Respiratory artifact: A second vital sign on the electrocardiogram

Apparent Atrial Dissociation and Electrical Alternans

“…First, the presence of respiratory artifact is usually a marker of severe respiratory distress; such patients usually require mechanical ventilation support. [4][5][6] Second, it allows precise calculation of the respiratory rate, a vital sign whose recording is frequently unreliable. 9 At a sweep speed of 25 mm per second, the respiratory rate can be calculated by measuring 1 or more respiratory artifact cycles in millimeters and dividing them into 1500 or its multiples.…”

“…The respiratory rate can also be approximated by counting the number of respiratory artifacts in a 10-second recording and multiplying it by 6. [4][5][6] According to such calculations, the respiratory rate for this patient was extremely fast at about 50 per minute, almost exactly half of the heart rate.…”

“…In the past, it was thought to be a marker of critical illness and high risk of imminent death . More recently it was found that in non–transplant-related apparent atrial dissociation, what appear to be dissociated P waves are actually respiratory artifacts reflecting the tonic initiation of inspiratory effort (gasping); they signal severe respiratory distress . The pseudo-P waves are usually followed by brief periods of high-frequency microoscillations that represent surface electrical activity of increased force of the accessory muscles of respiration .…”

“…Recognizing respiratory artifact is important for several reasons. First, the presence of respiratory artifact is usually a marker of severe respiratory distress; such patients usually require mechanical ventilation support . Second, it allows precise calculation of the respiratory rate, a vital sign whose recording is frequently unreliable .…”

“…4,5 The pseudo-P waves are usually followed by brief periods of high-frequency microoscillations that represent surface electrical activity of increased force of the accessory muscles of respiration. [4][5][6] However, in this patient, such microoscillations were initially not recorded (Figure , B). On further inquiry, it was found that the filter setting of the electrocardiograph was incorrect: the low-pass filter (highfrequency cutoff) was set at 40 Hz rather than the recommended 150 Hz, which eliminated the microoscillations from the ECG.…”