Saturday, October 25, 2014

New website:

Over the past few years I've been off on an adventure through time to learn about the history of asthma.  A few months ago I started publishing what I learned on this blog.    

This project has grown so large that I have decided to separate it from the RT Cave, and have created a new website called This is a history of asthma, and it's also a history of all diseases that cause difficult breathing, plus the history of inhalation and respiratory therapy.

So, if you are in any way interested in learning what it was like to deal with difficult breathing in such and such a time in our history, of if you want to know what it was like caring for these folks, you might want to check out this new site.

Plus if you decide you like Asthma History, feel free to share it with your friends who also might be interested.  

RT Cave Facebook Page
RT Cave on Twitter
Print Friendly and PDF

Friday, October 24, 2014

Myth Buster: FiO2 less than 60% is safe

One of the myths of respiratory therapy is if we get the FiO2 down to 60% we are safe.  In fact, most of us were taught in school that an FiO2 greater than 60% produced more side effects than an FiO2 less than 60%.

This apparently is a myth, and the following is the evidence:
  1. Register et al conducted a study with subjects under going open heart surgery, all of whom were breathing room air preoperatively  It was found that in subjects administered FiO2s of 0.50 postoperatively had a greater degree of hypoxemia on room air on postoperative day 2 than those given sufficient oygen to maintain SpO2 (greater than) 90%.  After repeating the study using only room air intra- and post-operatively, and finding that most subjects did not have a decrease in blood oxygen levels, as compared to preoperative values, it was postulated that the hypoxemia experienced in the first study was due to the use of oxygen during and after surgery.
  1. Garner et al exposed rats with peritonitis to FiO2 of 0.80, 0.4, or 0.21. Mortality was lowest in the FiO2 O.21 group, and highest in the Fio2 0.80 group.  Upon postmortem examination it was found that lung pathology did not differ between the groups but there was substantial liver damage with FiO2 (greater than) 0.21.  It was postulated that free radical formation caused the liver damage. 
This is yet another example that oxygen should not be administered unless necessary, and that every effort should be made to reduce oxygen as soon as possible.  Thankfully, most hospital oxygen protocols call for maintaining an SpO2 of somewhere in the range of 88-94%.  

  1. Blakeman, Thomas C., "Evidence for Oxygen in the Hospitalized Patient: Is more Really the Enemy of Good," Respiratory Care, October, 2013, volume 58, number 10, pages 1679-1693
RT Cave Facebook Page
RT Cave on Twitter
Print Friendly and PDF

Wednesday, October 22, 2014

Here's how NIV benefits CO2-retaining COPD patients

I often tell my patients that nothing I do cures any ailment.  To the contrary, I tell them that the procedures I perform treat acute symptoms, while the doctor and nurse do other things that will provide the cure.

A perfect example of this is with noninvasive ventilation (NIV) for treatment of acute respiratory distress due to chronic obstructive pulmonary disease (COPD). Savi et al, 2014, notes the following:
Noninvasive ventilation benefits patients with COPD, and it seems reasonable to expect that NIV would increase tidal volume and improve CO2 elimination, and thus reduce respiratory drive.
The note the studies have proven that NIV results in the following when used on COPD patient's presenting to the emergency room with flare-ups:
  • Reduction of treatment failure
  • Lower mortality
  • Fewer complications
  • Lower Intubation rates
However, the studies also conclude that:  "In these patients CO2 elimination is increased but overall ventilation-perfusion mismatch is not changed during NIV. 

What does improve ventilation, the authors note, are the following:
  • Treating precipitating factors (eg, infection with antibiotics)
  • Increase expiratory flow (eg, with beta agonists)
  • Reduce pulmonary inflammation (eg, with corticosteroids)
  • Manage gas exchange (eg, improve oxygenation)
Without NIV, studies have shown, patient's who have COPD with CO2 retainers should receive an FiO2 just enough to maintain an SpO2 of 88-92%, as higher FiO2s (either due to the loss of hypoxic drive, or V/Q mismatching) have been shown to cause a rise in PaCO2.  

