Measurement of Placental Oxygenation by Transabdominal Near-Infrared Spectroscopy

Abstract

The uteroplacental circulation in the placenta can have a major impact on the fetus. Near infrared spectroscopy (NIRS) is the noninvasive method of measuring changes in blood volumes and oxygen concentrations in living tissue. The purpose of this study is to monitor changes in placental tissue oxygen index (TOI) levels, in patients with intrauterine fetal growth restriction during pregnancy, using NIRS. We measured placental TOI values of 15 normal pregnant woman and 15 patients with intrauterine growth restriction admitted to our hospital. The placenta was assessed by ultrasound examination and NIRS was performed on all patients. The TOI values of the IUGR group when hospitalized was 78.6 +/- 1.6 (SD). This value was significantly higher than that of the controls (78.6 +/- 1.6 [SD] versus 70.2 +/- 0.4 [SD]). And the TOI values of the IUGR group, when measured before delivery, were 77.8 +/- 1.6 (SD). The TOI values of the IUGR group before delivery were significantly higher than those of the control group (77.8 +/- 1.6 [SD] versus 70.3 +/- 0.4 [SD]). We propose that NIRS is a candidate, noninvasive method for assessing placental oxygen dynamics on a real-time basis. In the near future it may contribute to perinatal medical practice.

Utility of near infrared spectroscopy for the screening of the growth restricted fetus

“…Simulated datasets for normal placental oxygenation levels and growth restricted placental oxygenation levels were created based on the compiled data of some of the aforementioned literature (Kawamura et al 2007;Suzuki et al 2009;Hasegawa et al 2010). To make the problem tractable, the two populations under investigation were assumed to be independent and normally distributed, and they were assumed to have distributions identical to those already published.…”

“…This is a relatively new application of NIRS and there are only a few studies currently available in the literature (Kakogawa et al 2005;Kawamura et al 2007;Suzuki et al 2009;Hasegawa et al 2010); some of which suggest that a measurable difference exists in the placental tissue oxygenation index (TOI, i.e. the proportion of oxyhemoglobin to total hemoglobin) of clinically normal patients when compared to patients with IUGR, pregnancy induced hypertension (PIH) and other anomalies (Kawamura et al 2007;Suzuki et al 2009). However, the small sample size of these studies, typically on the order of 15-20 patients per group make it difficult to ascertain the true value of NIRS with regards to placental TOI for the screening of IUGR, PIH, etc.…”

“…Until recently there were only untested hypotheses as to why maternal-fetal circulation insufficiencies lead to elevations in placental TOI. Kawamura et al (2007) suggested that increased placental TOI was due to placental dysfunction, namely diminished oxygen exchange in the intervillous space due to impaired villi. Suzuki et al (2009) reached a similar conclusion after investigating the TOI of patients with histologically confirmed chorangiosis.…”

Measurement of maternal cerebral tissue hemoglobin on near‐infrared time‐resolved spectroscopy in the peripartum period

“…9 Tissue oxygenation has been monitored using noninvasive measurement techniques, particularly nearinfrared spectroscopy (NIRS), 10 to assess tissue damage in various clinical fields worldwide. 11,12 We measured the tissue oxygen index using NIRS and successfully assessed relative oxygenation of the human and porcine placenta in normal and pathological states, such as fetal growth restriction, 13,14 placental chorangiosis, 15 acute fetal hypoxia, 16 and pregnancyinduced hypertension. 17 Radical changes have recently occurred in the monitoring of brain tissue oxygenation because of the use of NIRS to assess tissue oxygenation during anesthesia.…”

Cerebral oxygen saturation evaluated by near‐infrared time‐resolved spectroscopy (TRS) in pregnant women during caesarean section – a promising new method of maternal monitoring

“…NIRS has been utilized in various clinical fields all over the world (Mathieu & Mani, 2007;Vardi & Nini, 2008). A number of approaches to measuring tissue oxygenation using several types of NIRS have been proposed; that is, continuous wave near-infrared spectroscopy (Miura et al, 2000) by which only relative values of tissue oxygenation can be measured; phase-modulated spectroscopy (Franceschini et al, 2002) by which amplitude signals for phase, intensity and depth of modulation after passage can be measured; and tissue oxygen index, by which we successfully assessed the relative oxygenation of the human and porcine placenta in normal and pathological states, such as foetal growth restriction (Kawamura et al, 2007;Kakogawa et al, 2010a), placental chorangiosis (Suzuki et al, 2009), acute foetal hypoxia (Suzuki et al, 2012) and pregnancyinduced hypertension (Kakogawa et al, 2010b). With these methods, for converting the absorption of light to absolute concentrations of total haemoglobin and oxyhaemoglobin, it is necessary to measure the path length of light from the source to detector, because path length has been shown to be affected by factors such as skin and subcutaneous fat (McCully & Hamaoka, 2000).…”