Waveform Capnography Part 2

So we have covered the physiology of respiration, now we are going to cover the waveforms and what each part means.

We know that capnography is the measurement of exhaled CO2, so how does the monitor interpret the action of cellular respiration and ventilation into something we can use?

The capnography probe on many popular monitors used in EMS and transport services works by one of two principles, but how they measure the sample is basically the same. They both use infrared measuring of the exhaled gas and measure the absorption of the light by the gas molecules. This is called molecular coorelation spectroscopy. I’m going to expect you to understand it, I’m not even sure I understand it totally. So, on to how it measures a sample.

One method is “in line” capnography, meaning that the probe is attached directly onto the source and measured there. If you have ever seen a funny looking clip with a red light on an ET tube that leads back to the monitor, you’ve seen in line capnography. Many flight services like this because it supposedly gives a more accurate reading because it’s measuring at the source. Also it is less likely to be contaminated and is reusable because it is not in the way of being contaminated.

The other is “side stream” capnography. the probe is placed directly into the path of air travel and a small pump inside the monitor draws a sample in to the infrared sensor. This is a pretty popular monitoring method for EMS, and even now in hospital settings because the sampling devices are cheap and disposable, where as the in line devices are extremely expensive. I had a capnography probe interlinked with my pain pump during my last surgery to monitor for respiratory depression in case I accidentally overdosed myself.

So anyway, now that we know basically how the CO2 is measured and how it gets into the monitor, we need to talk about how it is displayed, and what each part of the displayed waveform means. The waveform has 4 phases, and once you understand these phases you will understand how to quickly interpret, diagnose, and treat respiratory emergencies.

Phase 0

Phase 0 is inspiration. This is where the amount of CO2 being inhaled is at 0 mmHg, which means that none is being exhaled. This is the sudden sharp drop and flat line of the waveform. Anatomical dead space is created here, where air inhaled does not come into contact with the alveoli for gas exchange. This includes gas in the mouth and trachea, anywhere but in the alveoli. The baroreceptors in the chest signal the brain that they are reaching their limit and inspiration ceases.

Phase I

This is where the expiration occurs. The pressure of exhaled CO2 rises as the respiration cycle continues as the pressure in the chest begins to drop.

Phase II

This is where the pressure of exhaled CO2 plateaus and begins to level off as expiration reaches the end of it’s cycle. The baroceptors in the chest signal the brain to stop exhalation and

Phase III

Phase III is where the CO2 level peaks and the brain’s baroceptors in the chest as well as the chemoreceptors in the brain signal that the oxygen concentration is low and to begin another inspiration cycle.

The computer in the monitor displays this in a waveform:

Next time we will talk about normal pressure ranges and the appearance of the waveform in different respiratory conditions as well as it’s usefulness in CPR.

Waveform Capnography Part 1

It’s been a long time since I’ve posted anything instructional, and looking at the sheer size of the topic I decided to separate this into multiple posts just to over it all. This post will cover the basics of waveform capnography as well as some anatomy and respiratory physiology that is important to understand as you begin to interpret waveforms.

So what is capnography?

Simply, capnography is a measurement of exhaled CO2. We already did this previously with colorimetric CO2, however, unlike colorimetric monitoring, capnography is not affected by alcoholic beverages or other carbon dioxide producing agents that are exhaled. Also capnography does not take “a few breaths” in order to display a change in the measurement, the change is instant when being viewed on the monitor.

You should also keep in mind that capnography and oxygen saturation are two different measurements. spO2 measures “how much” oxygen is attached to the available hemoglobin. As you also know, spO2 is easily fooled by carbon monoxide as it bind with hemoglobin. The spO2 sensor will detect carboxyhemoglobin and only see that something is bound to the hemoglobin and give a false reading. For an in depth video on hemoglobin, check out this video

Capnography will also be an accurate indicator of perfusion and the effectiveness of your or their respiration or ventilation at the cellular level. This is due to several physiological processes that occur with respiration. It is important to know because it is vital to understanding exactly how capnography works, and diagnosing and treating respiratory problems and illnesses more effectively.