However, this effect is negated with NIV.  Savi et al concludes:
During NIV with an FiO2 sufficient to maintain a normal PaO2, a further increase in FiO2 does not result in an increase in PaCO2 in CO2-rataining COPD patients, since no changes occur in (minute ventilation).
Crossley et al had similar results, concluding, that "CO2-retaining COPD patients following a period of mechanical ventilation with PaO2 in the normal range can safely receive supplemental oxygen without retaining CO2 or a depression of respiratory drive.  A new ventilation-perfusion relationship is established during ventilation to normoxia, and it is not altered by further increasing FiO2," Savi et all reports.

Since NIV helps COPD patients take deeper breaths, thus improving their ventilation (allowing them to blow off CO2), high levels of oxygen do not cause rising PaCO2 levels while a patient is receiving NIV therapy.  However, we often find that, while using NIV, many patients require less oxygen compared to prior to the NIV start.

Bottom line:  NIV is beneficial to CO2-retaining COPD patients because it increases their tidal volume, increases CO2 elimination, and reduces their drive to breathe.  By treating these symptoms, caregivers are provided an opportunity to do whatever is necessary to treat the cause of the exacerbation (even if that means utilizing higher oxygen levels).

  1. Savi, Augusto, Jucara Gasparetto Maccari, Tulio Frederico Tonietto, Ana Carolina Pecanha Antonio, Roselaine Pinheiro de Oliveira, Marcelo de Mello Rieder, Evelyn Cristina Zignani, Emerson Boschi da Silva, and Cassiano Teixeira, "Influence of FiO2 on PaCO2 During Noninvasive Ventilation in Patients With COPD," Respiratory Care, March, 2014, volume 59, number 3, pages 383-387

Tuesday, October 21, 2014

Respiratory Therapy Formulas and Normal Values

The following are the most common respiratory therapy formulas and normal values used by respiratory therapists.

1. Ideal Body Weight (IBW):
  • a. Female: 100 lb for 1st 5ft + 5lbs ea additional inch
  • b. Male: 106 lb for 1st 5 ft + 6lbs ea additional inch
2. Static Compliance: (VT/Static pressure – PEEP)
  • a. Normal = 60-100
  • b. less than 60 = lungs becoming less compliant
  • c. greater than 25 is acceptable
  • d. less than 25 is unacceptable
3. Desired FiO2 = Desired PaO2 + Known FiO2 divided by known PaO2
(Normal PaO2 on 21% or room air = 105)
4. Desired Ve= Known Ve*Known PaCO2 divided by desired PaCO2
5. Desired Vt = (Known PaCO2 x Known Vt)/Desired PaCO2
6. Desired f = (Known PaCO2 x Known f)/Desired PaCO2
7. RAW: PIP–Plateau/ Flow, or PIP–plateau
8. French size sx catheter = ETT size * 3/2
9. PAO2: (713 *Fio2 – PaCO2)/0.8or 0.1 if 100% O2
10. A-a gradient (ratio or A-ADO2): PAO2 – PaO2
  • a. Normal on RA = 10-40 or on 100% = 25 – 70
  • b. Increased 66-300 = acute lung injury
  • c. greater than 300 = severe shunting, ARDS (unacceptable)
11. To determine cause of hypoxia, refer to the A-a gradient:
  • a. If normal, hypoxia caused by hypoventilation,consider drug overdose, neuromuscular disorder.
  • b. If abnormal & SpO2 improves with increased FiO2. Consider PE, pneumothorax, asthma,emphysema, pneumonia, bronchitis, heartfailure, congenital heart disease, aging.
  • c. If abnormal & refractory hypoxemia occurs, hypoxia caused by shunting problem considerpneumonia, atelectasis, pulmonary edema or ARDS.
12. Shunt % = A-a gradient/20
  • normal=20%
  • if greater than 20 an increase in PEEP is indicated
13. a-A ratio: PaO2/PAO2
  • a. Normal = 80% (74% elderly)
  • b. 60% = V/Q imbalance
  • c. 15% = shunting
14. P/F Ratio: PaO2/FiO2
  • a. Normal = 300 – 500
  • b. Acute lung injury = 200 – 300
  • c. less than 200 = ARDS (shunt)
15. Expected PaO2 = FiO2 x5

