LUNG VOLUMES AND

CAPACITIES

BED SIDE PFT

Dr. Harith

Lung volumes and lung capacities refer to

the volume of air associated with different phases

of the respiratory cycle.

Lung volumes are directly measured; Lung

capacities are inferred from lung volumes.

Instrument is spirometry

LUNG VOLUMES

Four types

1. Tidal volume

2. Inspiratory reserve volume

3. Expiratory persevere volume

4. Residual volume

1) TIDAL VOLUME (TV):

VOLUME OF AIR INHALED/EXHALED

IN EACH BREATH DURING QUIET

RESPIRATION.

N – 6-8 ml/kg.

TV FALLS WITH DECREASE IN

COMPLIANCE, DECREASED

VENTILATORY MUSCLE STRENGTH.

2) INSPIRATORY RESERVE VOLUME (IRV):

MAX. VOL. OF AIR WHICH CAN BE

INSPIRED AFTER A NORMAL TIDAL

INSPIRATION

i.e. FROM END INSPIRATION

N- 1900 ml- 3300 ml.

3) EXPIRATORY RESERVE VOLUME (ERV):

MAX. VOLUME OF AIR WHICH CAN BE

EXPIRED AFTER A NORMAL TIDAL

EXPIRATION

i.e. FROM END EXPIRATION PT.

N- 700 ml – 1000 ml

700-1000ml

Residual Volume (RV):

Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) (1700-2100ml)

Indirectly measured (FRC-ERV)

CAPACITIES

Two or more Volumes combined together

Functional Residual Capacity (FRC):

Volume of air remaining in the lungs at

passive end expiration.

N- 2.3 -3.3 L OR 30-35 ml/kg

FRC = RV + ERV

FRC INCREASES WITH

Increased height

Erect position (30% more than in supine)

Decreased lung recoil (e.g. emphysema)

FRC DECREASES WITH

Obesity

Muscle paralysis (especially in supine)

Supine position

Restrictive lung disease (e.g. fibrosis, Pregnancy)

FRC does NOT change with age.

Total Lung Capacity (TLC):

Maximum volume of air

attained in lungs after maximal

inspiration.

N- 4-6 l or 80-100 ml/kg

TLC= VC + RV

Inspiratory Capacity (IC):

MAX. VOL. OF AIR WHICH CAN BE

INSPIRED AFTER A NORMAL TIDAL

EXPIRATION.

IC = IRV + TV

N-2400 ml – 3800 ml.

Expiratory Capacity (EC):

TV+ ERVN 1200-1700 ml

Vital Capacity (VC):

MAX. VOL. OF AIR EXPIRED AFTER A

MAX. INSPIRATION .

VC= TV+ERV+IRV

N- 3.1-4.8L. OR 60-70 ml/kg

Alteration in muscle power- d/t drugs, n-m dis., cerebral tumours.

Pulmonary diseases – pneumonia, chronic bronchitis, asthma, fibrosis,

emphysema, pulmonary edema,.

Space occupying lesions in chest- tumours, pleural/pericardial effusion,

kyphoscoliosis

Abdominal tumours, ascites.

Depression of respiration : opioids/ volatile agents

Abdominal splinting – abdominal binders, tight bandages, hip spica.

Abdominal pain – decreases by 50% & 75% in lower & upper

abdominal Surgeries respectively.

Posture – by altering pulmonary Blood volume.

HELIUM DILUTION METHOD

• 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 he is insoluble in blood)

C1 X V1 = C2 ( V1 + V2)

V2 = V1 ( C1 – C2)

C2

• V1= VOL. OF SPIROMETER

• V2= FRC

• C1= Conc.of He in the spirometer before equilibrium

• C2 = Conc, of He in the spirometer after equilibrium

2(10-5)

5

Volume above residual

where airway closure begins

Total volume in the lung

where airway closure begins

CLOSING VOLUME AND CAPACITY

BED SIDE PFT

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

Single breath count:

After deep breath, hold it and start counting till the next breath.

N- 30-40 COUNT

Indicates vital capacity

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” >150 L/MIN.

6” >60 L/MIN.

3” > 40 L/MIN.

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.

VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.

A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.

DEBONO 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.

FORCED EXPIRATORY TIME:

After deep breath, exhale maximally and forcefully & keep

stethoscope over trachea & listen.

Normal FET – 3-5 SECS.

Obstructive Lung Disease - > 6 SEC

Restrictive Lung Disease - < 3 SEC

MICROSPIROMETERS – MEASURE VC.

THANK YOU