The Effect of Lung Expansion and Positive End-Expiratory Pressure on Respiratory Mechanics in Anesthetized Children

Surfactant proteins analysis in perinatal deceased preterm twins among the Romanian population

The molecular basis of the evaluation of children suspected of having disorders of surfactant proteins is still under discussion. In this study, we aimed to describe the morphological characteristics and to evaluate the immunohistochemical expression of surfactant proteins (surfactant protein A [SPA], surfactant protein B, and pro-surfactant protein C) in the preterm twins that deceased due to unexplained respiratory distress syndrome (n = 12). Results showed statistically significant positive correlations between surfactant protein B expressions and pulmonary hemorrhage (ρ = 0.678; P < .05), SPA levels, and Apgar score (ρ = 0.605; P < .05) and also expressions of SPA and bronchopneumonia (ρ = 0.695; P < .05). The fetuses and neonates of the same gestational age showed differences among surfactant proteins regarding the immunostaining expression. Our data evidence a marked interindividual variability in the expression of all 3 surfactant proteins among the cases analyzed (n = 12), suggesting the intervention of some individual and epigenetic factors during gestation that might influence surfactant protein production and consequently survival rate.

Developmental respiratory physiology

Various developmental aspects of respiratory physiology put infants and young children at an increased risk of respiratory failure, which is associated with a higher rate of critical incidents during anesthesia. The immaturity of control of breathing in infants is reflected by prolonged central apneas and periodic breathing, and an increased risk of apneas after anesthesia. The physiology of the pediatric upper and lower airways is characterized by a higher flow resistance and airway collapsibility. The increased chest wall compliance and reduced gas exchange surface of the lungs reduce the pulmonary oxygen reserve vis-à-vis a higher metabolic oxygen demand, which causes more rapid oxygen desaturation when ventilation is compromised. This review describes the various developmental aspects of respiratory physiology and summarizes anesthetic implications.

Positive end-expiratory pressure improves elastic working pressure in anesthetized children

Background

Positive end-expiratory pressure (PEEP) has been demonstrated to decrease ventilator-induced lung injury in patients under mechanical ventilation (MV) for acute respiratory failure. Recently, some studies have proposed some beneficial effects of PEEP in ventilated patients without lung injury. The influence of PEEP on respiratory mechanics in children is not well known. Our aim was to determine the effects on respiratory mechanics of setting PEEP at 5 cmH₂O in anesthetized healthy children.

Methods

Patients younger than 15 years old without history of lung injury scheduled for elective surgery gave informed consent and were enrolled in the study. After usual care for general anesthesia, patients were placed on volume controlled MV. Two sets of respiratory mechanics studies were performed using inspiratory and expiratory breath hold, with PEEP 0 and 5 cmH₂O. The maximum inspiratory and expiratory flow (Q_I and Q_E) as well as peak inspiratory pressure (PIP), plateau pressure (P_PL) and total PEEP (tPEEP) were measured. Respiratory system compliance (C_RS), inspiratory and expiratory resistances (RawI and RawE) and time constants (K_TI and K_TE) were calculated. Data were expressed as median and interquartile range (IQR). Wilcoxon sign test and Spearman’s analysis were used. Significance was set at P < 0.05.

Results

We included 30 patients, median age 39 (15–61.3) months old, 60% male. When PEEP increased, PIP increased from 12 (11,14) to 15.5 (14,18), and C_RS increased from 0.9 (0.9,1.2) to 1.2 (0.9,1.4) mL·kg^− 1·cmH₂O^− 1; additionally, when PEEP increased, driving pressure decreased from 6.8 (5.9,8.1) to 5.8 (4.7,7.1) cmH₂O, and Q_E decreased from 13.8 (11.8,18.7) to 11.7 (9.1,13.5) L·min^− 1 (all P < 0.01). There were no significant changes in resistance and Q_I.

Conclusions

Analysis of respiratory mechanics in anesthetized healthy children shows that PEEP at 5 cmH₂O places the respiratory system in a better position in the P/V curve. A better understanding of lung mechanics may lead to changes in the traditional ventilatory approach, limiting injury associated with MV.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0611-8) contains supplementary material, which is available to authorized users.

Impact of positive end expiratory pressure on cerebral hemodynamic in paediatric patients with post-traumatic brain swelling treated by surgical decompression

Introduction

The objective of our present study is to evaluate the impact of different PEEP levels on cerebral hemodynamic, gas exchanges and respiratory system mechanics in paediatric patients with post-traumatic brain swelling treated with decompressive craniectomy (DC).

