐ 2500 ml VC
10 ‐ 15 SEC ‐ 2000 ml VC
5 ‐ 10 SEC ‐ 1500 ml VC

SCHNEIDER’S MATCH BLOWING TEST:
MEASURES Maximum Breathing Capacity.
Ask to blow a match stick from a distance of 6” (15 cms) with‐
 Mouth wide open
 Chin rested/supported
 No purse lipping
 No head movement
 No air movement in the room
 Mouth and match at the same level

• Can not blow out a match
– MBC < 60 L/min
– FEV1 < 1.6L
• Able to blow out a match
– MBC > 60 L/min
– FEV1 > 1.6L
• MODIFIED MATCH TEST:
DISTANCE MBC
9 >150L/MIN.
6 > 60L/MIN.
3 >40 L/MIN
6”

3) COUGH TEST:DEEP BREATH F/BY COUGH
 ABILITY TO COUGH
 STRENGTH
 EFFECTIVENESS
INADEQUATE COUGH IF: FVC < 20 ML/KG
FEV1 < 15 ML/KG
PEFR < 200 L/MIN.
*A wet productive cough / self propagated paraoxysms of coughing – patient susceptible
for pulmonary Complication.

4) FORCED EXPIRATORY TIME:
After deep breath, exhale maximally and forcefully & keep stethoscope
over trachea & listen.
N FET – 3‐5 SECS.
OBS.LUNG DIS. ‐ > 6 SEC
RES. LUNG DIS.‐ < 3 SEC

5) WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate)
N – MALES‐ 450‐700 L/MIN.
FEMALES‐ 350‐500 L/MIN.
<200 L/ MIN. – INADEQUATE
COUGH EFFICIENCY.
6) DE‐BONO WHISTLE BLOWING TEST: MEASURES PEFR.
Patient blows down a wide bore tube at the end of which is a whistle, on the side
is a hole with adjustable knob.
As subject blows → whistle blows, leak hole is gradually increased till
the intensity of whistle disappears.
At the last position at which the whistle can be blown , the PEFR can be read
off the scale.

STATIC LUNG VOLUMES AND CAPACITIES
• SPIROMETRY : CORNERSTONE OF ALL PFTs.
• John hutchinson – invented spirometer.
• “Spirometry is a medical test that measures the volume of air an individual
inhales or exhales as a function of time.”
• CAN’T MEASURE – FRC, RV, TLC

PREREQUISITES
 Do not smoke for at least 1 hour before the test.
 Do not drink alcohol for at least 4 hours before the test.
 Do not exercise heavily for at least 30 minutes before the test.
 Do not wear tight clothing that makes it difficult for you to take a deep
breath.
 Do not eat a large meal within 2 hours before the test.

SPIROMETRY‐Acceptability/ Repeatability Criteria
1. Good start of test‐ without any hesitation
2. No coughing / glottic closure
3. No variable flow
4. No early termination(> 6 sec)
5. No air leak
The two largest values for FVC and the two largest values for FEV1 should v
ary by no more than 0.2L.
A. Two largest FVC within 150 ml of each other
B. Upto 8 manoeuver can be repeated till criteria are met

Spirometry Interpretation: So what constitutes normal?
• Normal values vary and depend on:
I. Height – Directly proportional
II. Age – Inversely proportional
III. Gender
IV. Ethnicity

LUNG VOLUMES AND CAPACITIES
PFT tracings have:
Four Lung volumes: tidal volume,
inspiratory reserve volume,
expiratory reserve volume, and
residual volume
Five capacities: inspiratory capacity,
expiratory capacity, vital capacity,
functional residual capacity, and
total lung capacity
Addition of 2 or more volumes comprise a capacity.

• Tidal Volume (TV): volume of air inhaled or exhaled
with each breath during quiet breathing
(6‐8 ml/kg) 500 ml
• Inspiratory Reserve Volume (IRV): maximum volu
me of air inhaled from the end‐ inspiratory tidal
position.3000 ml
• Expiratory Reserve Volume (ERV): maximum
volume of air that can be exhaled from resting e
nd‐expiratory tidal position.1500 ml
• Residual Volume (RV):Volume of air remaining in
lungs after maximium exhalation (20‐25 ml/kg)
1200 ml
– Indirectly measured (FRC‐ ERV)
– It can not be measured by spirometry .

