End Tidal CO2 Guide 2

NIV FOR COPD: USING END-TIDAL CO2 TO IDENTIFY PATIENTS WHO BENEFIT

By Dave Lyman, Vice President of Respiratory and Sales, VGM & Associates

NIV FOR COPD:

USING END-TIDAL CO2 TO IDENTIFY PATIENTS WHO BENEFIT

By Dave Lyman, Vice President of Respiratory and Sales, VGM & Associates

Approximately5-10% of patients with chronic obstructive pulmonary disease (COPD) are carbon dioxide (CO2) retainers, meaning their lungs aren’t removing enough CO2 from the blood. There are over 1.5 million COPD patients on long-term oxygen therapy at home who have lung diseases serious enough to require supplemental oxygen therapy for the rest of their lives. To wait for these patients to be hospitalized before intervening with a life-improving, life-saving therapy, is both unethical and financially unsound.

Success of NIV in the Treatment of Chronic Ventilatory Failure in Patients With COPD

First, let’s consider how NIV treatment can benefit COPD patients who retain CO2. Ventilatory failure is thought to be the result of respiratory muscle insufficiency1 and alterations in central ventilatory control2. NIV works to:

1. Lower the work of breathing (WOB) of the ventilator muscles, allowing them to rest and begin to address the built-up lactic acidosis within them

a. Expiratory positive airway pressure (EPAP) alveolar recruitment

b. Inspiratory positive airway pressure (IPAP) ventilator support

2. Wash out dead space

3. Lower cardiac work: EPAP reduces preload and afterload on the heart, improving cardiac performance

Providers can help identify and provide equipment to patients who would benefit from NIV treatment, reducing readmissions.

There is more than sufficient support in the clinical literature for the use of noninvasive ventilation (NIV) in patients with chronic ventilatory failure. However, earlier intervention is needed to get the most positive impact possible. The home respiratory care provider is uniquely positioned to drive desirable outcomes. By implementing an end-tidal CO2 (EtCO2) protocol, providers can help identify COPD patients who would benefit from NIV treatment and provide the appropriate equipment to improve the patient’s quality of life and reduce hospital readmissions.

4. Repair sleep architecture/reset chemo receptors in the brain and peripheral nodes

In patients with chronic hypercapnic respiratory failure, long-term non-invasive positive pressure ventilation (NPPV) has been shown to improve important physiological variables such as arterial blood gas (ABGs) and lung hyperinflation3.

Clinical studies show improvements in:

• Exercise capacity and duration

» Six-minute walk distance4

» Exercise related dyspnea5

• Sleep quality6

• Improved quality of life (HRQL)7

• Reduced hospitalizations8

of patients with COPD are CO2 retainers

Now, let’s look at an example of how this presents in patient treatment.

EXAMPLE

A woman with exacerbated COPD presents with severe dyspnea (respiratory rate 40/min) and acute respiratory acidosis. After starting bi-level positive airway pressure (BiPAP), she looks and feels much better [her respiratory rate (RR) decreases to 24/min with good mental status]. Another ABG is taken an hour after staring NIV, but it shows no change.

Some would call this a “BiPAP failure” because the CO2 is unchanged, leading them to intubate her. However, this is actually a BiPAP success, because her dyspnea resolved.

Treat the patient, not the ABG. This concept was proven in a 1995 randomized controlled trial evaluating the use of BiPAP in COPD9. BiPAP improved mortality despite having no effect on ABG parameters after one hour.

While this is an acute scenario, it involves a COPD patient and demonstrates the problem with relying too heavily on ABG data (PaCO2) to determine if the therapy is successful. It is the improvement in lowering the WOB as demonstrated by lowered RR and improved cognition that is essential for success. This will be true for EtCO2 as well. We must advocate for a detailed respiratory assessment when identifying and managing these patients.

Understanding the PaCO2 to EtCO2 Gradient as It Applies to NIV

In healthy patients, EtCO2 measurements are 3-5 mmHg lower than PaCO2. This is due to dead space (no gas exchange) within the respiratory system. The area from the tip of your nose to the 17th generation alveoli (deep in the lung) does not take place in respiration (gas exchange). This anatomic dead space gas has zero CO2 and that is why we don’t measure exhaled CO2 until the end of the breath.

Patients like those with COPD never get to the end of a breath, their alveoli collapse early in exhalation, trapping CO2-laden air within the lung,

not allowing it to be exhaled. Ventilation/perfusion mismatching in the lung further exacerbates this process. This is referred to as physiologic dead space and it changes (progresses) during the disease process. So, we don’t really measure end-tidal but rather mid-tidal CO2.

