Near-infrared spectroscopy monitoring of cerebral oxygen during assisted ventilation

Effect of Nasal Continuous Positive Airway Pressure on Retinopathy of Prematurity in Preterm Newborns: A Comparative Analysis with Mechanical Ventilation and High-Flow Nasal Cannula Therapy

BACKGROUND Retinopathy of prematurity (ROP), originally described as retrolental fibroplasia, represents an abnormal growth of blood vessels in the premature retina that can occur in response to oxygen therapy. The association between ROP and invasive mechanical ventilation has been widely studied in the literature; however, the relationships between different types of ventilation and ROP have not been as well documented. This study aimed to compare the association of ROP incidence with mechanical ventilation (MV), nasal continuous positive airway pressure (nCPAP), and high-flow nasal cannula (HFNC) therapies in 130 pre-term infants with gestational ages <32 weeks. MATERIAL AND METHODS The study includes 130 premature newborns, out of which 54 underwent MV therapy, either alone or in combination with nCPAP or HFNC therapy, 63 underwent nCPAP therapy, either alone or in combination with MV or HFNC therapy, and 23 underwent HFNC therapy, either alone or in combination with MV or nCPAP therapy. The relationships between ROP and the 3 types of ventilation were analyzed by univariate followed by multivariate logistic regression. RESULTS When adjusting for covariates, only nCPAP and birth weight were significantly associated with ROP, the former being a strong risk factor, with an adjusted odds ratio (AOR) of 7.264 (95% CI, 2.622-20.120; P<0.001), and the latter being a weak protective factor, with an AOR of 0.998 (95% CI, 0.996-0.999; P<0.05). CONCLUSIONS The results showed nCPAP was a strong ROP risk factor, birth weight was a weak ROP protective factor, and MV and HFNC were not significantly associated with increased ROP risk.

Effect of the change of mechanical ventilation mode on cerebral oxygen saturation level in neonates

BACKGROUND

This study aimed to apply near-infrared spectroscopy (NIRS) to monitor cerebral oxygen saturation (SrO2) level in neonates before and after the change of mechanical ventilation mode, and thus, the effects of the change of mechanical ventilator mode on SrO2 level in neonates were assessed.

METHODS

This trial was designed as an observational study .A total of 70 neonates who were admitted to the Department of Neonatology of Beijing Luhe Hospital Affiliated to Capital Medical University (Beijing, China) between September 2019 and October 2021 and required respiratory support were included. The variations of SrO2 level before and after the change of mechanical ventilation mode, including changing from Synchronized intermittent mandatory ventilation (SIMV) to noninvasive ventilation (NIV, group 1), and from NIV to oxygen inhalation (group 2), were monitored by Enginmed EGOS-600 A. The changes of SrO2 level at 30 min before and 1 h after the change of ventilation mode were compared between the two groups.

RESULTS

The SrO2 level in the group 1 30 min before, as well as 10 min, 30 min, and 1 h after the change of ventilation mode was 62.54 ± 3.36%, 65.43 ± 3.98%, 64.38 ± 4.23%, and 64.63 ± 3.71%, respectively. The SrO2 level at all the points after the change of ventilation mode increased compared with 30 min before the change (P < 0.05). The SrO2 level in the group 2 at each time point was 62.67 ± 4.69%, 64.61 ± 5.00%, 64.04 ± 4.48%, and 64.55 ± 4.32%, respectively. Compared with 30 min before ventilator weaning, the SrO2 level at all the points after ventilator weaning increased (P < 0.05). Peak inspiratory pressure (PIP) excluding Nasal Continuous Positive Airway Pressure (NCPAP)) in group 1 was lower than that before extubation, and the difference was statistically significant (P = 0) (Table 7).

CONCLUSIONS

SrO2 level showed an increasing trend after the change of ventilation mode, and the increase of SrO2 level at 10 min after the change of ventilation mode was the most prominent. From SIMV to NIV, increased SrO2 levels may be associated with decreased PIP.