Materials and methods

A prospective physiologic study was carried out on 14 paediatric patients presenting with severe traumatic brain swelling treated with DC. Transcranial Doppler ultrasonography was performed on the middle cerebral artery bilaterally after DC. After assessment at ZEEP, intracranial pressure (ICP), cerebral perfusion pressure (CPP), mean arterial pressure (MAP), central venous pressure (CVP) and gas exchanges were recorded at PEEP 4 and PEEP 8.

Results

From ZEEP to PEEP 8, the compliance of respiratory system indexed to the weight of the patient significantly increased (P = 0.02) without ICP modifications. No significant variation of the MAP, CPP, Vmed, the total resistance of respiratory system and ohmic resistance of the respiratory system indexed to the weight of the patients was observed. CVP significantly increased between ZEEP and PEEP 8 (P = 0.005), and between PEEP 4 and PEEP 8 (P = 0.05).

Conclusions

PEEP values up to 8 cmH20 seem to be safe in paediatric patients with a severe post-traumatic brain swelling treated with DC.

Effect of Positive End-Expiratory Pressure on Optic Nerve Sheath Diameter in Pediatric Patients with Traumatic Brain Injury

Background:

The peak incidence of traumatic brain injury (TBI) has been reported in children and young adults. Intracranial pressure (ICP) as an important component can be measured with invasive technique, whereas noninvasive measurement of optic nerve sheath diameter (ONSD) is increasingly becoming popular. Positive end-expiratory pressure (PEEP) has been found to affect ICP. We aimed to compare the effect of different values of PEEP on ONSD and to obtain the correlation with ICP measurement.

Setting and Design:

Neurointensive Care Unit, Trauma Center, AIIMS, New Delhi.

Materials and Methods:

Pediatric patients with TBI, of either gender, between 1 and 18 years of age in whom ICP was measured using intraparenchymal Codman catheter admitted in neurointensive care unit were enrolled. For this crossover study, the sequence of PEEP (0 or 3 or 5 cm H₂O) was randomized and ONSD was measured. The mean of three ONSD values was taken as final value.

Statistical Method:

The ONSD, ICP, peak airway pressure, and hemodynamic parameters at various stages were compared using two-way repeated measures analysis of variance with Bonferroni correction. A P value of <0.05 was considered to be significant.

Results:

Ten patients (seven males, three females) participated in the study. There was no significant increase in ONSD values when PEEP was increased from 0 to 3 cm H₂O. However, increase in PEEP values from 3 to 5 cm H₂O showed significantly increased ONSD values.

Conclusion:

PEEP up to 3 cm H₂O can be safely applied in pediatric patients following TBI. Further increment of PEEP might accentuate the ICP values.

Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC)

Purpose

Much of the common practice in paediatric mechanical ventilation is based on personal experiences and what paediatric critical care practitioners have adopted from adult and neonatal experience. This presents a barrier to planning and interpretation of clinical trials on the use of specific and targeted interventions. We aim to establish a European consensus guideline on mechanical ventilation of critically children.

Methods

The European Society for Paediatric and Neonatal Intensive Care initiated a consensus conference of international European experts in paediatric mechanical ventilation to provide recommendations using the Research and Development/University of California, Los Angeles, appropriateness method. An electronic literature search in PubMed and EMBASE was performed using a combination of medical subject heading terms and text words related to mechanical ventilation and disease-specific terms.

Results

The Paediatric Mechanical Ventilation Consensus Conference (PEMVECC) consisted of a panel of 15 experts who developed and voted on 152 recommendations related to the following topics: (1) general recommendations, (2) monitoring, (3) targets of oxygenation and ventilation, (4) supportive measures, (5) weaning and extubation readiness, (6) normal lungs, (7) obstructive diseases, (8) restrictive diseases, (9) mixed diseases, (10) chronically ventilated patients, (11) cardiac patients and (12) lung hypoplasia syndromes. There were 142 (93.4%) recommendations with “strong agreement”. The final iteration of the recommendations had none with equipoise or disagreement.

Conclusions

These recommendations should help to harmonise the approach to paediatric mechanical ventilation and can be proposed as a standard-of-care applicable in daily clinical practice and clinical research.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-017-4920-z) contains supplementary material, which is available to authorized users.

