Figure 1.

Pulmonary artery wedge pressure determination. The figure shows three attempts to obtain a valid PAWP determination. The initial attempt corresponded to over wedge (A), with a rapid and linear increase in vascular pressure without the characteristic PAWP waveform. Therefore, the PAC was withdrawn. In the second determination, we observe an incomplete PAWP (B), with vascular pressures higher than the diastolic PAP and lacking the characteristic PAWP waveform. Hence the PAC was slightly advanced. In the third determination we observe a valid PAWP (C) with a vascular pressure that is lower than the diastolic PAP, while depicting characteristic waveform and the expected respiratory oscillation in vascular pressures. The white arrows pointing upwards mark the moment of PAC balloon inflation. The red arrows pointing upwards mark the time of PAC balloon deflation. The green arrow points the place for a valid PAWP determination (mid “a” wave at end-expiration). Y axis shows electrocardiographic leads in DII and V5, Resp, SPO₂ and PA vascular pressure determinations with pressure scale lines every 9 mmHg starting from 0 mmHg. PAWP, pulmonary artery wedge pressure; PAC, pulmonary artery catheter; PAP, pulmonary artery pressure; Resp, respiratory impedance; SPO₂, pulse oximetry; PA, pulmonary artery.