Relaxation Rate of the Respiratory Muscles and Prediction of Extubation Outcome in Prematurely Born Infants

Invasive ventilation at the boundary of viability: A respiratory pathophysiology study of infants born between 22 and 24 weeks of gestation

BACKGROUND

Invasive ventilation of infants born before 24 weeks of gestation is critical for survival and long-term respiratory outcomes, but currently there is a lack of evidence to guide respiratory management. We aimed to compare respiratory mechanics and gas exchange in ventilated extremely preterm infants born before and after 24 weeks of gestation.

METHODS

Secondary analysis of two prospective observational cohort studies, comparing respiratory mechanics and indices of gas exchange in ventilated infants born at 22-24 weeks of gestation (N=14) compared to infants born at 25-27 weeks (N=37). The ventilation/perfusion ratio (VA/Q), intrapulmonary shunt, alveolar dead space (VDalv) and adjusted alveolar surface area (SA) were measured in infants born at the Neonatal Unit of King's College Hospital NHS Foundation Trust, London, UK.

RESULTS

Compared to infants of 25-27 weeks, infants of 22-24 weeks had higher median (IQR) intrapulmonary shunt [18 (4 - 29) % vs 8 (2 - 12) %, p=0.044] and higher VDalv [0.9 (0.6 - 1.4) vs 0.6 (0.5 - 0.7) ml/kg, p=0.036], but did not differ in VA/Q. Compared to infants of 25-27 weeks, the infants of 22-24 weeks had a lower adjusted SA [509 (322- 687) vs 706 (564 - 800) cm2, p=0.044]. The infants in the two groups did not differ in any of the indices of respiratory mechanics.

CONCLUSION

Ventilated infants born before 24 completed weeks of gestation exhibit abnormal gas exchange, with higher alveolar dead space and intrapulmonary shunt and a decreased alveolar surface area compared to extreme preterms born after 24 weeks of gestation.

Peri-extubation settings in preterm neonates: a systematic review and meta-analysis

OBJECTIVE

To systematically review: 1) peri-extubation settings; and 2) association between peri-extubation settings and outcomes in preterm neonates.

STUDY DESIGN

In this systematic review, studies were eligible if they reported patient-data on peri-extubation settings (objective 1) and/or evaluated peri-extubation levels in relation to clinical outcomes (objective 2). Data were meta-analyzed when appropriate using random-effects model.

RESULTS

Of 9681 titles, 376 full-texts were reviewed and 101 included. The pooled means of peri-extubation settings were summarized. For objective 2, three experimental studies were identified comparing post-extubation CPAP levels. Meta-analyses revealed lower odds for treatment failure [pooled OR 0.46 (95% CI 0.27-0.76); 3 studies, 255 participants] but not for re-intubation [pooled OR 0.66 (0.22-1.97); 3 studies, 255 participants] with higher vs. lower CPAP.

CONCLUSIONS

Summary of peri-extubation settings may guide clinicians in their own practices. Higher CPAP levels may reduce extubation failure, but more data on peri-extubation settings that optimize outcomes are needed.

Predictors of extubation failure in newborns: a systematic review and meta-analysis

Extubation failure (EF) is a significant concern in mechanically ventilated newborns, and predicting its occurrence is an ongoing area of research. To investigate the predictors of EF in newborns undergoing planned extubation, we conducted a systematic review and meta-analysis. A systematic literature search was conducted in PubMed, Web of Science, Embase, and Cochrane Library for studies published in English from the inception of each database to March 2023. The PRISMA guidelines were followed in all phases of this systematic review. The Risk of Bias Assessment for Nonrandomized Studies tool was used to assess methodological quality. Thirty-four studies were included, 10 of which were overall low risk of bias, 15 of moderate risk of bias, and 9 of high risk of bias. The studies reported 43 possible predictors in six broad categories (intrinsic factors; maternal factors; diseases and adverse conditions of the newborn; treatment of the newborn; characteristics before and after extubation; and clinical scores and composite indicators). Through a qualitative synthesis of 43 predictors and a quantitative meta-analysis of 19 factors, we identified five definite factors, eight possible factors, and 22 unclear factors related to EF. Definite factors included gestational age, sepsis, pre-extubation pH, pre-extubation FiO2, and respiratory severity score. Possible factors included age at extubation, anemia, inotropic use, mean airway pressure, pre-extubation PCO2, mechanical ventilation duration, Apgar score, and spontaneous breathing trial. With only a few high-quality studies currently available, well-designed and more extensive prospective studies investigating the predictors affecting EF are still needed. In the future, it will be important to explore the possibility of combining multiple predictors or assessment tools to enhance the accuracy of predicting extubation outcomes in clinical practice.