A phase-II clinical trial of targeted cerebral near infrared spectroscopy using standardized treatment guidelines to improve brain oxygenation in preterm infants (BOx-II): A study protocol

BACKGROUND

Mortality and brain injury are common adverse outcomes in infants born <28 weeks. Conventional pulse oximetry may not detect subclinical changes prior to deterioration and fails to detect changes within the brain. Increasing evidence supports the use of cerebral near-infrared spectroscopy (NIRS) in the early care of preterm infants, yet the impact of specific interventions on cerebral oxygenation and the relationship between cerebral hypoxia and brain injury on MRI remain to be determined.

METHODS/DESIGN

100 infants <28 completed weeks of gestation will be recruited for a prospective, multicenter intervention trial. After informed consent, infants will undergo cerebral NIRS monitoring starting within 6 h of birth and continuing through 72 h. Infants with persistent cerebral desaturation will receive interventions following a standard treatment algorithm selected by the provider based on the patient's clinical condition. Providers will record the timing and choice of intervention(s) and term equivalent brain MRI will be performed for survivors. There are three objectives of this study: 1) to identify the relationship between cerebral hypoxia burden and brain injury on term-equivalent MRI. 2) to identify most common interventions after cerebral hypoxia, and 3) to quantify frequency of occult cerebral hypoxia events.

DISCUSSION

There is increasing evidence for the role of early cerebral NIRS monitoring in the neuroprotective care of preterm infants. This phase-II trial will provide essential data to improve the intervention approach, model the effect size of interventions on a wider extent of brain injury, and quantify the discrepancy between measurements of systemic and cerebral hypoxia.

A cervical compartment syndrome impairs cerebral circulation in post-thyroidectomy hemorrhage: data from an animal model

BACKGROUND

Post thyroidectomy hemorrhage is a potentially life-threatening complication. As the mechanism leading to hypoxemic brain damage and death is still unknown, our aim was to examine the underlaying pathophysiology in an animal model.

METHODS

A series of experiments was performed in our established model for post thyroidectomy hemorrhage in 6 pigs. First, post thyroidectomy hemorrhage was simulated with an artificial increase of cervical compartment pressure. Second, spontaneous bleeding into the cervical compartment was initiated. Primary outcome measure is the correlation between cerebral oxygenation and cervical compartment pressure.

RESULTS

With an increase in cervical compartment pressure apnea could be detected in all experiments. A significant 24.2% (9.5-34.4%) decrease of cerebral oxygenation at time of apnea (47.0%; 38.0-65.0%) compared to baseline values (63.5%; 56.0-74.0%; P=0.043) occurred due increase of cervical compartment pressure concurrent with an impaired cerebral perfusion. Apnea occurred about 200 sec after a 10% decrease of cerebral oxygenation, but 35 sec before a 10% decrease of peripheral oxygenation. Spontaneous bleeding into the cervical compartment causes an increase of cervical compartment pressure reaching levels of the mean arterial blood pressure 56.0 (35.0-72.0) mmHg.

CONCLUSIONS

Peripheral hypoxemia occurs with relevant delay in time after decrease of cerebral perfusion and cerebral hypoxemia, therefore cerebral hypoxemia seems to be causal for a central apnea. With this evidence of impaired cerebral perfusion and cerebral hypoxemia due to an increased cervical compartment pressure we can disprove the historic theory of tracheal collapse due to a compressive hematoma in post thyroidectomy hemorrhage. A cervical compartment syndrome seems to be causal, not only for brain hypoxemia but also an additional laryngo-pharyngeal mucosal edema.

