bedside respiratory assessment & spirometry

BEDSIDE RESPIRATORY ASSESSMENT & SPIROMETRYDr. Arjun chhetri

Dpt of Anaesthesiology

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

Lung Volumes

Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6-8 ml/kg)

Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.(1900-3300ml)

Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( 700-1000ml).

Lung Volumes

Residual Volume (RV): Volume of air

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

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) (3100-4800ml)

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

Lung Capacities

Functional Residual Capacity (FRC): Sum of RV and ERV

or the volume of air in the lungs at end-expiratory tidal position.(30-35 ml/kg) (2300-3300ml).

It can not be measured by spirometry)

VOLUMES, CAPACITIES AND THEIR CLINICAL SIGNIFICANCE

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 PT.

N- 1900 ml- 3300 ml.

CONTINUED………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

4) INSPIRATORY CAPACITY (IC) : MAX. VOL. OF AIR WHICH CAN BE INSPIRED

AFTER A NORMAL TIDAL EXPIRATION. IC = IRV + TV N-2400 ml – 3800 ml.

CONTINUED………..

4) VITAL CAPACITY: MAX. VOL. OF AIR EXPIRED AFTER A

MAX. INSPIRATION . MEASURED WITH VITALOGRAPH VC= TV+ERV+IRV N- 3.1-4.8L. OR 60-70 ml/kg VC IS COSIDERED ABNORMAL IF ≤ 80%

OF PREDICTED VALUE

FACTORS INFLUENCING VC

PHYSIOLOGICAL : physical dimensions- directly proportional to

ht. SEX – more in males : large chest size, more

muscle power. AGE – decreases with increasing age STRENGTH OF RESPIRATORY MUSCLES POSTURE – decreases in supine position PREGNANCY- unchanged or increases by

10% ( increase in AP diameter In pregnancy)

CONTINUED………

PATHOLOGICAL: DISEASE OF RESPIRATORY MUSCLES ABDOMINAL CONDITION : pain, dis. and

splinting

FACTORS DECREASING VITAL CAPACITY

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

2) Pulmonary diseases – pneumonia, chronic bronchitis, asthma, fibrosis, emphysema, pulmonary edema,.

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

4) Abdominal tumours, ascites.

5) Depression of respiration : opioids/ volatile agents

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

7)Abdominal pain – decreases by 50% & 75% in lower & upper abdominal Surgeries respectively.

8) Posture – by altering pulmonary Blood volume.

DIFFERENT POSTURES AFFECTING VC

POSITION TRENDELENBERG LITHOTOMY PRONE RT. LATERAL LT. LATERAL

DECREASE IN VC

14.5% 18% 10% 12% 10%

VC CONTINUED…….

VC correlates with capability for deep breathing and effective cough.

So in post operative period if VC falls below 3 times VC– artificial respiration is needed to maintain airway clear of secretions.

CONTINUED…….

6) TOTAL LUNG CAPACITY : Maximum volume of air attained in lungs

after maximal inspiration. N- 4-6 l or 80-100 ml/kg TLC= VC + RV7) RESIDUAL VOLUME (RV): Volume of air remaining in the lungs

after maximal expiration. N- 1570 – 2100 ml OR 20 – 25 ml/kg.

CONTINUED……

8) 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 Decreases under anaesthesia with spontaneous Respiration – decreases

by 20% With paralysis – decreases by 16%

FACTORS AFFECTING FRC

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) Anaesthesia FRC does NOT change with age.

Pulmonary Function Tests

The term encompasses a wide variety of objective tests to assess lung function

Provide objective and standardized measurements for assessing the presence and severity of respiratory dysfunction.

GOALS

To predict the presence of pulmonary dysfunction

To know the functional nature of disease (obstructive or restrictive. )

To assess the severity of disease To assess the progression of disease To assess the response to treatment To identify patients at increased risk of

morbidity and mortality, undergoing pulmonary resection.

To wean patient from ventilator in icu. Medicolegal- to assess lung impairment

as a result of occupational hazard. Epidemiological surveys- to assess the

hazards to document incidence of disease

To identify patients at perioperative risk of pulmonary complications

CONTINUED……..

INDICATIONS OF PFT IN PAC

GUIDELINES FOR PREOPERATIVE SPIROMETRY

Age > 70 yrs. Morbid obesity Thoracic surgery Upper abdominal surgery Smoking history and cough Any pulomonary disease

INDICATIONS FOR PREOPERATIVE SPIROMETRY

ACP GUIDELINES FOR PREOPERATIVE SPIROMETRY

Lung resection H/o smoking, dyspnoea Cardiac surgery Upper abdominal surgery Lower abdominal surgery Uncharacterized pulmonary disease(defined

as history of pulmonary Disease or symptoms and no PFT in last 60 days)

CONTRAINDICATIONS FOR PFT

1.Myocardial infarction within a month 2.Unstable angina 3.Recent thoraco abdominal surgery 4.Recent ophthalmic surgery 5.Thoracic or abdominal aneurysm 6.Pnemothorax

BED SIDE PFT

1) 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

BED SIDE PFT

2) Single breath count: After deep breath, hold it and start

counting till the next breath. N- 30-40 COUNT Indicates vital capacity

BED SIDE PFT

3) 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

BED SIDE PFT

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.

