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Respiratory > 5. Pulmonary Ventilation II > Flashcards

5. Pulmonary Ventilation II Flashcards

1
Q

Define TIDAL VOLUME (TV)

A

amount of AIR in a SINGLE INSPIRATION or EXPIRATION

500ml

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2
Q

what is FUNCTIONAL RESIDUAL CAPACITY (FRC)

A

volume of AIR that REMAINS IN THE LUNGS at the END of NORMAL RESPIRATION

2400ml

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3
Q

what is VITAL CAPACITY (VC)

A

Volume of AIR that CAN be EXHALED AFTER a MAXIMAL INSPIRATION

4800ml

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4
Q

what is RESIDUAL VOLUME (RV)

A

amount of AIR REMAINING IN LUNGS After MAXIMAL EXPIRATION

1200ml

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5
Q

what is TOTAL LUNG CAPACITY (TLC)

A

MAXIMUM VOLUME of AIR in the LUNGS AFTER MAXIMAL INSPIRATION

6000ml

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6
Q

what is AIRFLOW RESISTANCE of

A

Resistance of the RESPIRATORY TRACT to Airflow during INHALATION/EXPIRATION

  • NOT always CONSTANT
    eg asthma - increased resistance
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7
Q

AIRFLOW RESISTANCE influenced by

A
  • DIAMETER or Airways
  • LAMINAR (smooth) or TURBULENT (irregular) Airflow
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8
Q

what can we use to MEASURE LUNG VOLUMES

A
  • PLETHYSMOGRAPH or ‘BODY BOX’
    (not always user friendly)
  • SPIROMETRY
    (SIMPLE, MOST COMMON, can be done at bedside or at home)
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9
Q

what can SPIROMETRY MEASURE

A
  • EFFORT of expiration/inspiration
  • AMOUNT/VOLUME of air in/out
  • SPEED/FLOW of air that can be inhaled/exhaled

(take deepest breath in, exhale into sensor as hard and fast as possible pref 6 seconds, rapid inhalation)

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10
Q

SPIROMETRY gives us a FLOW VOLUME LOOP
describe how a NORMAL, ACCEPTABLE one should look

A

Expiratory Phase:
INITIAL RAPID INCREASE IN FLOW (patient emptying larger airways)
LINEAR DECLINE (emptying smaller branches)

Inspiratory: Semi-Circle below

  • gives indication of EFFORT
  • any OTHER type UNACCEPTABLE
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11
Q

SPIROMETRY also gives a TIME VOLUME CURVE which Gives us..

A

FEV1 (FORCED EXPIRATORY VOLUME, 1 SECOND)
- volume of air that can be Forcible blown out in 1 second after full inspiration, measured in Litres

FVC (FORCED VITAL CAPACITY)
- volume of air that can be Forcible blown out after full inspiration, measured in Litres

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12
Q

from FEV1, FVC we can get 4 possible SPIROMETRY OUTCOMES:

A
  • NORMAL
  • OBSTRUCTION (Obstructive Disease)
  • RESTRICTION (Restrictive Disease)
  • MIX OBSTRUCTION and RESTRICTION (mix obstructive and restrictive disease)
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13
Q

what is the CRITERIA for NORMAL SPIROMETRY for
FEV1/FVC RATIO, FEV1 Predicted %, FVC Predicted %

A

FEV1/FVC RATIO: 0.7-0.8

FEV1: Predicted ≥ 80%

FVC: Predicted ≥ 80%

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14
Q

how do you get the FEV1% Predicted and the FVC% Predicted

A

DIVIDE FEV1/FVC MEASUREMENTS by the AVERAGE FEV1/FVC in the Healthy Population for any person of SIMILAR AGE, HEIGHT, GENDER

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15
Q

what is the CRITERIA for OBSTRUCTIVE DISEASE from Spirometry

  • flow-volume loop for Obstructive Disease
A

FEV1/FVC RATIO: < 0.7
(LESS than 0.7)

  • regardless of % Predicted FEV1/FVC

Flow Volume Loop (see image)
- smaller initial increase, rapid decrease and curved off
- CONCAVE shape (curves inwards)

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16
Q

DISEASES associated with Airflow OBSTRUCTION

A
  • COPD (CHRONIC OSTRUCTIVE PULMONARY DISEASE)
  • ASTHMA (Uncontrolled)
  • BRONCHIECTASIS
  • CYSTIC FIBROSIS
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17
Q

CRITERIA for RESTRICTIVE DISEASES from Spirometry

A

FEV1/FVC RATIO: >0.8
(More than 0.8)

FEV1 % PREDICTED: REDUCED (Less than 80%)
FVC % PREDICTED: REDUCED (LESS than 80%)