Even though normal PaO2 is 105 on room air, a PaO2 of 200 on 100% FiO2 is not necessarily good. It should be 500. Therefore you know patient still not oxygenating effectively.
16. e-cylinder time remaining=0.30(PSI) / LPM
17. Oral intubation = 21-25cm @ lip.
18. Nasal intubation = 26-29cm
19. PEEP therapy = greater than 6-8 CWP
20. Humidity should be set at 37 degrees Celcius.
21.  Suction:Adult=100-120,Child=80-100,Infant=60-80
22.  Patient WOB (available on newer microprocessor ventilators)
  • a. Less than 0.8 = normal
  • b. Measures effectiveness of rise time and sensitivity.
  • c. Measured in spontaneous mode.
23.  Actual PaO2/ Expected PaO2 = % of patient expected PaO2:
  • a. Should be recorded daily
  • b. Shows if patient is oxygenating better
  • c. Better indicator than simply looking at actual PaO2 and FiO2
  • d. Normal = zero (patient requiring no supplememtal oxygen)
Examples of % expected PaO2: (Despite lower PaO2, patient still oxygenating better)
  • e. January 1 PaO2 40 on 100% FiO2 = 80%
  • f. January 5 PaO2 60 on 40% FiO2 = 30%
  • g. January 6 PaO2 55 on 50% FiO2 = 20%
Another example of % expected PaO2 (PaO2 looks good, but is patient really oxygenating?)
  • h. January 1 PaO2 200 on 100% FiO2 = 40%
  • i. January 5 PaO2 100 on 100% = 20%
  • j. January 6 PaO2 100 on 90% = 22%
24.  Temperature Conversion:
  • Celcus = Fahrenheit minus 32/ 9      
  • Fahrenheit = (Celcus*9)/32

RT Cave Facebook Page
RT Cave on Twitter
Print Friendly and PDF

Monday, October 20, 2014

Happy Respiratory Care Week

October 20-26 is Respiratory Care Week.  The theme this year is "Bringing Breath To Life."

Some say the best way to celebrate the event is to host activities in honor of respiratory therapists, or to educate people by making awareness of lung diseases like COPD and asthma to the community.

I, however, am of the belief the best way to celebrate it is to get free things, and it doesn't matter whether its in the form of knowledge or material items.

Happy Respiratory Care Week.

RT Cave Facebook Page
RT Cave on Twitter
Print Friendly and PDF

Sunday, October 19, 2014

4000-539 B.C.: First civilizations advance medicine, part 3

Inanna on the Ishtar Vase
(French museum Louvre)
She was the goddess of love,
war, fertility and lust,
and was associated
with the City of Urek.
(From  Wikepedia)
Everything in ancient Sumeria, Akkadia and Babylonia was created by the gods, even the people.  They were created from the mud of the land, mud that was brought in by the flow of the river, and spread over the land during the floods or inundations.

While the floods were feared, they were needed, because the mud contained the fertilizers necessary to fertilize the land so crops could be grown.  The mud was also fertilizer to mankind, and from this mud grew civilization.  The people were created by the gods with the implicit purpose to perform labor for the gods, and serve the gods. 

Even the king was a servant of the gods. Part of the king's responsibilities was to maintain order among the people, yet his job also was to perform celebrations to the gods.  One such celebration involved the king climbing to a room at the top of the Ziggurat "in which the fertility goddess Inanna lived. The king was married symbolically to a priestess representing the goddess.  Inanna would then see that the king's city prospered." (Foster, page 46)

The king's other job was to make sure each person did his part.  All food and all profits were taken to the temples and belonged to the gods, and in return each person was given whatever food he needed to feed his family.  The people worked hard from sun up to sun down, and in return for all the hard work the people were offered a promise by the god they worshiped of protection.  They made sure the sun rose to begin the day, and the moon came up at night.  They made sure the crops came up, and that the floods or disease did not take them away before they were harvested.  They made sure ideas were created to allow for better methods of taming the land and animals and people. They made sure the year began as expected, and that the floods came to fertilize the land before crops were planted.  He or she kept the people healthy, and gave them new life in the form of healthy children.  
Early chariots on the Standard of Ur, ca. 2600 BC. (from Wikepedia)

So long as the god was fed, clothed, housed, worshiped, and celebrated appropriately, they offered such protection.  When bad things happened, it was because the person, or the society, did something to offend one or another of the gods.  So belief in these gods provided an incentive for the people to be good, and to do what they were told by the ruling classes. This system allowed for the best use of resources.  