Study of the relationship between regional cerebral saturation and pCO2 changes during mechanical ventilation to evaluate modifications in cerebral perfusion in a newborn piglet model

Near-infrared spectroscopy (NIRS) could be a useful continuous, non-invasive technique for monitoring the effect of partial pressure of carbon dioxide (PaCO₂) fluctuations in the cerebral circulation during ventilation. The aim of this study was to examine the efficacy of NIRS to detect acute changes in cerebral blood flow following PaCO₂ fluctuations after confirming the autoregulation physiology in piglets. Fourteen piglets (<72 h of life) were studied. Mean arterial blood pressure, oxygen saturation, pH, glycemia, hemoglobin, electrolytes, and temperature were monitored. Eight animals were used to evaluate brain autoregulation, assessing superior cava vein Doppler as a proxy of cerebral blood flow changing mean arterial blood pressure. Another 6 animals were used to assess hypercapnia generated by decreasing ventilatory settings and complementary CO₂ through the ventilator circuit and hypocapnia due to increasing ventilatory settings. Cerebral blood flow was determined by jugular vein blood flow by Doppler and continuously monitored with NIRS. A decrease in PaCO₂ was observed after hyperventilation (47.6±2.4 to 29.0±4.9 mmHg). An increase in PaCO₂ was observed after hypoventilation (48.5±5.5 to 90.4±25.1 mmHg). A decrease in cerebral blood flow after hyperventilation (21.8±10.4 to 15.1±11.0 mL/min) and an increase after hypoventilation (23.4±8.4 to 38.3±10.5 mL/min) were detected by Doppler ultrasound. A significant correlation was found between cerebral oxygenation and Doppler-derived parameters of blood flow and PaCO₂. Although cerebral NIRS monitoring is mainly used to detect changes in regional brain oxygenation, modifications in cerebral blood flow following experimental PaCO₂ changes were detected in newborn piglets when no other important variables were modified.

Effect of Permissive Mild Hypercapnia on Cerebral Vasoreactivity in Infants: A Randomized Controlled Crossover Trial

BACKGROUND

Mechanical ventilation interferes with cerebral perfusion via changes in intrathoracic pressure and/or as a consequence of alterations in CO2. Cerebral vascular vasoreactivity is dependent on CO2, and hypocapnia can potentially lead to vasoconstriction and subsequent decrease in cerebral blood flow. Thus, we aimed at characterizing whether protective ventilation with mild permissive hypercapnia improves cerebral perfusion in infants.

METHODS

Following ethical approval and parental consent, 19 infants were included in this crossover study and randomly assigned to 2 groups for which the initial ventilation parameters were set to achieve an end-tidal carbon dioxide (Etco2) of 6.5 kPa (group H: mild hypercapnia, n = 8) or 5.5 kPa (group N: normocapnia, n = 11). The threshold was then reversed before going back to the initial set value of normo- or hypercapnia. At each step, hemodynamic, respiratory, and near-infrared spectroscopy (NIRS)-derived parameters, including tissue oxygenation index (TOI) and tissue hemoglobin index (THI), concentration of deoxygenated hemoglobin (HHb) and oxygenated hemoglobin (O2Hb), were collected. Concomitantly, sevoflurane maintenance concentration, ventilatory (driving pressure) and hemodynamic parameters, as mean arterial pressure (MAP), were recorded.

RESULTS

Targeting an Etco2 of 5.5 kPa resulted in significantly higher mean driving pressure than an Etco2 of 6.5 kPa (P < .01) with no difference between the groups in end-tidal sevoflurane, MAP, and heart rate. A large scatter was observed in NIRS-derived parameters, with no evidence for difference in Etco2 changes between or within groups. A mild decrease with time was observed in THI and MAP in infants randomly assigned to group N (P < .036 and P < .017, respectively). When pooling all groups together, a significant correlation was found between the changes in MAP and TOI (r = 0.481, P < .001).

CONCLUSIONS

Allowing permissive mild hypercapnia during mechanical ventilation of infants led to lower driving pressure and comparable hemodynamic, respiratory, and cerebral oxygenation parameters than during normocapnia. Whereas a large scatter in NIRS-derived parameters was observed at all levels of Etco2, the correlation between TOI and MAP suggests that arterial pressure is an important component of cerebral oxygenation at mild hypercapnia.

