Flow-Volume loop showing successful FVC maneuver. Positive values represent expiration, negative values represent inspiration. The trace moves clockwise for expiration followed by inspiration. (Note the FEV1, FEV1/2 and FEV3 values are arbitrary in this graph and just shown for illustrative purposes, they must be recorded as part of the experiment).

Example of [...]]]>

From Wikipedia, the free encyclopedia

Flow-Volume loop showing successful FVC maneuver. Positive values represent expiration, negative values represent inspiration. The trace moves clockwise for expiration followed by inspiration. (Note the FEV₁, FEV_1/2 and FEV₃ values are arbitrary in this graph and just shown for illustrative purposes, they must be recorded as part of the experiment).

Example of a modern PC based spirometer printout.

Spirometry (meaning the measuring of breath) is the most common of the Pulmonary Function Tests (PFTs), measuring lung function, specifically the measurement of 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.

[edit] Spirometry testing

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.

A modern USB PC-based spirometer.

Screen for spirometry readouts at right. The chamber can also be used for body plethysmography.

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:

• a volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along the X-axis
• 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

The most commonly used guidelines for spirometric testing and interpretation are set by the American Thoracic Society (ATS) and the European Respiratory Society (ERS).

[edit] 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. 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, particularly for inspiratory maneuvers.

[edit] 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, FEV_1* and FVC can only be underestimated, never overestimated.(*FEV1 can be overestimated in people with some diseases - a softer blow can reduce the spasm or collapse of lung tissue to elevate the measure)

Due to the patient cooperation required, spirometry can only be used on children old enough to comprehend and follow the instructions given (typically about 4–5 years old), 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.

[edit] Related tests

Spirometry can also be part of a bronchial challenge test, used to determine bronchial hyperresponsiveness to either rigorous exercise, inhalation of cold/dry air, or with a pharmaceutical agent such as methacholine or histamine.

Sometimes, to assess the reversibility of a particular condition, a bronchodilator is administered before performing another round of tests for comparison. This is commonly referred to as a reversibility test, or a post bronchodilator test (Post BD), and is an important part in diagnosing asthma versus COPD.

[edit] Parameters

The most common parameters measured in spirometry are Vital capacity (VC), Forced vital capacity (FVC), Forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, Forced expiratory flow 25–75% (FEF 25–75) and Maximal voluntary ventilation (MVV).^[1] Other tests may be performed in certain situations.

Results are usually given in both raw data (litres, litres per second) and percent predicted - the test result as a percent of the “predicted values” for the patients of similar characteristics (height, age, sex, and sometimes race and weight). The interpretation of the results can vary depending on the physician and the source of the predicted values. Generally speaking, results nearest to 100% predicted are the most normal, and results over 80% are often considered normal. However, review by a doctor is necessary for accurate diagnosis of any individual situation.

Functional residual capacity (FRC) cannot be measured via spirometry, but it can be measured with a plethysmograph or dilution tests (for example, helium dilution test).

Normal values for Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 Second (FEV1) and Forced Expiratory Flow 25–75% (FEF25–75%), according to a study in the United States 2007 of 3,600 subjects aged 4–80 years.^[2] Y-axis is expressed in litres for FVC and FEV1, and in litres/second for FEF25–75%.

[edit] Forced Vital Capacity (FVC)

Forced Vital Capacity (FVC) is the volume of air that can forcibly be blown out after full inspiration, measured in litres.

[edit] Forced Expiratory Volume in 1 Second (FEV1)

Forced Expiratory Volume in 1 Second (FEV₁) is the maximum volume of air that can forcibly blow out in the first second during the FVC manoeuvre, measured in liters. Along with FVC it is considered one of the primary indicators of lung function.

[edit] FEV1/FVC ratio (FEV1%)

FEV₁/FVC (FEV1%) is the ratio of FEV₁ to FVC. In healthy adults this should be approximately 75–80%. In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV₁ is diminished because of increased airway resistance to expiratory flow and the FVC may be increased (for instance by air trapping in emphysema). This generates a reduced value (<80%, often ~45%). In restrictive diseases (such as pulmonary fibrosis) the FEV₁ and FVC are both reduced proportionally and the value may be normal or even increased as a result of decreased lung compliance.