The first thing to understand about cellular respiration is that it takes several different actions working as one. It takes oxygen from the lungs, glucose from the liver, and in the body cells it takes insulin produced by the pancreas. Insulin acts as a transporter, carrying glucose into the cells from the bloodstream. Brain cells are the only cells in the body that use glucose directly from the bloodstream without needing insulin. This is because insulin can not cross the blood/brain barrier, which is why when the glucose level in the bloodstream drops confusion and neurological disruptions result until the glucose level is restored.

When you breathe in, oxygen and carbon dioxide exchange places at the capillary beds in the alveoli. The outgoing CO2 is waste product from the cells, which means that cellular metabolism is taking place. The membrane barrier in the alveoli is in fact so thin that it allows oxygen and carbon dioxide to diffuse at the molecular level using a pressure gradient. The oxygen is then picked up by the hemoglobin forming and carried to the cells. When it reaches a capillary, the barrier thins again allowing molecular exchange using the same pressure gradient. When measuring blood gases, there are several different terms used to express this function, PaCO2and PetCO2 are the most important.

PaCO2 is the partial pressure of CO2 in arterial blood. This number should be small and the PaCO2 actually serves many functions. Your brain regulates your breathing rate and blood pH by monitoring this. If the pH of your blood stream increases, this number will increase, which increases your respiratory rate and depth in an attempt to “blow off” the additional acid. You see this in active DKA patients, as it is a very early sign of acidosis.

PetCO2 is the partial pressure of CO2 at the end of expiration. This measures the concentration of the carbon dioxide in the alveoli as they empty. This is an important indicator of many different metabolic functions. The main ones we are interested in is cardiac output and and adequacy of ventilation. If cardiac output is low or ventilation is inadequate, the measurement will be low because carbon dioxide is not being exchanged at an adequate rate.

That’s enough physiology for now. In Part II we will begin covering the waveform, it’s parts, and how it relates to the physiology of respiration.

Sources

Kodali, Bhavani-Shankar. (June 2010). Capnography In Emergency Medicine – 1911. In Capnography. Retrieved from http://www.Capnography.com.

I’m Looking…

I’ve been having a hard time finding much to be happy about these days. Maybe it’s a sign of the times. Maybe satisfaction is relative, considering other times and similar situations where you weren’t satisfied you can achieve a level of satisfaction by comparing how you felt in other experiences. If I were to use that as my starting point, I’d say I’m not satisfied. It seems the cancer took more out of me than I had originally thought.

I’m not finding the things that once kept my interest, well, holding my interest. I find myself digging deeper into hobbies. I went from just playing airsoft to building my own guns, and by building I mean stripping it all the way down, polishing, rewiring, and repairing. I spend hours in the garage with my soldering iron and my screwdriver. I fix toys for fun, then sell those toys to buy other toys, and fix them. It’s a vicious (and expensive) cycle.

My work, however, doesn’t seem all that interesting. Turns out there is no one happy there either, so that only adds to my displeasure. The tank of compassion that I draw from to get through my day has run dry, probably drained in the cancer fight. I find myself far less tolerant of early morning calls for mundane complaints that everyone else just waits to see a doctor. I usually refill it by spending time with people that are as passionate as I am but seeing as how money is tight, I’m not going anywhere for a little bit.

All I really want it some security and some peace. News recently is that the city plans to annex the area that I live in, even though money is tight and services that are already stretched to their limits will be stretched even further. This does not bode well in my mind because it’s me they’re talking about me and my property and my family. The city does not have a good track record. Without the security and stability, there is no peace. I’m restless.

Is this what being burnt out feels like, or is this just part of the human condition?

Why It’s Important To Be Nice

I was scrolling Facebook and came across an article about an ambulance service in Maine leaving a widow on the side of the road while they were transporting her husband, who was in cardiac arrest. You can find the article here.

