Respiration

Humans and most animal subjects take in air in order to supply oxygen to the blood. Carbon dioxide is also generated by the body and needs to be released from the body into the air. The oxygen and carbon dioxide exchange is generally handled by some form of lungs. And it is the respiration process that pulls fresh air into the lungs (inhaling, for oxygen uptake), and then expels the air out afterwards (exhaling, to eliminate carbon dioxide). For humans and most animals, muscles in the chest continuously modulate the volume of air in the lungs, increasing the volume for inhaling, and reducing the volume for exhaling. This process is not fixed, and subject activity along with both physiological and psychological factors can affect the respiration process.

Equipment exists that can precisely measure the volume of air taken into and expelled from the lungs. This equipment is usually pretty large, and presupposes a tight fitting mask placed over the face and mouth, in order to ensure that all of the air flow is directed through the sensing equipment. It has also been observed that the temperature of air entering the lungs (inhaling) is generally different (usually lower) than the temperature of the air exhaled, which is warmed as it is inside the lungs. Some sort of sensitive temperature sensing element can also be used to sense the respiration process. This approach is not as accurate as volume measurement, and it also requires that the temperature sensing element be placed in the air flow path for the air entering the lungs, which means close to the mouth. Still, this approach is often used for sleep studies. In most cases, the expansion and contraction of the outer diameter of the chest usually supplies a sufficient enough respiration indication for many studies. This is the approach most often used for respiration physiometry with human and mammal subjects. A number of different transducer schemes have been used to accomplish this measurement. It must be noted that respiration is not the only physical process that can affect the chest diameter. Subject motion and activity can also affect this, and also need to be taken into account.

For many physiometry requirements, our 1132 Pneumotrace respiration transducer can be used. The sensing element involves an elastic band, and wrapping an adjustable strap around the subject's chest completes the mechanical attachment of the 1132 to the subject. The resulting signal reflects the expansion and contraction of the subject's chest resulting from respiration. And the 1132 is a piezo-electric device, and does not require any sort of excitation voltage in order to supply the respiration signal.

If you already have your own data collection system, we can supply our 2121 portable bioamplifier configured for the 1132 and respiration sensing. And, of course, the 1132 respiration based signal chain can be added as a channel to our other systems, such as our Biolog ambulatory recorders, or our SC2000 Simple Scope desk top systems.

Inhaling air changes another physical parameter of the chest, the actual impedance measured across the chest. Inhaling adds air to the cross section being measured, and the impedance drops. Exhaling removes air, and the impedance rises. Our Resp 1 Impedance Pneumograph uses bioimpedance to generate a respiration signal from such impedance changes measured across the chest. Combining self-balancing impedance sensing along with signal conditioning, the Resp 1 respiration output can be connected to your existing data collection equipment. Impedance respiration sensing can also be added to our other systems like our SC2000 Simple Scope systems.

If you still have questions, or if you don't see what you need, drop us a line, and we will see how we can help you!