[edit] Forced Expiratory Flow 25–75% or 25–50%

Forced Expiratory Flow 25–75% or 25–50% (FEF 25–75% or 25–50%) is the average flow (or speed) of air coming out of the lung during the middle portion of the expiration (also sometimes referred to as the MMEF, for maximal mid-expiratory flow). In small airway diseases such as asthma this value will be reduced, perhaps <65% of expected value. This may be the first sign of small airway disease detectable.

[edit] Forced Inspiratory Flow 25–75% or 25–50%

Forced Inspiratory Flow 25–75% or 25–50% (FIF 25–75% or 25–50%) is similar to FEF 25–75% or 25–50% except the measurement is taken during inspiration.

[edit] Peak Expiratory Flow (PEF)

Normal values for Peak Expiratory Flow (PEF), shown on EU scale.^[3]

Peak Expiratory Flow (PEF) is the maximal flow (or speed) achieved during the maximally forced expiration initiated at full inspiration, measured in litres per minute.

[edit] Tidal volume (TV)

Tidal volume (TV) is the During the normal, tidal breathing a specific volume of air is drawn into and then expired out of the lungs.

[edit] Total Lung Capacity (TLC)

Total Lung Capacity (TLC) is the maximum volume of air present in the lungs.

[edit] Diffusion capacity (DLCO)

Diffusing Capacity (DLCO) is the carbon monoxide uptake from a single inspiration in a standard time (usually 10 sec). This will pick up diffusion impairments, for instance in pulmonary fibrosis. This must be corrected for anemia (because rapid CO diffusion is dependent on hemoglobin in RBC’s a low hemoglobin concentration, anemia, will reduce DLCO) and pulmonary hemorrhage (excess RBC’s in the interstitium or alveoli can absorb CO and artificially increase the DLCO capacity).^{[dubious – discuss]}

[edit] Maximum Voluntary Ventilation (MVV)

Maximum Voluntary Ventilation (MMV) is a measure of the maximum amount of air that can be inhaled and exhaled in one minute, measured in liters/minute.

[edit] Others

Forced Expiratory Time (FET)
Forced Expiratory Time (FET) measures the length of the expiration in seconds.

Slow Vital capacity (SVC)
Slow Vital capacity (SVC) is the maximum volume of air that can be exhaled slowly after slow maximum inhalation.

[edit] Technologies used in spirometers

• Volumetric Spirometers
  • Water bell
  • Bellows wedge
• Flow measuring Spirometers
  • Fleisch-pneumotach
  • Lilly (screen) pneumotach
  • 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 tube
  • Hot-wire anemometer
  • Ultrasound

[edit] See also

• Peak flow meter
• Fowler method

[edit] References

1. ^ surgeryencyclopedia.com > Spirometry tests Retrieved on Mars 14, 2010
2. ^ Stanojevic S, Wade A, Stocks J, et al. (February 2008). “Reference ranges for spirometry across all ages: a new approach”. Am. J. Respir. Crit. Care Med. 177 (3): 253–60. doi:10.1164/rccm.200708-1248OC. PMID 18006882.
3. ^ Nunn, A. J., and I. Gregg. 1989. New regression equations for predicting peak expiratory flow in adults. Br. Med. J. 298: 1068-1070. Adapted by Clement Clarke for use in EU scale - see Peakflow.com > Predictive Normal Values (Nomogram, EU scale)

[edit] Further reading

• Miller, MR; Crapo R, Hankinson J et al. (July 2005). “General considerations for lung function testing”. European Respiratory Journal 26 (1): 153–161. PMID 15994402. http://erj.ersjournals.com/cgi/content/full/26/1/153.

[edit] External links

• Information on spirometry reimbursement and purchase.
• Detailed information on spirometric testing, interpretation and physiology at spirxpert.com
• History of spirometers and lung function testing at medizin.li
• General information on spirometry at spirometrie.info
• American Thoracic Society (ATS)
• European Respiratory Society (ERS)
• General Practice Airways Group
• Virtual patient spirometry

While these are all great goals, another important but often overlooked goal is to get rid of [...]]]> Basic Health Maintenance Plan
Many of us want to improve our health. Our common reponse is… “I want to quit smoking, lose weight, exercise, practice safe sex, use seatbelts, eat a healthier diet and be nicer to family and friends.”

While these are all great goals, another important but often overlooked goal is to get rid of that two-letter word “If.” You know, the one where you say: “Doctor, if I only knew to check my skin for those moles; if I only took the time to get my blood pressure checked; if I only got that mammogram when I should have.”

