Assessment of brain oxygenation in term and preterm neonates using near infrared spectroscopy

A Newcomer's Guide to Functional Near Infrared Spectroscopy Experiments

This review presents a practical primer for functional near-infrared spectroscopy (fNIRS) with respect to technology, experimentation, and analysis software. Its purpose is to jump-start interested practitioners considering utilizing a non-invasive, versatile, nevertheless challenging window into the brain using optical methods. We briefly recapitulate relevant anatomical and optical foundations and give a short historical overview. We describe competing types of illumination (trans-illumination, reflectance, and differential reflectance) and data collection methods (continuous wave, time domain and frequency domain). Basic components (light sources, detection, and recording components) of fNIRS systems are presented. Advantages and limitations of fNIRS techniques are offered, followed by a list of very practical recommendations for its use. A variety of experimental and clinical studies with fNIRS are sampled, shedding light on many brain-related ailments. Finally, we describe and discuss a number of freely available analysis and presentation packages suited for data analysis. In conclusion, we recommend fNIRS due to its ever-growing body of clinical applications, state-of-the-art neuroimaging technique and manageable hardware requirements. It can be safely concluded that fNIRS adds a new arrow to the quiver of neuro-medical examinations due to both its great versatility and limited costs.

Prone versus supine position for regional cerebral tissue oxygenation in preterm neonates receiving noninvasive ventilation

OBJECTIVE

The prone position was found to improve oxygenation and pulmonary functions in neonates receiving respiratory support. However, how this improvement changes brain tissue oxygenation has not been studied. We aimed to investigate how prone position effects regional cerebral oxygen saturation (rScO₂) and cerebral fractional oxygen extraction (FOE) in preterm neonates during noninvasive ventilation (NIV).

METHODS

Preterm neonates < 37 weeks gestational age (GA) stable on NIV were enrolled. NIV was defined as nasal continues positive airway pressure or intermittent positive pressure ventilation via binasal prongs. Near infrared spectroscopy was used to measure rScO₂. Monitoring was started when the infant was lying supine for at least 1 h and continued at the same body position at least for 1 h. Later the infant was changed to prone position and monitored for additional 3 h. Arterial oxygen saturation (SO₂) was also continuously monitored and FOE was calculated from rScO₂ and SO₂.

RESULTS

Mean GA and birth weight of the cohort (n = 32) were 30.63 ± 3.09 weeks and 1459 ± 581 g, respectively. There were 14 females and 18 males. Both SO₂ (95 ± 2.2% versus 96.2 ± 1.9%, p = .001) and rScO₂ (79.2 ± 3.4% versus 82.1 ± 3.2%, p < .001) were higher in prone position compared to supine position. Cerebral FOE (16.6 ± 0.8% versus 14.7 ± 0.8%, p < .001) and respiratory rate (57.3 ± 5.5 versus 55.6 ± 9.2, p = .003) were lower in prone position.

CONCLUSION

In preterm newborns, receiving nasal NIV for mild to moderate respiratory distress, arterial and cerebral oxygenations were better in prone position.

Investigating the Role of Near-Infrared Spectroscopy in Neonatal Medicine

Near-infrared spectroscopy (NIRS) is a clinical tool that provides a bedside method of noninvasively measuring continuous, "real-time" oxygen consumption and monitoring for potential ischemia of somatic tissues, particularly the brain, kidneys, and intestine in neonates. Although the concept of NIRS seems promising, its implementation into clinical practice has been inconsistent for various reasons, including difficulty in interpreting regional oxygen saturation (rSO2), the wide variation in types of NIRS monitors and probes, the cost of new equipment, different monitoring modalities, large discrepancies in both intra- and interindividual use, a lack of defined universal normative values, and little to no data on outcomes or potentially harmful interventions made based on rSO2 readings. We combine findings from previously published informational articles and studies on the use of NIRS in neonatal medicine to provide a comprehensive overview of this tool and identify potential indications for clinical use.

Cerebral oxygenation in preterm infants

BACKGROUND AND OBJECTIVE

Prone sleeping is a major risk factor for sudden infant death syndrome (SIDS) and preterm infants are at significantly increased risk. In term infants, prone sleeping is associated with reduced mean arterial pressure (MAP) and cerebral tissue oxygenation index (TOI). However, little is known about the effects of sleeping position on TOI and MAP in preterm infants. We aimed to examine TOI and MAP in preterm infants after term-equivalent age, during the period of greatest SIDS risk.

METHODS

Thirty-five preterm and 17 term infants underwent daytime polysomnography, including measurement of TOI (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and MAP (Finapress Medical Systems, Amsterdam, Netherlands) at 2 to 4 weeks, 2 to 3 months, and 5 to 6 months postterm age. Infants slept prone and supine in active and quiet sleep. The effects of sleep state and position were determined by using 2-way repeated measures analysis of variance and of preterm birth by using 2-way analysis of variance.

RESULTS

In preterm infants, TOI was significantly lower when prone compared with supine in both sleep states at all ages (P < .05). Notably, TOI was significantly lower in preterm compared with term infants at 2 to 4 weeks, in both positions (P < .05), and at 2 to 3 months when prone (P < .001), in both sleep states. MAP was also lower in preterm infants in the prone position at 2 to 3 months (P < .01).

CONCLUSIONS

Cerebral oxygenation is reduced in the prone position in preterm infants and is lower compared with age-matched term infants, predominantly in the prone position when MAP is also reduced. This may contribute to their increased SIDS risk.