Chelsea Lee, BSN, RNC-NIC: Hey Brad, thanks for joining me today! Dr. Choi’s presentation gave a lot of great insight into some impactful new research. I’m excited that we have the opportunity to dig a bit deeper into the findings and to hear your perspective on how it could affect patient care.

Bradley Sexauer, MBA, RRT-NPS: Absolutely. As a respiratory therapist, Dr. Choi’s presentation really caught my attention, so I’m glad we can sit down and talk a bit more about the findings. The research he shared is important because it can shift the way we treat patients with chronic hypercapnia and really puts a spotlight on how managing CO2 can make a big difference in their outcomes. I’m excited to show fellow RTs how these findings could impact their practice.

CL: To start, Dr. Choi established what seems to be a common belief within respiratory therapy: as long as a patient’s pH is normal, CO2 is not a concern; elevated pCO2 levels are simply thought of as “where these patients live.” Have you come across this mindset in your experience as a respiratory therapist?

BS: Definitely — when Dr. Choi shared this, it really resonated with me. Though my experience was in pediatrics, this belief existed there as well. As long as pH looked good, elevated CO2 levels were often dismissed or considered typical for patients with chronic hypercapnia.

CL: While extensive research exists on acute hypercapnia, there have been relatively few studies on its chronic effects. Dr. Choi co-authored a 2021 study that explored the impact of chronic hypercapnia, revealing startling findings: elevated rates of hospitalizations and mortality among affected patients. What do you make of the data?

BS: So what really struck me about these findings is how only a quarter of hypercapnic patients were prescribed outpatient NIV. It made me wonder if, in many of these cases, outpatient NIV therapy wasn’t considered until invasive ventilation became necessary. Like we discussed, there’s this prevailing notion that elevated CO2 levels are just where these patients live. So, they often don’t receive the attention they need until they’re in the ICU on mechanical ventilation. It’s more reactive than proactive — addressing ventilatory issues only after they’ve become critically ill.

As for mortality, hearing that CO2 was an independent risk factor was surprising, especially considering everything covered by the Charlson comorbidity index score: age, cardiac, neurological, cancer, pulmonary, endocrine history — all of these different factors in the patient’s history were adjusted for, yet chronic hypercapnia still independently increased mortality.

CL: Your point about the reactive nature of the current approach to treating these patients reminds me of another study Dr. Choi shared. In this one, NIV was used to reduce baseline PaCO2 by 20% or below 48 mmHg in COPD patients. The intervention group had a 1-year mortality rate of 12%, compared to 33% in the control group.² Can you talk more about how these findings challenge existing approaches?

BS: Yes, as Dr. Choi mentioned in his presentation, this study stands out as one of the first to highlight the mortality benefits that a long-term NIV strategy can have when used to lower PaCO2 levels. These findings challenge the idea that chronic hypercapnia in COPD patients is a benign finding. Instead, chronic hypercapnia should be considered a marker of disease severity that can be associated with an increase in mortality.

As clinicians, the criteria for NIV support shouldn’t be to wait until the patient requires an ICU admission or mechanical ventilation to finally attempt to address ventilatory issues — a much more proactive approach to addressing chronic hypercapnia needs to be taken. This data shows that this critical shift in practice could significantly enhance patient outcomes — specifically the most important one — their survival.

CL: Later in his presentation, Dr. Choi shared a particularly impactful study he and his colleagues at the University of Michigan conducted. Their findings were pretty dramatic, showing just how effective a targeted CO2 management strategy can be for improving outcomes. What do you make of their research?

BS: Yeah, I’m really impressed by these findings — seeing a jump in 2-year survival from 60% to 90% when pCO2 dropped by over 20% from baseline is pretty remarkable. It really hits home how vital it is to not only start NIV for patients with chronic hypercapnia, but also to closely monitor their pCO2 levels and aim for the greatest possible reduction from where they started.

CL: Any final thoughts on how this research has challenged or shifted your own mindset as a respiratory therapist?

BS: Yes, so with the majority of my experience in the acute care setting, I’ve often viewed NIV therapy as a means to manage acute illnesses rather than a longer term strategy for chronic hypercapnic patients. These studies have definitely shifted my perspective there. If we use NIV as a longer-term tool to maintain reductions in CO2 levels for patients with chronic hypercapnia, it could have the ability to make a significant impact on their survival.

It’s also shifted my mindset when it comes to what we should be looking at when it comes to long-term support. In my own experience, we have typically focused on parameters like oxygen saturation and work of breathing when assessing respiratory support settings for patients requiring long-term NIV or MV. However, we see with these studies; CO2 is another very important piece to the puzzle when it comes to optimizing care for these patients.

The takeaway message for RTs should be the significant value of incorporating CO2 monitoring and management into their practice, and how this can be extremely impactful in supporting better outcomes for this patient population.

CL: I have one more question. Considering the critical need to monitor CO2 levels in chronic hypercapnic patients, how can they be practically measured in an outpatient setting? Can you elaborate on the approach that Dr. Choi and his team use?

BS: Yes, proper CO2 management necessitates ongoing monitoring to ensure that patients are consistently maintaining reductions in levels. And in many cases, PCO2 monitoring is either being done too infrequently or even not at all. It’s one of the reasons these findings are so important.

Dr. Choi and his colleagues use transcutaneous monitoring in their clinic to evaluate their patients’ CO2 in an outpatient setting. Most of these types of settings are not going to have the capabilities to perform a blood gas on site. And, many of these patients have conditions that cause substantial V/Q mismatch, meaning a technology like end-tidal capnography would struggle to accurately represent the patient’s arterial CO2 values. Transcutaneous monitoring on the other hand can provide a more accurate estimate of PaCO2 in these patients, making it a good fit for the outpatient setting

As Dr. Choi mentioned, these values can be used to assess the effectiveness of ventilation strategies over time and fine-tune patients’ NIV settings as needed to achieve and maintain reductions in CO2 levels. And, as we’ve seen in the research presented, this can have a really significant impact for this patient group.

References:

1. Wilson, M.W., Labaki, W.W., Choi, P.J. Mortality and Healthcare Use of Patients with Compensated Hypercapnia. Ann Am Thorac Soc. 2021.

2. Köhnlein T., et al. Non-invasive positive pressure ventilation for the treatment of severe stable chronic obstructive pulmonary disease: a prospective, multicentre, randomised, controlled clinical trial. Lancet Respir Med. 2014.

3. Jimenez, J.V., et al. Lowering PCO2 with Non-Invasive Ventilation is Associated with Improved Survival in Chronic Hypercapnic Respiratory Failure. Respir Care. 2023.