Diaphragmatic ultrasound and patent ductus arteriosus in the newborn: A retrospective case series

Background

Patent ductus arteriosus (PDA) and diaphragmatic dysfunction are frequently seen in newborn infants but their relationship remains unknown. We aimed to use point of care ultrasound to compare diaphragmatic kinetics in infants with a PDA compared to in those without a PDA.

Methods

M-mode ultrasonography was used to measure the mean inspiratory velocity (V _I) in newborn infants with and without a haemodynamically significant PDA admitted in the Neonatal Unit at King's College Hospital during a three month period.

Results

Seventeen diaphragmatic ultrasound studies were reviewed from 14 infants with a median (IQR) gestational age of 26.1 (25.8-30.6) weeks, birth weight of 780 (660-1385) gr at a postnatal age of 18 (14-34) days. Eight scans had evidence of a PDA. The median (IQR) V_I was significantly lower in scans with a PDA [1.01 (0.78-1.86) cm/s] compared to the ones without a PDA [3.21 (2.80-3.59) cm/s, p < 0.001]. The median (IQR) gestational age was lower in infants with a PDA [25.8 (25.6-27.3) weeks] compared to infants without a PDA [29.0 (26.1-35.1) weeks, p = 0.007]. Using multivariable linear regression analysis the V_I was independently associated with a PDA (adjusted p < 0.001) but not with the gestational age (adjusted p = 0.659).

Conclusions

Patent ductus arteriosus was associated with a lower mean inspiratory velocity in neonates and this effect was independent of gestational age.

Neonatal abdominal support to address CPAP belly: Two cases report and literature review

Gaseous distension of the abdomen from the use of continuous positive airway pressure (CPAP) in the preterm population is of increasing concern for its unintended consequences. Methods to treat and prevent CPAP belly deserve further investigation. An intervention to provide abdominal support to address CPAP belly is presented in these case studies.

Weaning and extubation from neonatal mechanical ventilation: an evidenced-based review

Mechanical ventilation is a lifesaving treatment used to treat critical neonatal patients. It facilitates gas exchange, oxygenation, and CO2 removal. Despite advances in non-invasive ventilatory support methods in neonates, invasive ventilation (i.e., ventilation via an endotracheal tube) is still a standard treatment in NICUs. This ventilation approach may cause injury despite its advantages, especially in preterm neonates. Therefore, it is recommended that neonatologists consider weaning neonates from invasive mechanical ventilation as soon as possible. This review examines the steps required for the neonate's appropriate weaning and safe extubation from mechanical ventilation.

Cumulative hypoxia, socioeconomic deprivation and neurodevelopmental outcomes in preterm infants

BACKGROUND

Hypoxia can adversely affect cognition, while socioeconomic deprivation has also been associated with impaired neurodevelopment in the newborn. We aimed to assess the impact of hypoxia and socioeconomic deprivation on the neurodevelopmental outcomes of preterm infants.

METHODS

Retrospective cohort study at a tertiary neonatal unit between 2015 and 2018. The motor, cognitive and language domain scores of the Bayley-III assessment were recorded at 24 months of corrected gestational age. The percentage of time with pulse oximetry (SpO₂) < 75% was measured from the nursing records, from admission to 36 weeks postmenstrual age in infants born < 30 weeks gestational age. The multiple deprivation index (MDI) and the main care giver's education domain of the MDI were also recorded.

RESULTS

A total of 93,767 data points from 80 infants (34 male) with a median (IQR) gestational age of 27.9(25.9-29.0) weeks and a birth weight of 0.94(0.74-1.23) kg were analysed. The median (IQR) motor score [103(91-110)] was significantly related to the median (IQR) time with SpO₂ < 75% [1.5(0.9-3.4)%, adjusted p = 0.020]. The median (IQR) cognitive score [100(90-105)] was negatively significantly related to the time with SpO₂ < 75% (adjusted p = 0.012) and the median (IQR) education decile of the MDI [7(6-9), adjusted p = 0.011]. The median (IQR) language score [91(77-100)] was significantly positively related to the education domain of the MDI (adjusted p = 0.025).

CONCLUSIONS

Hypoxia in preterm infants exerted a negative impact on motor function and cognition and conversely, higher educational attainment had a positive impact on cognition and language.

