Respiratory Spectrographic Acoustic Analysis
Respiratory monitoring is especially important when opiates are used to combat postoperative pain, as is common in orthopedic patients on PCA. Capnographic monitoring (measuring CO2 levels in real-time) is one excellent method of respiratory monitoring, but is expensive and a nuisance to keep the nasal prongs correctly placed. We offer here an approach based on spectrographic analysis. Image: Color spectrographic display of breath sounds as recorded using a miniature microphone embedded into a patient oxygen mask (http://www.southmedic.com/products/oxymask-adult.php). The microphone used was a Realistic model 30-3013 electret design, with the signal amplified using an ordinary audio amplifier. The signal was displayed in color spectrographic form using the Spectrogram 16 software package. Notice how expiration is of longer duration than inspiration in this test subject (me). [Uncalibrated color scale: RED > YELLOW > GREEN > BLUE > BLACK]. A similar arrangement was used for an invention known as the LMA Audio Monitor (for use in patient respiratory acoustic monitoring during general anesthesia utilizing a supraglottic airway such as the Laryngeal Mask Airway - see http://journals.lww.com/anesthesiology/Fulltext/2003/07000/ The_Laryngeal_Mask_Airway__Audio_Monitor_.51.aspx) and for an advanced heart sound monitor (http://www.biomedical-engineering-online.com/content/10/1/42).
