Through measuring V(D) and V(D)/V(T) important information about lung ventilation can be obtained and the SBT is an easy method to use for this purpose. From the relationships of the variables with tidal volume (VT), the values at 1. The single breath test (SBT) can be used for clinical evaluation of V(D) and V(D)/V(T) in anaesthetized ventilated dogs. The ICC revealed an excellent consistency for both methods. Linear regression analysis revealed a correlation coefficient (r(2)) of 0.79, 0.94, and 0.83 for PēCO(2), V(D) and V(D)/V(T), respectively. Intra-class correlation coefficient (ICC) was used to measure consistency of each method.įour measurement pairs were obtained in all 20 dogs for method SBT and MC. Method MC and SBT were compared using Bland-Altman plots and linear regression. Physiologic dead space variables (V(D) and V(D)/V(T)) were calculated manually (method MC) or automatically (method SBT) using the Bohr-Enghoff equation. Validation of Bohr dead space measured by volumetric capnography: reply to Graf. At four time points arterial partial pressure of CO(2) (PaCO(2)) was measured. Mixed expired CO(2) partial pressure (PēCO(2)) was measured by two methods: method MC by analysis, using an infrared capnograph, of the expired gas collected in a mixing box and method SBT which calculated it automatically by a device consisting of a mainstream capnograph and a pneumotachograph. Twenty client-owned dogs, ASA I and II undergoing anaesthesia for clinical purposes.įollowing pre-medication, induction of anaesthesia, and intubation of the trachea, intermittent positive pressure ventilation was commenced. V D calculated using Bohr’s equation accurately measures V D,phys. => anatomical dead space increases by 20mL for each L of lung volumeĮ.g.To compare physiologic dead space (V(D)) and physiologic dead space to tidal volume (V(T)) ratio (V(D)/V(T)) obtained by an automated single breath test for carbon dioxide (CO(2)) (method SBT) and a manual calculation (method MC) in ventilated healthy dogs. where V D is dead-space volume (i.e., volume not participating in gas exchange), V T is total exhaled volume, PACO 2 is the partial pressure of carbon dioxide in alveolar air, and PeCO 2 is the partial pressure of carbon dioxide in mixed expired air. ![]() => at infancy, anatomical dead space is higher for body weight (3.3mL/kg) => modified: V D/V T = (P aCO2 - P ECO2)/P aCO2Īdditional notes Factors influencing anatomical dead space NB: P ECO2 is the partial pressure in MIXED expired gas, NOT end-tidal gasĮnghoff modification - using measured arterial PaCO2 as an estimate of the ideal alveolar PACO2
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