Volume pulse wave and respiratory diseases

We always record the volume pulse wave and oxygen saturation by using a pulse oximeter. The volume pulse wave fluctuation was induced by respiration; we have used this phenomenon to diagnose or assess respiratory diseases. First, differential diagnosis of sleep disorders, that is, central apnea, obstructive apnea, and respiration in upper airway resistance, by using only a pulse oximeter. Second, we used this phenomenon to evaluate dyspnea. When a big volume pulse wave fluctuation exists, most patients feel dyspnea, if they are awake and alert. Then, we monitored coughs by recording the volume pulse wave. Due to the pleural pressure change induced by the cough, the volume pulse wave reveals a characteristic form. This form changes with the intensity of the cough. Then we can evaluate the frequency and intensity of the cough. For recording the volume pulse wave, the pulse oximeter will be widely applicable in respiratory diseases.