Parameters Influencing Brain Oxygen Measurement by Regional Oxygen Saturation in Postcardiac Arrest Patients with Targeted Temperature Management

In several studies, regional cerebral oxygen saturation (rSO₂) has been measured in patients with postcardiac arrest syndrome (PCAS) to analyze the brain's metabolic status. However, the significance of rSO₂ in PCAS patients remains unclear. In the present study, we investigated the relationship between rSO₂ and physiological parameters. Comatose survivors of out-of-hospital PCAS with targeted temperature management (TTM) at 34°C for 24 hours were included. All patients were monitored for their rSO₂ and additional parameters (arterial oxygen saturation [SaO₂], hemoglobin [Hb], mean arterial pressure [MAP], arterial carbon dioxide pressure [PaCO₂], and body temperature]) measured at the start of monitoring and 24 and 48 hours after return of spontaneous circulation (ROSC). Patients were divided into favorable and unfavorable groups, and the correlation between rSO₂ and these physiological parameters was evaluated by multiple regression analysis. Forty-nine patients were included in the study, with 15 in the favorable group and 34 in the unfavorable group. There was no significant difference in the rSO₂ value between the two groups at any time point. The multiple regression analysis of the favorable group revealed a moderate correlation between rSO₂ and SaO₂, Hb, and PaCO₂ only at 24 hours (coefficients: 0.482, 0.422, and 0.531, respectively), whereas that of the unfavorable group revealed moderate correlations between rSO₂ and Hb values at all time points, PaCO₂ at 24 hours and MAP at 24 and 48 hours. rSO₂ was moderately correlated to MAP in unfavorable patients. To optimize brain oxygen metabolic balance for PCAS patients with TTM measuring rSO₂, we suggest total evaluation of each parameters of SaO₂, Hb, MAP, and PaCO₂.

Respiratory Care for the Ventilated Neonate

Invasive ventilation is often necessary for the treatment of newborn infants with respiratory insufficiency. The neonatal patient has unique physiological characteristics such as small airway caliber, few collateral airways, compliant chest wall, poor airway stability, and low functional residual capacity. Pathologies affecting the newborn's lung are also different from many others observed later in life. Several different ventilation modes and strategies are available to optimize mechanical ventilation and to prevent ventilator-induced lung injury. Important aspects to be considered in ventilating neonates include the use of correct sized endotracheal tube to minimize airway resistance and work of breathing, positioning of the patient, the nursing care, respiratory kinesiotherapy, sedation and analgesia, and infection prevention, namely, the ventilator-associated pneumonia and nosocomial infection, as well as prevention and treatment of complications such as air leaks and pulmonary hemorrhage. Aspects of ventilation in patients under ECMO (extracorporeal membrane oxygenation) and in palliative care are of increasing interest nowadays. Online pulmonary mechanics and function testing as well as capnography are becoming more commonly used. Echocardiography is now a routine in most neonatal units. Near infrared spectroscopy (NIRS) is an attractive tool potentially helping in preventing intraventricular hemorrhage and periventricular leukomalacia. Lung ultrasound is an emerging tool of diagnosis and can be of added value in helping monitoring the ventilated neonate. The aim of this scientific literature review is to address relevant aspects concerning the respiratory care and monitoring of the invasively ventilated newborn in order to help physicians to optimize the efficacy of care.

Changes in cerebral oxygenation based on intraoperative ventilation strategy

Introduction

Cerebral oxygenation can be monitored clinically by cerebral oximetry (regional oxygen saturation, rSO₂) using near-infrared spectroscopy (NIRS). Changes in rSO₂ have been shown to precede changes in pulse oximetry, providing an early detection of clinical deterioration. Cerebral oximetry values may be affected by various factors, including changes in ventilation. The aim of this study was to evaluate the changes in rSO₂ during intraoperative changes in mechanical ventilation.