From what I can gather from the article, the family was from Nova Scotia and were skiing in Maine when her husband smashed into a tree. The ski patrol rapidly moved the husband (the patient) off the mountain and to a clinic, where the facility called for an ambulance while they attempted to stabilize him. According to the article, the ski clinic did not perform any assessment, and according to the patient’s wife, neither did the paramedics. She insisted that they listen to his chest, start an IV, and take his blood pressure while they were packing him for transport and splinting his elbow. She says that they spent 30 minutes performing these actions.

Beyond poor care, the widow’s other complaint is that she was told to sit up front. Which if there is a lot of activity in the back, I could understand because  I don’t want potentially hysterical or intrusive family members in the back while I’m working something critical. To add insult to injury, she was let out of the ambulance and subsequently left on the side of the road. I don’t know the reasoning behind this, maybe she got hysterical or argumentative, I don’t know but there better be a good reason for that.

Clinical assumptions aside (and I did raise my eyebrow a few times), I bet the crew was less than considerate to the family, and perhaps in response to her insistence of being in the middle of things which could have perceived as being in their way. But had the situation been handled with a little more tact, I bet this would barely have generated a complaint at all.

You as a provider have a fiduciary responsibility, that is, having the characteristics of trust. If you display behavior that is not consistent of being worthy of trust, then the patients will not trust you to deliver the best care and certainly not for their family. This is important in all cases, but even more so in cases that involve poor outcomes, because poor outcomes could equal lawsuits even if you delivered stellar care, simply on the assumption that because you acted poorly that you performed equally as poor.

Remember that family members, unless they are physically in your way, often are merely trying to help. If you explain that their help is appreciated but not needed, they would be more than happy to step aside and let you do your job. You should up the level of insistence as they up their belligerence. My lieutenant has pulled many family members aside while we were working and explained that we have a job to do, and handled them with tact even when the outcome was poor. We often hear back about how well we did even though the job was botched or simply didn’t end well.

It’s as much about protecting yourself as it is your reputation. Appear to be trustworthy, and people will trust you despite how bad of a job you did, and will forgive you for your mistakes.

The Death of Joe Paterno

I’ve been watching football for a very long time, in fact, as long as I can remember. My dad was a Penn State man, having spent a good deal of his life in Pennsylvania and in Lewistown, which is only a few miles away from State College. You could say that I am familiar with the school and it’s football history. I even visited the college one time on a trip back from visiting the University of Maryland.

One of the constants in Penn State as I seen was Joe Paterno. The old guy with the thick glasses and almost brooding sense on the sideline. I was reared on the legend that is, was, Joe Paterno.

It cut deep to see him dragged through the mud as if he were the guiltiest of them all when the Sandusky scandal broke in November, and I felt the loss of his termination. It cut even deeper still when they announced he had cancer, having just survived cancer myself I knew what he was experiencing, or was about to experience.

When I heard of his death at 9:35 am EST, I wasn’t surprised, chemotherapy and radiation are tough mothers to handle, and it even brought me down as strong as I thought I was.

It really pissed me off to see people continuing to beat him, even after his death. It says something about a society that kicks a man when he’s down, and then continues to kick a dead man. I even think about those Marines in Afghanistan. Is there no respect for the dead any more?

Years ago I was in ROTC and I was playing the opposing force on a squad training lane. After I had been “killed,” they were doing systematic searches. One cadet proceeded to berate a dead me and make obscene remarks. It was brought out during the after action review. “I am making a report to your cadre,” a senior cadet told him, “as well as giving you a ‘no go’ for this exercise.” There were other remarks given that are not appropriate for the interwebs, and the point was made. You do not treat dead men, even those of your enemy, with disrespect.

I was even asked where my sense of humor was relating to Paterno’s death. I find nothing funny about it.

Cancer is not funny.

The death of any person is not funny.

Rest in Peace Joe, you’ve done more for more than can be counted.

Health Literacy and Actual Literacy

I was pondering why despite the accessibility of medicaid these days, and the large number of people we pick up that are on it and still in bad shape or go straight to triage, why the access to health care is still not enough.

