Investigations in Respiratory Diseases And the Lung Function Tests

The Plain chest radiograph: 1-Pneumonia, Bronchogenic carcinoma, Pulmonary Tuberculosis, and Pleural Effusion can be detected very easily by Plain radiograph. 2-Lateral Film provides additional information about the nature and position of the lung lesion. 3-Follow up chest radiograph is very useful for monitoring the progress of the disease and the advantage of the therapeutic regimen.

Computed Tomography (CT): Computed Tomography of the chest is very sensitive and accurate in determining the position, the size, and the consistency (calcification or cavitation) of any mass lesion. Pre-operative assessment of mediastinal spread in patients with lung cancer. High-resolution CT is very useful in diagnosis of interstitial fibrosis, bronchiectasis and pulmonary embolism.

133 Xe gas is inhaled (ventilation scan). 99m Tc-labelled albumin are injected I.V (perfusion scan); Pulmonary embolism we will detect filling-defect in the perfusion scan and doesn't match the ventilation scan. Asthma and COPD will show a matched Ventilation-perfusion defect.

Positron emission tomography (PET) whole-body PET[ 18_ fluorodeoxyglucose(FDG)] very useful in staging lung cancer. Pulmonary angiography for the positive detection of pulmonary embolism.

Laryngoscopy Direct or indirect examination. Bronchoscopy Mediastinoscopy Pleural aspiration and biopsy Skin tests; Tuberclin test and skin hypersensitivity tests Immunological and serological tests

Counter-immunoelectrophoresis of Sputum, blood or urine (e.g. for pneumococcal antigen). Blood for antibody titres for specific organisms(Mycoplasma,legionella,chlamedia or viruses).Preciptating antibodies for fungi e.g Aspergillus. Microbiological investigations. Histopathological investigations

Purpose of Pulmonary Function Testing is to know 1-How much air volume can be moved in and out of the lungs 1-How much air volume can be moved in and out of the lungs 2-How fast the air in the lungs can be moved in and out 2-How fast the air in the lungs can be moved in and out 3-How stiff are the lungs and chest wall - a question about compliance 3-How stiff are the lungs and chest wall - a question about compliance 4-The diffusion characteristics of the membrane through which the gas moves (determined by special tests) 4-The diffusion characteristics of the membrane through which the gas moves (determined by special tests) 5-How the lungs respond to chest physical therapy procedures 5-How the lungs respond to chest physical therapy procedures

Screening for the presence of obstructive and restrictive diseases Evaluating the patient prior to surgery in patients: a. older than years of age b. known to have pulmonary disease c. obese (pathologically obese) d. have a history of smoking, cough or wheezing e. will be under anesthesia for a lengthy period of time f. undergoing an abdominal or a thoracic operation Pulmonary Function Tests are used for:

Pulmonary Volumes 1-Tidal volume: The volume of air inspired or expired with each normal breath(0.5 L) for young man. 2-Inspiratory reserve volume: is the extra vol. of air that can be inspired over & above the normal tidal volume(3 L). 3-Expir.reseve vol.: is the extra vol. of air that can be expired by forceful expiration after the end of tidal expiration(1.1 L). 4-Residual vol.: The volume of air remaining in the lungs after forceful expiration(1.2L).

1-Inspir.capacity(The tidal vol. plus the Inspir. Reserve(3.500 L) A person can breathe beginning at the end of normal expir.level distending the lung to maximum amount. 2-Functinal residual capacity: Inspiratory reserve volume plus residual volume, The amount of air that remains in the lungs at the end of expiration(2300 millit).

3- Vital capacity: Inspiratory reserve volume plus expiratory reserve volume:The maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent &then expiring to maximum extent(4.6 L). 4-Total lung capacity: maximum vol.to which the lungs can expands(5.8 L).

The vol. of air that normally remains in the lungs between breaths. Residual volume= functional residual capacity Minus the Expiratory reserve volume Total lung capacity=Inspiratory capacity plus the functional residual capacity.

It’s the total amount of new air moved into the respiratory passages each minute. It’s equal the : Tidal volume times the Respiratory rate(12X0.5). Minute respiratory volume Minute respiratory volume averages(6liter/minute) and can increase up to 30 times the normal, Normally a person can stand half to two thirds these values for no longer than 1 minute. A person can live for short time with a minute vol. of as low as 1.5liter/min & respiratory rate of as low as 2-4 breathes minute

Normally the volume of the tidal air is enough to fill the respiratory passage ways as far as the terminal bronchioles. Small portion of the inspired air flowing all the way into the alveoli. The air move this last distance from the terminal bronchioles into the alveoli by Diffusion caused by the kinetic motion of molecules.

Forced Vital Capacity FVC: - This is the total amount of air that you can forcibly blow out after full inspiration, measured in liters. Forced Expiratory Volume in 1 Second FEV 1: - The amount of air that you can forcibly blow out in one second, measured in liters. These two tests considered one of the primary indicators for the lung function test.

FEV 1 / FVC - This is the ratio of FEV 1 and FVC, to determine the amount of the FVC that can be expelled in one second. In healthy adults this should be approximately 80%. Peak Expiratory Flow PEF: - The speed of the air moving out of your lungs at the beginning of the expiration, measured in liters per second.

Forced Expiratory Flow 25-75% or 25-50% This is the average flow (or speed) of air coming out of the lung during the middle portion of the expiration (sometimes referred as the maximal mid-expiratory flow MMEF).

Forced Inspirtory FIF 25-75% or 25-50%: Flow 25%-75% or 25%-50% - This is similar to FEF 25%-75% or 25%-50% except the measurement is taken during inspiration. Forced Expiratory Time FET: - This measures the length of the expiration in seconds.

Normal flow volume loop has a rapid peak expiratory flow rate. Gradual decline in flow back to zero. The Inspiratory portion of the loop is a deep curve plotted on the negative portion of the flow axis.

FEV1 is reduced disproportionately more than the FVC resulting in an FEV1/FVC ratio less than %. This reduced ratio is the primary criteria for diagnosing obstructive lung disease by spirometry. FEV1 > 80% predicted normal % mild % moderate < 50% severe

Expiratory flow-volume curve is normal Inspiratory flow reaches a low plateau value. Typically the FVC and FEV1 are in the normal range. The pattern of the expiratory flow-volume curve is normal the high pressure in extrathoracic airways distends the airway. upper airway obstruction example due to paralysis of the vocal cords.

The End