INTRODUCTIONIn physiology so far, you have been introduced to the concept of cellular or internal respiration, which refers to the cellular metabolic processes that break down nutrient molecules, using O2 and producing CO2. The respiratory system of the body (lungs, airways and muscles) is not directly involved in this process, rather it is involved in the exchange of O2 and CO2 between the blood (brought to the alveoli in the lungs) and the inspired air (filling the alveoli in the lungs).

RESPIRATION Respiration is composed of four steps: 1) ventilation (or breathing) 2) gas exchange in the lungs 3) circulation of blood between the lungs and tissues 4) gas exchange at cellular/tissue level between the blood and cells/tissues

BREATHINGDuring inspiration, air is forced into the lungs due to expansion of the thoracic cavity. Expansion of the thoracic cavity is caused by the contraction (flattening out) of the diaphragm at the bottom of the rib cage and the contraction of the external intercostal (between rib) muscles, causing the ribs to move upwards and outwards. The expansion of the thoracic cavity increases thoracic volume and decreases thoracic pressure so that the net flow of air is down its pressure gradient and into the lungs. During exercise, the body's need for oxygen increases dramatically and ventilation rate is increased. The depth of breathing also increases during exercise during exercise due to the anatomical dead space of the respiratory system. The anatomical dead space is the air in the nose, mouth, larynx, tracheas, bronchi and bronchioles. This air reaches the alveoli first upon inspiration. This air also has a higher concentration of CO2 because of its prolonged exposure to the tissues. Therefore, increasing the depth of a breath increases the proportion of "fresh air" that gets to the alveoli, increasing gas exchange.

INTRODUCTION OF SPIROMETRYSpirometry is a method for measuring lung volumes during ventilation. It is used to assess lung function and is particularly helpful for diagnosing obstructive lung diseases. During this laboratory, we will be using spirometry to understand how lung volumes change during exercise. During resting respiration, only a small portion (about one tenth) of the lung capacity is used. This allows plenty of reserve capacity for those occasions (such as strenuous exercise) when the body requires much greater flow of oxygen to generate energy. Furthermore, the lungs are never completely empty. Even when a lung is removed, and collapses, sufficient air is trapped inside to permit it to float in water.

SPIROMETRY

RESPIRATORY FUNCTION TESTS

PULMONARY FUNCTION TESTS

SPIROMETRYMeasurement of volume and/or flow rate of air breathed in and/or out of the lungs under the specific condition of maximal effort, according to established criteria and standards

Study of procedure of measurement of lung volumes and capacities

SPIROMETERAn apparatus used to calculate the lung volumes and capacities

Divided into two categories

Diagnostic spirometers

Monitoring spirometers

STUDENT WET SPIROMETER

PARTS OF SPIROMETER

PARTS OF A SPIROMETERMAIN TANKTHERMOMETEROPEN FLOATCOUNTER WEIGHTSODALIME CONTAINERVALVE LEVERCORRUGATED RUBBER TUBENOSE CLIPINK PEN

MAIN TANKRectangular metallic tank with a raised platformDrain hole in the baseWater level marked on side wallPlatform has three openings i.e. one for oxygen and two large ones connected to corrugated tubes for inlet and outlet of air and gases

THERMOMETERAttached to side of platform Records temperature of contents of tank

OPEN FLOATHinged on one side of tank Has two arms on which weight restsOne side is graduated in liters marked from 0-9 liters

COUNTER WEIGHTAdjusts the balance and position of the float

SODA LIME CONTAINERConnected with outer corrugated tubeAbsorbs CO2 from expired air

VALVE LEVERAdjusts corrugated tube connections to atmosphere and spirometer

T- TUBEConnects the mouth piece to corrugated tubes Its stem is connected to the mouth piece One limb consisting expiratory valve is connected to outer tube Other limb consisting inspiratory valve is connected to inner tube

CORRUGATED RUBBER TUBETwo in numberOne inner and the other outer at the base of the tankConnected to a plate at one end and connected to limbs of T-tube at the other end

MOUTH PIECEConnected to the stem of T-tube

PLAIN RUBBER TUBE Two in number Inner tube for filling the oxygen into the float Outer tube for drainage of water Lumens of these tubes can be occluded by adjusting screws

NOSE CLIPClose the nostrils while breathing through mouth

INK PENCan be filled by ordinary inkAdjusted on kymograph with writing lever to write on the graph paper mounted on revolving drum

PRINCIPLE OF SPIROMETRY

SPIROGRAMGraphical representation of lung volumes and capacities using a spirometer

TYPICAL READINGS ON A SPIROGRAM

SPIROGRAM (NORMAL VS ABNORMAL)

LUNG VOLUMES AND CAPACITIESTidal volume Functional residual capacity Inspiratory capacity Inspiratory reserve volume Expiratory reserve volume Residual volume Vital capacity Total lung capacity Forced expiratory volume in one (first) second