Knowledge Is Key
The first defense against the “if” factor is to take charge of your health and learn what you need to do, and when you need to do it, to keep your body running at tip-top shape. After all, when you buy a car, you maintain it according to schedule. So why not have a similar schedule to maintain your body?

Sure, making all those appointments may cost some money and be time-consuming, and while it isn’t much fun to get poked and prodded and tested, the point is to keep preventable diseases from stealing your time, your health and very possibly your life.

The Starting Line
To get you started, here is a general health schedule for people age 20 and above. Please remember that it is a recommendation only. Your personal health schedule may involve other tests, such as a fasting blood glucose test to screen for diabetes, and it may need to be more frequent if you have a medical condition that necessitates it.

The Complete Physical
People age 20 to 45 should have a physical exam once every five years; those who are 45-65 should have a physical every two years. After 65, a yearly exam is recommended (unless you have a condition that requires you to be examined more frequently).

Dental Checkup
Your teeth should be cleaned and examined every six months to a year. This would change, of course, if a specific problem needed to be addressed. If you smoke or chew tobacco products, these exams may save your life.

Eye Exam
Generally you need to undergo an eye exam every two years if you wear glasses or contacts or yearly if you have diabetes or other eye problems. If you have good vision, get a complete eye exam starting at age 40 every two years. This schedule will be adjusted by your eye specialist based upon your exam.

Colon Exam
Colon cancer is the third most common form of cancer among men and women. Early detection is crucial because colorectal cancer, which runs in families (10 to 15 percent of all colon cancers are inherited), is a very deadly form of cancer, killing about 40 percent of its victims. I know this exam is no fun and makes many people feel embarrassed. But what’s to be embarrassed about? After all, we’re talking about your life.

According to the American Cancer Society (ACS), age 50 is a key milestone to begin screening for this type of cancer. However, please know that many physicians begin testing at age 40, especially if there’s a history of colon cancer in your family.

Here are the recommended screening options:

* Yearly fecal occult blood test (FOBT), which screens for blood in the stool (even if you can’t see blood in your stool it may be there!).
* A flexible sigmoidoscopy every five years (in addition to an annual FOBT).
* Double-contrast barium enema every five years.
* Colonoscopy every 10 years. This test is increasing in popularity due to its reliability and accuracy.

Please don’t be scared off by these tests. Your physician may recommend only one or two of these diagnostics to screen for colon cancer. If colon cancer runs in your family, be sure to tell your physician and ask if you need a colonoscopy sooner rather than later.

Skin Check
There are two types of skin cancer: melanoma and non-melanoma. Melanoma, if not found and treated early, is a killer. Non-melanoma skin cancer is not deadly but it can spread and cause a lot of skin damage if it’s not caught and treated at an early stage. So clearly, the key to treating skin cancer is early detection.

Every three months, check your skin for new moles or any changes in size, shape or color of existing moles. Look for:

* Irregular, notched or ragged looking moles.
* Moles bigger than a pencil eraser, which is about 4 to 5 millimeters (1/2 inch).
* Moles that have an inconsistent color or a combination of colors, including shades of tan, blue, black, brown, red or even white. Moles also may fade from their regular color.
* Asymmetrical moles (each half of the mole looks different from the other).

If you ever notice a suspicious mole, marking, lump, sore or change in the way your skin feels, please see your healthcare professional.

It’s also a good idea to have someone check your back, scalp and the tops of your ears for moles. Have a healthcare professional check your skin at least once every two to three years when you’re in your 20s and 30s, and then yearly after the age of 40. More frequent checkups may be in order if you have more than 50 moles, a history of skin cancer, fair skin, if you spend a lot of time outdoors or had several bad cases of sunburn as a child.

Healthy Heart Tests

Blood-pressure check: Have your blood pressure checked every other year if it’s normal and you don’t take any blood-pressure medications. If you have high blood pressure, or if high blood pressure runs in your family, your blood pressure must be measured at least once per year. Also, if you’re overweight, African American, have known heart disease or you smoke, you must have your blood pressure checked at least once a year. People often underestimate the dangers of uncontrolled high blood pressure because “they can’t feel it or notice any problems.” If left unchecked, uncontrolled high blood pressure can increase your risk for heart attack, stroke and liver and kidney damage.

Electrocardiogram: Get a baseline at age 40 or earlier if you have a family history of heart disease or you’re experiencing symptoms of heart disease. Your physician will discuss any follow-up screening based upon your personal health assessment.

