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 testing
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Diagnose certain types of lung disease (such as asthma, bronchitis, and emphysema)
Find the cause of shortness of breath
Measure whether exposure to chemicals at work affects lung function
Check lung function before someone has surgery
Assess the effect of medication
Measure progress in disease treatment
Types of spirometer
Whole body plethysmograph
Main article: body plethysmography
This 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.
Pneumotachometer
This 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 spirometer
Electronic 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 spirometer
Main article: Incentive spirometer
This spirometer is specially designed to improve one's functioning of the lungs.
Peak flow meter
Main article: Peak expiratory flow
This device is useful for measuring the ability of a person breathing out air.
Windmill-type spirometer
Used 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 spirometer
Tilt-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.
ndications
Spirometry is indicated for the following reasons:
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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 testing
A 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.
Spirometer
The spirometry test is performed using a device called a spirometer, which comes in several
different varieties. Most spirometers display the following graphs, called spirograms:
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a volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along the Xaxis
a flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total
volume inspired or expired on the X-axis
Procedure
The 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 test
The 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 spirometers
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Volumetric Spirometers
o Water bell
o Bellows wedge
Flow measuring Spirometers
o Fleisch-pneumotach
o Lilly (screen) pneumotach
o Turbine/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)
o Pitot tube
o Hot-wire anemometer
o Ultrasound
determined 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:
This 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-today 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 rate
From Wikipedia, the free encyclopedia
This 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.
Measurement
Human 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,[2] and capnography which are commonly implemented in patient monitoring.
Normal range
The 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]
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birth to 6 weeks: 30–60 breaths per minute
6 months: 25–40 breaths per minute
3 years: 20–30 breaths per minute
6 years: 18–25 breaths per minute
10 years: 15–20 breaths per minute
adults: 12–20 breaths per minute
Minute volume
Respiratory 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 value
The 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.[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 rates
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Apnea
DyspneaTachypnea
mpedance
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), kneeiliac 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.