Carbon dioxide levels of 10 mmHg or less measured 20 minutes after initiation of advanced cardiac life support accurately predicted death in cardiac arrest patients with electrical activity but no pulse. Case studies have shown that patients with high CO2 levels are more likely to be resuscitated than those without. The higher the CO2 level monitored by the capnography machine, the more likely the person will be resuscitated. Differences between survivors and non-survivors can be detected in 20-minute end-tidal carbon dioxide levels. Patients with asphyxial cardiac arrest have markedly increased initial CO2 readings. These readings will drop within a minute. High readings come from the buildup of CO2 in the lungs. These readings from the capnography machine can help determine whether clinicians are dealing with a traditional cardiac arrest or an asphyxial cardiac arrest.
Another important use of capnography machines is to monitor patients undergoing pain management or sedation. Capnography can provide evidence of hypoventilation and apnea. By monitoring a patient's CO2 levels, clinicians can report problems before breathing levels change. In patients who are sedated or intubated, it is important to pay attention to the vital signs of the capnography machine. The small notch above the wave indicates when a person is breathing independently and awakened from sedation. At this point the clinician may wish to provide additional information to prevent the patient from waking up.
Capnography monitoring of CO2 levels in non-intubated patients is an excellent method for assessing COPD and asthma severity. It can also help determine how effective a treatment is. Patients with bronchospasm experience a shark fin-like waveform as the patient struggles to exhale. This shape is due to uneven emptying of the alveoli. Many studies have now linked this shape to bronchospasm. You can tell the severity by the shape on the graph.
Asthma patients can also monitor their CO2 levels with a capnography machine. Asthma varies greatly with severity. A patient with mild asthma will have CO2 levels drop below 35 as the patient struggles to breathe and hyperventilates to compensate. As the asthma worsens, the patient returns to normal CO2 levels. When asthma becomes severe, CO2 levels can rise to dangerous levels above 60. This is because the patient is tired and there is little air flow. Successful treatment can help reduce or eliminate the "shark fin" wave and return carbon dioxide levels to a normal range.