Types of spirometer



A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs. A spirometer measures ventilation, the movement of air into and out of the lungs. The spirogram will identify two different types of abnormal ventilation patterns, obstructive and restrictive. There are various types of spirometers which use a number of different methods for measurement (pressure transducers, ultrasonic, water gauge).A Spirometer is the main piece of equipment used for basic Pulmonary Function Tests (PFTs). Lung diseases such as asthma, bronchitis, and emphysema can be ruled out from the tests. In addition, it is often used for finding the cause for shortness of breath, assessing the effects of contaminants on lung functions, effect of medication, and progress for disease treatment.[1]Reasons for testingDiagnose certain types of lung disease (such as asthma, bronchitis, and emphysema)Find the cause of shortness of breathMeasure whether exposure to chemicals at work affects lung functionCheck lung function before someone has surgeryAssess the effect of medicationMeasure progress in disease treatmentTypes of spirometerWhole body plethysmographMain article: body plethysmographyThis type of spirometer gives a more accurate measurement for the components of lung volumes as compared to other conventional spirometers. A person is enclosed in a small space when the measurement is taken.PneumotachometerThis spirometer measures the flow rate of gases by detecting pressure differences across the fine mesh. One advantage of this spirometer is that the subject under investigation can breathe in fresh air during the experiment.[4]Fully electronic spirometerElectronic spirometers have been developed that compute airflow rates in a channel without the need for fine meshes or moving parts. They operate by measuring the speed of the airflow with techniques such as ultrasonic transducers, or by measuring pressure difference in the channel. These spirometers have greater accuracy by eliminating the momentum and resistance errors associated with moving parts such as windmills or flow valves for flow measurement. They also allow improved hygiene between patients by allowing fully disposable air flow channels.Incentive spirometerMain article: Incentive spirometerThis spirometer is specially designed to improve one's functioning of the lungs.Peak flow meterMain article: Peak expiratory flowThis device is useful for measuring the ability of a person breathing out air.Windmill-type spirometerUsed specially for measuring forced vital capacity without using water and has broad measurements ranging from 1000 ml to 7000 ml. It is more portable and lighter as compared to traditional water-tank type spirometer. This spirometer should be held horizontally while taking measurements because of the presence of rotating disc.Tilt-compensated spirometerTilt-compensated type spirometer also known as the AME Spirometer EVOLVE. This new spirometer can be held horizontally while taking measurements but should the patient lean too far forward or backwards the spirometer's 3D-tilt sensing compensates and indicates the patient position. [5]Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs), measuring lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is an important tool used for generating pneumotachographs, which are helpful in assessing conditions such as asthma, pulmonary fibrosis, cystic fibrosis, and COPD.ndicationsSpirometry is indicated for the following reasons:to diagnose or manage asthma[1][2][3]to detect respiratory disease in patients presenting with symptoms of breathlessness, and to distinguish respiratory from cardiac disease as the cause[4]to measure bronchial responsiveness in patients suspected of having asthma[4]to diagnose and differentiate between obstructive lung disease and restrictive lung disease[4]to follow the natural history of disease in respiratory conditions[4]to assess of impairment from occupational asthma[4]to identify those at risk from pulmonary barotrauma while scuba diving[4]to conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery[4]to measure response to treatment of conditions which spirometry detects[4]to diagnose the vocal cord dysfunction.Spirometry testingA modern USB PC-based spirometer.Device for spirometry. The patient places his or her lips around the blue mouthpiece. The teeth go between the nubs and the shield, and the lips go over the shield. A noseclip guarantees that breath will flow only through the mouth.Screen for spirometry readouts at right. The chamber can also be used for body plethysmography.SpirometerThe spirometry test is performed using a device called a spirometer, which comes in several different varieties. Most spirometers display the following graphs, called spirograms:a volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along the X-axisa flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axisProcedureThe basic forced volume vital capacity (FVC) test varies slightly depending on the equipment used.Generally, the patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, for as long as possible, preferably at least 6 seconds. It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction. Sometimes, the test will be preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the rapid breath in (forced inspiratory part) will come before the forced exhalation.During the test, soft nose clips may