Background: Spontaneous inspiration causes a characteristic decrease of the mitral valve (MV) and pulmonary venous (PV) flow velocities obtained by Doppler echocardiography in patients with constrictive pericarditis (CP). This has been explained by the decrement it causes in the intrathoracic pressure. Positive pressure ventilation (PPV) causes an increment of intrathoracic pressure with mechanical inspiration. Therefore the pattern of respiratory variation produced during PPV may differ from that seen during spontaneous breathing.
Objective: Our goal was to describe the effect of PPV on the pattern and magnitude of respiratory variation of MV and PV flow velocities in CP.
Methods: We performed intraoperative pulsed Doppler transesophageal echocardiography on 15 patients (13 men, mean age 52+/-15 years) with CP after general anesthesia and before sternotomy and pericardial stripping. The peak velocity and time-velocity integral (TVI) of the mitral inflow E and A waves and the PV systolic and diastolic waves were measured at onset of inspiration and expiration for 3 to 6 respiratory cycles. Respiratory phase was monitored with a heat-sensitive nasal thermistor. The percent change in Doppler flow velocities from mechanical inspiration (INS) to mechanical expiration (EXP) was calculated with the formula %change = INS - EXP / INS x 100.
Results: The peak velocity of the mitral inflow E wave was significantly higher during mechanical inspiration than expiration (57 +/-14.5 versus 47+/-13.9 cm/s, P<.001). This represented a percent change of 18%+/-7.9% from expiration to inspiration. The mean TVI of the mitral inflow E was also higher during mechanical inspiration than expiration (P = .02). The peak velocity of the PV D wave was higher during mechanical inspiration than expiration (39+/-17.8 versus 28+/-14.7 cm/s, P<.001). This represented a mean percent change of 28%+/-13.8%. The mean value of the TVI for the PV D wave was also significantly greater during mechanical inspiration than expiration (P <.05).
Conclusions: Positive pressure ventilation reverses the pattern of respiratory variation of the MV and PV flow velocities in CP. The percent change in the peak velocities of the MV and PV flows produced by PPV is the same range reported in CP during spontaneous breathing.