Useful Investigations for Evaluating the Respiratory System.ppt

Useful Investigations for Evaluating the Respiratory System.ppt

1. Useful Investigations for
Evaluating the
Respiratory System
By
C COnyedum FWACP.FCCP
Professor/Consultant Chest
Physician.

2. Background
•Investigations are not to be taken in
isolation
•Interpretation and application is in
conjunction with well detailed clinical
information got from history and
physical examination findings

3. Introduction
•Modalities available include;
•Methods for assessing functional
changes
•Measurements of gas exchange
•Imaging techniques.
•Techniques for acquiring biologic
specimens and examinations

4. Assessment of functional
changes
•Tests of ventilatory function
•Peak expiratory flow rate
•-simple and cheap, does not need
electricity. Patient takes a full inspiration
to TLC and then blows out forcefully into
the peak flow meter.
•Portable and can be used at the bed side,
mainly used to monitor airflow limitation in
asthma/COPD
•It is effort dependent.

5. Spirometry
•This measures FEV
1, FVC, FEV
1/FVC,
FEF
25%-75%etc.
•Like the Peak flow rate results are related
to height, sex, age, race.
•The technique involves a maximum
inspiration and forced expiration (for as
long as possible until all air has been
expelled from the lungs) into the
spirometer.
•The act of respiration triggers the moving
record chart which measures volume
against time.

6. Peak flow meter

7. spirometer

8. Spirometry tracings

10. Lung volume assessment
•Body plethysmography–for
measuring TLC and RV, airway
resistance
•Helium dilution-TLC+RV
•The equipments are expensive and
bulky.

11. Measurements of gas
Exchange
•1. Blood gases
•2. O2 saturation-Pulse oximetry
•3. Gas transfer factor—DL
CO

12. Measurement of arterial
blood gases.
•Measurement of partial pressures of O2
and CO2 within the arterial blood is
essential in mgt of cases of respiratory
failure and severe asthma.
•Samples should be analysed immediately or
immersed in iced water.
•Sample should be adequately
anticoagulated.
•Bubbles of air must be expelled.
•In CO poisoning, the partial pressure may
still be well despite poor saturation.

13. Pulse Oximetry
•Non invasive, for continuous
monitoring.

14. Pulse Oximetry
•Using probes clipped to a finger or
ear lobe, it calculates O
2saturation
based on measurements of absorption
of two wavelengths of light in
pulsatile cutaneous arterial blood.
(differential absorption of two wavelengths of light by
oxygenated and nonoxygenated blood)
•The result is calculated and displayed
instantaneously.

15. Pulse Oximetry
•The oximeter is insensitive to changes in
arterial PO
2above 60mmHg (cf The
oxyhaemoglobin dissociation curve)
•Decrease peripheral perfusion affects the
result like other factors like PH,temp, 2,3
DPG..
•Other forms of Hb such as carboxylHb
and methemoglobin are not distinguishable
from oxyHb when the two wavelengths of
lights are used (CO-oximeter).
•The saturation results does not say
anything about CO
2elimination

16. Diffusion Capacity
•A small conc of CO(0.3%) is inhaled, usually
in a single breath that will be held for 10s.
•The CO is diluted by the gas already in the
alveoli and is also taken by the Hb as the
erythrocytes course thro the pulm
capillary system.
•The conc of CO in the exhaled gas is
measured and the DL
COis calculated as the
qty of CO absorbed per minute per mmHg
pressure gradient from the alveoli to the
pulmonary capillaries.

17. Imaging studies
•Routine Radiography
•Computed Tomography
•Magnetic Resonance imaging
•Scintigraphic Imaging(IV albumin macroaggregates
labelled with technetium 99m and xenon gas inhaled)
•Pulmonary Angiography (CT angio)
•Ultrasound for pleural abnormalities.(of
limited use in lung parenchymal lesions as
ultrasound energy is rapidly dissipated in
air.

18. Chest Xray
•Most are done in PA mode. The lung
fields, heart, mediastinum, vascular
structures, and thoracic cage are
visualized.
•Lateral films are done when
lesions/pathology are suspected
behind the heart or deep in the
diaphragmatic sulci

19. CHEST CT
•Chest CT is widely used to clarify radiographic
abnormalities detected by CXR. Advantages of chest CT
compared with CXR include
•(1) ability to distinguish superimposed structures due to
cross-sectional imaging;
•(2) superior assessment of tissue density, permitting
accurate assessment of the size and density of pulmonary
nodules and improved identification of abnormalities
adjacent to the chest wall, such as pleural disease;

20. Chest CT contd
•(3) with the use of IV contrast, ability to
distinguish vascular from nonvascular
structures, which is especially useful in
assessing hilarand mediastinalabnormalities;
•(4) with CT angiography, ability to detect
pulmonary emboli;
•(5) due to superior visible detail, improved
recognition of parenchymal and airway diseases,
including emphysema, bronchiectasis,
lymphangiticcarcinoma, and interstitial lung
disease.

