Design of a Plethysmograph for the Measurement of Pulmonary Mechanics and Intrapleural Pressure in Small Animals during Exposure without Surgical Intervention

摘要

The real-time measurement of changes in respiratory mechanics, primarily dynamic compliance (C(sub dyn)) and airway resistance (R(sub L)), is often used to assess the pulmonary toxicity of inhaled materials and irritants thought to elicit an airway reactivity response. A simple volume displacement plethysmograph used for measurement of ventilation in spontaneously breathing rats was modified for the determination of C(sub dyn) and R(sub L) by including measurement of intrapleural pressure (Ppl). Accurate estimates of Ppl were obtained by measurement of esophageal pressure (Pes) using trans-oral insertion of a water filled catheter. Measurement of Pes did not require surgical intervention as is often required for measurement of Ppl directly. The use of conventional head-out plethysmography to measure ventilation and respiratory mechanics during exposure usually precludes the use of trans-oral insertion of an esophageal catheter to measure Pes. Thus, invasive methods must be used to measure Ppl. The combination head-out plethysmograph/nose-only exposure tube (PET), presently described, was found suitable for measurement of R(sub L) and C(sub dyn) using trans-oral catheterization for determination of Pes during exposure. Use of PET required did not require surgical intervention, did not obstruct the animal's normal breathing, and did not require extraordinary procedures for connection to a nose-only exposure chamber. Ventilation, breath waveform, and respiratory mechanics measurements in 36 Long Evans rats demonstrated that neither short-term restraint in the PET nor subsequent insertion of the esophageal catheter significantly altered ventilation or individual breath structure. R(sub L) and C(sub dyn) measured in normal rats using the PET did not differ from R(sub L) and C(sub dyn) determined using more conventional plethysmographic methods.