Respiratory rate: The neglected vital sign

Heart Health

by Baylor Scott & White Health

Aug 12, 2021

During or after a patient undergoes surgery, the way they breathe can be one of the most important indicators of their medical status. Physicians closely monitor the rate which air passes through the lungs. Good breath flow is a good sign compared to irregular or noisy breathing that raises serious red flags.

An increasing respirator rate can be an early warning sign of a major adverse event, such as developing sepsis, and a decreasing respiratory rate may indicate opioids-included respirator depression.

Now, researchers think they may have identified a device that can expand this monitoring to patients in the recovery ward and raise those red flags much earlier. The device, which is the mere size of a small Band-Aid, could add to the safety of patients admitted to the hospital.

Michael Ramsay, MD, and president of the Baylor Research Institute (BRI) recent spearheaded a study that appeared in Anesthesia and Analgesia, the flagship journal for the International Anesthesia Research Society, that reviewed the effectiveness of an acoustic respiratory rate monitor.

An acoustic respiratory rate monitor measures patients’ breathing patterns through sounds. The small device is placed on the neck of the patient and is equipped with acoustic technology that translated respiratory sounds into an electronic signal. It’s basically a digital stethoscope that transmits breath sounds to a remote monitor.

The study was conducted to see how the new device stacked up to the current technology for respiration monitoring in accuracy, precision and reliability.

“Existing technology that measures exhaled carbon dioxide (capnometer) is placed in a very sensitive area under the nose, is frequently dislodged and is not wireless,” Dr. Ramsay said.

“It is uncomfortable and not secure. The signal displayed may go up or down with hypoventilation depending on whether the patient is taking slow deep breaths or shallow breaths. Shallow breathing does not cause adequate alveolar gas exchange and therefore does not reflect the true carbon dioxide level in the lungs.”

The new device, he said, measures respiratory rate,  an important component of ventilation, and displays the quality of the breath sound. It is unobtrusive to the patient and wireless.

Throughout the study, researchers monitored 33 post-surgical adults that were connected to both an acoustic monitor and a capnometer.

The team found that while both devices were reliable, the acoustic technology was statistically more accurate and precise than the capnometer. While their performance differences were modest, the accuracy of the acoustic sensor was proven as a reliable form of respiratory recording technology.

Among their findings, the team saw that the acoustic device accurately recorded breath rate both automatically and continually.

“That’s the key,” Dr. Ramsay said. “Having continuous respiratory records is vital, because with enhanced breath monitors, physicians could potentially be alerted when a patient’s condition worsens.”

Plus, since the device is positioned on the neck, where it can serve as a steady monitor (rather than inserted into a patient’s nasal tubes, where it could be dislodged) the monitor enhances patient comfort.

“All patients who receive intravenous opioids after surgery are at risk for respiratory depression. Some patients have a very high risk because of co-morbid conditions such as sleep apnea. This type of unobtrusive technology will allow continual monitoring and perhaps more importantly close the loop between the nurse and the patient by automatically alerting the nurse if there is a deterioration in the patient,” Dr. Ramsay said.

In other words: “the monitor is always being monitored.”

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