Intratidal recruitment/derecruitment persists at low and moderate positive end-expiratory pressure in paediatric patients

In paediatric patients positive end-expiratory pressure (PEEP) is traditionally set lower than in adults. We investigated whether moderately higher PEEP improves respiratory mechanics and regional ventilation. Therefore, 40 children were mechanically ventilated with PEEP 2 and 5cmH₂O. Volume-dependent compliance profiles were analysed as a measure of intratidal recruitment/derecruitment. Regional ventilation was assessed using electrical impedance tomography. Mean compliance was 17.9±9.9mLcmH₂O^-1 (PEEP 2cmH₂O), and 19.0±10.9mLcmH₂O^-1 (PEEP 5 cmH₂O, p<0.001). Strong intratidal recruitment/derecruitment occurred in 40% of children at PEEP 2 cmH₂O, and 36% at PEEP 5 cmH₂O. Children showing strong recruitment/derecruitment were 33 (PEEP 2 cmH₂0) and 20 (PEEP 5 cmH₂0) months younger than children showing moderate recruitment/derecruitment. A higher PEEP improved peripheral ventilation. In conclusion, mechanically ventilated paediatric patients undergo intratidal recruitment/derecruitment which occurs more prominently in younger than in older children. A PEEP of 5cmH₂O does not fully prevent intratidal recruitment/derecruitment but homogenizes regional ventilation in comparison to 2cmH₂O.

Lung recruitment manoeuvres do not cause haemodynamic instability or oxidative stress but improve oxygenation and lung mechanics in a newborn animal model: an observational study

BACKGROUND

Lung recruitment manoeuvres in neonates during anaesthesia are not performed routinely due to concerns about causing barotrauma, haemodynamic instability and oxidative stress.

OBJECTIVE

To assess the influence of recruitment manoeuvres and positive end-expiratory pressure (PEEP) on haemodynamics, oxidative stress, oxygenation and lung mechanics.

DESIGN

A prospective experimental study.

SETTING

Experimental Unit, La Paz University Hospital, Madrid, Spain.

ANIMALS

Eight newborn piglets (<48 h) with healthy lungs under general anaesthesia.

INTERVENTIONS

The recruitment manoeuvres in pressure-controlled ventilation (PCV) were performed along with a constant driving pressure of 15 cmH2O. After the recruitment manoeuvres, PEEP was reduced in a stepwise fashion to find the maximal dynamic compliance step (maxCDyn-PEEP). Blood oxidative stress biomarkers (lipid peroxidation products, protein carbonyls, total glutathione, oxidised glutathione, reduced glutathione and activity of glutathione peroxidase) were analysed.

MAIN OUTCOME MEASURES

Haemodynamic parameters, arterial partial pressure of oxygen (paO2), tidal volume (Vt), dynamic compliance (Cdyn) and oxidative stress biomarkers were measured.

RESULTS

The recruitment manoeuvres did not induce barotrauma. Haemodynamic instability was not detected either in the maximum pressure step (overdistension step 5) or during the entire process. No substantial differences were observed in blood oxidative stress parameters analysed as compared with their baseline values (with 0 PEEP) or the values obtained 180 min after the onset of the recruitment manoeuvres (optimal PEEP). Significant maximal values were achieved in step 14 with an increase in paO2 (32.43 ± 8.48 vs. 40.39 ± 15.66 kPa; P = 0.037), Vt (47.75 ± 13.59 vs. 73.87 ± 13.56 ml; P = 0.006) and Cdyn (2.50 ± 0.64 vs. 4.75 ± 0.88 ml cmH2O; P < 0.001). Maximal dynamic compliance step (maxCdyn-PEEP) was 2 cmH2O.

CONCLUSION

Recruitment manoeuvres in PCV with a constant driving pressure are a well tolerated open-lung strategy in a healthy-lung neonatal animal model under general anaesthesia. The recruitment manoeuvres improve oxygenation parameters and lung mechanics and do not cause barotrauma, haemodynamic instability or oxidative stress.

Chest CT in children: anesthesia and atelectasis

BACKGROUND

There has been an increasing tendency for anesthesiologists to be responsible for providing sedation or anesthesia during chest CT imaging in young children. Anesthesia-related atelectasis noted on chest CT imaging has proven to be a common and troublesome problem, affecting image quality and diagnostic sensitivity.

OBJECTIVE

To evaluate the safety and effectiveness of a standardized anesthesia, lung recruitment, controlled-ventilation technique developed at our institution to prevent atelectasis for chest CT imaging in young children.

MATERIALS AND METHODS

Fifty-six chest CT scans were obtained in 42 children using a research-based intubation, lung recruitment and controlled-ventilation CT scanning protocol. These studies were compared with 70 non-protocolized chest CT scans under anesthesia taken from 18 of the same children, who were tested at different times, without the specific lung recruitment and controlled-ventilation technique. Two radiology readers scored all inspiratory chest CT scans for overall CT quality and atelectasis. Detailed cardiorespiratory parameters were evaluated at baseline, and during recruitment and inspiratory imaging on 21 controlled-ventilation cases and 8 control cases.

