Transcript Investigations of Respiratory System

Investigations of Respiratory
System
A- Imaging
- Plain CXR
A PA film provides information on the lung fields , heart
,mediastinum , vascular structures and the thorathic
cage. additional information can be obtained from a
lateral film.
Structures of CXRs
1- Trachea , that should be central
2- Mediastinum, can be widened in many diseases like (
retrosternal goiter, Lymph nodes enlargement, aortic
aneurysm and oesophageal dilatation)
3- The diaphragm , Rt side is usually slightly higher than
the Lt side.
Causes of raised hemi diaphragm; collapsed lungs ,
phrenic nerve palsy, hepatomegaly and sub phrenic
abscess)
4- Hila, Lt hilum is higher than the Rt hilum, and hila can be
pulled up and down by fibrosis or collapse.
5- Bone and soft tissues
6- Lung fields, shadows can be divided in to;
- Nodular shadows; could be due
Neoplasis ( primary lung Ca, metastasis, or adenoma)
Infection ( pneumonia, hydatid cyst)
Granuloma ( TB, sarcoidosis)
- Reticular shadow; usually due to acute interstitial
changes (cardiac or non cardiac). e.g pulmonary fibrosis.
- Alveolar shadow; usually due to pulmonary oedema , but
could be due to ARDS, drugs, smoke inhalation.
• CT scan
It is superior to CXR in determining the position and size of
a pulmonary lesion and whether calcification or
cavitations is present.
It is now routinely used in the assessment of patients with
suspected lung cancer and facilitate guided
percutaneous needle biopsy.
HRCT (high resolution), that uses thin section to provide a
detail assessment of pulmonary parenchymal diseases
( interstitial lung disease , bronchiectasis)
• Ultra sound of chest cavity;
is sensitive to detect plural effusion , may also be used to
improve the diagnostic field of plural biopsy.
• Ventilation – perfusion scan;
the main value of this technique is to detect pulmonary
thrombi or embolism, a filling defect in the perfusion scan
accompanied by preserved ventilation is highly
suggestive of recent PE.
• Positron Emission Tomography PET scan;
In new technology to investigate pulmonary nodules ,
staging of mediastinal lymph nodes and distal
metastasis.
• CT- pulmonary angiography
• Is widely available and gold standard to diagnose PE.
B- Endoscopic Examinations;
• Laryngoscopy; larynx may be inspected directly with a
mirror or indirectly with a laryngoscope.
• Bronchoscopy;
The trachea , large bronchi and lung segments can all be
inspected by either flexible or rigid bronchoscope.
Diagnostic indication of flexible bronchoscopy;
- Suspected cases of Lung ca,
- slowly resolving pneumonia,
- pneumonia in the immunocompramised patients,
- interstitial lung disease, and
- collecting lavage for AFB and culture in suspected cases
of TB , with –ve sputum.
• Mediastinoscopy;
Through a small incision at the supra sternal notch under
GA, to get an access to the mediastinum.
C- Other investigations
• Plural aspiration and biopsy.
• Sputum examination , for microbiological ( AFB, Culture,
Gram stain ) and cytological examinations
• Pulse oximetry
Allow a non invasive assessment of peripheral O2
saturation, it provides a useful tool for monitoring those
who are acutely ill or at risk of deterioration.
• Peak expiratory flow rate (PEF).
Is measured by a maximum forced expiration through a
peak flow meter , it should be monitored regularly in
asthmatic patients monitor response to therapy and
disease control.
• Arterial blood gas analysis
It is heparinized blood taken from , the radial , brachial and
femoral arteries to check, PH, PaO2, PaCO2 and HCO3.
Type I respiratory failure; PaO2 < 8Kpa , PaCO2 either
Normal or reduced.( hypoxia only), PH is normal.
Type II respiratory failure ; PaO2 < 8Kpa , PaCO2 >6Kpa
( hypoxia and hypercapnia), PH could be normal , high or
low.
• Pulmonary Function Tests.
Are used to aid diagnosis, assess functional impairments
and monitor treatment or progression of diseases.
Abbreviations used in RFT
FEV1 forced expiratory volume in 1 second
FVC forced vital capacity
VC vital capacity
TLC total lung capacity
FRC function residual capacity
RV residual volume
TLco Gas transfer factor for carbon monoxide
Kco Gas transfer per unit lung volume.
• FEV1 is disproportionately reduced in obstructive lung
disease ( asthma, COPD, bronchial obstruction) and the
ratio of FEV1/ VC will be <70%. When there is an airflow
obstruction the test should be repeated following
administration of inhaled or nebulised B2 agonist
( salbutamol) to see the reversibility to normal or >15%
that would give the diagnosis of asthma .
FEV1 and VC will both reduce in restrictive lung disease
(Pulmonary Fibrosis) that will make the FEV1/VC ratio ,
>80%.
• Flow volume loop , measures flow at various lung
volumes , characteristic patterns are seen in intra
thorathic airway obstruction like ( asthma , Emphysema),
and extra thorathic airway obstruction( tracheal
stenosis).
• Lung volume can be measured by dilution of inhaled gas
( usually helium), or by determining the pressure /
volume relationship of the thorax by body
plethysmography.
Lung volume increases in obstructive diseases and
decreases in restrictive diseases.
• The gas transfer across the alveoli can be calculated by
measuring carbon monoxide uptake from a single
inspiration in a standard time ( usually 10 seconds) ,it is
low in emphysema and lung fibrosis ( obstructive and
restrictive ) , but very high in pulmonary haemorrhage.