High-Flow Nasal Cannula, BiPAP, or Venturi: What Every SLP Must Know Before Recommending PO
Imagine you’re meeting Mrs. Elena Rodriguez for the first time. She’s a vibrant 78-year-old admitted for pneumonia and now managing an exacerbation of her chronic obstructive pulmonary disease (COPD). She's sitting upright in bed, speaking in short, choppy sentences, and is on a high-flow nasal cannula (HFNC) at 55 liters per minute, with an FiO2 of 60%. Elena is hungry and begs for a yogurt, but her respiratory rate is consistently in the low 40s. What would you do in this situation? Don’t worry, you’ll be able to decide with much more confidence by the end of this article…
As SLPs, we know that swallowing and breathing are closely connected. Any changes in one system can impact the other. Knowing this, it’s essential to consider both when assessing and treating our patients. This article addresses a common question: "What does a patient's oxygen support mean for swallowing?" The key lies in understanding how the type and level of respiratory support reflect the patient's underlying physiological stability. Let’s get into it…
How is Oxygen Support Provided, and How Does It Affect Swallowing?
The Basics
FiO2 stands for the fraction of inspired oxygen. It's the concentration of oxygen in the air we breathe. The air around you right now is approximately 21% oxygen. Anything over that is supplemental oxygen used to help a patient suffering from or at risk of hypoxia (a lack of oxygen).
When a patient's FiO2 and flow rate are adjusted, it may mean a change in swallowing function for three main reasons:
The oxygen-delivering device itself may require a mask, blocking the oral cavity from receiving PO.
The device may create high levels of flow and pressure, which may inadvertently force a bolus or residue into the airway.
The patient may be experiencing a decline in respiratory function, disrupting the ability to coordinate breathing and swallowing (Like what we saw with Elena).
Breathing-Swallowing Coordination
Since the pharyngeal swallow shares the upper airway with the respiratory system, breathing and swallowing must harmonize in a high-stakes dance to ensure they don't occur simultaneously. Like a well-practiced waltz, the two typically work together seamlessly, allowing the larynx to remain open when breathing but to close when food or liquid makes its way down the pharynx. This dance may be disrupted in those with respiratory insufficiency requiring oxygen therapy.
A normal resting respiratory rate is approximately 12–18 breaths per minute. A patient suffering from respiratory disease may require 30, 40, or even more breaths per minute to maintain adequate lung volume. What does this mean for swallowing?
A swallow can take up to two seconds from start to finish, especially in older patients with dysphagia.
A respiratory rate of 30 means the lungs require a breath every 2 seconds. Anything over 30 means the lungs will ask for a breath more than every 2 seconds. I know, I know… math. But stick with me here…
If a swallow takes 2.0 seconds and breathing occurs, say, every 1.8 seconds, there is no wiggle room for the swallow before the lungs need to take a breath.
The patient can try to hold their breath for a bit longer, but this will inevitably result in shortness of breath and a worsening respiratory rate. Breathing is the priority. So, eventually, the body will breathe while swallowing or inhale right after the swallow, potentially sucking in the bolus on its way down or the residue after the swallow. This is why examining the patient's respiratory rate before and during meals is essential to understanding how they will be able to tolerate PO and what their risk of aspiration is.
Respiratory Support Levels and Swallowing Considerations
Let’s talk about the devices our respiratory team uses to support our patients now. Here's a simplified breakdown of common devices used to deliver oxygen and air flow to the patient and how they might relate to swallowing. Use this list as a resource to keep you on track when you’re seeing patients in your facility.
Nasal Cannula (NC): Delivers low-flow oxygen. The NC itself typically doesn’t interfere with the swallow. An increase in FiO2 and flow rate may suggest a worsening respiratory status, and titrating down often indicates improved respiratory function. However, we must always consider the whole picture, including alertness, cough strength, PO tolerance, and any signs of respiratory distress during trials.
Non-rebreather and Venturi Mask: These provide higher levels of FiO2, which may interfere with oral intake because they require a mask that goes over the mouth and nose. It's best to discuss the patient's candidacy for a large-bore nasal cannula (which provides more FiO2 vs. a standard NC) or a high-flow nasal cannula (discussed next) with the respiratory team. This eliminates the need for a mask and allows an unobstructed path to the oral cavity for PO intake.
High-Flow Nasal Cannula (HFNC): HFNC provides higher flow rates and FiO2 than NC, non-rebreather, and venturi masks and adds some positive airway pressure, which can’t be achieved with the devices above. FiO2 and flow rate can be adjusted separately depending on the patient’s needs. However, altering airway pressures can increase the risk of aspiration. The more flow, the higher the pressure. Consider an instrumental swallowing evaluation and closely monitoring these patients to ensure meal safety.
Non-invasive Ventilation (NIV): This includes BiPAP and CPAP, which are masks that provide high air pressure levels. Swallowing with NIV is not indicated due to the barrier created by the mask and concerns of pressure buildup in the pharynx.
Mechanical Ventilation: Requires intubation or a tracheostomy tube and offers a variety of modes and settings to adjust ventilatory support based on the patient's needs. Swallowing assessments and interventions after the patient is extubated or while on the vent with a tracheostomy tube are highly individualized and involve monitoring closely with the respiratory team over time.
Is There Such a Thing as Too Much Oxygen?
Like most medical treatments, oxygen therapy has risks and benefits. Two key considerations are CO2 retention and oxygen toxicity.
CO2 Retention: Too much oxygen can lead to a buildup of carbon dioxide in the blood of some patients with chronic lung conditions. Their bodies may rely on low oxygen levels to stimulate breathing. However, this is less of a concern with short-term oxygen use and lower FiO2 levels.
Oxygen Toxicity: High oxygen levels over a long period can damage the lungs. This is usually only a concern in patients requiring high FiO2 for extended durations.
Our sicker patients may be on very high oxygen levels for a short time while their lungs heal. These levels may rise as high as 100% FiO2. While this is concerning, the literature doesn’t provide us with any strict cutoff for when a patient requires NPO status. Keep in mind that patients requiring high levels of oxygen support need to be carefully considered for swallowing, as they are often unstable. A thorough discussion with the interdisciplinary team and the patient is necessary to determine the pros and cons of PO intake and formulate a plan of care.
The Big Picture and the Rest of Elena's Story
It's important to remember that these are just general guidelines. Each patient is unique, and factors like underlying lung disease, neurological status, and overall medical stability play a significant role in helping us determine the best path forward. Always prioritize a holistic approach, considering all aspects of the patient's status and collaborating closely with the respiratory team.
As for Ms. Rodriguez, the best decision was to defer the oral feeding trial. You collaborated with the respiratory team, emphasizing that her high respiratory rate indicated an unstable status as it was way outside of the normal range, and perhaps more importantly, was way above her normal range. Over the next three days, with proper medical management, her respiratory rate trended down to 24, and her HFNC was weaned as well. With a stable, lower respiratory rate, you were confident in her ability to coordinate breathing and swallowing, leading to a FEES and diet advancement. By prioritizing her respiratory stability, you not only ensured her safety but also paved the way for a more successful and lasting return to oral intake.
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