RESULTS

Significant differences were noted between groups for both quality and atelectasis scores with optimal scoring demonstrated in the controlled-ventilation cases where 70% were rated very good to excellent quality scans compared with only 24% of non-protocol cases. There was no or minimal atelectasis in 48% of the controlled ventilation cases compared to 51% of non-protocol cases with segmental, multisegmental or lobar atelectasis present. No significant difference in cardiorespiratory parameters was found between controlled ventilation and other chest CT cases and no procedure-related adverse events occurred.

CONCLUSION

Controlled-ventilation infant CT scanning under general anesthesia, utilizing intubation and recruitment maneuvers followed by chest CT scans, appears to be a safe and effective method to obtain reliable and reproducible high-quality, motion-free chest CT images in children.

Respiratory function during anesthesia: effects on gas exchange

Anaesthesia causes a respiratory impairment, whether the patient is breathing spontaneously or is ventilated mechanically. This impairment impedes the matching of alveolar ventilation and perfusion and thus the oxygenation of arterial blood. A triggering factor is loss of muscle tone that causes a fall in the resting lung volume, functional residual capacity. This fall promotes airway closure and gas adsorption, leading eventually to alveolar collapse, that is, atelectasis. The higher the oxygen concentration, the faster will the gas be adsorbed and the aleveoli collapse. Preoxygenation is a major cause of atelectasis and continuing use of high oxygen concentration maintains or increases the lung collapse, that typically is 10% or more of the lung tissue. It can exceed 25% to 40%. Perfusion of the atelectasis causes shunt and cyclic airway closure causes regions with low ventilation/perfusion ratios, that add to impaired oxygenation. Ventilation with positive end-expiratory pressure reduces the atelectasis but oxygenation need not improve, because of shift of blood flow down the lung to any remaining atelectatic tissue. Inflation of the lung to an airway pressure of 40 cmH2O recruits almost all collapsed lung and the lung remains open if ventilation is with moderate oxygen concentration (< 40%) but recollapses within a few minutes if ventilation is with 100% oxygen. Severe obesity increases the lung collapse and obstructive lung disease and one-lung anesthesia increase the mismatch of ventilation and perfusion. CO2 pneumoperitoneum increases atelectasis formation but not shunt, likely explained by enhanced hypoxic pulmonary vasoconstriction by CO2. Atelectasis may persist in the postoperative period and contribute to pneumonia.

Relationship between postoperative lung atelectasis and position of the endotracheal tube in pediatric living-donor liver transplantation

OBJECTIVE

The aims of current study were: 1) to evaluate the incidence of lung atelectasis; and 2) to investigate whether or not the position of the endotracheal (ET) tube is associated with this complication.

METHODS

The medical records and chest roentgenograms of 183 pediatric patients who underwent living-donor liver transplantation were retrospectively reviewed and analyzed. Patients without atelectasis were grouped in group I (GI) and those with atelectasis in group II (GII). The patients' characteristics and ET tube level between groups were compared with unpaired Student's t test. Multiple binary logistic regressions were also performed to identify the important risk factors associated with lung atelectasis.

RESULTS

Right upper lung (RUL) atelectsis could be found in ET tube at any level from T1 to T5, with incidence rates of 12.7%, 15.2%, 26.3%, 6.7%, and 100% for T1, T2, T3, T4, and T5, respectively. The incidence of atelectasis is 16.6%, and all of the atelectasis occurred in the RUL. No significant difference between groups was observed in the patients' characteristics, except for the amount of preoperative ascites. The likelihood of this risk factor could not be confirmed by multivariate binary logistic regression analysis.

CONCLUSIONS

The incidence of lung atelectasis in our study was 16.6%, which all occurred in the RUL. No predictive risk factor from the patients' characteristics could be found, and no correlation between the level of the ET tube and the occurrence of RUL atelectasis could be observed.