It comes down to something called health literacy.

I define it as the ability to recognize and comprehend a problem with health, understand it’s level of seriousness, and access the appropriate level of care to meet that need. A lack of health literacy increases the likelihood of minor injuries and illnesses to become major, or problems that are chronic to become chronically acute. It’s one of the many reasons that without an education component, creating access to “free” health care will become a money pit.

But there is even a problem with that, that the new health care law ties reimbursements to visits, and that hospitals will receive less funding per patient if they have recurring visitors. After having several hospital stays myself for major and minor operations and getting educated by nurses and seeing my wife come home and beat her head against a wall after reading charts on patients that have chronic problems managed poorly, I know what the hospitals go through to teach people about their condition. It means that despite their best efforts to educate, some people will still go back to their normal state once they leave the hospital. It will inevitably lead to another hospital visit, and the hospital won’t get the money the deserve because a patient came back to them.

You can’t explain anything about health to anyone if they don’t understand in the first place, hence why to me health literacy is so closely tied to actual literacy. We even have universal access to basic education, and we see what the government has done with that. I’m a product of public education, as is my wife, and probably my son will be as well. It was engrained into us that school was important, so we went. I don’t see that much where I work these days. Basic literacy in inner cities is so poor that health literacy fails as well, and the fire department and the hospitals bear the brunt of it with people that are either not sick enough to justify the ride or so sick from something that could have been prevented.

Want to help health care? My suggestion: teach a kid to read, write, and think critically. Only when people understand their own health will the health of us all improve.

Considerations

I was looking at stats for my fire blog the other day and strange how it still generates traffic even though I haven’t updated it since like July.

I’m still around, and I’ll probably be posting fast and furious over this 4 days off and into next set as I get a slow station to hang out at.

I’ve got a few humorous stories to share.

I’m also considering other options for just about everything, blogging, life, all that.

Not much more else I can say for now, just listen to EMS Garage and First Few Moments.

Old Friends, New Challenges

I was befriended on Facebook by an old girlfriend from high school recently.

Strangely enough, I’m surprised to be seeing anything from her at all. She was kinda the type that was in trouble frequently due to domestic issues. She was kind of a goofy rebel. Which was attractive to me at the time. And she had a baby at 16, not mine of course.

The only sour note was that our relationship ended in a way that was less than desirable. And by less than desirable, I mean she ended up in juvenile detention for 90 days while I went to my senior prom (which she was supposed to attend, with me) stag, and I ended up dancing with her best friend at the time. I think she had a crush on me too, and she was the same type of girl. I met Amanda a few weeks later and got a second chance at a senior prom, but that is another story for another time.

I was attracted to the wrong kind of woman, clearly.

We reconnected briefly after I finished paramedic school, but only briefly. What was once there was no longer there, and at the time the prospect of raising someone else’s children didn’t appeal to me especially when she could have no more.

So what’s the point?

Just a reflection on the past, and how foolish I was in my younger days.

I think of a New Year’s celebration as a time of reflection back through where we have come in the past year, and where we plan to go. I had high hopes for 2011 but ended up getting laid low for a while (see “Cancer” above) which made 2011 probably the worst year I’ve had in recent memory.

I’ve had 2 surgeries, 9 weeks of chemotherapy, which put me off work for about 8 months. 2/3 of the year. Chemo seems all but a nasty memory, and the surgeries left deep scars, but I’m officially in the clear. Old challenges long conquered. The only problem is now I see more people getting sick, two friends recently confided in me that they have cancer or still have cancer, and either the treatment has yet to begin or is still in progress. It’s like 2011 was a year of deep sadness and sickness.

