[Influencing respiratory gas analytical lung function parameters by intravenous injection of clenbuterol in horses with chronic lung diseases].
In a placebo-controlled drug study data were collected about flow, volume and expiratory CO2-concentration in 13 horses with chronic obstructive pulmonary disease before and until 2.5 h after intravenous injection of clenbuterol. An ultrasonic flow measuring unit and an infrared-CO2-analyser (Spiroson Scientific) were used. functional deadspace and expiratory mixed volume were calculated. In addition the effect on the partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood was tested and the alveolo-arterial oxygen difference (AaDO2) determined. The volume of the functional deadspace directly after injection of clenbuterol was 24% bigger than the one after placebo injection. 45 min after injection there was no significant difference anymore. The PaO2 showed a decrease with a maximum difference of 11.6 mmHg to the starting value at 45 min after the injection of clenbuterol. As the PaCO2 didn't show significant changes this resulted in an increase of the AaDO2 of up to 15 mmHg (45 min p. inj.). All these alterations had a short-term character and started approaching their basic values 45 min p. inj.. Only the PaO2 did not reach the starting level 150 min after injection of clenbuterol. The expiratory mixed volume didn't show a straight tendency. On the one hand the results indicate that the functional deadspace is an interesting pathophysiological parameter. On the other hand the combined presentation of the changes in blood gas-tension and deadspace volume after the injection of clenbuterol gives indications, that the increase of anatomic deadspace caused by bronchospasmolysis combined with a delayed opening of alveoli, that were not ventilated beforehand, are the reason for the initial decrease in PaO2. Other reasons are discussed.
Sander
K
K
Klinik für Pferde, Tierärztliche Hochschule Hannover.
Deegen
E
E
Ohnesorge
B
B
D000818:Animals; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D002245:Carbon Dioxide / Q000097:blood; D002976:Clenbuterol / Q000627:therapeutic use*; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy* / Q000503:physiopathology; D006736:Horses; D007275:Injections, Intravenous / Q000662:veterinary; D008176:Lung Volume Measurements / Q000662:veterinary; D008297:Male; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D010313:Partial Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary*; D012129:Respiratory Function Tests / Q000662:veterinary
D001993:Bronchodilator Agents; D002245:Carbon Dioxide; D010100:Oxygen; D002976:Clenbuterol