21. Chest ultrasound
•For the visualization of the pleural
space.
•The diaphragm and adjoining solid
structures are equally seen
•Very useful in guiding needle biopsy
of the pleura and aspiration of the
space.
•Endobronchial ultrasound (EBUS)
using specialised bronchoscope is
useful in assessing peribronchial

22. •Doppler echocardiographic
assessment of the tricuspid
regurgitant jet helps to establish
accurate information of pulmonary
artery pressure thereby helpful in
pulmonary hypertension assessment.
•cardiac catheterization is invasive

23. Nuclear medicine imaging
•Ventilation-perfusion lung scans can be used
to assess for pulmonary thromboembolism
but have also largely been replaced by CT
angiography.
•But still useful in peri-operative assessment
of patients undergoing lung resection
•Positron emission tomographic (PET)
scanning assesses the uptake
•and metabolism of a radiolabeled glucose
analog.

24. Nuclear medicine imaging
•Because malignant lesions usually have increased
metabolic activity, PET scanning, especially when
combined with CT images in PET/CT, is useful to
assess pulmonary nodules for potential malignancy and
to stage lung cancer.
•PET studies are limited in assessing lesions <1 cm in
diameter; false-negative screening for malignancy can
result from lesions with low metabolic activity, such as
bronchioloalveolarcell carcinoma.
•False-positive PET signals can be observed in
inflammatory conditions such as pneumonia.

25. Invasive techniques
Bronchoscopy
•Bronchoscopy provides direct visualization of the
tracheobronchial tree, typically to the
subsegmentallevel.
•The fiberopticbronchoscope is used in most
cases, but rigid bronchoscopy is valuable in
specific circumstances, including massive
hemorrhageand foreign body removal.

26. Bronchoscopy contd.
•Flexible fiberoptic bronchoscopy
allows visualization of the airways;
•identification of endobronchial
abnormalities, including tumors and
sites of bleeding; and collection of
diagnostic specimens by washing,
brushing, biopsy, or lavage.

27. •Bronchoalveolarlavage (BAL) is an adjunct to
fiberopticbronchoscopy, permitting collection of cells
and fluid from distal air spaces.
•Additional bronchoscopicapproaches to obtain tissue
samples from locations adjacent to the trachea or
large bronchi for cytologicassessment of malignancy
include
•Transbronchialneedle aspiration (TBNA). TBNA can
•be supplemented with endobronchialultrasound
(EBUS), which can allow guided aspiration of hilarand
mediastinallymph nodes.

28. Other Procedures
Percutaneous Needle Aspiration of the Lung
•A needle can be inserted through the chest wall and into a
pulmonary lesion to aspirate material for cytologicand
microbiologic studies.
•Percutaneous needle aspiration is usually performed under
CT. Owing to the small size of the sample obtained, sampling
error is a limitation of the procedure.
Thoracentesis
•Thoracentesisshould be performed as an early step in the
evaluation of a pleural effusion of uncertain etiology.
Analysis of pleural fluid can determine the etiologyof the
effusion. Large-volume thoracentesis
can be therapeutic by palliating dyspnea.

29. Mediastinoscopy
•Tissue biopsy of mediastinalmasses or lymph nodes is often required
for cancer diagnosis and staging. Mediastinoscopyis performed from a
suprasternal approach, and a rigid mediastinoscopeis inserted—from
which biopsies can be obtained. Lymph nodes in the aortopulmonary
location typically require a parasternal mediastinotomyto provide
access for biopsy.
Video-Assisted Thoracic Surgery
•Video-assisted thoracic surgery (VATS)/thoracoscopy, is widely used
for the diagnosis of pleural lesions as well as peripheral parenchymal
infiltrates and nodules.
•VATS involves passing a rigid scope with a camera through a trocar
and into the pleural space; instruments can be inserted and
manipulated through separate intercostal incisions. VATS has largely
replaced “open biopsy,” which requires a thoracotomy.

30. Other Techniques for
acquiring biologic specimens
Collection of sputum (spontaneous or induced).
•Sputum can be obtained by spontaneous
expectoration or induced by inhalation of an
irritating aerosol like hypertonic saline.
•Sputum is distinguished from saliva by the
presence of bronchial epithelial cells and alveolar
macrophages as opposed to squamous epithelial
cells.
•Sputumexam should include gross inspection for
blood, color, and odor, as well as Gram’s stain and
routine bacterial culture.

31. •Sputum is examined and cultured for
bacteria, fungi, parasites and viruses.
•Also for Mycobacteria: ZN stain /
Gene Xpert
•Sputum Antigen tests …pneumococcal
Ag(CIE),
•FAT for influenza

32. Other Techniques for
acquiring biologic specimens
•Bacterial culture of expectorated sputum may
be misleading due to contamination with
oropharyngealflora. Sputum samples can also
be assessed for a variety of other pathogens,
including mycobacteria, fungi, and viruses.
•Sputum samples induced by hypertonic saline
can be stained for the presence of
Pneumocystis jiroveci.
•Cytologicexamination of sputum samples can
be used as an initial screen for malignancy.

33. Others
•Blood antibody tests for mycoplasma,
legionella, chlamydia, etc
•Exercise testing
•Skin Prick tests
•HB+PCV