LUNG CAPACITIES
• Total Lung Capacity (TLC): Sum of all volume
compartments or volume of air in lungs after
maximum inspiration (4‐6 L)
• Vital Capacity (VC): TLC minus RV or maximum
volume of air exhaled from maximal inspiratory
level. (60‐70 ml/kg) 5000ml. VC ~ 3 TIMES TV
FOR EFFECTIVE COUGH
• Inspiratory Capacity (IC):Sum of IRV and TV or
the maximum volume of air that can be inhaled
from the end‐expiratory tidal position.
(2400‐3800ml).
• Expiratory Capacity (EC): TV+ ERV

Functional Residual Capacity
– Sum of RV and ERV or the volume of air in the lungs at end‐expiratory tidal position
.(30‐35 ml/kg) 2500 ml
– Decreases
In supine position(0.5‐1L),Obese pts ,Induction of anesthesia: by 16‐ 20%
FUNCTION OF FRC
1. Oxygen store
2. Buffer for maintaining a steady arterial po2
3. Partial inflation helps prevent atelectasis
4. Minimizes the work of breathing

Measuring RV, FRC
It can be measured by
– nitrogen washout technique
– Helium dilution method
– Body plethysmography

N2 Washout Technique
• The patient breathes 100% oxygen, and all the nitrogen in the lungs is
washed out.
• The exhaled volume and the nitrogen concentration in that volume are
measured.
• The difference in nitrogen volume at the initial concentration and at the final
exhaled concentration allows a calculation of intrathoracic volume, usually
FRC.

Helium Dilution technique
Patient breathes in and out of a spirometer filled with 10% helium and 90% o2,
till conc. In spirometer and lung becomes same (equilibirium).
As no helium is lost; (as it is insoluble in blood)
C1 X V1 = C2 ( V1 + V2)
V2 = V1 ( C1 – C2)/C2
V1=VOL.SPIROMETER
V2= FRC
C1= Conc.of He in the spirometer before equilibrium
C2 = Conc, of He in the spirometer after equilibrium

Body Plethysmography
• Plethysmography (derived from greek word meaning enlargement).
• Based on principle of BOYLE’S LAW(P*V=k)
• Priniciple advantage over other two method is it quantifies non‐ com
municating gas volumes.
• A patient is placed in a sitting position in a closed body box with a known
volume
• The patient pants with an open glottis against a closed shutter to produce
changes in the box pressure proportionate to the volume of air in the chest
• As measurements done at end of expiration, it yields FRC

Dynamic lung volumes/forced spirometry
FORCED SPIROMETRY/TIMED EXPIRATORY
SPIROGRAM
Includes measuring:
•Pulmonary mechanics – to assess the ability of the lung to move large vol of
air quickly through the airways to identify airway obstruction
• FVC
• FEV1
• Several FEF values
• Forced inspiratory rates(FIF’s)
• MVV

FORCED VITAL CAPACITY
• The FVC is the maximum volume of air that can be breathed out as forcefully
and rapidly as possible following a maximum inspiration.
• Characterized by full inspiration to TLC followed by abrupt onset of expiration to
RV
• Indirectly reflects flow resistance property of airways.

FVC
 Interpretation of % predicted:
 80-120%
 70-79%
 50%-69%
 <50%
Normal
Mild reduction
Moderate reduction
Severe reduction

Measurements Obtained from the FVC Curve and their
significance
• Forced expiratory volume in 1 sec(FEV1 )‐‐‐the volume exhaled during the first
second of the FVC maneuver.
• Measures the general severity of the airway obstruction
• Normal is 3‐4.5 L
FEV1 – Decreased in both obstructive & restrictive lung disorders(if patient’s vital ca
pacity is smaller than predicted FEV1).
FEV1/FVC – Reduced in obstructive disorders.
Interpretation of % predicted:
>75% Normal
60%‐75% Mild obstruction
50‐59% Moderate obstruction
<49% Severe obstruction

Measurements Obtained from the FVC Curve and their significance

Forced midexpiratory flow 25‐75% (FEF25‐75 )
• Max. Flow rate during the mid‐expiratory part of FVC
maneuver.
 Measured in L/sec
 May reflect effort independent expiration and the status of the
small airways
 Highly variable
 Depends heavily on FVC
• N value – 4.5‐5 l/sec. Or 300 l/min.
 Interpretation of % predicted:
 >60% Normal
 40‐60% Mild obstruction
 20‐40% Moderate obstruction
 <10% Severe obstruction