This leads to PaCO2 to EtCO2 differences of 20 mmHg or more, meaning that EtCO2 does not correlate with PaCO2 in the face of advanced lung disease. Even trending EtCO2 does not give useful data with COPD patients.

The patient doesn’t necessarily need to be a CO2 retainer to benefit from NIV.

To be clear, the patient doesn’t necessarily need to be a CO2 retainer to benefit from NIV, but current literature is very supportive of using CO2 retention as a primary indicator that the patient would benefit from NIV.

The PaCO2 to EtCO2 gap in COPD makes it less than an ideal comparison to PaCO2, so its use in ventilator management is minimal.

So Why Use EtCO2 to Identify and Manage NIV Patients?

Put simply, it is the most accurate technology available to clinicians in the alternate care environment. It also provides the necessary data we need to identify and manage patients with a disease severe enough to warrant the use of NIV to improve and extend the patient’s life.

Furthermore, NIV may be beneficial for COPD patients even before they become or are identified as CO2 retainers. CMS, after all, does not currently require the patient be a CO2 retainer for reimbursement. And doctors already refer COPD patients for NIV at time of hospital discharge to help prevent readmits within 30 days.

Still, home care companies are worried about putting inappropriate patients on therapy and want

to protect themselves in case of an audit. Many home care companies are triaging their COPD O2 patients to see if they are appropriate candidates for NIV. This is why it’s important to understand the best protocol for using EtCO2 to screen for patients who would benefit from NIV. But what is the best way to screen this large population?

EtCO2 Protocol

• ABGs are the gold standard for identifying CO2 retention, but the concept of performing over 1.5 million blood gases for screening purposes is unrealistic as it poses unacceptable risks and costs.

• Transcutaneous CO2 technology is not approved for home care and sensor application and maintenance are still unresolved for this patient population without clinical support.

• EtCO2 technology does not have the sufficient correlation with PaCO2 to be used in ventilator management but is the ideal technology for screening large populations of COPD patients to help identify patients with CO2 retention.

» EtCO2 measurements in patients with CO2 retention have a much larger PaCO2 to EtCO2 gap than healthy patients (3-5 mmHg). So, a COPD patient who has a measured EtCO2 of 45 mmHg will have a PaCO2 that is significantly higher.

» How much higher? Unknown. Once a patient has been identified as a CO2 retainer, he is referred to their attending physician who can now decide whether or not to draw an ABG.

Identify Via Magic Number

In making the decision to place a patient on longterm oxygen therapy (LTOT), physicians use multiple data points to determine if the patient would benefit—pulmonary function tests, cardiac tests, and lots of clinical data points. The same is true for NIV.

LTOT also requires a magic number. The patient’s peripheral capillary oxygen saturation (SpO2) must be 88% or below for five minutes during an overnight study. With that number, reimbursement begins.

Any EtCO2 reading of 45 or higher identifies a patient with CO2 retention.

While CMS does not require CO2 retention as a prerequisite for reimbursement, there is still a magic number—45 mmHg. Normal PaCO2 levels are 35-45 mmHg. EtCO2 reads 2-5 mm lower than PaCO2, so any EtCO2 reading of 45 or higher identifies a patient with CO2 retention. Clinical literature indicates the patients with a PaCO2 of 52 mmHg are the most appropriate patients for NIV.

Since there is sufficient clinical evidence/support for NIV in patients who retain CO2, the home care provider can feel safe by looking only for those CO2 retainers amongst the LTOT populations. This is to prevent placing NIV on everyone and gives them clear justification for reimbursement for appropriate therapy for these patients (i.e., audit protection).

A COPD patient with an EtCO2 of 45 could actually be closer to a PaCO2 of 65 due to their disease process. This isn’t actually an issue, though. We are trying to identify—not quantify—CO2 retainers to be placed on therapy. Remember though, EtCO2 may be significantly lower than PaCO2 in COPD, so using EtCO2 alone as an identifier will always under identify CO2 retainers.

The home care provider will/should assess the patient when they are set up for the overnight test. Like a physician, they will look at RR, heart rate (HR), mucous clearance (cough), and even pulmonary function testing in some providers’ policies and procedures. This provides a more indepth assessment and will help identify patients that EtCO2 alone might miss.

With a CO2 Retainer Identified and Placed on NIV, How Do I Use EtCO2 Data in My Decision Making?

We have already reviewed why EtCO2 will ALWAYS be lower than PaCO2 and EtCO2 does not correlate with PaCO2 for trending in spontaneously breathing patients. As a result, do not use EtCO2 measurements for managing the ventilator settings.

