Real-time images of tidal recruitment using lung ultrasound

Effect of an Individualized Lung Protective Ventilation on Lung Strain and Stress in Children Undergoing Laparoscopy: An Observational Cohort Study

BACKGROUND

Exaggerated lung strain and stress could damage lungs in anesthetized children. The authors hypothesized that the association of capnoperitoneum and lung collapse in anesthetized children increases lung strain-stress. Their primary aim was to describe the impact of capnoperitoneum on lung strain-stress and the effects of an individualized protective ventilation during laparoscopic surgery in children.

METHODS

The authors performed an observational cohort study in healthy children aged 3 to 7 yr scheduled for laparoscopic surgery in a community hospital. All received standard protective ventilation with 5 cm H2O of positive end-expiratory pressure (PEEP). Children were evaluated before capnoperitoneum, during capnoperitoneum before and after lung recruitment and optimized PEEP (PEEP adjusted to get end-expiratory transpulmonary pressure of 0), and after capnoperitoneum with optimized PEEP. The presence of lung collapse was evaluated by lung ultrasound, positive Air-Test (oxygen saturation measured by pulse oximetry 96% or less breathing 21% O2 for 5 min), and negative end-expiratory transpulmonary pressure. Lung strain was calculated as tidal volume/end-expiratory lung volume measured by capnodynamics, and lung stress as the end-inspiratory transpulmonary pressure.

RESULTS

The authors studied 20 children. Before capnoperitoneum, mean lung strain was 0.20 ± 0.07 (95% CI, 0.17 to 0.23), and stress was 5.68 ± 2.83 (95% CI, 4.44 to 6.92) cm H2O. During capnoperitoneum, 18 patients presented lung collapse and strain (0.29 ± 0.13; 95% CI, 0.23 to 0.35; P < 0.001) and stress (5.92 ± 3.18; 95% CI, 4.53 to 7.31 cm H2O; P = 0.374) increased compared to before capnoperitoneum. During capnoperitoneum and optimized PEEP, children presenting lung collapse were recruited and optimized PEEP was 8.3 ± 2.2 (95% CI, 7.3 to 9.3) cm H2O. Strain returned to values before capnoperitoneum (0.20 ± 0.07; 95% CI, 0.17 to 0.22; P = 0.318), but lung stress increased (7.29 ± 2.67; 95% CI, 6.12 to 8.46 cm H2O; P = 0.020). After capnoperitoneum, strain decreased (0.18 ± 0.04; 95% CI, 0.16 to 0.20; P = 0.090), but stress remained higher (7.25 ± 3.01; 95% CI, 5.92 to 8.57 cm H2O; P = 0.024) compared to before capnoperitoneum.

CONCLUSIONS

Capnoperitoneum increased lung strain in healthy children undergoing laparoscopy. Lung recruitment and optimized PEEP during capnoperitoneum decreased lung strain but slightly increased lung stress. This little rise in pulmonary stress was maintained within safe, lung-protective, and clinically acceptable limits.

EDITOR’S PERSPECTIVE

Comparison of chest radiograph and lung ultrasound in children with acute respiratory failure

PURPOSE

Chest x-ray (CXR) is the standard imaging used to evaluate children in acute respiratory distress and failure. Our objective was to compare the lung-imaging techniques of CXR and lung ultrasound (LUS) in the evaluation of children with acute respiratory failure (ARF) to quantify agreement and to determine which technique identified a higher frequency of pulmonary abnormalities.

METHODS

This was a secondary analysis of a prospective observational study evaluating the sensitivity and specificity of LUS in children with ARF from 12/2018 to 02/2020 completed at the University of Wisconsin-Madison (USA). Children > 37.0 weeks corrected gestational age and ≤ 18 years of age admitted to the PICU with ARF were evaluated with LUS. We compared CXR and LUS completed within 6 h of each other. Kappa statistics (k) adjusted for maximum attainable agreement (k/kmax) were used to quantify agreement between imaging techniques and descriptive statistics were used to describe the frequency of abnormalities.