Patients and methods

Following the approval of the institutional review board (IRB), tissue and cerebral oxygenation were monitored intraoperatively using NIRS. Prior to anesthetic induction, the NIRS monitor was placed on the forehead and over the deltoid muscle to obtain baseline values. NIRS measurements were recorded each minute over a 5-min period during general anesthesia at four phases of ventilation: 1) normocarbia (35–40 mmHg) with a low fraction of inspired oxygen (FiO₂) of 0.3; 2) hypocarbia (25–30 mmHg) and low FiO₂ of 0.3; 3) hypocarbia and a high FiO₂ of 0.6; and 4) normocarbia and a high FiO₂. NIRS measurements during each phase were compared with sequential phases using paired t-tests.

Results

The study cohort included 30 adolescents. Baseline cerebral and tissue oxygenation were 81% ± 9% and 87% ± 5%, respectively. During phase 1, cerebral rSO₂ was 83% ± 8%, which decreased to 79% ± 8% in phase 2 (hypocarbia and low FiO₂). Cerebral oxygenation partially recovered during phase 3 (81% ± 9%) with the increase in FiO₂ and then returned to baseline during phase 4 (83% ± 8%). Each sequential change (e.g., phase 1 to phase 2) in cerebral oxygenation was statistically significant (p < 0.01). Tissue oxygenation remained at 87%–88% throughout the study.

Conclusion

Cerebral oxygenation declined slightly during general anesthesia with the transition from normocarbia to hypocarbic conditions. The rSO₂ decrease related to hypocarbia was easily reversed with a return to baseline values by the administration of supplemental oxygen (60% vs. 30%).

Different ventilation techniques and hemodynamic optimization to maintain regional cerebral oxygen saturation (rScO2) during laparoscopic bariatric surgery: a prospective randomized interventional study

PURPOSE

The purpose of this study was to assess the changes in regional cerebral oxygen saturation (rScO₂) in response to different ventilation strategies: inspired oxygen concentration (FiO₂), end-tidal carbon dioxide (EtCO₂), and positive end expiratory pressure (PEEP) in addition to optimizing mean arterial pressure (MAP) in obese patients subjected to laparoscopic bariatric surgery in the reverse trendelenburg position.

METHODS

50 obese patients were randomly assigned into one of two groups. Each group is 25 patients. Control patients subjected to a ventilation strategy aimed to maintain FiO₂ 0.4 and EtCO₂ 30 mmHg without PEEP. Study patients were assigned to specific protocol; T0, baseline rScO₂; T1, 5 min following induction; T2, PP/RTP (10 min after pneumoperitoneum and reverse trendelenburg position); T3, PEEP 10 cmH₂O; T4, FiO₂ 1.0; T5, EtCO₂ 40 mmHg and T6, MAP/BL; MAP back to baseline in both groups.

MAIN RESULTS

10 min after PP/RTP, there was a significant decrease in rScO₂ in both groups. At T4, with FiO₂ 1.0, there was significant improvement in rScO₂ when compared to T2. At T5, with EtCO₂ 40 mmHg, rScO₂ significantly enhanced when compared to EtCO₂ 30 mmHg. At T4 and T5, we observed highly significance difference between both groups. At the end of the procedure and when MAP increased back to baseline (T6) in both groups, rScO₂ statistically increased in both groups when compared to T2.

CONCLUSION

In obese patients, subjected to laparoscopic bariatric surgery in reverse trendelenburg position, adjustment of ventilation strategies and hemodynamic optimization succeeded to improve rScO₂.

Changes in Near-Infrared Spectroscopy After Congenital Cyanotic Heart Surgery

BACKGROUND

Since oxygen saturation from pulse oximetry (SpO₂) and partial pressure of arterial oxygen (PaO₂) are observed to improve immediately after surgical correction of cyanotic congenital heart disease (CHD), we postulate that cerebral (CrO₂) and somatic (SrO₂) oximetry also improves immediately post-correction. We aim to prospectively examine CrO₂ and SrO₂, before, during, and after surgical correction as well as on hospital discharge in children with cyanotic CHD to determine if and when these variables increase.

