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Saturday, January 12, 2013

History of Incentive Spirometry

Why were incentive Spirometers needed?

During the 1950s physicians had access to effective anesthetics and methods of breathing for patients while they were under, such as bag mask ventilator (Ambu-Bags) and eventually positive pressure ventilators.  It was during this time that surgeries became common place in hospitals.  Yet it didn't take long for physicians to realize that even while the operation may be successful, about 20 percent of these patients developed post operative respiratory complications that confounded caring for these patinets.  (2)

The most common surgery during this time was abdominal surgeries.  By 1957 it was well documented that about 20 percent of patients getting abdominal surgeries (particularly upper abdominal surgeries) were retaining secretions and developing pneumonia.  It was ultimately determined this was happening because these patients weren't taking deep enough breaths.  (2)

Studies showed that during normal breathing, shallow breaths may result in collapse of some alveoli, yet at a certain point the person will naturally take in a deep breath that supplies "sufficient pressure to reopen the collapsed alveoli."  A study performed in 1964 showed that these deep breaths, generally referred to as a sigh or yawn, occur normally about five to ten times every hour.  (2)

Furthermore, studies showed this normal pattern of breathing was abolished by general anesthesia and by narcotics like morphine that were needed to keep these patients comfortable.  Shallow breathing that results from both pain from thoracic or upper abdominal surgeries, anesthesia and pain relievers causes a prolonged abnormal breathing pattern (shallow and without sighs).

Due to this shallow breathing these patinets were unable to clear secretions, and this resulted in retained secretions.  The end result of shallow breathing and retained secretions were alveolar regions that weren't being ventilated (hypoventilation) adequately, and this was resulting in atelectasis.  To further complicate things, retained secretions create a breeding ground for bacteria, and pneumonia may result. 

Other studies in the 1960s confirmed that patients with Chronic Bronchitis, Emphysema, or patients who are heavy smokers, and people who are overweight, tend to have reduced lung volumes to begin with are are at the greatest risk for developing post operative complications.  This group, it was learned, had to be treated especially careful. 

Generally it was learned that only a small portion of patients with atelectasis develop pneumonia, but the challenge became knowing which patients were at greatest risk.  Yet pneumonia further complicates caring for a patients, and sometimes ends in death.  In fact, studies done in the 1970s showed that respiratory failure was the cause or a contributing factor in about 50 percent of postoperative deaths.  (6)

The question left to the experts was what to do to prevent and treat post operative complications.

The first treatment for post operative atelectasis is?

Since it was difficult to know for sure which patinets would develop post operative complications, it became obvious that all such patinets had to be treated prophylacally in the hopes of preventing any problems.  If atelectasis or pneumonia developed anyway, those conditions were treated accordingly with oxygen, antibiotics, or mechanical ventilation if needed.  Yet the ultimate goal was to prevent the need for those treatments. 

One of the simplest solutions suggested was get these patient moving as soon as possible, although with some surgeries this may not be possible. Certainly cough and deep breathing (C&DB) exercises would be encouraged, but many patients had no incentive to do this when the nurse or doctor wasn't around. It was likewise learned by studies that most post operative patients didn't take a deep enough breath to be therapeutic.  (1)

When the first Intermittent Positive Pressure Breathing machines were introduced to the market in the mid 1950s these were thought to force enough air into a patients lungs to prevent post operative complications.  It was common for patients to get 10-15 minute IPPB treatments with Isuprel.

Yet studies in the 1970s showed this therapy to be ineffective because most patients were not allowing the machines to fill their lungs with air.  Other studies showed the tidal volume achieved through such therapy was still not enough to be therapeutic. 

Through the next two decades such IPPB therapy was phased out.  I wrote about the IPPB Revolution in respiratory therapy in this post

Another option that became available was blow bottles, where the patient was encouraged to exhale forcefully to prevent these symptoms. It was basically a glorified method to help the patient clear secretions.  According to Dennis Glover in his book, "The History of Respiratory Therapy" the "patient exhales into a bottle partially filled with water, which creates resistance to his or her effort."  (4)

Yet this therapy was soon learned to be ineffective because, as Glover explained, it further collapsed the airways, which was the opposite effect as desired.  Blow bottle therapy was also proven to be more painful for the patient than inhaling, considering most muscles of respiration are for expiration.  Therefore it was determine the best way to prevent and treat atelectasis was inhaling, not exhaling.  (1)

So the market was open for some sort of device here.  This inspired many medical experts, and entrepreneurs pent on profiting from this new need, into getting creative. It provided a new use for an old device that was actually first used way back in 1840 to prevent consumption as I wrote here.

