Functional Residual Capacity and Airway Resistance of the Rat Measured with a Heat- and Temperature-Adjusted Body Plethysmograph

• Published in: The Journal of Physiological Sciences Vol. 56; no. 6; pp. 449 - 454
• Main Authors: Tajiri, Sakurako, Kondo, Tetsuri, Yamabayashi, Hajime
• Format: Journal Article
• Language: English
• Published: Japan PHYSIOLOGICAL SOCIETY OF JAPAN 01.12.2006; BioMed Central
• Subjects: Administration, Inhalation; airway resistance; Airway Resistance - drug effects; Airway Resistance - physiology; Animals; Body Temperature - physiology; bodyplethysmograph; Bronchoconstriction - drug effects; Bronchoconstriction - physiology; Bronchoconstrictor Agents - administration & dosage; Bronchoconstrictor Agents - pharmacology; Functional Residual Capacity - physiology; functional residual volume; Hot Temperature; Humidity; Lung - physiology; Male; Methacholine Chloride - administration & dosage; Methacholine Chloride - pharmacology; obstructive lung disease; Plethysmography, Whole Body - methods; Plethysmography, Whole Body - veterinary; rat; Rats; Rats, Wistar
• ISSN: 1880-6546; 1880-6562
• DOI: 10.2170/physiolsci.RP004506

The functional residual capacity (FRC) and airway resistance (Raw) of the rat were measured, using a newly designed body plethysmograph (BPG), the inner environment of which was maintained at body temperature and was water-vapor saturated. The subjects were anesthetized and tracheally intubated male Wistar rats (n = 15). After measuring the FRC and Raw, we analyzed the effects of inhaled methacholine (Mch, 0–8 mg/ml) on Raw.The determined FRC was 5.37 ± 0.22 ml (mean ± SE). An almost linear relationship between box pressure and respiratory flow was obtained when the difference between box-gas temperature and the rectal temperature of the rat was less than 1.0°C. The Raw at FRC was 0.230 ± 0.017 cmH2O/ml/s. It increased proportionally with increases in the Mch concentration. When the dynamic changes in Raw were analyzed, the Raw was found to progressively increase during expiration; this increase continued throughout inspiration. Thus in the rat, Raw is not simply a function of changes in lung volume. In conclusion, the humidity- and temperature-adjusted BPG provided an absolute and possibly dynamic value of Raw.