Have you ever been called for respiratory distress to find your COPD patient in respiratory failure, air hungry, and resisting any sort of treatment you throw their way? In my experience, without RSI capabilities, these can be some of the toughest patients to manage. They are super anxious, they don't care about the next 20 minutes, they only care about the next 2 seconds. Eventually their respiratory volumes decline as does their respiratory rate. Simple math would dictate their minute volumes have been substantially reduced and as you transport to the hospital, they go into a stupor and their GCS no longer remains 15. This rapid progression culminating in a now altered mental status needs to be aggressively managed. The effects of CO2 on the central nervous system are complex. We know from trauma lecture that CO2 levels can affect cerebral blood flow (this can be good or bad) think about hyperventilation in TBI and increased ICP -- in that case we are trying to lower CO2 thru hyperventilation to give the brain more room within the cranial vault via cerebral vasoconstriction.
Now back to the scenario -- the patient above is most likely suffering from extreme hypercapnia or CO2 narcosis. The delineating feature of CO2 narcosis is this depressed level of consciousness. In our line of work however, it is essential to be proactive in our approach and recognize earlier signs that our patient may be headed down this path. O2 therapy, beta-2 agonist, steroids, and non-invasive procedures like CPAP can help the patients turn the corner in short order. Some long-standing myths have been debunked as well and are important to mention here. Hypoxic drive isn't a thing -- place the respiratory distress patient on high flow oxygen. CPAP can also be established in some patients with a decreased GCS... give it a shot. It could still prevent an intubation down the road. Don't forget Magnesium is a weapon to be explored in asthma as well. Additionally, while we realize the buildup of CO2 is being driven by the failure of the pulmonary system, we must also appreciate that hypercapnia has multiple end-organ effects contributing to the patient's deterioration/morbidity/mortality. Many etiologies contribute to hypercapnia; chronic obstructive pulmonary disease (COPD) is just one of many.
Keep in mind that even in the absence of lung disease some patients are at higher risk of CO2 retention just because of their native body habitus. The mechanisms are still tied to hypoventilation, but in this case their obesity is a major contributing factor. This may be a new term for you that your EMS program didn't go over and it's called Pickwickian syndrome. It fits inside this blog nicely. It goes without saying that respiratory system mechanics are affected significantly by obesity and fat distribution. Due to reduced pulmonary distensibility, obese patients suffer reduced ventilation in the lower pulmonary lobes. The alveoli close before the expiration, thus producing a characteristic breathing pattern of low tidal volume and an increased respiratory rate, causing an increase in the dead ventilation space. Decreased ventilation of the lower lobes causes alterations in the ventilation-perfusion (V/Q), thus triggering hypoxemia.
Outside of the classic findings of cyanosis, pursed lips, intercostal retractions and increased respiratory effort, on physical exam you may also find a phenomenon called Asterixis, or flapping hand tremor, is a neurological disorder that causes a person to lose motor control of certain parts of their body. It’s most common in the wrist and fingers and it can cause the muscles to abruptly and intermittently become lax, resulting in a “flapping” motion. Asterixis typically looks like irregular and involuntary jerking motions of the hands– hence where the name flapping hand tremors came from. In reality it's not a tremor per se, but actually considered a negative myoclonus.
In closing, the illustration below provides a nice overview of acid base balance -- as it relates to this blog, pay close attention to the respiratory acidosis row - as hypoventilation is a very common cause of CO2 retention. This FREE quick reference chart amongst others can be found on our website to help you prepare for the cognitive exam. Remember the lungs (respiratory) and kidneys (metabolic) are always working in a harmonious fashion to keep us at or near homeostasis. It's all about balance.
August 26, 2024
Author: Joshua Ishmael, MBA, MLS(ASCP)CM, NRP
Pass with PASS, LLC
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