So this brings us to the Incentive Spirometer

The idea of taking a deep breath to prevent post and treat post operative patients was first mentioned in medical literature in 1915 by  MacMahon.  He worked with soldiers who were injured in battle, and recognized many were developing post operative respiratory complications.  He recommended chest physiotherapy, exercise and taking deep breaths.  (9)

In this way, MacMahon may have been the first to describe forced expiration to prevent and treat post operative respiratory complications.  He wrote:  "the patient breathes in through the nose and the lower ribs are felt to be strongly expanding. The mouth is opened wide and the abdominal muscles slowly and strongly contracted, so that the air is driven from the lungs." (9)

By the 1960s there was ample evidence that taking in a deep breath and holding it for 3-5 seconds was an effective means of preventing atelectasis.  This technique worked similar to a sigh or yawn.  In 1966 a study was performed that showed taking a deep breath without a breath hold was not effective in preventing atelectasis, so emphasis must be made on the slow, deep breath with breath hold.  This method -- the sigh --was also proven to treat atelectasis by returning the lungs to normal.  (2)

Yet studies already suggested that patients didn't do a good enough job of this on their own, without coaching, or without some sort of a device.  It was for this reason that some sort of device was needed.  (2)  In 1966 a report was written recomminding deep breathing exercises every hour. (7) And another report in 1980 even played on this suggesting perhaps the reason IPPB didn't work as effectively as incentive spirometry is because IPPB therapy is only done every four hours.  (6)  Thankfully that researcher didn't get his way, or RTs would have been even more inundated with IPPB therapies that were ultimately proven to be an embarassemnt to the RT profession. 

Spirocare Incentive Spirometer (1975)
The incentive spirometer was invented in 1970 by R.H. Bartlett and written about in his article "Physiology of Yawning & Its Application to Post Operative Care which appeared in Surgical Forum in 1970.  The device was neat because it was a device that sat on the bedside table and acted as a reminder -- an incentive if you will -- for them to remember to take breaths. 

The device encouraged the patient to take in a deep breath, with a breath hold, that was "reproduceable"  and similated the required yawn.  It also gave positive feedback because the patient could see actual results, and goals could be set. (2)

The first incentive spirometer (IS) wasn't like the disposable plastic units we use today.  It was an electric device that lit up when the desired volume was reached. 

Like the modern devices, the patient would put his mouth on a mouthpiece, and inhale.  A bellow inside the device would rise on inspiration, which could be measured if between 200 and 2000 ml.  After treatment the patinet was encouraged to cough, and expectorate secretions if possible.

Playing on the concept invented by, Marion Laboratories trademarked the Spirocare electric incentive spirometer in 1975, according to  It was called the Sprirocare Electronic Incentive Breathing Excersisor.  The trademark actually didn't expire until 1997, although the devices ceased being used long before that in favor of the modern, plastic disposable, less expensive units.

The following is from an advertisement in the January 1974 issue of Chest (Volume 65/ number 1, January 1974, page A-15): 
"Meet Spirocare, the new incentive breathing exercisor.  A self-contained, portable instrument, designed to assist the postoperative or chronic pulmonary patient.
Operation is extremely simple:  You select an air volume goal for your patient.  The patient then inhales through a disposable impellaway flowmeter.  As the volume of inhaled air increases, the patient can see the illuminated numbers light up until the preselected goal is reached.  A visual conter records the number of times the goal is achieved. 
The device is interesting to watch, so patient motivation is easily maintained.  Cross contamination is eliminated through use of the disposable impellaway flowmeter.
The Spirocare unit offers precise flow-rate measurements from 200cc/sec to 10,000 cc/sec.  An internal optical scanning system provides digital output and illuminated signals based on the computer-couinted rotation of the impeller.  It is easily the most sophisticated instrument of its type. 
Today's there are many brands of incentive spirometers, and they are plastic, made for individual use, and disposable. The concept is the same, however.  Most such devices have some sort of object, like a ball or balls or bellow, that the patient has to keep above a line.  After taking about ten such breaths with a breath hold the patient is encouraged to cough.  (1) Once again, the goal here is to mimic a sigh, which was proven to prevent hypoventilation, atelectasis, and further postoperative complications. 