Cholesterol check: The timing of this screening test is debatable. What’s not debatable is that heart disease is the No. 1 killer of men and women in our country. The National Cholesterol Education Program recommends that cholesterol be checked at age 20, then every five years after that as long as your cholesterol is in the normal range. If it’s elevated, your physician will test your triglycerides (another type of fat in the blood), LDL (bad cholesterol) and HDL (the good guy). Your follow-up cholesterol tests will be adjusted as needed, depending upon the treatment plan (diet, exercise, medication) and its results.

C-Reactive Protein (CRP): This may be one blood test you haven’t heard of, but according to the American Heart Association, CRP has become a powerful new predictor of cardiovascular risk. Researchers have found that you can still be at risk for heart disease if your CRP is high and your cholesterol levels are normal. The good news is that CRP can be treated with the medications we use to treat high cholesterol, namely, the “statin” drugs, or niacin. This test may become widely used over the next several years.

Women’s Health

Mammogram: This procedure’s ability to detect breast cancer is controversial. I recommend a baseline mammogram at age 40, then yearly after that. If you have a family history of breast cancer, I’d recommend a mammogram at age 35, especially since breast cancer is inherited about five to 10 percent of the time.

Remember to do a monthly breast self-exam beginning at age 20 and have a physician perform this exam at least once every two to three years when you are in your 20s and 30s, and yearly after age 40.

Numerous studies have shown that an annual mammogram combined with a breast exam by a healthcare practitioner cuts a woman’s risk of dying from breast cancer by more than a third. If you ever notice a change in your breasts, please don’t hesitate to visit your healthcare professional. Even if your mammogram is normal, but you feel something isn’t right, talk to your doctor.

Pap Smear and Pelvic Exam:
For women 18 and over, this should be done yearly. If you’re sexually active at a younger age, these exams should start then. The Pap smear has reduced deaths from cervical cancer by more than 50 percent since it was introduced in the 1940s. Make sure your physician uses a lab that meets the standards set by the College of American Pathologists, and also ask if the Pap smears are rechecked by the new computerized methods, or by using the thinprep technique. Some of these newer methods enable the lab to give more accurate results. If you’ve reached menopause, it’s still important to get both tests.

Healthy Bones
Bone Density: This important screening test for osteoporosis (thinning and weakening of the bone) can detect low-bone density before the bones weaken and fracture. Some 28 million Americans are at risk for osteoporosis, while 10 million of them have the disease (80 percent are women).

In spite of this huge number, the National Osteoporosis Foundation estimates that only 29 percent of U.S. women with osteoporosis are diagnosed, even though osteoporosis is the major cause of at least 90 percent of all hip and spine fractures in older women. It’s recommended that women speak with their physicians about bone-mineral-density testing and that they receive a bone-density test by age 65 — at the latest.

Younger women who are very thin, smoke, drink excess alcohol, or who have a bone fracture after age 40 or a family history of osteoporosis, may need to have a bone-mineral-density test at age 50, or earlier. The results of the test will help determine whether medications are needed to halt the progression of osteoporosis.

A Real Man’s Test

Prostate Exam: Guys, there are many opinions on screening recommendations for the early detection of prostate cancer. Even so, don’t be embarrassed to discuss the prostate exam with your physician. The 1997 guidelines by the American Urological Assocation suggest that all men over 50 get a digital rectal exam and a PSA (blood test). If prostate cancer runs in the family, then males at age 40 should get a digital rectal examination and a PSA. Further follow-up screening is based upon the results, your personal philosophy and health history.

The Senior Person

Immunizations: Adults 65 or older should be vaccinated against pneumococcal pneumonia. Those with heart, liver or lung disease, or those with cancer or who take medications that lower the body’s natural defense system, may need the vaccination at an earlier age.

It’s also important to keep up to date with your other vaccinations, including a tetanus/diphtheria booster (needed at least once every 10 years), and to ask if you need the hepatitis B vaccination, or the influenza vaccine.

Lastly, ask your healthcare professional when you should be screened for diabetes and whether you’re due for a thyroid check. A base-line screening bloodtest called a TSH is often recommended at age 50, especially for women.

Follow Up On Your Tests
Don’t assume everything is normal if you don’t hear from your physician. Take charge of your own health. Follow up on the results of any tests you get, and make sure you understand the results and what they mean for your health.

Remember, you are the CEO of your personal healthcare. The key to a healthier you is prevention. Of course, everyone is different, but the recommendations I’ve just laid out will get you started on the path to health.