Respiratory muscle function in the newborn: a narrative review

Our aim was to summarise the current evidence and methods used to assess respiratory muscle function in the newborn, focusing on current and future potential clinical applications. The respiratory muscles undertake the work of breathing and consist mainly of the diaphragm, which in the newborn is prone to dysfunction due to lower muscle mass, flattened shape and decreased content of fatigue-resistant muscle fibres. Premature infants are prone to diaphragmatic dysfunction due to limited reserves and limited capacity to generate force and avoid fatigue. Methods to assess the respiratory muscles in the newborn include electromyography, maximal respiratory pressures, assessment for thoraco-abdominal asynchrony and composite indices, such as the pressure-time product and the tension time index. Recently, there has been significant interest and a growing body of research in assessing respiratory muscle function using bedside ultrasonography. Neurally adjusted ventilator assist is a novel ventilation mode, where the level of the respiratory support is determined by the diaphragmatic electrical activity. Prolonged mechanical ventilation, hypercapnia and hypoxia, congenital anomalies and systemic or respiratory infection can negatively impact respiratory muscle function in the newborn, while caffeine and synchronised or volume-targeted ventilation have a positive effect on respiratory muscle function compared to conventional, non-triggered or pressure-limited ventilation, respectively. IMPACT: Respiratory muscle function is impaired in prematurely born neonates and infants with congenital anomalies, such as congenital diaphragmatic hernia. Respiratory muscle function is negatively affected by prolonged ventilation and infection and positively affected by caffeine and synchronised compared to non-synchronised ventilation modes. Point-of-care diaphragmatic ultrasound and neurally adjusted ventilator assist are recent diagnostic and therapeutic technological developments with significant clinical applicability.

Diaphragmatic electromyography during a spontaneous breathing trial to predict extubation failure in preterm infants

BACKGROUND

Premature attempts at extubation and prolonged episodes of ventilatory support in preterm infants have adverse outcomes. The aim of this study was to determine whether measuring the electrical activity of the diaphragm during a spontaneous breathing trial (SBT) could predict extubation failure in preterm infants.

METHODS

When infants were ready for extubation, the electrical activity of the diaphragm was measured by transcutaneous electromyography (EMG) before and during a SBT when the infants were on endotracheal continuous positive airway pressure.

RESULTS

Forty-eight infants were recruited (median (IQR) gestational age of 27.2 (25.6-30.4) weeks). Three infants did not pass the SBT and 13 failed extubation. The amplitude of the EMG increased during the SBT [2.3 (1.5-4.2) versus 3.5 (2.1-5.3) µV; p < 0.001]. In the whole cohort, postmenstrual age (PMA) was the strongest predictor for extubation failure (area under the curve (AUC) 0.77). In infants of gestational age <29 weeks, the percentage change of the EMG predicted extubation failure with an AUC of 0.74 while PMA was not associated with the outcome of extubation.

CONCLUSIONS

In all preterm infants, PMA was the strongest predictor of extubation failure; in those born <29 weeks of gestation, diaphragmatic electromyography during an SBT was the best predictor of extubation failure.

IMPACT

Composite assessments of readiness for extubation may be beneficial in the preterm population. Diaphragmatic electromyography measured by surface electrodes is a non-invasive technique to assess the electrical activity of the diaphragm. Postmenstrual age was the strongest predictor of extubation outcome in preterm infants. The change in diaphragmatic activity during a spontaneous breathing trial in extremely prematurely born infants can predict subsequent extubation failure with moderate sensitivity and specificity.

Evaluation of Short-term Outcomes of Tracheostomy Procedures in a NICU Population With High Ventilator Settings

OBJECTIVE

To investigate whether tracheostomy placement in infants requiring high ventilator pressure is safe and effective.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary children's hospital.

METHODS

Fifty ventilator-dependent neonatal intensive care unit patients who underwent tracheotomy from 2009 to 2018 were included. Patients requiring high ventilator pressures were compared to those requiring low ventilator pressures. Demographics, comorbidities, and surgical and clinical data were recorded.

RESULTS

Thirty-two percent (n = 16) had low ventilator settings at the time of tracheostomy tube placement, and 68% (n = 34) had high ventilator settings. The median peak inspiratory pressure of the high ventilator group was 29.5 cm H₂O, positive end-expiratory pressure (PEEP) was 8 cm H₂O, mean airway pressure was 13 cm H₂O, pressure support (PS) was 14 cm H₂O, PS above PEEP was 6 cm H₂O, and inspiratory time was 0.65 seconds. The high ventilator cohort had a higher median age at the time of surgery compared to the low ventilator group (P = .02). Female patients were more likely to have high ventilator settings (P = .02). There were no intraoperative complications or deaths within the first 7 days of tracheostomy tube placement. Pneumonia incidence and rate of mortality during admission did not vary by ventilator settings (P = .92 and P = .94, respectively).

CONCLUSION

Few differences in tracheostomy tube placement outcomes were observed for patients with high ventilator settings compared to low ventilator settings. These data demonstrate that patients requiring high ventilator pressures can benefit from tracheostomy tube placement with no additional short-term risks.