RESULTS

Eighty-eight children had LUS completed, 32 with concomitant imaging completed within 6 h are included. There was fair agreement between LUS and CXR derived diagnoses with 58% agreement (k/kmax = 0.36). Evaluation of imaging patterns included: normal, 57% agreement (k = 0.032); interstitial pattern, 47% agreement (k = 0.003); and consolidation, 65% agreement (k = 0.29). CXR identified more imaging abnormalities than LUS.

CONCLUSIONS

There is fair agreement between CXR and LUS-derived diagnoses in children with ARF. Given this, clinicians should consider the benefits and limitations of specific imaging modalities when evaluating children with ARF. Additional studies are necessary to further define the role of LUS in pediatric ARF given the small sample size of our study.

Update on the use of ultrasound in the diagnosis and monitoring of the critical patient

Hemodynamic and respiratory complications are the main causes of morbidity and mortality in in critical care units (CCU). Imaging techniques are a key tool in differential diagnosis and treatment. In the last decade, ultrasound has shown great potential for bedside diagnosis of respiratory disease, as well as for the hemodynamic assessment of critically ill patients. Ultrasound has proven to be a useful guide for identifying the type of shock, estimating cardiac output, guiding fluid therapy and vasoactive drugs, providing security in the performance of percutaneous techniques (thoracentesis, pericardiocentesis, evacuation of abscesses/hematomas), detecting dynamically in real time pulmonary atelectasis and its response to alveolar recruitment maneuvers, and predicting weaning failure from mechanical ventilation. Due to its dynamic nature, simple learning curve and absence of ionizing radiation, it has been incorporated as an essential tool in daily clinical practice in CCUs. The objective of this review is to offer a global vision of the role of ultrasound and its applications in the critically ill patient.

Prediction of weaning readiness off nasal CPAP in preterm infants using point-of-care lung ultrasound

This study's primary aim was to assess whether end-expiratory lung ultrasound severity score (expLUSsc) at Day 3 of life, the second week of life, and before weaning off nasal continuous positive airway pressure (nCPAP) can predict the weaning readiness off nCPAP trial in preterm infants. The secondary aim was to evaluate the value of adding lung tidal recruitment (LTR) to expLUSsc (expLUSsc-plus-LTR) to improve predictability. We conducted a prospective study on premature infants <33 weeks of gestation. Point-of-care lung ultrasound (POC-LUS) was performed on Day 3, the second week of life, before and after the trial off nCPAP. expLUSsc, pleural thickness, and LTR were assessed. A receiver operator curve was constructed to evaluate the ability of POC-LUS to predict the weaning readiness off nCPAP. A total of 148 studies were performed on 39 infants, of them 12 weaned off nCPAP from the first trial and 27 infants failed attempts off nCPAP. An expLUSsc cut-off 8 before the first trial of weaning off nCPAP has a sensitivity and specificity of 88% and 90%, and positive and negative predictive values of 87% and 92%, respectively, with area under the curve (AUC) was 0.87 (CI: 0.8-0.93), p < .0001. If LTR is added to an expLUSsc cut-off 8 (expLUSsc-plus-LTR) before the first trial of weaning, then sensitivity and specificity of 95% and 90%, and positive and negative predictive values of 88% and 90%, respectively, with AUC was 0.95 (CI: 0.91-0.99), p < .0001. In conclusion, this study demonstrated the ability of POC-LUS to predict the weaning readiness off nCPAP in premature infants. The use of this simple bedside noninvasive test can potentially avoid the exposure of premature infants to multiple unsuccessful weaning cycles.

Atelectasis and lung recruitment in pediatric anesthesia: An educational review

General anesthesia is associated with development of pulmonary atelectasis. Children are more vulnerable to the development and adverse effects of atelectasis. We review the physiology and risk factors for the development of atelectasis in pediatric patients under general anesthesia. We discuss the clinical significance of atelectasis, the use and value of recruitment maneuvers, and other techniques available to minimize lung collapse. This review demonstrates the value of a recruitment maneuver, maintaining positive end-expiratory pressure (PEEP) until extubation and lowering FiO₂ where possible in the daily practice of the pediatric anesthetist.

