Tuesday, September 09, 2014

1871-1900: Pneumatometers as Spirometers x

By the 1870s various engineers were tinkering with the Hutchinson Spirometer with the intent of improving upon it  Yet in 1871 Dr. L. Waldenburg invented a device that some physicians believed was better than the spirometer for diagnosing various airway diseases.

The main problem with spirometry was that volumes varied based on height and age.  This problem appeared to be remedied with the invention of the pneumatometer which measured more the force of a patient's exhalation, and therefore gave a better picture of the patients lung muscle strength.

This was a portable device that could be used to provide pressure changes to be used therapeutically to treat various diseases, such as emphysema, croup, bronchitis, and asthma.  The first such device was introduced by Hawke in 1870 called the Hawke Apparatus.  This device was nice because "air in the receiver can be condensed (increase in pressure) or rarified (decrease in pressure), and used in either of these conditions for respiration." (1)

Hawke believed his apparatus would be especially useful in croup and emphysema.  He believed that since emphysema resulted in air being trapped into the lungs, that expiring against rarified air (which was basically suction) this would help empty this air from the lungs. In croup he believed condensed (positive pressure, pressure support) should be inspired. He later recommended inspiration of compressed air for consumption.(1)

After Hawke wrote about his apparatus he received "favorable results," although this type of device wasn't truly accepted by the medical community until Waldenburg improved upon it with his own device, called the Waldenburg Apparatus.  And the neat thing about Waldenburg's apparatus is it had a graduated scale so you could measure the degree of pressure changes.  This was nice for two reasons:
  1. You could measure the amount of pressure used to benefit the patient, which allowed similar settings to be used at future visits or uses, and allowed physicians a guide to setting up future patients.
  2. You could use it as a spirometer to measure the force of a patients exhalation, and to measure vital capacity.
It was likewise different from the spirometer -- even better -- because "spirometry deals with the vital capacity of the chest, which depends chiefly upon the circumference and height of the thorax, whilst in pneumatometry the height of the thorax has no influence." (3)

"U-shaped tube, open to the atmosphere and suitably mounted, is filled with mercury in both branches to the same level, which is marked zero. One branch is connected with a rubber tube and mouthpiece (or mask or nosepiece) used by the person under observation, whose expiratory and inspiratory force is measured by the ascent or descent of the mercury in the other branch, as shown upon a millimetric scale (Fig. 1)." (2, page 25)

So, "When the patient expires through the tube, the column of mercury sinks in the proximal limb of the manometer and rises in the distal, while with inspiration these movements are of course reversed, and in either case the amount of displacement is to be read off on the scale." (3, page 146)

Likewise, "Since the level of the mercury when at rest corresponds in both limbs to the zero of the scale, the reading obtained must, of course, be doubled to represent the true difference in the level of the two columns." (4, page 146)

Keeping in mind expiratory pressure is normally greater than inspiratory presssure, Waldenburg (and later other physicians) determined the following normal values for forced inspiratory and expiratory pressures for males and females (3 and 4):
  • Male inspiratory pressure:  70-100
  • Male epiratory pressure:  90-130
  • Female inspiratory pressure: 50-80
  • Female expiratory pressure: 70-80
The diagnostic purposes are as follows (3):

1.  Expiratory pressure is increased in relation to inspiratory in:
  • Phthisis (even at a very early stage), 
  • Stenosis of the air passages
  • Pulmonary congestion
  • Pneumonia
  • Pleurisy
  • Any abdominal affections as impede respiration by pressing the diaphragm upwards.
2.  Expiratory pressure is diminished until it becomes equal to or below the inspiratory in:
  •  pulmonary emphysema.
Other than for diagnostic purposes, this test can indicate: (2)
  1. The power of the respiratory muscles
  2. The mobility of the thorax and expansion of the lungs
  3. Elasticity of the parenchyma of the lungs. 
So, by performing tests on both the Hawke and Waldenburg apparatus's, physicians discerned the following facts: (1)
  1. Emphysema results in imperfect expiration, while inspiration is normal or increased (the natural result of increased use of inspiratory muscles)
  2. Catarrh of small bronchi results in imperfect expiration, and normal inspiration
  3. Phthisis (tuberculosis, consumption) results in a decreased inspiration, and later expiration is imperfect.  
  4. Stenosis of respiratory ducts results in imperfect inspiration, but expiration is normal
  5. Inflammation of lung tissue and pleura results in similar effect as phthisis
There were a variety of similar products on the market, although Waldenbur's continued to be the preferred pneumatometer for both as a pressure apparatus and spirometer, at least through the turn of the 20th century, according to most sources I used as references.  
    1. Rose, A., "Treatment of Disease of Respiration and Circulation by the Pneumatic Method," New York, The Medical Record: A Weekly Journal of Medicine and Surgery, Edited by George F. Shrady, M.D., Volume 10, Jan. 2, 1875 to Dec. 25, 1875, New York, William Good and Co., page 577
    2. Tissier,Paul Lewis Alexandre, edited by Solomon Solis Cohen, "Pneumotherapy: Including Aerotherapy and inhalation methods," volume X, 1903, Philadelphia, P. Blakiston's Sons and Co., pages 296-224.  If the profession of respiratory therapy existed in their era, we would be reading their books.  However, as it was, their books were written for the medical profession. All of the material from this post is from Tissier's book unless otherwise noted in the above paragraphs. Tissier page 72
    3. Brunton, Lauder T, The Practitioner: A Journal of Therapeutics and Public Health, Vol. XVII, July to December, 1876, London, MacMillan, "Pneumotachometry," page 216
    4. Brown, John James Graham, "Medical Diagnosis," 2nd edition, 1884, New York and London, Birmingham and Co., "Pneumotameter," pages 25-26
    5. Effects on the heart are questionable, although most studies conclude the pneumatometer  benefits asthma, bronchitis, emphysema, phthisis

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