Bed side tests of Pulmonary function VC & FEV, Can be readily performed BED SIDE PULSE OXIMETRY Useful Or Pulmonary Function Tests (PFTs). Bed side tests of Pulmonary function. 1. Snider’s Match Blowing test. – Mouth wide open. – Match held at 15 cm distance. – Chin supported. PFTs can be divided in various categories. Mechanical Ventilatory Functions of Lung / Chest wall Bedside pulmonary function tests. Respiratory.
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Pulmonary function tests is a general term used to indicate a series of maneuvers or investigations that are performed to help measure lung functions. It evaluates one or more aspects of the respiratory system. Although they do not provide a diagnosis per se, vedside abnormalities as observed in the tests performed aid in establishing the diagnosis.
The American College of Physicians ACP have modified the guidelines to decrease unnecessary ordering of preoperative spirometry. This is the cornerstone of all the PFTs. Spirometry is a medical test that measures the bexside of air an individual inhales or exhales as a function of time.
John Hutchinson invented the spirometer. Modern spirometers with the computer technology render distinct advantage over the earlier generation spirometers. They are programmed to detect factors that can affect readings and results like cough, late peak flows, premature effort termination and variation in manoeuvres. Before beginning the study, one must be sure that the patient is able to follow instructions.
Following precautions are to be observed. Spirometry is effort dependant and suboptimal results may be obtained if patient has chest or abdominal pain due to any cause or unable to follow instructions. Due to the risk of cross infection, patients with active respiratory infections such as tuberculosis, are deferred but not precluded.
Static lung volumes are determined using methods in which airflow velocity does not play a role. The sums of two or more lung volume subdivision constitute a lung capacity and are expressed in liters L at body temperature.
This technique was introduced in by Darling, Cournand and Richards. When the N2 level falls to zero, all N2 present in the lungs at the beginning of the test has been washed out.
The total volume of gas expired and Ppft in the expired gas is measured. N2 tissue extraction is calculated as Body Surface Area x This is a closed circuit method using helium. The patient re-breathes from the closed circuit. The CO2 is absorbed by absorbent while O2 is added through valve. As the helium mixes with the air in the lungs its concentration falls.
Stabilization of the helium concentration indicated by a rate of bedwide of less than 0. Plethysmography is derived from Greek word meaning enlargement. A patient is placed in a sitting position in a closed body box with a known volume. The patient pants with an open glottis against a closed shutter to produce changes in the box pressure proportionate to the volume of air in the chest. Measurements done at end fpt expiration, it yields FRC.
Includes measuring lft pulmonary mechanics in order to assess the ability of the lungs to move large volumes bedsidd air quickly through the airways to identify bedaide obstruction. The FVC is the maximum volume of air that can be breathed out as forcefully and pdt as possible following a maximum inspiration. It is characterized by full inspiration to TLC followed by abrupt onset of expiration to RV and indirectly reflects flow resistance property of airways.
Taking into consideration factors like age, sex and ethnicity, the value of FRC is predicted and the Pf spirogram is interpreted as the percentage of the predicted.
Forced expiratory volume in 1 sec is the volume exhaled during the first second of the FVC manoeuvre. It is a useful measure of how quickly lft lungs can be emptied and thus measures the general severity of the airway obstruction.
Reduced values are observed in obstructive disorders. Assuming maximal effort this flow rate is still indicative of the condition of fairly large to medium size bronchi. This landmark is at the midpoint of the FVC and indicates the status of medium to small airways. The damage done by most chronic pulmonary diseases show up in the smallest airways first and early indications of this damage begin to appear toward the end of the expiratory part of the Flow Volume Loop.
This value is very dependent on the total volume beeside FVC and tends to be highly variable from test to test. Normal value is 4. Peak Expiratory Flow Rate: Maximum flow rate during an FVC manoeuvre occurs in initial 0.
After a maximal inspiration, the patient expires as forcefully and quickly as he can and the maximum flow rate of air is measured. It gives a crude estimate of lung function, reflecting larger airway function.
Though being effort dependant it is highly reproducible. It is measured by a peak flow meter, which measures how much air litres per minute is being blown out or by spirometry. The peak flow rate in normal adults varies depending on age and height. The maximum volume of air that can be breathed in and out of the lungs in 1 minute by maximum voluntary effort is MVV.