Murine mechanical ventilation stimulates alveolar epithelial cell proliferation

High tidal volume mechanical ventilation can cause inflammation and lung damage. Mechanical strain is also necessary for normal lung growth. The current work was performed to determine if mechanical ventilation with clinically utilized tidal volumes stimulates a proliferative response in the lung. Six- to 8-week-old C57/Bl6 mice, anesthetized with ketamine/xylozine, were ventilated for 6 hours with 10 mL/kg tidal volume, positive end-expiratory pressure (PEEP) 3cm H(2)O. Pulmonary function testing demonstrated decreased compliance within 3 hours of ventilation. Assessment of bronchoalveolar lavage (BAL) demonstrated no significant increase in lactate dehydrogenase, total lavagable cell number, or total protein after ventilation. There was evidence of inflammation in the lungs of ventilated mice, with an increased percentage of lymphocytes and neutrophils in BAL, and an increase in macrophage inflammatory protein (MIP)-2 and interleukin (IL)-1beta message in lung tissue. Immunohistochemistry of inflation-fixed lungs demonstrated increased alveolar cell proliferation, as measured by both proliferating cell nuclear antigen and Ki67 staining. Dual staining confirmed that proliferating cells labeled with proSP-B, demonstrating that ventilation induces proliferation of alveolar type II cells. Ventilation did not increase apoptosis in alveolar type II cells, as measured by TUNEL staining. Ventilation at low tidal volumes leads to a mild inflammatory response and alveolar epithelial cell proliferation.

[Peri-operative atelectasis and alveolar recruitment manoeuvres]

Respiratory complications are a significant cause of post-operative morbidity and mortality. Peri-operative atelectasis, in particular, affects 90% of surgical patients and its effects can be prolonged, due to changes in respiratory mechanics, pulmonary circulation and hypoxaemia. Alveolar collapse is caused by certain predisposing factors, mainly by compression and absorption mechanisms. To prevent or treat these atelectasis several therapeutic strategies have been proposed, such as alveolar recruitment manoeuvres, which has become popular in the last few years. Its application in patients with alveolar collapse, but without a previous significant acute lung lesion, has some special features, therefore its use is not free of uncertainties and complications. This review describes the frequency, pathophysiology, importance and treatment of peri-operative atelectasis. Special attention is paid to treatment with recruitment manoeuvres, with the purpose of providing a basis for the their rational and appropriate use.

Alveolar recruitment strategy and PEEP improve oxygenation, dynamic compliance of respiratory system and end-expiratory lung volume in pediatric patients undergoing cardiac surgery for congenital heart disease

OBJECTIVE

Optimizing alveolar recruitment by alveolar recruitment strategy (ARS) and maintaining lung volume with adequate positive end-expiratory pressure (PEEP) allow preventing ventilator-induced lung injury (VILI). Knowing that PEEP has its most beneficial effects when dynamic compliance of respiratory system (Crs) is maximized, we hypothesize that the use of 8 cm H(2)O PEEP with ARS results in an increase in Crs and end-expiratory lung volume (EELV) compared to 8 cm H(2)O PEEP without ARS and to zero PEEP in pediatric patients undergoing cardiac surgery for congenital heart disease.

METHODS

Twenty consecutive children were studied. Three different ventilation strategies were applied to each patient in the following order: 0 cm H(2)O PEEP, 8 cm H(2)O PEEP without an ARS, and 8 cm H(2)O PEEP with a standardized ARS. At the end of each ventilation strategy, Crs, EELV, and arterial blood gases were measured.

RESULTS

EELV, Crs, and P(a)O(2)/FiO(2) ratio changed significantly (P < 0.001) with the application of 8 cm H2O + ARS. Mean P(a)CO(2)- PETCO(2) difference between 0 PEEP and 8 cm H2O PEEP + ARS was also significant (P < 0.05).

CONCLUSION

An alveolar recruitment strategy with relative high PEEP significantly improves Crs, oxygenation, P(a)CO(2)- PETCO(2) difference, and EELV in pediatric patients undergoing cardiac surgery for congenital heart disease.

Thoracic malformation with early-onset scoliosis: effect of serial VEPTR expansion thoracoplasty on lung growth and function in children

The effect on pulmonary function of serial VEPTR expansion thoracoplasty was studied longitudinally in anesthetized children with spondylothoracic dysplasia using a special mobile unit. The median age of 24 children at the start of surgery was 4.6 years (1.8-10.8) and most exhibited a moderate-to-severe restrictive lung defect. After a median of 3.2 years (1.0-6.5), their forced vital capacity (FVC) was found to have increased by an average of 11.1%/year. The rate of increase was greater in children who were younger than 6 years at the start of the study than in older children (14.5% versus 6.5%, p<0.01). The average specific respiratory system compliance (C(rs)) was mildly-to-moderately decreased at the start, and over the study it decreased on average to 56% of the initial value in spite of clinically successful expansion thoracoplasty and lung growth, indicating increasing stiffness of the thorax with growth.