TIDAL VOLUME (VT)Amount of air that enters OR leaves the lungs in a single respiratory cycle is called tidal volume 500 ml

FUCTIONAL RESIDUAL CAPACITY (FRC) Volume of air in the lungs at the end of a passive expiration or with the glottis open and all respiratory muscles relaxed Considered to be neutral or equilibrium point for respiratory system 2700 ml

INSPIRATORY CAPACITY (IC)Maximal volume of air that can be inspired from functional residual capacity 4000 ml

INSPIRATORY RESERVE VOLUME (IRV)Additional amount of air that can be inhaled after a normal inspiration 3500 ml

EXPIRATORY RESERVE VOLUME (ERV)Amount of air that can be expired after normal expiration 1500 ml

RESIDUAL VOLUME (RV)Amount of air in the lungs after a maximal expiration 1200 ml

N.B: residual volume and any capacity of lung containing residual volume e.g. TLC and FRC can not be measured with a spirometer directly!

VITAL CAPACITY (VC)Maximal volume of air that can be inspired after a maximal inspiration 5500 ml

TOTAL LUNG CAPACITY (TLC)The amount of air in the lungs after a maximal inspiration 6700 ml

FORCED EXPIRATORY VOLUME IN ONE/FIRST SECOND (FEV1)Amount of air expired with force in one second

MAXIMUM VOLUNTARY VENTILATION (MVV)Volume of air exhaled in a specified period (1minute), during rapid and forced breathingAlso called as maximum breathing capacity 125-170 L/min

AMERICAN ASSOCIATION FOR RESPIRATORY CARE(AARC) CLINICAL PRACTICE GUIDELINES OBJECTIVE OF SPIROMETRY

Assessment of ventilatory function Includes, though not limited to, measurement of FVC, FEV1 and other forced expiratory flow measurementsIt may also include measurement of MVVEither a volume-time or flow-volume is acceptable on a spirogram! Other parameters that may be obtained by spirometry are FEF max (PEF), FEF 75%, FEF 50%, FEF 25% and FIF max (PIF)

DIFFERENT SETTINGS IN WHICH SPIROMTRY IS USEDFor pulmonary function or research labsOn bedside, in acute, subacute or extended care and skilled nursing facilities In clinics, treatment facility or physician office In workplace or homeFor public screening for epidemiological purposes (occupational hazards)

INDICATIONSDetection for presence or absence of lung dysfunction and/or presence of other abnormal diagnostic tests (CXR, ABGs)Assessment of severity of known lung disease Assessment of change in lung function over time or following administration of, or change of, therapy Assessment of potential effects or response to environment or occupational exposure Assessment of risk for surgical procedures known to affect lung function Assessment of impairment or disability (for legal reasons, rehabilitation, military recruitments etc)

RELATIVE CONTRAINDICATIONSHemoptysis (may aggravate!)Pneumothorax Unstable cardiovascular statusThoracic, abdominal or cerebral aneurysm (danger of rupture of vessels due to increased thoracic pressure)Recent ophthalmic, thoracic, cerebral or abdominal surgeryPresence of acute disease that might interfere with test performance e.g., nausea & vomiting

HAZARDSAlthough spirometry is a very safe process for assessment of lung function, following have rarely been observed!

PneumothoraxIncreased intracranial pressure DizzinessChest pain Contraction of nosocomial infectionsBronchospasm

ACCEPTABILITY CRITERIANUMBER OF TRIALSAt least 3 acceptable FVC maneuversGood and rapid startNo coughNo early termination of exhalation A minimum exhalation time of 6 seconds is recommended

REPRODUCABILITY 2 largest FVCs from acceptable maneuvers should not vary by more than 200 ml 2 largest FEV1s from acceptable maneuvers should not vary by more than 200 ml

RELATED TOPICS Total ventilationAlveolar ventilation Increases in depth of breathing Increases in rate of breathing Dead spacesRespiratory zone

TOTAL VENTILATION (VE)It refers to the minute volume or minute ventilation Total volume of air moved in or out of lungs per minute VE=VT * f =500 * 15 =7500 ml/minute

(where VT is tidal volume and f is respiratory rate )

ALVEOLAR VENTILATION (VA)Represents air delivered to respiratory zone per minute Since first 150 ml of each inspiration comes from anatomic dead space, it does not contribute to alveolar ventilation Every additional ml of air however contributes to alveolar ventilation VA=(VT-VD) * f =(500-150) * 15 =350 * 15 =5250 ml/minute N.B: Alveolar ventilation per inspiration is 350 ml

RESPIRATORY ZONE & DEAD SPACESPULMONARY DEAD SPACESANATOMIC DEAD SPACE PHYSIOLOGIC DEAD SPACE ALVEOLAR DEAD SPACE RESPIRATORY ZONE

MEASURING LUNG VOLUMES USING A WET SPIROMETERAt rest:

1. Measure resting heart rate and respiration rate for each subject.

2. Attach a disposable mouthpiece to the valve. Clamp the subject's nostrils closed and have the subject breathe normally to adjust to the apparatus. DO NOT INHALE from the spirometer - ONLY EXHALE into the spirometer.