With better use of resources, and because crops were so well controlled, some people had time to specialize in things other than producing and preparing food. For this reason, people started to specialize.  Some people became basket weavers, others became potters, some became priests, some became scribes, some became physicians, some became merchants, some became traders.  (Foster, page 43) 

And chances are that whatever family you were born into, you performed the same job as your father or mother; there was very little chance for advancement in society, or change.  The people must have, at times, become overwhelmed by feelings of burnout, apathy and inanition from performing very hard work, and working long hours, usually from sun up to sun down.  

This must have made life very gloomy for the Sumerians.  Their open borders must have made them fear invasion from the north, south, east and west.  They also feared invasion from spirits and demons from the air around them, spirits and demons that were ubiquitous, peering among the trees, the clouds, and even from under the beds in homes, and in the back of dark closets (kind of like what appears in kids' rooms to this day).  They also had to fear the floods, and locusts and other bugs that could destroy crops and kill animals needed to feed themselves and their families.  They also had to fear plagues that killed many of their friends and family, and the fact that eight out of ten infants either died in birth or in the first year of life didn't help matters either.

So they had a very gloomy view of life, and they also had a gloomy view of death. Many of their legends suggest they believed in hell after death, and so they learned to worship their gods for the day, year and life in general to continue.  Perhaps the only solace among these people was worshiping the god, and "hope" that life would continue.  Yet at some point this view of gloom or nothingness after death failed to motivate the people, who took little pride in their lives as a result.  So at some point one member of the ruling classes created a legend of glory and riches after death. This type of mythology must have provided a better incentive to get the people to behave in this life to prosper in the next.

Since all the work was done by the peasants, which were most of the people, some people had time to sit around and think.  One of the first problems they had to think about was how to keep track of crops.  They needed to measure land, and they needed to keep track of who brought in food and who didn't.  They needed to keep track of all sorts of such official records, and they had no means to do it.  This problem was resolved when they invented the cuneiform (wedge-shaped)  system of writing sometime around 3200 B.C., and many believe this was the final requirement for the creation of the world's first civilization.

The first form of writing was picturesque, where the picture represented an idea. Yet eventually the writing was created where small wedge shaped pictures, pictograms, were drawn into onto clay with stylus, perhaps a small reed.  The characters were adapted by the Sumerians, Akkadian (Babylonians), and the Persian, according to

The words were read from right to left.  Yet sometime around 2000 B.C. a group of people called the Phoenicians developed a society at the eastern end of the Mediterranean (what is now Syria, Lebanon and Israel).  They were famous for their ports, such as in Tyre, where other nations sent ships to trade goods and services.  They were also seafarers, and built great ships for traveling the seas looking for people to trade with.

Phoenicians originally lived in the land of Canaan and were called Canaanites, although the ancient Greeks referred to them by a red (phoinos) die they exported, and this is how they obtained the name Phoenicians.  (Kingfisher, page 90-91)

The Phoenicians are believed by many to be the first to create a written language, even before the Sumerians, and even before the Egyptians. (need reference). Although some speculate they adapted their alphabet from Semitic speaking people in Egypt.  Either way, their language used symbols to represent sounds, was read left to right, and consisted of 30 letters (all consonants). (Kingfisher, page 90-91)

Because they were traders, and came into contact with many other nations, they were able to share their culture, including their language.  Perhaps it's for this reason they are often referred to as the inventors of the alphabet and phonics (use of sounds to create speech and words). During the ancient Babylonian civilization the Phoenician language was adapted into Mesopotamian culture.

The invention of writing is key to our history of asthma and respiratory therapy, because without it there is no way that medical recipes could have been written down and shared from one generation to the next. It made it so that each generation didn't have to start from scratch, and knowledge could be learned and expanded upon.  The accumulation of such knowledge is what has allowed modern asthma experts -- the scientists, researchers, and physicians -- to advance asthma wisdom to where it is today (and it's pretty impressive as far as I'm concerned). Yet it would take a while for this form of writing to be adapted by the main civiliations.

