Respiratory-induced variability of pulmonary arterial pressure measurements in cattle.

The purpose of this study was to investigate the variability of the peak systolic (PAPs) and the end diastolic (PAPd) pulmonary arterial pressures induced by intrapleural pressure changes in cattle. The pleural pressure (Ppl), the electrocardiogram and the pulmonary arterial pressure (PAP) were simultaneously recorded in five healthy calves under three different conditions, i.e. normoxia (N), normoxia with an added airflow resistance (R) and hypoxia (H). PAPs, PAPd and their corresponding transmural pressures were measured and averaged over 10 successive regular cardiac cycles. The maximum Ppl changes (max delta Ppl) were measured on the same tracings. The variance and coefficients of variation were calculated for each set of vascular measurements. Max delta Ppl was significantly increased with regard to N values during R and H conditions. This increase in max delta Ppl induced a simultaneous rise in the variability of PAP measurements, while in each condition, this variability was greatly lowered by use of the corresponding transmural pressure. It was concluded that, in calves with high max delta Ppl, the influence of respiration on PAP becomes considerable. In such cases, the use of transmural pressures rather than luminal pressures can greatly reduce the variability of these pulmonary pressure measurements and therefore increase their sensitivity.