BIG PICTURE Continuous capnography offers a complete analysis of a patient's ventilation, perfusion and metabolism.

Capnography identifies potential respiratory events well before you have the sneaking suspicion that something seems amiss. Without the monitoring modality, critical minutes may pass before you notice the patient is experiencing hypoventilation, airway obstruction or obstructive sleep apnea that could lead to respiratory arrest, cardiac arrest, hypoxic brain injury and even death. Nothing beats the close observation of expert nurses and anesthesia providers, but even your most attentive caregivers would benefit from being backed up by capnography.

Real-time feedback
Continuous capnography is a breath-to-breath measurement of exhaled carbon dioxide at each phase of the respiratory cycle, gathered either through an advanced airway device (intubated) or a nasal cannula-type device (non-intubated). The word continuous is important, because a respiratory depression can occur when you're away from the patient's bedside. Continuous capnography should be seen as a trending tool that provides a complete picture of a patient's ventilation, perfusion and metabolism.

On a capnography monitor, you see a real-time waveform (capnogram) — a normal waveform appears as a square-shaped or rectangular box — and a numeric reading (capnometry) showing the measurement of exhaled CO₂. "Normal" end tidal CO₂ is in the range of 35 to 45 mmHg. If the patient's respiratory rate increases (hyperventilation), the CO₂ waveform becomes smaller than the baseline and more frequent, and the numeric reading falls below the normal range. If respiration decreases (hypoventilation), the waveform becomes taller and less frequent, and the numeric reading rises above the normal range. If the square waveform starts to collapse, there's an airway obstruction. If the square becomes a flat line, the patient is not breathing.

I began my healthcare career when pulse oximetry was considered a wonderful new monitoring tool. It still useful, but it also has its limitations. For example, if you see a troublesome oxygen saturation reading, you may simply choose to increase the oxygen flow without considering the potential causes for the change, such as a medication that might be relaxing the patient's airway. As a result, turning up the oxygen would only mask the true nature of the problem. Also, after a shift in oxygen delivery, several minutes can elapse before a pulse oximeter provides an accurate reading, meaning the patient may already be in distress by the time you know it. With capnography, you find out in real time.

Expanded use
Despite its superior ability to detect medication-induced respiratory events, capnography isn't as ubiquitous as other forms of vital signs monitoring. Why? Cost may be one barrier to adoption, as capnography can require a significant capital investment. But I think improving patient outcomes and the potential for saving lives outweigh budgetary concerns.

In addition, some clinicians may feel confident that monitoring other vital signs — blood pressure, body temperature, heart rate and blood oxygen levels — is sufficient. Others may resist adding another monitoring tool to the mix, because they believe doing so would create additional work without significant payoff. Both assumptions, in my estimation, are inaccurate.

At the end of 2013, our organization started down the road toward making continuous capnography the standard of care for all adult and pediatric patients before, during and after procedural sedation or surgical procedures. We chose this route because continuous capnography is the earliest possible warning system for detecting the onset of opioid-induced respiratory depression (see "Spot the First Signs of Respiratory Compromise").

Ultimately, after trialing continuous capnography in our surgery units, PACU, interventional radiology, electrophysiology lab and emergency trauma center, we decided to expand its use to include non-invasive monitoring. Our current policy is to use capnography monitoring for all adult and pediatric vented and non-vented patients during the administration of anesthesia and recovery. OSM

EARLY WARNING SYSTEM
Spot the First Signs of Respiratory Compromise

NO COMPROMISE Continuous capnography alerts staff to opioid-induced respiratory depression, identified as a top threat to patient safety.

Opioids can cause respiratory depression that puts patients in jeopardy. ECRI Institute, a healthcare research firm in Plymouth Meeting, Pa., says the condition is of particular concern in patients who receive opioids such as morphine, hydromorphone and fentanyl, and especially if:

• they receive another drug that has a sedating effect;
• they have sleep apnea or another condition that predisposes them to respiratory compromise; or
• they receive more medication than intended, such as in the case of a dosing error.

ECRI listed undetected opioid-induced respiratory depression as a top threat to patient safety in its Top 10 Health Technology Hazards for 2017 report. In the report, ECRI recommends implementing measures to "continuously monitor the adequacy of ventilation of these patients."

— Bill Donahue