Peak expiratory flow rates
• Maximum flow rate during an FVC maneuver occurs in initial 0.1 sec
• After a maximal inspiration, the patient expires as forcefully and quickly as he can and the
maximum flow rate of air is measured.
• Forced expiratory flow between 200‐1200ml of FVC
• It gives a crude estimate of lung function, reflecting larger airway function.
• Effort dependant but is highly reproductive
• It is measured by a peak flow meter, which measures how much air (litres per minute)
is being blown out or by spirometry
• The peak flow rate in normal adults varies depending on age and height.
• Normal : 450 ‐ 700 l/min in males
300 ‐ 500 l/min in females
• Clinical significance ‐ values of <200/l‐ impaired coughing & hence likelihood of post‐op
complication

Maximum Voluntary Ventilation (MVV) or maximum
breathing capacity (MBC)
• Measures ‐ speed and efficiency of filling & emptying of the lungs during increased
respiratory effort
• Maximum volume of air that can be breathed in and out of the lungs in 1 minute by
maximum voluntary effort
• It reflects peak ventilation in physiological demands
• Normal : 150 ‐175 l/min.
• <80% ‐ gross impairment
• The subject is asked to breathe as quickly and as deeply as possible for 12 secs
and the measured volume is extrapolated to 1min.
• Periods longer than 15 seconds should not be allowed because prolonged
hyperventilation leads to fainting due to excessive lowering of arterial pCO2 and H+
• MVV is markedly decreased in patients with
A. Emphysema
B. Airway obstruction
C. Poor respiratory muscle strength

FLOW VOLUME LOOPS
 “Spirogram” Graphic analysis of flow at various lung volumes
 Measures forced inspiratory and expiratory flow rate
 Augments spirometry results
 Principal advantage of flow volume loops vs. typical standard spirometric descriptions ‐
identifies the probable obstructive flow anatomical location.
• First 1/3rd of expiratory flow is effort dependent and the final 2/3rd near the RV is effort
independent
• Inspiratory curve is entirely effort dependent
• Ratio of
– maximal expiratory flow(MEF)
/maximal inspiratory flow(MIF)

FLOW VOLUME LOOPS and DETECTION OF UPPER
AIRWAY OBSTRUCTION
• flow‐volume loops provide information on upper airway obstruction:
Fixed obstruction: constant airflow limitation on inspiration and expiration—
such as
1. Benign stricture
2. Goiter
3. Endotracheal neoplasms
4. Bronchial stenosis

Variable intrathoracic obstruction: flattening of expiratory
limb.
1.Tracheomalacia
2. Polychondritis
3.Tumors of trachea or main bronchus
• During forced expiration – high pleural pressure – increased intrathoracic
pressure ‐ decreases airway diameter. The flow volume loop shows a
greater reduction in the expiratory phase
• During inspiration – lower pleural pressure around airway tends to decrease
obstruction

Variable extrathoracic obstruction:
1.Bilateral and unilateral vocal cord
paralysis
2. Vocal cord constriction
3. Chronic neuromuscular disorders
4. Airway burns
5. OSA
• Forced inspiration‐ negative transmural pressure inside airway tends to collapse it
• Expiration – positive pressure in airway decreases obstruction
• inspiratory flow is reduced to a greater extent than expiratory flow

ASTHMA
 Peak expiratory flow reduced so maximum height of the loop is reduced
 Airflow reduces rapidly with the reduction in the lung volumes because
the airways narrow and the loop become concave
 Concavity may be the indicator of airflow obstruction and may present
before the change in FEV1 or FEV1/FVC

EMPHYSEMA
Airways may collapse during forced expiration because of destruction of the supporting lung
tissue causing very reduced flow at low lung volume and a characteristic (dog‐leg)
appearance to the flow volume curve

REVERSIBILITY
• Improvement in FEV1 by 12‐15% or 200 ml in
repeating spirometry after treatment with
Sulbutamol 2.5mg or ipratropium bromide by
nebuliser after 15‐30 minutes
• Reversibility is a characterestic feature
of B.Asthma
• In chronic asthma there may be only partial
reversibility of the airflow obstruction
• While in COPD the airflow is irreversible
although some cases showed significant
improvement