In the meantime, cuneiform was the main form of writing among most of the people of Mesopotamia.  Cuneiform was learned by scribes, who used a stylus, and carved these pictures onto clay tablets that were then heated and sun dried or dried in ovens, and were portable.  This made it possible to record events, such as when the floods occurred, when the sun rose and set. This made it possible to create the first books and the first calendars. This made it possible to monitor the level of the waters.  This made it possible to track the planets and stars, and write down recipes of food and medicine, and myths and legends and  religion.  It made it possible for ideas to grow and mature, and, thus, it made it possible for civilization to begin.

This made it possible to write books, with each stone tablet representing one page.  Each page was marked by the symbol of the god, and this was probably done so the god would protect it and bless the person who used the information inside.  This was essential, because priest/physicians needed the help of the gods in curing their patients.  And each tablet had the last word of the last tablet so the reader knew what sequence to read them, and which tablets went together. (Sigerist, page 383)

So the various tribes of Mesopotamia blended their cultures together in forming the civilization of Sumeria and allowing it to grow and prosper.  For example, the Phoenicians are often credited as being the first to make glass, and they introduced glass making to the Sumerians.  (Hooper, The Chaldeans are often credited as being the first sky gazers, and they introduced divination and medicine to the Sumerians.  As Sumerian civilization died out, Sumerian culture was adapted by the Babylonians, Assyrians, and Persians.  

It's also believed that Thales, the first Greek philosopher who lived around 50 B.C., was a Phoenician.  As he traveled Mesopotamia, and later introduced his philosophy to Greece, he must have spread both Phoenician, Sumerian, Babylonian, Assyrian, and Persian culture to Greece. Among the wisdom he would have taught the Greeks was of Mesopotamian medicine.  (Hooper,

References:  See post "2000 B.C.:  Assyrian physicians will treat your dyspnea"

Saturday, October 18, 2014

4000-539 B.C.: First civilizations advance medicine, part 2

So with Urek as the capital of Sumeria, its god, the god of the sky, became the chief among all the gods.  He was Lord of the Heavens, Lord of the Constellations, Lord of the spirits and demons. The great legends and myths of Urek became known to all the people of Sumeria.  They all learned of legends and myths such as how the gods created the world from mud, and how a mighty king of Urek by the name of Galgamesh set off on a great adventure with his friend Enkidu to defeat the monsters and demons that were wreaking havoc on the world.  After the gods killed Enkidu, a saddened Galgamesh set off on a quest to find eternal life.

Galgamesh met a man named Utnapishtim who was granted eternal life by the gods after he survived the Deluge with one of all the animals (a story similar to that of Noah).  Utnapishtim told Galgamesh about a magic herb that would grand eternal life that was at the bottom of the sea.  Galgamesh found the magic herb, but it was stolen by a serpent, who then developed the ability of renewed life by shedding it's skin.

Still, there would have been ongoing disagreements among the rules of the other city-states, and at various times one or another of these city-states ruled over Sumeria, with its god moving to the head of the hierarchy of Sumerian gods.  It's legends were learned by the people.  Yet even as this happened, the legends and gods of the previous ruling city-states continued to be worshiped.

In either case, Sumeria started out as a democracy and ended as a monarchy. One person made himself king, ruler of all Sumeria, and he chose his successor when he died (which probably was his son in most cases).  (Foster, page 46) 

An assembly of elders and warriors of the monarchy were required by the gods to make sure all the people did the work of the gods, and so members of the monarchy had time to sit around and think.  They also had time to collect things other than simply food and things that were essential to life.  They learned they could obtain more "things" by taxing the slaves of the gods, who were more than willing to offer the goods they produced because they believed in the myths created by the kings and the king's people.  

Through taxes the kings collected items of pottery and gold.  They collected wood carvings.  They collected an abundance of food.  They made the god's slaves build for them some of the most impressive structures of all the land, and the people did this because they thought they were doing the work of the gods.  So in this way, Sumerians were among the first to amass a collection of material items, many of which have been discovered by archeologists.  The Sumerians and Babylonians worshiped these items as opposed to the gods, and perhaps it was in this way the Biblical story of the Tower of Babel unfolded

