Flowmetric comparison of respiratory inductance plethysmography and pneumotachography in horses.
Respiratory inductance plethysmographic (RIP) and pneumotachographic (Pn) flows were compared dynamically in horses with bronchoconstriction. On a breath-by-breath basis, RIP was normalized to inspiratory volume from Pn, and peak [peak of subtracted final exhalation waveform (SFE(max))] and selected area [integral of subtracted final waveform during first 25% of exhaled volume (SFE(int))] differences between RIP and Pn flows during early expiration were measured in three settings: 1) healthy horses (n = 8) undergoing histamine bronchoprovocation; 2) horses with naturally occurring lower airway obstruction (AO) (n = 7); and 3) healthy horses (n = 6) given lobeline. HCl to induce hyperpnea. In setting 1, histamine challenge induced a dose-dependent increase in SFE(max) and SFE(int) differences. A test index of airway reactivity (interpolated histamine dose that increased SFE(max) by 35%) closely correlated (r(s) = 0.93, P = 0.001) with a conventional index (histamine dose that induced a 35% decrease in dynamic compliance). In setting 2, in horses with AO, SFE(max) and SFE(int) were markedly elevated, and their absolute values correlated significantly (P < 0.005) with pulmonary resistance and the maximum change in transpulmonary pressure. The effects of bronchodilator treatment on the SFE(max) and SFE(int) were also highly significant (P < 0.0001). In setting 3, hyperpnea, but not tachypnea, caused significant (P < 0.01) increases in SFE(max) but not in SFE(int). In conclusion, dynamic comparisons between RIP and Pn provide a defensible method for quantifying AO during tidal breathing, without the need for invasive instrumentation.
Hoffman
A
A
Department of Clinical Sciences, Tufts University School of Veterinary Medicine, North Grafton, MA 01536, USA. andrew.hoffman@tufts.edu
Kuehn
H
H
Riedelberger
K
K
Kupcinskas
R
R
Miskovic
M B
MB
D000403:Airway Resistance; D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D016084:Bronchoconstriction; D001993:Bronchodilator Agents / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006736:Horses; D008120:Lobeline; D010991:Plethysmography / Q000295:instrumentation / Q000379:methods*; D012123:Pulmonary Ventilation; D012120:Respiration Disorders / Q000139:chemically induced / Q000503:physiopathology; D019141:Respiratory System Agents; D012212:Rheology / Q000295:instrumentation; D014839:Vomiting / Q000503:physiopathology
D001993:Bronchodilator Agents; D019141:Respiratory System Agents; D006632:Histamine; D008120:Lobeline