be used to prevent air escaping through the nose. Filter mouthpieces may be used to prevent the spread of microorganisms.Limitations of testThe maneuver is highly dependent on patient cooperation and effort, and is normally repeated at least three times to ensure reproducibility. Since results are dependent on patient cooperation, FVC can only be underestimated, never overestimated.Due to the patient cooperation required, spirometry can only be used on children old enough to comprehend and follow the instructions given (6 years old or more), and only on patients who are able to understand and follow instructions — thus, this test is not suitable for patients who are unconscious, heavily sedated, or have limitations that would interfere with vigorous respiratory efforts. Other types of lung function tests are available for infants and unconscious persons.Another major limitation is the fact that many intermittent or mild asthmatics have normal spirometry between acute exacerbation, limiting spirometry's usefulness as a diagnostic. It is more useful as a monitoring tool: a sudden decrease in FEV1 or other spirometric measure in the same patient can signal worsening control, even if the raw value is still normal. Patients are encouraged to record their personal best measures.Technologies used in spirometersVolumetric Spirometers Water bellBellows wedgeFlow measuring Spirometers Fleisch-pneumotachLilly (screen) pneumotachTurbine/Stator Rotor (normally incorrectly referred to as a turbine. Actually a rotating vane which spins because of the air flow generated by the subject. The revolutions of the vane are counted as they break a light beam)Pitot tubeHot-wire anemometerUltrasounddetermined by measuring airflow and the corresponding changes in lung volume. Airflow can be measured directly with a pneumotachometer and a transducer. A pneumotachometer converts the flow of gases through it into a proportional signal of pressure difference on either side of a central mesh whose design ensures a signal linearity over a range of flow rates with a minimum dead space. ?.this type of pneumotachometer, flow is derived from the pressure difference over a small, fixed resistance, offered by a fine metal mesh inside the plastic cone. The trumpet-like shape of the pneumotachometer is designed to achieve laminar flow over a wide range of flows (up to 12 L/sec). (When high flows give rise to a turbulent flow pattern, the pressure drop across the resistance would change more than proportionally with flow). Two small plastic tubes attached on either side of the mesh transmit the pressure difference across the mesh to the differential pressure transducer. The transducer converts the pressure signal into a changing voltage that is recorded by the PowerLab and displayed with the Chart software. The volume, V, is then calculated as the integral of flow: left0This integration represents a summation over time; the volume traces that you will see in the Chart View during the experiment are obtained by adding successive sampled values of the flow signal and scaling the sum appropriately.? The integral is initialized to zero every time a recording is started.? The difference in the temperature of the ambient air and the air exhaled during expiration must be considered in accurate measurements of tidal volume. Since the volume of gases depends on temperature, recorded tidal volume has to be corrected accordingly. Correction must be used to convert flow and volume measured at ambient conditions to the conditions within the lungs. ?The ambient conditions are called ATPS (Ambient Temperature and Pressure, Saturated with water vapour).? The conditions within the lungs are called BTPS (Body Temperature and Pressure, Saturated).?Conditions affecting pneumotachometry?The volumetric accuracy of pneumotachometry is primarily dependent on the flow condition. Day-to-day variation in ambient temperature and thus pneumotachometer temperature will affect pneumotachometer sensitivity as a result of change in gas viscosity. Moisture accumulation in the flow head, and non-ideal distribution of air flow across the wire mesh, may result in a drift in the zero setting. This component of drift is minimized by the use of disposable droplet filters.Respiratory rateFrom Wikipedia, the free encyclopediaThis article is about the measurement of breathing. For the parameter used in ecological and agronomical modelling, see respiration rate.Look up Respiratory rate in Wiktionary, the free dictionary.The respiratory rate (RR), also known as the respiration rate, ventilation rate, ventilatory rate, ventilation frequency (Vf), respiration frequency (Rf), pulmonary ventilation rate, or breathing frequency, is the rate (frequency) of ventilation, that is, the number of breaths (inhalation-exhalation cycles) taken within a set amount of time (typically 60 seconds). A normal respiratory rate is termed eupnea, an increased respiratory rate is termed tachypnea and a lower than normal respiratory rate is termed bradypnea.Breathing (which in organisms with lungs is called ventilation and includes inhalation and exhalation) is a part of respiration. Thus, in precise usage, the words breathing and ventilation are hyponyms, not synonyms, of respiration; but this prescription is not consistently followed, even by most health care providers, because the term respiratory rate (RR) is a well-established term in health care, even though it would need to be consistently replaced with ventilation rate if the precise usage were to be followed.MeasurementHuman respiration rate is measured when a person is at rest and involves counting the number of breaths for one minute by counting how many times the chest rises. An optical breath rate sensor can be used for monitoring patients during a magnetic resonance imaging scan.