Imaging the Injured Lung: Mechanisms of Action and Clinical Use

Acute respiratory distress syndrome (ARDS) consists of acute hypoxemic respiratory failure characterized by massive and heterogeneously distributed loss of lung aeration caused by diffuse inflammation and edema present in interstitial and alveolar spaces. It is defined by consensus criteria, which include diffuse infiltrates on chest imaging-either plain radiography or computed tomography. This review will summarize how imaging sciences can inform modern respiratory management of ARDS and continue to increase the understanding of the acutely injured lung. This review also describes newer imaging methodologies that are likely to inform future clinical decision-making and potentially improve outcome. For each imaging modality, this review systematically describes the underlying principles, technology involved, measurements obtained, insights gained by the technique, emerging approaches, limitations, and future developments. Finally, integrated approaches are considered whereby multimodal imaging may impact management of ARDS.

Lung Ultrasonography for Assessing Lung Aeration in Acute Respiratory Distress Syndrome: A Narrative Review

Acute respiratory distress syndrome (ARDS) constitutes a high burden for intensive care units. Although several methods are proposed to monitor aeration in ARDS, availability, costs, simplicity, and hazards (eg, ionizing radiation) limit the use of many of them at patients' bedsides. Given the widespread use of lung ultrasonography (US) in intensive care units, research is growing regarding its use to monitor aeration in patients with ARDS. We reviewed the actual role of lung US in ARDS and its potential impact in practice. Lung US can be readily used for assessing aeration, although, as a main limitation, a normal lung cannot be distinguished from hyperinflation. Additionally, an improvement in aeration by lung US does not always correlate with an increase in oxygenation. Lung US can be considered the main imaging method for monitoring aeration in ARDS, but in view of its limitations, it should not be used in isolation. Further studies are needed to validate lung US in large ARDS populations.

Utility of Perioperative Lung Ultrasound in Pediatric Cardiac Surgery

Background

Pediatric cardiac patients are at risk for perioperative respiratory insufficiency. The objective of this study was to assess the utility of perioperative lung ultrasound examination in pediatric cardiac surgery.

Methods

In this randomized, controlled trial, children (5 yr old or younger) undergoing cardiac surgery were allocated into a control (n = 61) or intervention (n = 61) group. The control group received only lung ultrasound examinations at the end of surgery and 6 to 12 h after surgery. The intervention group received lung ultrasound examinations and an ultrasound-guided recruitment maneuver depending on ultrasound findings after inducing anesthesia, at the end of surgery, and 6 to 12 h after surgery. Primary outcomes were incidences of intra- and postoperative desaturation, and postoperative pulmonary complications. Multiple comparisons were corrected (P ≤ 0.017) in the primary outcome analysis.

Results

Of the 120 children included in the analysis, postoperative desaturation (64% vs. 27%; P &lt; 0.001; odds ratio [OR], 0.210; 95% CI, 0.097 to 0.456) occurred more in the control group. The incidences of intraoperative desaturation (36% vs. 19%; P = 0.033; OR, 0.406; 95% CI, 0.176 to 0.939) and postoperative pulmonary complications (12% vs. 3%; P = 0.093; OR, 0.271; 95% CI, 0.054 to 1.361) were similar between the groups. Lung ultrasound scores were better in the intervention group than in the control group. Duration of mechanical ventilation was longer in the control group than in the intervention group (38 ± 43 vs. 26 ± 25 h; 95% CI of mean difference, 0 to 25; P = 0.048).

Conclusions

Perioperative lung ultrasound examination followed by ultrasound-guided recruitment maneuver helped decrease postoperative desaturation events and shorten the duration of mechanical ventilation in pediatric cardiac patients.

Recruitment manoeuvres in anaesthesia: How many more excuses are there not to use them?

