When a signal begins blocking and squaring off at the top, what is typically the cause?

When a signal appears to be blocking and squaring off at the top, it is typically due to the gain (sensitivity) being set too high. In polysomnography, if the gain is increased excessively, the amplitude of the signals can exceed the measurable range of the device, resulting in a clipped signal. This clipping manifests as a squared-off appearance, reflecting that the true amplitude of the physiological signal is not accurately captured because the measuring instrument cannot process the input that exceeds its maximum capacity.

This phenomenon highlights the importance of appropriately setting the gain to capture physiologic signals accurately without distortion. If the signal is clipped due to high gain, it may lead to misinterpretation of the patient's data, complicating diagnosis and treatment. Proper signal processing starts with optimal gain settings, ensuring that the signals are within the operational range of the recording equipment for accurate representation.