[1] Respiration rates may increase with fever, illness, or other medical conditions. When checking respiration, it is important to also note whether a person has any difficulty breathing.Inaccuracies in respiratory measurement have been reported in the literature. One study compared respiratory rate counted using a 90 second count period, to a full minute, and found significant differences in the rates.[citation needed] Another study found that rapid respiratory rates in babies, counted using a stethoscope, were 60–80% higher than those counted from beside the cot without the aid of the stethoscope.[citation needed] Similar results are seen with animals when they are being handled and not being handled—the invasiveness of touch apparently is enough to make significant changes in breathing.Various other methods to measure respiratory rate are commonly used, including impedance pneumography, HYPERLINK "" \l "cite_note-Grenvik-2" [2] and capnography which are commonly implemented in patient monitoring.Normal rangeThe Average respiratory rate reported in a healthy adult at rest is usually given as 12–18 breaths per minute[3][4] but estimates do vary between sources, e.g., 12–20 breaths per minute, 10–14,[5] between 16–18,[6] etc. With such a slow rate, more accurate readings are obtained by counting the number of breaths over a full minute. Average resting respiratory rates by age are:[7][8]birth to 6 weeks: 30–60 breaths per minute6 months: 25–40 breaths per minute3 years: 20–30 breaths per minute6 years: 18–25 breaths per minute10 years: 15–20 breaths per minuteadults: 12–20 breaths per minuteMinute volumeRespiratory minute volume is the volume of air which is inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from the lungs in one minute.Diagnostic valueThe value of respiratory rate as an indicator of potential respiratory dysfunction has been investigated but findings suggest it is of limited value.One study found that only 33% of people presenting to an emergency department with an oxygen saturation below 90% had an increased respiratory rate.[ HYPERLINK "" \o "Wikipedia:Citation needed" citation needed] An evaluation of respiratory rate for the differentiation of the severity of illness in babies under 6 months found it not to be very useful. Approximately half of the babies had a respiratory rate above 50 breaths per minute, thereby questioning the value of having a "cut-off" at 50 breaths per minute as the indicator of serious respiratory illness.It has also been reported that factors such as crying, sleeping, agitation and age have a significant influence on the respiratory rate.[citation needed] As a result of these and similar studies the value of respiratory rate as an indicator of serious illness is limited.Abnormal respiratory ratesApneaDyspneaTachypneampedance plethysmography (IPG) has been used to estimate blood flow and quantify body fluid volumes. . Typically this has been employed to estimate thoracic blood flow, designated "impedance cardiography. However, the technique has far more potential. The technique is based upon a simple model which regards the body as composed of various electrical segments comprising simple resistors and capacitors as shown in the figure. Measurements of baseline resistance, R0, and pulsatile resistance changes, ΔR, are made.. Disposable EKG electrodes will be attached as described above. The IPG introduces a high frequency (50 kHz), low amperage (0.1 mA RMS) constant current signal between the foot and hand. Resistance changes normalized to segment length and cross section yield relative volume changes. Pulsatile ΔR are used to obtain relative blood flow (ml/100 ml of body tissue/min) of each body segment.??IPG can be used to detect internal volume shifts including those produced during orthostatic stress. We used a Tetrapolar High Resolution Impedance Monitor (THRIM) four-channel digital impedance plethysmograph (UFI, Inc). to measure volume shifts in four anatomic segments designated the thoracic segment, the splanchnic segment, the pelvic segment incorporating lower pelvis to upper leg, and the leg segment Ag/AgCl EKG electrodes were attached to the left foot and left hand, which served as current injectors. Additional electrodes were placed in pairs representing anatomic segments as follows: ankle-upper calf just below the knee (the leg segment), knee-iliac crest (pelvic segment), iliac crest-midline xyphoid process (the splanchnic segment), and midline xyphoid process to supraclavicular area (the thoracic segment). The IPG introduces a high frequency (50 kHz), low amperage (0.1 mA RMS) constant current signal between the foot and hand electrodes. This is completely insensible to the subjects. Electrical resistance values are measured using the segmental pairs as sampling electrodes. Anatomic features were selected as the most appropriate locations for comparing changes within and across patients.?? ................
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