Jerzy Gagan

Pressure changes during embryo transfer

OBJECTIVE To investigate the pressure changes in the transferred load during mock ET. DESIGN Experimental setup. SETTING Academic Research Institute of Mechanical Engineering and private centers of reproductive medicine. PATIENTS(S) None. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Laboratory simulations of ET into a rigid transparent uterine model equipped with a pressure sensor. RESULT(S) Injection of a transferring load during mock ET could increase pressure locally up to 155 mm Hg in <0.1 seconds. The recorded pressure increase slope reached values as high as 72,000 mmHg/s, and the pressure decrease slope reached 144,000 mmHg/s. The pressure buildup in the transferred liquid was proportional to the ejection speed of the transferred load. CONCLUSION(S) ET can cause rapid pressure fluctuations in the transferred liquid. Therefore, it is advisable to transfer the embryo gently with minimum ejection speed, to avoid exposing the embryo to the steep pressure gradient.

Fluid dynamics during embryo transfer.

OBJECTIVE To study fluid dynamics during ET. DESIGN Computational fluid dynamics were applied to calculate fluid velocity changes, dynamic pressure differences, and shear stress in the transferred load for the following injection speeds: 0.1, 1, 6, 12, and 20 m/sec. SETTING Academic research institute of mechanical engineering and reproduction biotechnology and private centers of reproductive medicine. PATIENT(S) None. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Fluid velocity, dynamic pressure, and shear stress during injection of the transferred load. RESULT(S) An increase of injection speed for the transferred load increased the shear stress, dynamic pressure, and velocity differences acting on the embryo. The narrowing of the catheter lumen diameter by 20% amplified the transferred fluid velocity by 78%. An embryo positioned in proximity to the catheters wall was exposed to considerably higher shear stress, dynamic pressure, and velocity difference than an embryo in the center of the catheters lumen. CONCLUSION(S) The transfer of an embryo should be conducted gently and with minimal injection speed. Any narrowing of the catheter lumen should be eliminated. Preferably the embryo should be kept far from the catheters wall during injection of the transferred load.