One of the best indicators that a patient has a problem as a result of inadequate breathing is low oxygen saturation levels in their blood. This can be measured using a pulse oximeter, which measures the amount of oxygen present in the blood. If the saturation level is below normal, it may indicate that the patient is not breathing adequately and may require medical intervention. Other signs may include shortness of breath, rapid breathing, or cyanosis (bluish discoloration of the skin or mucous membranes due to lack of oxygen).