While the goal of therapy should be to reduce PaCO2, remember we are treating a patient, not a parameter.

Manage the patient, not the CO2. While the goal of therapy should be to reduce PaCO2, remember we are treating a patient, not a parameter.

Questions to Consider When Treating a Patient

• Are they getting enough sleep? (Sleep testing)

• Are they using less effort to breathe? (Assess accessory muscle use)

• Has their quality of life improved? (Use validated questionnaires for follow up)

• Has RR returned to baseline or improved?

• Has mucociliary clearance improved?

• Have activities of daily living (ADLs) improved?

If EtCO2 Is a Late Indicator of Impending Failure in Chronic Disease, How Should I Use It?

Respiratory rate and flow patterns change quickly in the face of impending failure and are the best predictors of failure. EtCO2 plays a critical role in both.

How do you get an accurate respiratory rate on a COPD patient?

• EtCO2 and only EtCO2.

How do you get an indication of flow patterns without pulmonary function?

• EtCO2 and only EtCO2. The shape of the EtCO2 waveform is created by the expiratory flow changes in slope are indicative of changes in disease state.

NIV is part of a disease management program—it is not the program.

Remember, NIV is part of a disease management program—it is not the program. Respiratory assessment and management are crucial to success (e.g., medication selection and adherence, nutritional counseling, referral to a pulmonary rehab program, COPD education via app, etc.). Focus on the shark fin as a way to tell if a patient is bronchospastic and needs education on medication use.

Do not forget to get device data from the ventilator. Has RR, VT, MV improved/stabilized? You’ll need to combine device data and patient assessment data to get a better picture of how the therapy is working.

Showing Value

Respiratory providers play a crucial role in patients’ healthcare. As time goes on, payers will increasingly expect respiratory providers to prove they can impact outcomes. Because of their access to patients, providers are uniquely positioned to deliver on that expectation.

ABG isn’t a viable option for screening large populations of COPD patients for potential CO2 retainers. But through EtCO2, providers can make identifications in the patients’ homes and significantly reduce the number of hospital readmissions. This leads to greater potential revenue for the provider and—more importantly—better quality of life for the patient.

Ready to get started? Read on for a list of VGM Respiratory partners and services that can help you get a program started, or reach out to us at respiratory@vgm.com.

FREQUENTLY ASKED QUESTIONS

When is the best time to measure EtCO2?

When the patient is not on the ventilator. We want to see if the therapy has improved the patient’s condition while they are off the ventilator. Focus on RR and pattern for signs of deterioration.

How often should I recommend the physician get an ABG?

This is best done prior to therapy initiation and then annually. Some studies recommend every 90 days, but this is completely up to the prescribing physician.

VGM members have access to discounted pricing from our preferred contract partners and service providers. They create a pathway of patient care—from testing to reimbursement—helping you grow your NIV business and show your value through reduced readmissions.

REFERENCES

1 Begin P, Grassino A, Inspiratory muscle dysfunction and chronic hypercapnia in chronic obstructive pulmonary disease. American Review of Respiratory Disease 1991; 143: 905-912.

2 Gea J, A Rocca, Pathophysiology of muscle dysfunction in COPD. Journal of Applied Physiology 2013;114: 12222-34.

3 Windisch W, Kostic S, Outcome of patients with stable COPD receiving controlled noninvasive positive pressure ventilation aimed at maximal reduction of PaCO2. Chest 2005; 128: 657-62.

4 Funck GC, Breyer MK, Long-term noninvasive ventilation in COPD after acute on chronic respiratory failure. Respiratory Medicine 2011; 105: 427-34.

5 Tsolaki V, Pastaka C, One-year non-invasive ventilation in chronic hypercapnic COPD: effect on quality of life. Respiratory Medicine 208; 102: 904-11.

6 Meecham Jones DJ, Paul EA, Nasal pressure support ventilation plus oxygen compared with oxygen alone in hypercapnic COPD. Am J Resp Critical Care Medicine 1995; 152:538-44.

7 Windisch W, Quality of life in home mechanical ventilation on health-related quality of life. Eur Resp J 2008; 32: 1328-36.

8 Coughlin S, Wei E Retrospective Assessment of Home Ventilation to Reduce Rehospitalization in Chronic Obstructive Pulmonary Disease J Clin Sleep Med 2015;11- 663-70.

9 Brochard, L., Mancebo, J., Wysocki, M., Lofaso, F., Conti, G., Rauss, A. (1995, September 28). Noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease.