Right Diaphragmatic Peak Motion Velocities on Pulsed Wave Tissue Doppler Imaging in Neonates: Method, Reproducibility, and Reference Values

The Application of Diaphragm Ultrasound in Chronic Obstructive Pulmonary Disease: A Narrative Review

Chronic Obstructive Pulmonary Disease (COPD) is a prevalent condition that poses a significant burden on individuals and society due to its high morbidity and mortality rates. The diaphragm is the main respiratory muscle, its function has a direct impact on the quality of life and prognosis of COPD patients. This article aims to review the structural measurement and functional evaluation methods through the use of diaphragmatic ultrasound and relevant research on its application in clinical practice for COPD patients. Thus, it serves to provide valuable insights for clinical monitoring of diaphragm function in COPD patients, facilitating early clinical intervention and aiding in the recovery of diaphragm function.

Ultrasound evaluation of diaphragm kinetics after minimally invasive surfactant administration

PURPOSE

Concerns remain on different alveolar deposition of surfactant between LISA and INSURE methods. Ultrasound evaluation of diaphragm kinetics may provide clinical evidence on this issue, as indirect representation of the respiratory system compliance.

METHODS

This was a prospective-observational pilot study. The inclusion criterion was CPAP-supported infants ≤ 32 weeks with RDS receiving surfactant via minimally invasive technique. 52 patients randomized for surfactant administration via LISA or INSURE methods were enrolled. Right diaphragm (RD) global mean peak velocity (MPV) by Pulsed-Wave Tissue Doppler Imaging (PTDI) was recorded before and two hours after surfactant administration with simultaneous measurements of oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) (SF ratio). Mechanical ventilation ≤ 72 h from birth represented treatment failure.

RESULTS

LISA infants had significantly higher gestational age (p = 0.029) and birth weight (p = 0.030) with lower CRIB-II scores (p = 0.030) than INSURE infants. LISA infants showed higher median MPV at baseline RD-PTDI US assessment (p = 0.024), but post-surfactant median MPV and other the investigated variables were similar at the adjusted analysis for gestational age and sedation. 8/52 (15%) infants who failed treatment had a significantly lower SF ratio (p = 0.002) and higher median MPV at RD-PTDI US (p = 0.004) after surfactant administration, despite the higher CPAP support level before (p = 0.007) and after (p = 0.001) surfactant administration. A full course of antenatal steroids was protective against mechanical ventilation (p = 0.038).

CONCLUSIONS

Different minimally invasive surfactant administration techniques do not appear to influence diaphragm kinetics evaluated by RD-PTDI US.

The Role of Ultrasonography in the Process of Weaning from Mechanical Ventilation in Critically Ill Patients

Weaning patients from mechanical ventilation (MV) is a complex process that may result in either success or failure. The use of ultrasound at the bedside to assess organs may help to identify the underlying mechanisms that could lead to weaning failure and enable proactive measures to minimize extubation failure. Moreover, ultrasound could be used to accurately identify pulmonary diseases, which may be responsive to respiratory physiotherapy, as well as monitor the effectiveness of physiotherapists' interventions. This article provides a comprehensive review of the role of ultrasonography during the weaning process in critically ill patients.

Effects of caffeine on diaphragmatic activity in preterm infants

BACKGROUND

Caffeine is the first-choice drug for the treatment for apnea of prematurity (AOP) in preterm infants and it has been reported that it improves the diaphragm activity. The aim of this study was to evaluate by ultrasound possible changes in diaphragm contractility and motility induced by caffeine.

METHODS

We studied 26 preterm infants with gestational age ≤34 weeks treated with caffeine for the prevention or treatment of AOP. Diaphragmatic ultrasound was performed 15 min (T₀ ) before and 60 min (T₆₀ ) after the loading (20 mg/kg) or maintenance (5 mg/kg) dose of caffeine.

RESULTS

Diaphragmatic excursion (DE) and thickness at the end of inspiration (DT-in) and expiration (DT-ex), as well as peak velocity of the excursion at the end of inspiration (DT-in) and expiration (DT-ex) increased after administration of both loading and maintenance dose of caffeine.

CONCLUSIONS

Ultrasounds confirmed that caffeine improves the activity of diaphragm in preterm infants improving its thickness, amplitude of excursions, and contraction velocity. These results are consistent with the effectiveness of caffeine in treating AOP and decreasing the risk of failure of noninvasive respiratory support in preterm infants with respiratory distress syndrome (RDS).