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18
Q

FLOW-VOLUME LOOP for RESTRICTIVE Disease

A

SIMILAR SHAPE to Normal
but SMALLER as reduced volume
(smaller peak, steeper decline to lower volume)
(see image)

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19
Q

DISEASES Associated with RESTRICTIVE Defect

A

Pulmonary:
- LUNG FIBROSIS
- PNEUMOCONIOSIS (Coal Miner’s lung)
- PULMONARY OEDEMA (Heart Failure)

Extrapulmonary:
- THORACIC CAGE DEFORMITY
- OBESITY
- PREGNANCY
- NEUROMUSCULAR DISORDERS

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20
Q

CRITERIA for MIXED/OBSTRUCTIVE Spirometry

A

FEV1: LESS than 80% Predicted (REDUCED)
FVC: LESS than 80% Predicted (PREDICTED)

FEV1/FVC RATIO: NORMAL (0.7-0.8)
(obstructive low ratio, restrictive high so balances)

CLINICAL HISTORY also important to differentiate

eg. co-existent COPD and Pulmonary Fibrosis

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21
Q

how is the FLOW VOLUME LOOP when there is UPPER AIRWAYS OBSTRUCTION

A

BOX-SHAPE

NO initial sharp RISE

slight rise, levels off, convex curve back down at end
(see image)

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22
Q

possible CAUSES for UPPER AIRWAYS OBSTRUCTION

A
  • LARGE GOITRE / ENLARGED THYROID
  • LARYNGEAL CARCINOMA / THYROID CANCER
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23
Q

what can we use SPIROMETRY for - PURPOSE in CLINICAL APPLICATION

A
  • DIAGNOSIS of respiratory disease
  • provide SEVERITY LEVELS for a number of respiratory conditions (eg COPD)
  • Evaluate PROGRESS of respiratory diseases
  • TREATMENT Response
24
Q

possible SIDE-EFFECTS of SPIROMETRY

A
  • feel LIGHT-HEADED
  • FACE may go RED
  • HEADACHE (increase intercranial pressure)
  • FAINTING - reduced venous return or vasovagal attack
  • Transient (temporary) URINARY INCONTINENCE (Unintentional PASSING of URINE)
25
Q

LIMITATIONS of SPIROMETRY

A
  • DEPENDENT on PATIENT COOPERATION and EFFORT
  • therefore LUNG VOLUME can be UNDERESTIMATED ONLY (never overestimated)
  • usually REPEATED AT LEAST 3 TIMES to ensure Reproducibility, each FVC result within 5% or less than 150ml Variation
  • STABLE ASTHMATICS have NORMAL SPIROMETRY RESULT (can only see if uncontrolled) therefore limiting USEFULNESS as DIAGNOSTIC TOOL
  • Look at Flow-Volume Loop to assess quality and effort of the test (NOT always available in some commercial spirometers)
26
Q

because SPIROMETRY is DEPENDENT on PATIENT COOPERATION what does this mean for the LUNG VOLUME

A

CAN ONLY be UNDERESTIMATED

(NEVER OVERSTIMATED)

27
Q

why does SPIROMETER have Limited Usefulness as a DIAGNOSTIC TOOL

A

only detects ASTHMA if UNCONTROLLED

  • STABLE ASTHMA has NORMAL RESULT
28
Q

list some ABDOMINAL WALL muscles that are used for EXPIRATION (as well as INTERNAL INTERCOSTALS)

A
  • RECTUS ABDOMINUS
  • INTERNAL and EXTERNAL OBLIQUES
  • TRANSVERSUS ABDOMINUS
29
Q

RESPIRATORY MUSCLE STRENGTH can be ASSESSED by MEASURING…

A
  • MAXIMAL INSPIRATORY PRESSURE (MIP / PImax)
    reflects strength of Inspiratory Muscles
  • MAXIMAL EXPIRATORY PRESSURE (MEP / PEmax)
    reflects strength of Expiratory Muscles
30
Q

how to MEASURE RESPIRATORY MUSCLE STRENGTH (MIP & MEP)

A
  • MECHANICAL PRESSURE GAUGE
    seal lips firmly around mouthpiece

MIP / INSPIRATORY MUSCLE STRENGTH:
- Exhale Slowly and Completely
- PULL/SUCK in hard

MEP / EXPIRATORY MUSCLE STRENGTH:
- Inhale Completely
- BLOW as HARD as possible

(see reference values in images)
(higher ranges in males)
(MEP HIGHER than MIP values)

31
Q

which RESPIRATORY MUSCLES tend to be Stronger (give higher values)

A

EXPIRATORY

MEP VALUES HIGHER

32
Q

CLINICAL APPLICATIONS of RESPIRATORY MUSCLE STRENGTH
(PURPOSE)

A
  • DIAGNOSIS of Respiratory MUSCLE WEAKNESS
  • Assessment of the SEVERITY of Resp. MUSCLE WEAKNESS
  • FOLLOW the COURSE of the Resp Muscle WEAKNESS - PROGRESSION
33
Q

potential CAUSES of RESPIRATORY MUSCLE WEAKNESS

A
  • NEUROMUSCULAR Diseases
  • MND (Amyotrophic Lateral Sclerosis)
  • Myasthenia Gravis (at neuromuscular junction)
  • Polymyositis (Muscular Inflammation)
  • Guillain-Barre Syndrome (Demyelination)
  • systemic conditions that affect Skeletal Muscle Strength
  • Thyrotoxicosis / Overactive Thyroid
  • Malnutrition
34
Q

what is DIFFUSION CAPACTIY (TLCO / DLCO)

A

Measures the ABILITY of the LUNGS to EXTRACT OXYGEN FROM INHALED AIR TO PULMONARY CAPILLARIES

35
Q

DIFFUSION CAPACITY can be determined by which 2 FACTORS

A
  • DIFFUSION
    from/across alveoli, into blood capillary, into Hb
  • HAEMOGLOBIN LEVEL
36
Q

what does HAEMOGLOBIN have a HIGHER AFFINITY for than OXYGEN

A

CARBON MONOXIDE

  • 210 X Greater affinity

(CO also surrogate for O2)

37
Q

what can be a SURROGATE MARKER to MEASURE DIFFUSION CAPACITY

A

UPTAKE of CARBON MONOXIDE (CO) by HAEMOGLOBIN

38
Q

how to MEASURE DIFFUSION CAPACITY

A
  1. BLOW OUT all air possible, LEAVING only RESIDUAL LUNG VOLUME
  2. INHALE Quickly GAS MIXTURE of 0.3% CO, 10% HELIUM,
    (CO surrogate for O2)
  3. HOLD BREATH for 10 SECONDS
  • Helium is Freely Distributed throughout Alveolar space but DOES NOT CROSS ALVEOLAR/CAPILLARY MEMBRANE
  • CO continuously MOVES from ALVEOLI INTO BLOOD
  1. EXHALES and EXHALE GAS ANALYSED
  • measure DIFFERENCE in CO and HELIUM CONCS. in INSPIRED and EXPIRED GAS
39
Q

how is DIFFUSION CAPACITY (TLCO) Reported

A

as mL/min/mmHg

as a PERCENTAGE OF A PREDICTED VALUE

40
Q

what can AFFECT TLCO (diffusion capacity) RESULTS from test

A

CIGARETTES - HIGH CO
- can lead to falsely high TLCO

DO NOT SMOKE for at least 4-6 HOURS BEFORE the test

41
Q

what is the NORMAL reference range for DIFFUSION CAPACITY (TLCO)

A

76 - 140 %

42
Q

CLINICAL APPLICATIONS.
OBSTRUCTIVE LUNG DISEASES (FEV1/FVC RATIO < 0.7)
how is TLCO for EMPHYSEMA? CHRONIC BRONCHITIS? UNCONTROLLED ASTHMA?

A

Emphysema:
- REDUCED TLCO
(TLCO excellent index for the DEGREE of anatomical emphysema on CT scan)

Chronic Bronchitis:
- NORMAL TLCO

Uncontrolled Asthma:
- NORMAL or HIGH TLCO

43
Q

CLINICAL APPLICATIONS.
RESTRICTIVE LUNG DISEASES (FEV1/FVC RATIO > 0.8)
how is TLCO for
Pulmonary Causes - LUNG FIBROSIS, OEDEMA?

Extrapulmonary Causes - THORACIC CAGE DEFORMITY, OBESITY, PREGNANCY, NEUROMUSCULAR DISORDERS?

A

Pulmonary Causes - LUNG FIBROSIS, OEDEMA:
- REDUCED TLCO

Extrapulmonary Causes - THORACIC CAGE DEFORMITY, OBESITY, PREGNANCY, NEUROMUSCULAR DISORDERS:
- NORMAL TLCO

44
Q

When can you have INCREASED TLCO

A
  • ASTHMA
  • POLYCYTHEMIA (high conc. RBCs in blood)
  • PULMONARY HAEMORRHAGE (Bleeding in lungs, blood binds to O2)
  • LEFT-TO-RIGHT INTRACARDIAC SHUNTING
  • EXERCISE
45
Q

what is TRANSFER COEFFICIENT (KCO) and what is the CALCULATION for it

A

TLCO CORRECTED for ALVEOLAR VOLUME

KCO = DLCO / VA

TRANSFER COEFFICIENT = DIFFUSION CAPACITY (DLCO/TLCO) /
ALVEOLAR VOLUME (VA)