METHODS

This is a prospective observational trial. Eligibility criteria included children below 18 years of age with cyanotic CHD who required any cardiac surgical procedure. CrO₂ and SrO₂ measurements were summarized at six time-points for comparison: (1) pre-cardiopulmonary bypass (CPB); (2) during CPB; (3) post-CPB; (4) Day 1 in the pediatric intensive care unit (PICU); (5) Day 2 PICU; and (6) discharge. Categorical and continuous variables are presented as counts (percentages) and median (interquartile range), respectively.

RESULTS

Twenty-one patients were analyzed. 15 (71.4%) and 6 (28.6%) patients underwent corrective and palliative surgeries, respectively. In the corrective surgery group, SpO₂ increased immediately post-CPB compared to pre-CPB [99 (98, 100) vs. 86% (79, 90); p < 0.001] and remained in the normal range through to hospital discharge. Post-CPB CrO₂ did not change from pre-CPB [72.8 (58.8, 79.0) vs. 72.1% (63.0, 78.3); p = 0.761] and even decreased on hospital discharge [60.5 (53.6, 62.9) vs. 72.1% (63.0, 78.3); p = 0.005]. Post-CPB SrO₂ increased compared to pre-CPB [87.3 (77.2, 89.5) vs. 72.7% (65.6, 77.3); p = 0.001] but progressively decreased during PICU stay to a value lower than baseline at hospital discharge [66.9 (57.3, 76.9) vs. 72.7% (65.6, 77.3); p = 0.048].

CONCLUSION

CrO₂ and SrO₂ did not increase after corrective surgery of cyanotic CHD even up to hospital discharge. Future larger studies are required to validate these findings. (This study is registered with ClinicalTrials.gov ID: NCT02417259.).

Cerebral Autoregulation, Brain Injury, and the Transitioning Premature Infant

Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia-reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside.

Practical Use of Near-Infrared Spectroscopy in Carotid Surgery

Carotid endarterectomy (CEA) is the gold standard for the treatment of symptomatic patients with atherosclerotic carotid disease. However, benefit of the CEA procedure depends on the rate of peri- and postoperative adverse neurological events. Therefore, brain monitoring is important in detecting cerebral ischemia during and after CEA and also allows to prompt appropriate action. Traditional methods of cerebral monitoring are being replaced by novel, easy-to-use techniques that allow continued monitoring of regional cerebral oxygen saturation. In this review, we present the recent literature data related to the mechanism of cerebral oximetry and its practical use during and after CEA.

Effect of ventilation on cerebral oxygenation in patients undergoing surgery in the beach chair position: a randomized controlled trial

BACKGROUND

Surgery in the beach chair position (BCP) may reduce cerebral blood flow and oxygenation, resulting in neurological injuries. The authors tested the hypothesis that a ventilation strategy designed to achieve end-tidal carbon dioxide (E'(CO₂)) values of 40-42 mm Hg would increase cerebral oxygenation (Sct(O₂)) during BCP shoulder surgery compared with a ventilation strategy designed to achieve E'(CO₂) values of 30-32 mm Hg.

METHODS

Seventy patients undergoing shoulder surgery in the BCP with general anaesthesia were enrolled in this randomized controlled trial. Mechanical ventilation was adjusted to maintain an E'(CO₂) of 30-32 mm Hg in the control group and an E'(CO₂) of 40-42 mm Hg in the study group. Cerebral oxygenation was monitored continuously in the operating theatre using near-infrared spectroscopy. Baseline haemodynamics and Sct(O₂) were obtained before induction of anaesthesia, and these values were then measured and recorded continuously from induction of anaesthesia until tracheal extubation. The number of cerebral desaturation events (CDEs) (defined as a ≥20% reduction in Sct(O₂) from baseline values) was recorded.

RESULTS

No significant differences between the groups were observed in haemodynamic variables or phenylephrine interventions during the surgical procedure. Sct(O₂) values were significantly higher in the study 40-42 group throughout the intraoperative period (P<0.01). In addition, the incidence of CDEs was lower in the study 40-42 group (8.8%) compared with the control 30-32 group (55.6%, P<0.0001).