PROTOCOLObtain the following lung volumes for each subject by carefully following each set of instructions: Each group member should measure resting heart rate and respiration rate and the resting lung volumes below. Then each group should choose one set of data to be entered on the computer/notebook to be used as class data.

RESTING LUNG VOLUMESTidal Volume:

Breathe normally a few times. Inspire normally and blow a normal exhalation into the tube. Record this volume as Tidal Volume.

RESTING LUNG VOLUMES (continued..)Inspiratory reserve volume:

Inhale as deeply as possible, then blow into the mouthpiece until you've emptied what you've forcefully inspired, but do not forcefully exhale (return to a normal level of exhalation). This is your inspiratory capacity (IC) To calculate inspiratory reserve volume, subtract tidal volume value from inspiratory capacity value (IRV=IC-TV). Breathe normally a few times.

RESTING LUNG VOLUMES (continued..)Expiratory reserve volume:

After a normal exhalation, exhale as forcefully and fully as possible into the mouthpiece. Record this volume as expiratory reserve volume.

Breathe normally a few times.

RESTING LUNG VOLUMES (continued..)Vital Capacity:

Breathe in as deeply as possible, and then exhale into the mouthpiece as fully as possible. Record this volume as Vital Capacity.

Breathe normally a few times.

PEAK FLOW MEASUREMENT1) Use one hand to hold your paper mouth piece over the opening of the Peak Flow Meter and use the other hand to cover the back side opening of the Peak Flow Meter.

2) Inhale as deeply as possible, then blow into the mouthpiece as fast and as forcefully as you can.

3) Insert the rubber tubing into the paper mouth piece. Repeat steps 1 and 2 above.

4) Record the flow rate (L/min)

OBSTRUCTIVE

In obstructive lung conditions, the airways are narrowed, usually causing an increase in the time it takes to empty the lungs. Obstructive lung disease can be caused by conditions such as emphysema, bronchitis, infection (which produces inflammation), and asthma.

Lung function values in obstructive disease FEV1 often increases after using medicine that expands the airways in people with reversible obstructive disease like asthma.

Lung function testResult as predicted for age, height, sex, weight, or raceForced vital capacity (FVC)Normal or lower than predicted valueForced expiratory volume (FEV1)LowerFEV1 divided by FVCLowerForced expiratory flow 25% to 75%LowerPeak expiratory flow (PEF) LowerMaximum voluntary ventilation (MVV)LowerSlow vital capacity (SVC)Normal or lowerTotal lung capacity (TLC) (VT) Normal or higherFunctional residual capacity (FRC)HigherResidual volume (RV) HigherExpiratory reserve volume (ERV)Normal or lowerRV divided by TLC ratioHigher

RESTRICTIVEIn restrictive lung conditions, there is a loss of lung tissue, a decrease in the lungs' ability to expand, or a decrease in the lungs' ability to transfer oxygen to the blood (or carbon dioxide out of the blood). Restrictive lung disease can be caused by conditions such as pneumonia, lung cancer, scleroderma, pulmonary fibrosis, sarcoidosis, or multiple sclerosis. Other restrictive conditions include some chest injuries, being very overweight (obesity), pregnancy, and loss of lung tissue due to surgery.

Lung function values in restrictive disease

Lung function testResult as predicted for age, height, sex, weight, or raceForced vital capacity (FVC)Lower than predicted valueForced expiratory volume (FEV1)Normal or lowerFEV1 divided by FVCNormal or higherForced expiratory flow 25% to 75%Normal or lowerPeak expiratory flow (PEF) Normal or lowerMaximum voluntary ventilation (MVV)Normal or lowerSlow vital capacity (SVC)LowerTotal lung capacity (TLC) (VT)LowerRV divided by TLC ratioNormal or higherFunctional residual capacity (FRC)Normal or lower

Residual volume (RV) Normal, lower, or higher

Expiratory reserve volume (ERV)Normal or lower

TABLE 1. Respiratory Diseases and Conditions Commonly Associated With a Restrictive Breathing Pattern.

CENTRAL NERVOUS SYSTEM AND CHEST BELLOWS LUNGS

Polio Pneumonia Obesity Sarcoidosis Myasthenia gravis Lung fibrosisGuillain Barr syndrome Acute respiratory failure associated with pulmonary edema Flail chest (multiple broken ribs)Hyaline membrane disease Diaphragm paralysisAdvanced lung cancerSpinal cord disease Congestive heart failurePickwickian syndrome Pleural effusion and pleural disease

TABLE 2. Diseases or Conditions That May be Associated With Obstruction to Airflow

Lower Airway Obstruction: AsthmaChronic bronchitis Emphysema Cystic fibrosis Sarcoidosis

Upper Airway Obstruction: CroupLaryngotracheobronchitis Epiglottitis Various tumors and foreign bodies that may involve the upper airway