It reflects peak ventilation in physiological demands. The subject is asked to breathe as quickly and as deeply as possible for 12 s and the measured volume is extrapolated to 1min.
As a general guide, the value should correlate closely to the FEV1 x MVV is markedly decreased in patients with Emphysema, Airway obstruction and with poor respiratory muscle strength. This test is usually performed whenever spirometry is done. If people have weakness in the muscle of breathing this test can help identify these difficulties.
The MVV is a test of ultimate effort dependency and is often discarded by physicians. Disability criteria however still require an actual MVV to be done! A number of motor neuron diseases, resulting in respiratory muscle weakness can lead to respiratory failure. These affect not only the chest wall but the diaphragm too. A fall in VC below 1 l warrants mechanical support in such patients. This measures inspiratory muscle function wherein the patient generates as much as inspiratory pressure against blocked mouth piece.
The pressure generated Maximum inspiratory pressure — MIP is therefore a function of inspiratory muscle rather than lung volumes and does not change significantly throughout the test. The normal value is cm-H2O.
This measures expiratory muscle function wherein the patient generates as much as expiratory pressure against blocked mouth piece. It measures forced inspiratory and expiratory flow rate, augments spirometry results. The principal advantage of flow volume loops vs. The Inspiratory curve is entirely effort dependent.
Pulmonary Function Tests
There is a constant airflow limitation on inspiration and expiration as in Benign stricture of trachea, Goiter, Endotracheal neoplasms, and bronchial stenosis. A flattening of expiratory limb is observed eg. Tracheomalacia, Polychondritis, Tumors of trachea or main bronchus. During forced expiration, high pleural pressure develop causing an increased intrathoracic pressure, thereby decreasing airway diameter. The flow volume loop shows a greater reduction in the expiratory phase.
During inspiration, lower pleural pressure around airway tends to decrease obstruction. A forced inspiration causes negative transmural pressure inside the airway which tends to collapse it. During expiration, positive pressure in airway decreases obstruction. Hence, inspiratory flow is reduced to a greater extent than expiratory flow. This can be observed in Bilateral and unilateral bedsude cord paralysis, Vocal cord constriction, Chronic neuromuscular disorders, Airway burns and Obstructive sleep apnoea.
Peak expiratory flow is reduced hence maximum height of the loop is reduced. As the airways narrow, airflow reduces rapidly and the loop becomes concave.
The airways collapse during forced expiration because of destruction of the supporting lung tissue leading to reduced flow at low lung volume.
Pulmonary Function Test
It is a characteristic feature of B. Asthma whereas in chronic asthma there may be only partial reversibility. In COPD, the airflow is irreversible although some cases may show significant improvement.
Peak expiratory flow may be preserved or even higher than predicted leading to tall, narrow and steep flow volume loop in expiratory phase. The Normal value at room air ranges from 8 mmHg in young adults up to 25 mmHg in 8th decade decrease in PaO2. It implies the maximum transfer ability of the lung and is governed by its structural and functional properties.
The gas has to travel through several barriers as it moves from the alveolus to the haemoglobin binding site, hence the term transfer factor.
Pulmonary Function Test | Indian Society of Anaesthesiologists
It is commonly determined by the use of CO, as its uptake is easy to measure and it follows the same diffusion pathway that of oxygen. The breath is then held for 10 to 12 s. Slower lung fillings reduces CO uptake and a sub maximal effort from residual volume reduces alveolar volume and produces low DLCO.
This is a simple test that is easy to perform with minimal equipment. It is interpreted as in the following table:. The 6MWT is a practical simple test that only requires a ft hallway.
Walking is an activity performed daily by all but the most severely impaired patients. This test measures the distance that a patient can quickly walk on a flat, hard surface in a period of 6 minutes the 6MWD.
As a relatively simple measure of aerobic exercise capacity, the 6MWT has been utilized in a variety of medical conditions affecting the cardiopulmonary system. It should be recognized that the test is a global assessment and does not specifically identify the respiratory system as the source of the limitation. The test subject walks back and forth along a m flat course, with progressive increases in pace imposed by audio signals, until no longer able to maintain the pace.
The incremental shuttle walk distance ISWD is generally used as an index of cardiorespiratory fitness and has been suggested as a prognostic indicator in patients with chronic disease. PFTs is an important tool which add to or aid in exclusion of a diagnosis.