The writers of the Hebrew Bible made bold predictions regarding the Babylonians, and to the plight of archaeologists and historians, the boldest of these predictions came true.  As noted by Plinio Prioreschi in is 1998 history of medicne:
"The Mesopotamian civilization differed greatly from its contemporary and neignboring Egyptian civilization.  It has been pointed out that whereas the latter was characterized by confidence in the powers of man and by a frontier spirit full of youthful self-reliant arrogance, the 'mood' of the Mesopotamian civilization is well expressed in a quotation from the Galgamesh Epic: 'mere man -- his days are numbered; whatever he may do, he is but wind.' As if to express the same difference, the Egyptian pyramids still stand to proclaim the power of man, whereas the prophecy of Jeremiah (51:37) that 'Babylon shall become heaps' has come to pass, as all that was built in Mesopotamia has crumbled to dust."(Prioreschi, pages 427-8)
So the melancholy nature of the people of Mesopotamia was well known, and this may have played a role in their ruthless nature.  And perhaps this was the reason the various Sumerian city-states created laws,  or codes, that people were required to follow.  Many of these rules were very strict, such as an eye for an eye, a tooth for a tooth, and a hand for a hand.  It was all an experiment, you must understand, because they had no examples to learn from.  This was completely unlike the members of the Constitutional Convention when they got together in Philadelphia around 4,700 years later, who had many examples to learn from as they were creating the U.S. Constitution. The problems faced by the Sumerians had never been faced before, and the solutions were the first solutions.
Sumerians, Babylonians, and Assyrians created armies and armed them with
knives, swords, spears, and arrows.  This was necessary both to control the
people amid society, but also to protect themselves from enemy nations and,
of course, to fight wars.  (Weaponsandwarfarecom)

Another problem was motivating people to do the work, and to fight wars.  Perhaps the first democracies didn't work because, left alone, people weren't willing to make the sacrifices necessary for the collective. Or perhaps these weren't true democracies, and they weren't formed correctly.  Perhaps a ruler was only chosen during times of strife, and between strife people and city-states were left to do as they pleased, and this was part of the problem, or why problems ensued.

Of course, the founding fathers learned all those years later that democracies never work, because they require every person to stay up on politics, and Lord knows people don't do this.  With most people refusing to vote, or not understanding the need to, or not being interested, one person in power almost always becomes the divine ruler.  This is what happened in ancient Rome, and in ancient Greece, and many times, over and over, throughout history.  Yet the people around Mesopotamia did not know this as they were creating the first governments.

So, perhaps due to the failures of democracies, for whatever reason, monarchies were established.  Perhaps the most powerful king of one of the city-states stood up to the challenge and was accepted as king of the civilization.  It became his job to motivate the people to do the work of the gods, as, after all, they were created by the gods to be servants for those gods.  At least that's what the people were told.  This was the best way, perhaps, for the ruling parties to obtain and maintain order.  This was the best way to make progress.

Picture of Ziggurat in the public domain.
Yet even the king himself was a servant to his god, and this god lived in a temple. Such temples were impressive structures that were built on hills or mounds.  Some of these city-states may have been built around such mounds, although some of the mounds may have been created by human labor. The mighty temples upon them were called Ziggurats. 

Public buildings were built around these temples, and among these buildings were palaces for the ruling class, homes for the priests and even schools and libraries. Wrapped around these mounds were homes made of mud brick and reed sticks that were "closely packed together along narrow, winding streets." (Kingfiisher) 

Surrounding these were many fields where crops were grown (mostly grain) and tamed animals roamed.  Surrounding these were nearby towns, much like today's cities have suburbs. (Foster, 38-39)
The Tower of Babel by Pieter Bruegel the Elder (1563)(from Wikepedia)

The purpose of the Ziggurat was to provide a home for the god or goddess of the city-state to live. These temples were impressive structures, and originally they were made of mud-brick, the same as the individual homes.  When there were floods sometimes the mud would wash away, and the people would  band together to rebuild the temples.  When they did this they made the temples bigger and larger than before, and far more impressive  As greater knowledge and material was obtained, these temples were made of rock, material that did not wash away by the floods.  Many of these structures, although warn by centuries of the rain and sun beating upon them, are still available for modern people to enjoy. Some speculate that the temple built by the people in the city-state of Babylon was the Tower of Babel referred to in the Bible. (Foster, page 39)

To be continued...

References:  See post "2000 B.C.:  Assyrian physicians will treat your dyspnea"
RT Cave Facebook Page
RT Cave on Twitter
Print Friendly and PDF