Normal range of values for contractility and relaxation parameters of inspiratory muscles in healthy children: An exploratory study

OBJECTIVES

To estimate normal range of values for the contractility and relaxation parameters of inspiratory muscles and compare them by sex, age, nutritional status and level of physical activity in healthy children.

WORKING HYPOTHESIS

We hypothesized that healthy children present similar range of values for the contractility and relaxation parameters of inspiratory muscles.

STUDY DESIGN

Exploratory study conducted between 2017 and 2018.

PATIENT-SUBJECT SELECTION

Healthy children aged 6 to 11 years without history of respiratory, cardiac, cerebrovascular or neuromuscular disease as well as no nasal congestion, influenza or known septum deviation were included.

METHODOLOGY

Anthropometric, spirometry and respiratory muscle strength data were assessed. Maximum rate of pressure development (MRPD), maximum relaxation rate (MRR), time constant of decay curve (τ), contraction time (CT) and half-relaxation time (½ RT) were calculated from the nasal inspiratory pressure curve.

RESULTS

The sample was composed of 110 children (55 boys) with 1.045 as mean z-BMI-score. MRPD range of values was 8.09% to 10.86% rise/10 ms, MRR range of values was 8.09% to 10.86% fall/10 ms, τ range of values was 36.41 to 49.88 ms, CT range of values was 200 to 276 ms, ½ RT range of values was 117.5 to 148 ms and MRPD/MRR range of values was 0.71 to 1.04. The contractility and relaxation parameters did not present significant differences among children when compared by sex, age, nutritional status, or level of physical activity groups (P > .05).

CONCLUSIONS

The contractility and relaxation parameters present similar values among children and they are not influenced by age, sex, nutritional status or physical activity level.

Does heart rate variability improve prediction of failed extubation in preterm infants?

Background Prematurity and its respective comorbidities may result in longer periods of mechanical ventilation in intensive care units (ICU). A method for the assessment of organic maturity would be useful for this population. Heart rate variability (HRV), as an indicator of homeostasis, is a well-established tool for this approach. The objective of the study was to assess HRV in intubated preterm infants in ICU immediately prior to extubation and correlate HRV with clinical evaluation outcomes. Methods A total of 46 preterm infants, 13 (28.2%) males, were prospectively studied and divided into a group with failed extubation (FEG: n=11) and a group with successful extubation (SEG: n=35). HRV was evaluated in time, frequency and nonlinear domains with a Polar RS800 device. HRV measurements were assessed with Kubios HRV Premium Software and statistically analyzed with the StatsDirect Statistical Software, version 1.9.2015 (2002). P<0.05 values were considered as statistically significant. Results There were no significant differences between heart rate variables of failed and successful extubation when analyzing the total group. However, the analysis of the sub-group of preterm infants weighing less than 1000 g showed a clear differentiation between the groups, when the nonlinear variables (approximate entropy, sample entropy and multiscale entropy 1, 2 and 3) were used, demonstrating that the group with successful extubation shows greater complexity and, therefore, relatively greater autonomic stability. Conclusion HRV was effective in predicting failed extubation in preterm infants when evaluated in a nonlinear domain and in preterm infants weighing less than 1000 g.

Effect of maturity and infection on the rate of relaxation of the respiratory muscles in ventilated, newborn infants

AIM

To assess the respiratory muscle time constant of relaxation (τ), an index of respiratory muscle function in ventilated newborns.

METHODS

Sixty-two infants (42 born prematurely) with a median gestational age of 29 [interquartile range (IQR) 26-37] weeks were prospectively studied. Measurement of τ was taken during spontaneous breathing on endotracheal continuous positive airway pressure prior to extubation, and τ was calculated from the reciprocal of the slope of the airway pressure decline versus time. Infants were classified as having had systemic or respiratory infection (positive microbiology) if they had any positive bacterial blood or respiratory culture prior to measurement.

RESULTS

Measurement of τ was taken at a median post-natal age of 6 (IQR 3-29) days. The median τ was higher in premature infants [17.4 (IQR 7.7-28.3) sec/cmH₂ O] compared to term infants [6.8 (IQR 4.4-8.7) sec/cmH₂ O, p < 0.001]. The median τ was higher in infants who had had positive microbiology [17.6 (IQR 9.9-29.1) sec/cmH₂ O] compared to infants with negative microbiology [8.0 (IQR 6.3-17.9) sec/cmH₂ O, p = 0.034]. τ was related to gestational age (r = -0.265, p = 0.003) and weight at measurement (r = -0.269, p = 0.002).

CONCLUSION

Respiratory muscle function in ventilated newborns is negatively affected by prematurity and previous systemic or respiratory infection.