Pulmonary recruitment manoeuvres (RM) are intended to reopen collapsed lung areas. RMs are present in nature as a physiological mechanism to get a newborn to open their lungs for the first time at birth, and we also use them, in our usual anaesthesiological clinical practice, after induction or during general anaesthesia when a patient is desaturated. However, there is much confusion in clinical practice regarding their safety, the best way to perform them, when to do them, in which patients they are indicated, and in those where they are totally contraindicated. There are important differences between RM in the patient with adult respiratory distress syndrome, and in a healthy patient during general anaesthesia. Our intention is to review, from a clinical and practical point of view, the use of RM, specifically in anaesthesia.

Respiratory monitoring in adult intensive care unit

INTRODUCTION

The mortality of patients with respiratory failure has steadily decreased with the advancements in protective ventilation and treatment options. Although respiratory monitoring per se has not been proven to affect the mortality of critically ill patients, it plays a crucial role in patients' care, as it helps to titrate the ventilatory support. Several new monitoring techniques have recently been made available at the bedside. The goals of monitoring comprise alerting physicians to detect the change in the patients' conditions, to improve the understanding of pathophysiology to guide the diagnosis and provide cost-effective clinical management. Areas covered: We performed a review of the recent scientific literature to provide an overview of the different methods used for respiratory monitoring in adult intensive care units, including bedside imaging techniques such as ultrasound and electrical impedance tomography. Expert commentary: Appropriate respiratory monitoring plays an important role in patients with and without respiratory failure as a guiding tool for the optimization of ventilation support, avoiding further complications and decreasing morbidity and mortality. The physician should tailor the monitoring strategy for each individual patient and know how to correctly interpret the data.

Doppler images of intra-pulmonary shunt within atelectasis in anesthetized children

BACKGROUND

Doppler images of pulmonary vessels in pulmonary diseases associated with subpleural consolidations have been described. Color Doppler easily identifies such vessels within consolidations while spectral Doppler analysis allows the differentiation between pulmonary and bronchial arteries. Thus, Doppler helps in diagnosing the nature of consolidations. To our knowledge, Doppler analysis of pulmonary vessels within anesthesia-induced atelectasis has never been described before. The aim of this case series is to demonstrate the ability of lung ultrasound to detect the shunting of blood within atelectatic lung areas in anesthetized children.

FINDINGS

Three anesthetized and mechanically ventilated children were scanned in the supine position using a high-resolution linear probe of 6-12 MHz. Once subpleural consolidations were detected in the most dependent posterior lung regions, the probe was rotated such that its long axis followed the intercostal space. In this oblique position, color Doppler mapping was performed to detect blood flow within the consolidation. Thereafter, pulsed waved spectral Doppler was applied in the previously identified vessels during a short expiratory pause, which prevented interferences from respiratory motion. Different flow patterns were identified which corresponded to both, pulmonary and bronchial vessels. Finally, a lung recruitment maneuver was performed which leads to the complete resolution of the aforementioned consolidation thereby confirming the pathophysiological entity of anesthesia-induced atelectasis.

CONCLUSIONS

Lung ultrasound is a non-invasive imaging tool that not only enables the diagnosis of anesthesia-induced atelectasis in pediatric patients but also analysis of shunting blood within this consolidation.

Ultrasonography for the assessment of lung recruitment maneuvers

Lung collapse is a known complication that affects most of the patients undergoing positive pressure mechanical ventilation. Such atelectasis and airways closure lead to gas exchange and lung mechanics impairment and has the potential to develop an inflammatory response in the lungs. These negative effects of lung collapse can be reverted by a lung recruitment maneuver (RM) i.e. a ventilatory strategy that resolves lung collapse by a brief and controlled increment in airway pressures. However, an unsolved question is how to assess such RM at the bedside. The aim of this paper is to describe the usefulness of lung sonography (LUS) to conduct and personalize RM in a real-time way at the bedside. LUS has favorable features to assess lung recruitment due to its high specificity and sensitivity to detect lung collapse together with its non-invasiveness, availability and simple use.