CONCLUSIONS

Cerebral oxygenation is significantly improved during BCP surgery when ventilation is adjusted to maintain E'(CO₂) at 40-42 mm Hg compared with 30-32 mm Hg.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01546636.

Functional residual capacity (FRC) and lung clearance index (LCI) in mechanically ventilated infants: application in the newborn with congenital diaphragmatic hernia (CDH)

INTRODUCTION

Functional residual capacity (FRC) and lung clearance index (LCI) are sensitive parameters for early detection of airway disease in infancy. The closed helium dilution method has been applied to assess lung volume and ventilation inhomogeneity (VI) in spontaneously breathing infants.

AIMS

The aims of this study were as follows: (1) to assess applicability of the helium gas dilution technique in mechanically ventilated infants with high-risk congenital diaphragmatic hernia (CDH) and to evaluate changes in breathing patterns, lung volume, and VI during the first days of life before and after surgery, and (2) to analyze the possible correlation between changes in lung volume, cerebral hemodynamics, and oxygenation before and after surgical correction of CDH through near-infrared spectroscopy (NIRS) monitoring.

METHODS

Lung function tests were performed by multibreath washout traces with an ultrasonic flowmeter and helium gas dilution technique. For all babies, three acceptable FRC and LCI measurements were collected for each test (mean and SD of three measurements were calculated) before surgery (T0), 24 h after surgery (T1) during mechanical ventilation, and within 24 h after extubation in spontaneous breathing (T2). Cerebral and splanchnic hemodynamics were continuously monitored by NIRS during mechanical ventilation to evaluate relationships between changes in lung volume and capillary-venous oxyhemoglobin saturation in tissues. Fraction of inspired oxygen delivered was adjusted to keep oxygen saturation between 90% and 95%.

RESULTS

Thirteen CDH infants were studied; median GA = 38 weeks (range 35-41) and median BW = 3000 g (range 1850-3670). FRC and LCI significantly improved after extubation when compared with pre-surgical values. No differences were found in tidal volume (Vt) and NIRS monitoring before and after surgery and after extubation. Neither LCI nor FRC was correlated with NIRS values.

CONCLUSIONS

Helium gas dilution technique is an applicable and reliable technique to measure lung volumes and ventilation inhomogeneity also in ventilated infants. NIRS is a non-invasive technique to monitor tissue oxygenation during surgery and mechanical ventilation. In CDH newborns these preliminary data show an improvement in both FRC and LCI after extubation.

Changes in regional tissue oxygenation saturation and desaturations after red blood cell transfusion in preterm infants

OBJECTIVE

The study investigated the ability of near-infrared spectroscopy (NIRS) to detect subgroups of preterm infants who benefit most from red blood cell (RBC) transfusion in regard to cerebral/renal tissue oxygenation (i) and the number of general oxygen desaturation below 80% (SaO(2) <80%) (ii).

STUDY DESIGN

Cerebral regional (crSO(2)) and peripheral regional (prSO(2)) NIRS parameters were recorded before, during, immediately after and 24 h after transfusion in 76 infants. Simultaneously, SaO(2) <80% were recorded by pulse oximetry. To answer the basic question of the study, all preterm infants were divided into two subgroups according to their pretransfusion crSO(2) values (<55% and ≥55%). This cutoff was determined by a k-means clustering analysis.

RESULT

crSO(2) and prSO(2) increased significantly in the whole study population. A stronger increase (P<0.0005) of both was found in the subgroup with pretransfusion crSO(2) values <55%. Regarding the whole population, a significant decrease (P<0.05) of episodes with SaO(2) <80% was observed. The subgroup with crSO(2) baselines <55% had significant (P<0.05) more episodes with SaO(2) <80% before transfusion. During and after transfusion, the frequency of episodes with SaO(2) <80% decreased more in this group compared with the group with crSO(2) baselines ≥55%.

CONCLUSION

NIRS measurement is a simple, non-invasive method to monitor regional tissue oxygenation and the efficacy of RBC transfusion. Infants with low initial NIRS values benefited most from blood transfusions regarding SaO(2) <80%, which may be important for their general outcome.