RESTRICTIVE PATTERN
Characterized by reduced lung volumes/decreased lung compliance
Examples:
1. Interstitial Fibrosis
2. Scoliosis
3. Obesity
4. Lung Resection
5. Neuromuscular diseases
6. Cystic Fibrosis

RESTRICTIVE PATTERN‐ flow volume loop
• low total lung capacity
• low functional residual capacity
• low residual volume.
• Forced vital capacity (FVC) may be low;
however, FEV1/FVC is often normal or greater
than normal due to the increased elastic
recoil pressure of the lung.
• Peak expiratory flow may be preserved or
even higher than predicted leads to tall
,narrow and steep flow volume loop in
expiratory phase.

TESTS FOR GAS EXCHANGE FUNCTION
ALVEOLAR‐ARTERIAL O2 TENSION GRADIENT:
 Sensitive indicator of detecting regional V/Q inequality
 N value in young adult at room air = 8 mmHg to up to 25 mmHg
 AbN high values at room air is seen in asymptomatic smokers & chr. Bronchitis
A‐a gradient = PAO2 ‐ PaO2
* PAO2 = alveolar PO2 (calculated from the alveolar gas equation)
* PaO2 = arterial PO2 (measured in arterial gas) PAO2:
(PB ‐ PH2O)*FiO2 ‐ (PaCO2/RQ)

DIFFUSING CAPACITY
• Rate at which gas enters the blood divided by its driving pressure ( gradient
– alveolar and end capillary tensions)
• Measures ability of lungs to transport inhaled gas from alveoli to pulmonary
capillaries
• Normal‐ 20‐30 ml/min/mm Hg
• Depends on:
‐ thickeness of alveolar—capillary membrane
‐ hemoglobin concentration
‐ cardiac output

SINGLE BREATH TEST USING CO
• Pt inspires a dilute mixture of CO and hold the breath for 10 secs.
• CO taken up is determined by infrared analysis:
• DlCO = CO ml/min/mmhg
PACO – PcCO
• DLO2 = DLCO x 1.23
• Why CO?
A) High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly
build up in plasma
B) Under N condition it has low blood conc ≈ 0
C) Therefore, pulm conc.≈0

FACTORS EFFECTING DLCO
Predicted DLCO for Hb= Predicted DLCO * (1.7 Hb/10.22 + Hb)

CARDIOPULMONARY INTERACTION
• Stair climbing and 6‐minute walk test
• This is a simple test that is easy to perform with minimal equipment.
Interpretated as in the following table:

• Shuttle walk
• The patient walks between cones 10 meters apart with increasing
pace.
• The subject walks until they cannot make it from cone to cone
between the beeps.
• Less than 250m or decrease SaO2 > 4% signifies high risk.
• A shuttle walk of 350m correlates with a VO2 max of 11ml.kg‐ 1.min‐1

Cardiopulmonary Exercise Testing
 Non invasive technique
 Effort independent
 To test ability of subjects physiological response to cope with metabolic
demands

Preoperative assessment of thoracotomy patients
• As an anesthesiologist our goal is to :
1) to identify pts at risk of increased post‐op morbidity & mortality
2) to identify pts who need short‐term or long term post‐op ventilatory support
.
Lung resection may be f/by – inadequate gas exchange, pulm HTN &
incapacitating dyspnoea.

Assessment of lung function in thoracotomy pts
Calculating the predicted postoperative
FEV1 (ppoFEV1) and TLCO (ppoTLCO):
There are 5 lung lobes containing
19 segments in total with the division of each lobe.
Ppo FEV1=preoperative FEV1 * no. of segments left after
resection / 19
• Can be assessed by ventilation perfusion scan. For eg:
A 57-year-old man is booked for lung resection
. His CT chest show a large RUL mass
confirmed as carcinoma: ppoFEV1= 50*16/19
=42%

Assessment of lung function in thoracotomy pts

Combination tests
• There is no single measure that is a ‘Gold standard ‘ in predicting post‐op
complications

Pulmonary function criteria suggesting increased risk of post‐
operative pulmonary complications for various surgeries

pulmonary function tests

More Related Content

What's hot (20)

Similar to pulmonary function tests (20)

More from madhu chaitanya (8)

Recently uploaded (20)

pulmonary function tests