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Horizontal and Vertical Line Graphs

Line y = # is parallel to x-axis and line x = # is parallel to y-axis

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Credit: U.S. Air Force
Source: http://www.flickr.com/photos/militaryhealth/7782847994
License: CC BY-NC 3.0

The doctors stand around staring at a screen, watching as a graph peaks and dips. The peaks come to be farther and farther apart, and then suddenly, the line goes flat. “We’ve lost him, doctor,” the nurse says. The television show moves on to the next crisis, and the camera shifts away from the monitor. But what does the flat line mean? Why is “flatlined” synonymous with “dead”?

Every Heartbeat

The machine featured on the television show is called an electrocardiogram machine, or EKG (or ECG). The EKG measures electrical activity in the heart. Your heart beats because one part of it, the SA node, generates electrical impulses. Located in the upper right chamber of your heart, the SA node sets the pace of your heartbeat. If it ceases to follow a steady pattern, you will develop an irregular heartbeat. If the SA node fails to function or becomes blocked, another node, known as the AV node, normally can take over. However, it’s not as effective in the role of pacemaker, resulting in a usually slower and weaker heartbeat. If the AV node also fails, there will be no more electrical impulses. Instead of showing heartbeats, the EKG will display a horizontal line, indicating that there are no longer changes in the heart’s electrical activity over time. It means that the patient has died.   

Credit: Juhan Sonin
Source: http://www.flickr.com/photos/38869431@N00/8123108787
License: CC BY-NC 3.0

Doctors use EKG machines to detect problems in a patient’s heart before a heart attack occurs. Some hospitals offer portable EKG machines. These can monitor a patient over several days, to see how his heart responds to normal situations. There have even been EKG applications developed for smartphones, as shown in the screenshot above. These apps allow doctors to diagnose arrhythmias and heart attacks anywhere, even on an airplane. This mobile technology may be especially useful to doctors in the developing world who can’t afford to maintain expensive machines that require reliable sources of power.

See for yourself: http://www.youtube.com/watch?v=r13uYs7jglg

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Watch the videos below to see more mobile heart rate monitors in action.



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Image Attributions

  1. [1]^ Credit: U.S. Air Force; Source: http://www.flickr.com/photos/militaryhealth/7782847994; License: CC BY-NC 3.0
  2. [2]^ Credit: Juhan Sonin; Source: http://www.flickr.com/photos/38869431@N00/8123108787; License: CC BY-NC 3.0

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