BED SIDE TEST

4) COUGH TEST: DEEP BREATH F/BY COUGH ABILITY TO COUGH STRENGTH EFFECTIVENESSINADEQUATE 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.

Tracheal auscultation/ 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

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.

PEFR(peak expiratory flow rate) Simple and cheap test. Patient ask to take full inspiration to TLC

and then blow out forcefully into peak flow meter.

Lips must be placed tightly around the mouthpiece.

Best three test is recorded. Not a good measure of airflow limitation. Best used to monitor progression of

disease and Rx. Coughing is ineffective if peak flow is

<200l/min.

SPIROMETRY

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.”

Measures VC, FVC, FEV1, PEFR. CAN’T MEASURE – FRC, RV, TLC.

PREPERATION

Prior explanation to the patient Not to smoke /inhale bronchodilators 6

hrs prior or oral bronchodilators 12hrs prior.

Remove any tight clothings/ waist belt/ dentures

Pt. Seated comfortably If obese, child < 12 yrs- standing

Nose clip to close nostrils. Exp. Effort shld last ≥ 4 secs. Should not be interfered by coughing,

glottic closure, mechanical obstruction. 3 acceptable tracings taken & largest

value is used.

RECORDED PARAMETER

Normally forced vital capacity(FVC) is reported along with FEV1.

Ratio of FEV1/FVC (IN %).

Measurements Obtained from the FVC Curve

FEV1---the volume exhaled during the first second of the FVC maneuver

FEF 25-75%---the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (<2 mm in diameter) airways

FEV1/FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases

Spirometry Interpretation: Obstructive vs. Restrictive Defect

Obstructive Disorders Characterized by a

limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through narrowed airways from bronchospasm, inflammation, etc.)

Examples: Asthma Emphysema Cystic Fibrosis

Restrictive DisordersCharacterized by reduced lung volumes/decreased lung complianceExamples:Interstitial FibrosisScoliosisObesityLung ResectionNeuromuscular diseasesCystic Fibrosis

Spirometry Interpretation: Obstructive vs. Restrictive Defect

Obstructive Disorders FVC nl or↓ FEV1 ↓ FEF25-75% ↓ FEV1/FVC ↓ TLC nl or ↑

Restrictive Disorders FVC ↓ FEV1 ↓ FEF 25-75% nl to ↓ FEV1/FVC nl to ↑ TLC ↓

Spirometry Interpretation

FVC Interpretation of %

predicted: 80-120% Normal 70-79% Mild

reduction 50%-69% Moderate

reduction <50% Severe reduction

FEV1

Interpretation of % predicted: >75% Normal 60%-75% Mild

obstruction 50-59% Moderate

obstruction <49% Severe

obstruction <25 y.o. add 5% and >60

y.o. subtract 5

Spirometry Interpretation

FEF 25-75% Interpretation of %

predicted: >79% Normal 60-79% Mild

obstruction 40-59% Moderate

obstruction <40% Severe

obstruction

FEV1/FVC Interpretation of

absolute value: 80 or higher

Normal 79 or lower

Abnormal

FLOW VOLUME LOOPS

Measured in respiratory function department.

Peak flow at different lung vol are recorded.

Although more complex to interpret, provide more accurate regarding ventilatory function.

Provide useful data abt severity of obstructive & respiratory disease.

How is a flow-volume loop helpful?

Methacholine challenge test Also known as bronchial challenge test. Primarily used to diagnose bronchial

hyper-reactivity. Methacholine is an agent that, when

inhaled, causes the airways to spasm and narrow if asthma is present.

During this test, patient inhale increasing amounts of methacholine aerosol mist before and after spirometry.

CONTD….

Considered positive, meaning asthma is present, if the lung function drops by at least 20%.

A bronchodilator is always given at the end of the test to reverse the effects of the methacholine.

Therapeutic uses are limited by its adverse cardiovascular effects, such as bradycardia and hypotension.

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 N range 17- 25 ml/min./mmhg. DLO2 = DLCO x 1.23

DLCO decreases in- Emphysema, lung resection, pul. Embolism,

anaemia Pulmonary fibrosis, sarcoidosis- increased

thickness DLCO increases in:(Cond. Which increase pulm, bld flow) Supine position Exercise Obesity L-R shunt

CONTINUED………..

2) 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) C2V1= VOL. OF SPIROMETERV2= FRCC1= Conc.of He in the spirometer before equilibriumC2 = Conc, of He in the spirometer after equilibrium

TESTS FOR CARDIOPLULMONARY INTERACTIONS

QUALITATIVE- history, exam, ABG, stair climbing test

QUANTITATIVE- 6 minute walk test

CONTINUED…….

1) STAIR CLIMBING TEST: If able to climb 3 flights of stairs without stopping/dypnoea at

his/her own pace- ↓ed morbidity & mortality If not able to climb 2 flights – high risk

2) 6 MINUTE WALK TEST:- Gold standard- C.P. reserve is measured by estimating max. O2 uptake during

exercise- Modified if pt. can’t walk – bicycle exercises- If pt. is able to walk for >2000 feet during 6 min pd,- VO2 max > 15 ml/kg/min- If 1080 feet in 1 min : VO2 of 12ml/kg/min- Simultaneously oximetry is done & if Spo2 falls >4%- high risk

Thank you