So, are incentive spirometers better than other methods?

Various studies were done in the 1970s that ultimately proved that blow bottle therapy and IPPB therapy were innefective in treating post operative atelectasis.  One such study in 1978 compared the three methods and showed that all three improved atelectasis to some degree, with the incentive spirometer being the most effective with the least side effects. (5)

A study reported in the study, IPPB therapy, done ineffectively, often resulted in air in the stomach and this resulted in about 9 percent of patients having distended stomachs, and 20% having stomach complications. There was also a high incidence of post operative nausea in patients receiveing IPPB therapy (16%), as compared with insentive spirometery and blow bottle therapy (2%).

Ultimately, the incentive spirometer was recomended by the researchers as it resulted in 15% of post operative patients using it developing post operative complications compared with 30% of patients using IPPB therapy developing complications. However, blow bottle therapy resulted in an incidence of only 8% experiencing post operative complications.  (5)

The greatest advantage was that incentive spirometer and blow bottle therapy costs about half as much as IPPB therapy.  As per 1978 dollars, the cost of setting up all three treatments was $9.00, but the cost of subsequent IPPB treatments was $7.50 compared with $3.00 for IS and blow bottle therapy.  (5)

The ultimate results of this study were that IS and blowby therapy were both superior to IPPB therapy.  It didn't take long, however, of both IPPB and blow bottle therapy to both be phased out in favor of IS therapy.  However, while blow bottle therapy was quickly phased out, IPPB therapy was slower to be phased out.  Some doctors continue to prescribe it for some comlicated post operative cases and are convinced it does some good. 

In 2001 a group of researchers collected the entire database of studies regarding the incentive spirometer, and they concluded that "the evidence does not support the use of IS for decreasing the incidence of PPCs (postoperative pulmonary complications) following cardiac or upper abdominal surgery.  (10)  Other researchers and authors concur that "there is little evidence to support the use of IS in airway clearance, but it is still used today. (9)


Regardless of lack of evidence that the IS is effective in preventing and treating postoperative pulmonary complications, most medical professionals recommend its use. Most hospitals have protocols that call for a respiratory therapist to give one to all post operative patients, and properly instruct them on its use.

Likewise, despite lack of evidence supporting it's effectiveness, many quality assurance programs insist on an IS being ordered for the patient to meet reimbursement criteria.  So needless to say, IS therapy is still commonly prescribed. In fact, it's quite common to see a respiratory therapist trudging into patient rooms with an incentive spirometer in hand.

  1. 1.  Bartlett, R. H. et al., "Physiology of Yawning & Its Application to Post Operative Care," Surgical Forum, 1970, pp. 222-224. . "Doctors Test Yawn Box," Boston Evening Globe, Oct. 14, 1970.. 
  2. Craven, J, et al, "The Evaluation of the Incentive Spirometer in the Management of Posoperative Pulmonary Complications," British Journal of Surgery, 1974, vol 61, pages 793-97
  3. George, Ronald B, et all, "Chest Medicine: Essentials of Pulmonary and Critical Care Medicine," 2005, Philadelphia, page 567 
  4. Glover, Dennis, "The history of Respiratory Therapy: Discovery and Evolution," 2010, Indiana, page 79
  5. Leigh, I.G., et al, "A comparative study of IPPB, the Incentive Spirometer, and Blow Bottles; The Prevention of Atelectasis Following Cardiac Surgery," Ann Thorac Surg, 1978; 25; 197-200
  6. Kigen, Colleen M, "Chest Physical Therapy for the Postoperative or Traumatic Injury Patient," Physical Therapy, 1981; 61; pages 1724-1736
  7. Ward, R.H., et al, "An evaluation of post operative respiratory meneuvers," Surg Gynecol Obstet, 1966, 123; pages 51-54
  8. MacMahon, C, "Breathing and physical exercises for use caes of wounds in the pleura, lung and diaphragm," Lancet, 1915, pages 769-70
  9. Pryor, JA, "Physiotherapy for airway clearance in adults," European Respiratory Journal, 1999, 14, pages 1418-24
  10. Overland, Tom J., et al, "The Effect of Incentive Spirometry on Postoperative Pulmonary Complications: A Systemic Review," Chest, September 2001, vol. 120, no. 3, pages 971-978

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