(Proportion of the Alveolar Volume that is able to Diffuse into capilarries)

VA is ALVEOLAR VOLUME AFTER MAXIMAL INHALATION
( TLC approx 6000 ml)

46
Q

what is TRANSFER COEFFICIENT (KCO) and what is the CALCULATION for it

A

TLCO CORRECTED for ALVEOLAR VOLUME

VA is ALVEOLAR VOLUME AFTER MAXIMAL INHALATION
( TLC approx 6000 ml)

KCO = DLCO / VA

TRANSFER COEFFICIENT = DIFFUSION CAPACITY (DLCO/TLCO) /
ALVEOLAR VOLUME (VA)

(Proportion of the Alveolar Volume that is able to Diffuse into capilarries)

47
Q

effect of VA DECREASE on KCO eg in PNEUMONECTOMY

A

DECEREASED VA

-> INCREASED KCO

(smaller division of DLCO)

eg. pneumonectomy, VA decreases due to dicrete LOSS of alveolar units. Blood Diverted to remaining lung

48
Q

Effect of VA DLCO REDUCTION on KCO eg. in PE (blood clots)

A

DLCO DECREASE
VA NORMAL

-> DECREASE KCO

(division of a SMALLER Numerator)

due to impairment of alveolar/capillary interface

49
Q

what is the ALVEOLAR-ARTERIAL GRADIENT (A-a GRADIENT)

A

DIFFERENCE between :
the ALVEOLAR CONC. of O2 (A)
and
ARTERIAL CONC. of O2 (a)

50
Q

what is the ALVEOLAR-ARTERIAL A-a GRADIENT used for

A

to Determine the REASONS for HYPOXIA (LOW OXYGEN)

/ DIAGNOSING the SOURCE of HYPOXEMIA

51
Q

how do ALVEOLAR OXYGEN (PAO2) and ARTERIAL OXYGEN (PaO2) DIFFER

A

ALVEOLAR OXYGEN ALWAYS HIGHER (PAO2)
by at least 5-10 mmHg

even in a healthy person

52
Q

A-a GRADIENT can either be…

A

ELEVATED or NORMAL

ELEVATED A-a gradient suggests DEFECT in DIFFUSION

eg. in ventilation perfusion MISMATCH such as PE (pulmonary embolism) ELEVATED A-a gradient as oxygen not effectively transferred from alveoli to book

  • in high Altitude, NORMAL A-e gradient
    ARTERIAL LOW only because ALVEOLAR LOW
53
Q

CHANGES in VENTILATION during EXERCISE

A

VENTILATION INCREASES

  • due to INCREASED TIDAL VOLUME and RESPIRATORY RATE to meet INCREASED OXYGEN DEMANDS
  • MINUTE VENTILATION might INCREASE from resting values 5-6 l/min
    to > 100 L/MIN
  • OXYGEN CONSUMPTION INCREASES LINEARLY with increasing work rate
    until VO2 MAX ACHIEVED
54
Q

what is VO2 MAX
and how is it expressed

A

MAXIMUM amount OXYGEN that an individual CAN UTILISE during PEAK EXERCISE

  • expressed as ml/kg/min
    (ML of O2 used in 1 MINUTE per KG of BODYWEIGHT)
55
Q

VO2 MAX is determined by which 3 FACTORS
(LIMITED BY..)

A
  • MAXIMUM ABILITY of CARDIOVASCULAR System to DELIVER OXYGEN TO Exercising Skeletal MUSCLE
  • the ABILITY of EXERCISING MUSCLE to EXTRACT OXYGEN FROM BLOOD
  • INCREASE EXERCISE ENDURANCE
56
Q

How to measure VO2 MAX

A
  • GRADED EXERCISE TEST eg. treadmill, stationary exercise bike

-exercise INTENSITY progressively INCREASED

  • MEASURE VENTILATION, O2, CO2 conc. of inhaled and exhaled air
  • VO2 MAX ACHIEVED when OXYGEN CONSTUMPTION remains at STEADY STATE
    despite INCREASING WORK LOAD
    (increases and then levels off - VO2 max)
57
Q

VO2 MAX is the MOST objective assessment of FUNCTIONAL CAPACITY in patients with…

A

CHRONIC HEART FAILURE (CHF)

  • LOW VO2 MAX (less 50% predicted) lower survival (less chance 2 year survival)
    (therefore should be considered for transplantation)

if higher than 50% predicted, higher rates survival

Respiratory (16 decks)

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