Relationship Between Inspiratory Pressure and Tidal Volume in the Anesthetized Canine

摘要

Houndsundergoingprolongedorcomplicatedsurgicalproceduresareoftenunderventilated,asindicatedbybloodgasandend-tidalCOsubxmlns="http://pub2web.metastore.ingenta.coms/"2/sub(CO2)valueswhenusingpublishedventilatoryguidelines.Weinvestigatedtherelationshipbetweenbodyweight,tidalvolume,andinspiratorypressuredeliveredbytheventilator(lunginflationpressure)in59anesthetizedhounds(19to33kg).Animalswereventilatedunderpositivepressurecontrolandnoninvasivelyinstrumentedtomonitorbloodpressure,ECG,oxygensaturation,CO2,andtidalvolume.Weight,sex,andthoraxmeasurementswererecorded.Alldogsweremonitoredatlunginflationpressuresof10,14,and18cmHsubxmlns="http://pub2web.metastore.ingenta.coms/"2/subO,withmeasurementsrecordedonceCO2stabilized.Veterinaryguidelinesrecommendtidalvolumesof10to15ml/kgofbodyweightandlunginflationpressuresof15to25cmHsubxmlns="http://pub2web.metastore.ingenta.coms/"2/subO.Wheninflationpressurewasbelowguidelines(10),tidalvolumewas#8220;normal#8221;(10to15ml/kg),buttheanimalswereunderventilated.Wheninflationpressurewas#8220;normal#8221;(14or18cmHsubxmlns="http://pub2web.metastore.ingenta.coms/"2/subO),tidalvolumewasaboveguidelines.Physiologicvariableswerenormalonlywheninflationpressurewas14cmHsubxmlns="http://pub2web.metastore.ingenta.coms/"2/subO.Weightandthoraxdepthaccountedfor32and6%,respectively,oftidalvolumevariability,andtidalvolumevariedby±250mlatanygivenbodyweightandinflationpressure.Noneofthemeasuredphysicalvariablesaccuratelypredictedtidalvolume.Thesedatasuggestthattheinconsistencyintidalvolumeisduetoapreviouslyundescribedvariabilityinrespiratorycomplianceintheanesthetizedhoundandthattheguidelinesforventilationduringsurgeryneedfurtherinvestigation.