RESUMO
Equatorial compression of the fetal head is known to occur during labor; its effect on trancutaneous scalp PO2 (PtCO2) was investigated in acute experiments in four fetal lambs. Fetal PtCO2, and oxygen tension (PaO2) and flow in a carotid artery were continuously measured. Equatorial head compression was obtained by inflating a cuff around the fetal head. A strong relationship was shown to exist between PtCO2 and PaO2 values in the normoxemic and hypoxemic fetus. Stepwise compression of the fetal head resulted in a PtCO2 of zero at cuff pressures of 40 to 50 mmHg. Laborlike fetal head compression with an intensity of 50 to 70 mmHg and a duration of one minute resulted in a 30 to 60% fall in PtCO2. Fetal PaO2 remained stable in all experiments. The present findings indicate that values of PtCO2 during fetal head compression do not reflect fetal arterial oxygen tension. This questions the reliability of transcutaneous PO2 monitoring as a method of intrapartum surveillance.
Assuntos
Feto/fisiologia , Cabeça , Oxigênio/análise , Prenhez , Pressão , Animais , Dióxido de Carbono/análise , Eletrodos Implantados , Feminino , Métodos , Oxigênio/fisiologia , Gravidez , Couro Cabeludo , Ovinos/fisiologia , TransdutoresRESUMO
The reliability of pulse oximetry and transcutaneous oxygen tension (tcPO2) was investigated in hypoxemic neonates and older infants with chronic hypoxemia due to bronchopulmonary dysplasia (BPD). It was found that during severe hypoxemia (tcPO2 less than 40 mmHg and saturation less than 80%) pulse oximetry showed a better correlation with arterial saturation than tcPO2 with arterial oxygen tension. During mild hypoxemia and normoxemia (tcPO2 40-90 mmHg and saturation 80-95%) tcPO2 and pulse oximetry both showed a good correlation with arterial values. Above 95% saturation and a corresponding tcPO2 of 70-120 mmHg, the correlation between arterial and transcutaneous PO2 was better than that between pulse oximetric and arterial saturation. Computer recording and analysis of tcPO2 and pulse oximetry improves the quality of both noninvasive oxygenation parameters in older infants with BPD.
Assuntos
Monitorização Transcutânea dos Gases Sanguíneos , Hipóxia/sangue , Oximetria , Síndrome do Desconforto Respiratório do Recém-Nascido/sangue , Peso ao Nascer , Idade Gestacional , Humanos , Recém-Nascido , Estenose da Valva Pulmonar/sangue , Tetralogia de Fallot/sangueRESUMO
A flexible data acquisition system was designed for an Apple IIe computer. For implementation, we used a microcomputer capable of recording 4 channels simultaneously with a selectable sample rate; this information was saved on a floppy disc and the recordings could be evaluated later. This evaluation is accomplished by reproducing the analog signals on display and calculating a histogram after deleting artefacts in the signal.