Diaphragm Ultrasound in Critically Ill Patients on Mechanical Ventilation—Evolving Concepts

Mechanical ventilation (MV) is a life-saving respiratory support therapy, but MV can lead to diaphragm muscle injury (myotrauma) and induce diaphragmatic dysfunction (DD). DD is relevant because it is highly prevalent and associated with significant adverse outcomes, including prolonged ventilation, weaning failures, and mortality. The main mechanisms involved in the occurrence of myotrauma are associated with inadequate MV support in adapting to the patient’s respiratory effort (over- and under-assistance) and as a result of patient-ventilator asynchrony (PVA). The recognition of these mechanisms associated with myotrauma forced the development of myotrauma prevention strategies (MV with diaphragm protection), mainly based on titration of appropriate levels of inspiratory effort (to avoid over- and under-assistance) and to avoid PVA. Protecting the diaphragm during MV therefore requires the use of tools to monitor diaphragmatic effort and detect PVA. Diaphragm ultrasound is a non-invasive technique that can be used to monitor diaphragm function, to assess PVA, and potentially help to define diaphragmatic effort with protective ventilation. This review aims to provide clinicians with an overview of the relevance of DD and the main mechanisms underlying myotrauma, as well as the most current strategies aimed at minimizing the occurrence of myotrauma with special emphasis on the role of ultrasound in monitoring diaphragm function.

Intra-Rater Reliability of Shear Wave Elastography for the Quantification of Respiratory Muscles in Adolescent Athletes

The aim of this study was to assess the intra-rater reliability and agreement of diaphragm and intercostal muscle elasticity and thickness during tidal breathing. The diaphragm and intercostal muscle parameters were measured using shear wave elastography in adolescent athletes. To calculate intra-rater reliability, intraclass correlation coefficient (ICC) and Bland-Altman statistics were used. The reliability/agreement for one-day both muscle measurements (regardless of probe orientation) were at least moderate. During the seven-day interval between measurements, the reliability of a single measurement depended on the measured parameter, transducer orientation, respiratory phase, and muscle. Excellent reliability was found for diaphragm shear modulus at the peak of tidal expiration in transverse probe position (ICC_3.1 = 0.91-0.96; ICC₃.₂ = 0.95), and from poor to excellent reliability for the intercostal muscle thickness at the peak of tidal inspiration with the longitudinal probe position (ICC_3.1 = 0.26-0.95; ICC₃.₂ = 0.15). The overall reliability/agreement of the analysed data was higher for the diaphragm measurements (than the intercostal muscles) regardless of the respiratory phase and probe position. It is difficult to identify a more appropriate probe position to examine these muscles. The shear modulus/thickness of the diaphragm and intercostal muscles demonstrated good reliability/agreement so this appears to be a promising technique for their examination in athletes.

A narrative review of diaphragmatic ultrasound in pediatric critical care

The use of point of care ultrasound (POCUS) at the bedside has increased dramatically within emergency medicine and in critical care. Applications of POCUS have spread to include diaphragmatic assessments in both adults and children. Diaphragm POCUS can be used to assess for diaphragm dysfunction (DD) and atrophy or to guide ventilator titration and weaning. Quantitative, semi-quantitative and qualitative measurements of diaphragm thickness, diaphragm excursion, and diaphragm thickening fraction provide objective data related to DD and atrophy. The potential for quick, noninvasive, and repeatable bedside diaphragm assessments has led to a growing amount of literature on diaphragm POCUS. To date, there are no reviews of the current state of diaphragm POCUS in pediatric critical care. The aims of this narrative review are to summarize the current literature regarding techniques, reference values, applications, and future innovations of diaphragm POCUS in critically ill children. A summary of current practice and future directions will be discussed.

How to improve CPAP failure prediction in preterm infants with RDS: a pilot study