When I was working this year, it seemed like the people we were transporting and treating were sicker and required more of our skill and more of our talent to, at times, even just stabilize. My colleagues and I worked what seemed to be miracles, or we were just extremely lucky. Health care truths have finally caught up with the economy and the ugly truth that the destitute are just sicker seemed more pronounced this year. We looked to government to answer, and as government usually does answered with a flurry of half-measures in health care. The first phases of the Affordable Care Act took place, and despite the coming expansion of Medicare/Medicaid, I have an eerie feeling that it will do no good and may even exacerbate the problem. The truth I realized from all this that you are responsible for yourself and knowing about your health status, and if you don’t know, don’t care, don’t know to care, or don’t care to know, then no new law is going to change anything. We should expect business as usual.

I pray my pessimism  is unfounded.

Hopefully 2012 will be better. I know it will be better.

New Hours for DC – Outside Looking In

I have a couple friends on DCFD.

One very close friend, an acquaintance, and several Facebook friends (which is more like playing “six degrees of separation”)

I first read about the DCFD schedule shake up a few weeks ago, and now it looks like it will actually happen.

I’ve gotta say that the plan looks ok on paper, but I remember back in the day working those kinds of shift rotations and not enjoying it too much. Talking to my wife this morning, her question through the whole things was “ok, when do I get to work?”

I don’t think Chief Ellerbe thought this through. The effect on families with two incomes will be drastic, as spouses that used to be able to work on the off days will no longer be able to if the schedule works out that one stays home while the other works. You may find firefighters working days and nights back to back just to maintain the balance, which would be stressful if you can’t find the trades or swap.

Plus, Ellerbe wants the “cost savings” and lay off 400 people, which more than likely would be made from the bottom of the seniority list working up. Imagine if 400 people disappeared from the roster overnight? The overtime would be horrendous, and it wouldn’t be a short term cost until people could get moved around. People would quickly tire of being worked to death and held over until a replacement could be found (if at all) and just simply call in or quit. so the losses would probably extended BEYOND the original 400, and pretty soon you’d be depleted, and with DCFD’s reputation, hiring would be nearly impossible. It’s a slippery slope.

Decades of poor management and even poorer leadership and common sense have left DCFD a shell of what it’s former self, and that former self and even farther memory. Political hacks given a badge and a shirt and sent in to lead a department that was already in pieces, and hack it to even smaller pieces. Somehow only the people in the business and the people on the streets of DC see something wrong, the politicians fail to understand what will ACTUALLY happen if this goes through.

I know if we lost 400 people in Memphis, in the same way, we would lose pretty all our paramedics except for a handful, who would probably move on to something better. I am going to imagine that DC is in the same boat.

Blogging Doldrums

I’m in that space where I am uninspired by anything, and it’s hard to force to write something. It just doesn’t sound right.

It just seems that there is little going on right now, very little controversy to write about anything. Does it sound bad that I need some controversy to get me going?

I have been very reflective lately though, about things that have transpired and seeing a big pattern or a series of unfortunate (or fortunate) events that have created the situation in which we now reside. After talking to some old sages while working overtime the other day and remembering some old conversations I’ve had with colleagues in the past brought me to a simple question: What if this is really all we have? Are there really no new ideas?

Sure, we have innovators in emergency services out there that supposedly “create” something new, but is it really creation, or is it recycling and renovation?

I read a book over the summer called “On Killing,” it’s a book on the US Army reading list about conditioning soldiers to fire their weapons by creating hyper-realistic situations. They researched the rates of fire and damage patterns from past wars and compared them to the Vietnam war and found that firing rates were faster simply because it was easier, but it was still easily faked. Through the creation of realistic training the Army found it could make units much more effective but creating muscle memory where soldiers will fire their weapons out of instinct.

Several months ago I covered part of a mass casualty exercise put on by Jim Logan and Dr. Joe Holley where they recreated an MCI incident. The training was as close to realistic as it could possibly be made, and it is a smash hit every time it is put on. Personally, I loved it.

It is also proven fact that firefighters, when exposed to live fire in training, and the training fires made as realistic as possible, will respond in those patterns every time out of habit and instinct.

So what am I getting at? It has been well known since the 1970′s that we can produce responses based on realistic training, so we are applying military training techniques to other areas of life. To me, it seems that we’re just renovating and recycling.