We aimed to test the diagnostic accuracy in predicting continuous positive airway pressure (CPAP) failure in premature infants with respiratory distress syndrome (RDS) by integrating oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂) (SF ratio) with the measurement of peak velocity of the right diaphragmatic excursions (RD-PV), during the inspiration (I-Peak) and expiratory (E-Peak) phases, performed by pulsed-wave Tissue Doppler imaging. This is a prospective, observational pilot study conducted over a 2-year period. Neonates at ≤ 32 weeks gestation supported by early CPAP were eligible. Natural surfactant was delivered via a minimally invasive technique. We performed serial measurements of SF ratio and RD-PV during the early post-natal hours to test the accuracy in predicting surfactant administration as well as invasive ventilation support within 72 h from birth because of the RDS worsening. Of 56 preterm infants enrolled, 34 (61%) failed CPAP support. SF ratio showed a significant inverse relationship with both Silverman-Andersen score at birth (rho = - 0.417; P = .001) and RD-PV [E-Peak] (rho = - 0.361; P = .007). We achieved a high accuracy in predicting CPAP failure (AUC = 95%; 95% CI, 89-100%) by integrating gender, SF ratio, and RD-PV [E-Peak] at the restricted, multivariate analysis.Conclusions: SF ratio and RD-PV, as measured by pulsed-wave Tissue Doppler, may help physicians to improve their confidence in optimizing therapeutic options in preterm infants with RDS. What is Known: • Continuous positive airway pressure is the recommended first-line treatment for respiratory distress syndrome in preterm infants, but failure rates remain unacceptably high. • Choosing the optimal treatment in terms of non-invasive ventilation effectiveness and timeliness of surfactant administration for these patients is often challenging, also due to our inability to identify a worsening respiratory failure. What is New: • The integration of oxygen saturation, as measured by SpO₂/FiO₂, with right diaphragm peak motion velocities, as measured by pulsed-wave tissue Doppler, allows for high prediction accuracy of non-invasive ventilation support failure in premature infants at risk of respiratory distress syndrome. • These measurements may help physicians in providing optimal supportive therapy for these patients.

Tissue Doppler Imaging of the Diaphragm in Healthy Subjects and Critically Ill Patients

Rationale: Tissue Doppler imaging (TDI) is an echocardiographic method that measures the velocity of moving tissue.

Objectives: We applied this technique to the diaphragm to assess the velocity of diaphragmatic muscle motion during contraction and relaxation.

Methods: In 20 healthy volunteers, diaphragmatic TDI was performed to assess the pattern of diaphragmatic motion velocity, measure its normal values, and determine the intra- and interobserver variability of measurements. In 116 consecutive ICU patients, diaphragmatic excursion, thickening, and TDI parameters of peak contraction velocity, peak relaxation velocity, velocity–time integral, and TDI-derived maximal relaxation rate were assessed during weaning. In a subgroup of 18 patients, transdiaphragmatic pressure (Pdi)-derived parameters (peak Pdi, pressure–time product, and diaphragmatic maximal relaxation rate) were recorded simultaneously with TDI.

Measurements and Main Results: In terms of reproducibility, the intercorrelation coefficients were >0.89 for all TDI parameters (P < 0.001). Healthy volunteers and weaning success patients exhibited lower values for all TDI parameters compared with weaning failure patients, except for velocity–time integral, as follows: peak contraction velocity, 1.35 ± 0.34 versus 1.50 ± 0.59 versus 2.66 ± 2.14 cm/s (P < 0.001); peak relaxation velocity, 1.19 ± 0.39 versus 1.53 ± 0.73 versus 3.36 ± 2.40 cm/s (P < 0.001); and TDI-maximal relaxation rate, 3.64 ± 2.02 versus 10.25 ± 5.88 versus 29.47 ± 23.95 cm/s² (P < 0.001), respectively. Peak contraction velocity was strongly correlated with peak transdiaphragmatic pressure and pressure–time product, whereas Pdi-maximal relaxation rate was significantly correlated with TDI-maximal relaxation rate.

Conclusions: Diaphragmatic tissue Doppler allows real-time assessment of the diaphragmatic tissue motion velocity. Diaphragmatic TDI-derived parameters differentiate patients who fail a weaning trial from those who succeed and correlate well with Pdi-derived parameters.

Respiratory muscle ultrasonography: methodology, basic and advanced principles and clinical applications in ICU and ED patients-a narrative review

Respiratory muscle ultrasound is used to evaluate the anatomy and function of the respiratory muscle pump. It is a safe, repeatable, accurate, and non-invasive bedside technique that can be successfully applied in different settings, including general intensive care and the emergency department. Mastery of this technique allows the intensivist to rapidly diagnose and assess respiratory muscle dysfunction in critically ill patients and in patients with unexplained dyspnea. Furthermore, it can be used to assess patient-ventilator interaction and weaning failure in critically ill patients. This paper provides an overview of the basic and advanced principles underlying respiratory muscle ultrasound with an emphasis on the diaphragm. We review different ultrasound techniques useful for monitoring of the respiratory muscle pump and possible therapeutic consequences. Ideally, respiratory muscle ultrasound is used in conjunction with other components of critical care ultrasound to obtain a comprehensive evaluation of the critically ill patient. We propose the ABCDE-ultrasound approach, a systematic ultrasound evaluation of the heart, lungs and respiratory muscle pump, in patients with weaning failure.