Strategies and Challenges in the Treatment of Dental Enamel.

Enamel tissue, the hardest body tissue, which covers the outside of the tooth shields the living tissue, but it erodes and disintegrates in the acidic environment of the oral cavity. On the one hand, mature enamel is cell-free and, if damaged, does not regenerate. Tooth sensitivity and decay are caused by enamel loss. On the other hand, the tissue engineering approach is challenging because of the unique structure of tooth enamel. To develop an exemplary method for dental enamel rebuilding, accurate knowledge of the structure of tooth enamel, knowing how it is created and how proteins interact in its structure, is critical. Furthermore, novel techniques in tissue engineering for using stem cells to develop enamel must be established. This article aims to discuss current attempts to regenerate enamel using synthetic materials methods, recent advances in enamel tissue engineering, and the prospects of enamel biomimetics to find unique insights into future possibilities for repairing enamel tissue, perhaps the most fascinating of all tooth tissues.

Strategies for lung- and diaphragm-protective ventilation in acute hypoxemic respiratory failure: a physiological trial.

BACKGROUND: Insufficient or excessive respiratory effort during acute hypoxemic respiratory failure (AHRF) increases the risk of lung and diaphragm injury. We sought to establish whether respiratory effort can be optimized to achieve lung- and diaphragm-protective (LDP) targets (esophageal pressure swing - 3 to - 8 cm H2O; dynamic transpulmonary driving pressure ≤ 15 cm H2O) during AHRF. METHODS: In patients with early AHRF, spontaneous breathing was initiated as soon as passive ventilation was not deemed mandatory. Inspiratory pressure, sedation, positive end-expiratory pressure (PEEP), and sweep gas flow (in patients receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO)) were systematically titrated to achieve LDP targets. Additionally, partial neuromuscular blockade (pNMBA) was administered in patients with refractory excessive respiratory effort. RESULTS: Of 30 patients enrolled, most had severe AHRF; 16 required VV-ECMO. Respiratory effort was absent in all at enrolment. After initiating spontaneous breathing, most exhibited high respiratory effort and only 6/30 met LDP targets. After titrating ventilation, sedation, and sweep gas flow, LDP targets were achieved in 20/30. LDP targets were more likely to be achieved in patients on VV-ECMO (median OR 10, 95% CrI 2, 81) and at the PEEP level associated with improved dynamic compliance (median OR 33, 95% CrI 5, 898). Administration of pNMBA to patients with refractory excessive effort was well-tolerated and effectively achieved LDP targets. CONCLUSION: Respiratory effort is frequently absent  under deep sedation but becomes excessive when spontaneous breathing is permitted in patients with moderate or severe AHRF. Systematically titrating ventilation and sedation can optimize respiratory effort for lung and diaphragm protection in most patients. VV-ECMO can greatly facilitate the delivery of a LDP strategy. TRIAL REGISTRATION: This trial was registered in Clinicaltrials.gov in August 2018 (NCT03612583).

Abdominal Muscle Use During Spontaneous Breathing and Cough in Patients Who Are Mechanically Ventilated: A Bi-center Ultrasound Study.

BACKGROUND: Ultrasound may be useful to assess the structure, activity, and function of the abdominal muscles in patients who are mechanically ventilated. RESEARCH QUESTION: Does measurement of abdominal muscle thickening on ultrasound in patients who are mechanically ventilated provide clinically relevant information about abdominal muscle function and weaning outcomes? STUDY DESIGN AND METHODS: This study consisted of two parts, a physiological study conducted in healthy subjects and a prospective observational study in patients who were mechanically ventilated. Abdominal muscle thickness and thickening fraction were measured during cough and expiratory efforts in 20 healthy subjects, and prior to and during a spontaneous breathing trial in 57 patients being ventilated. RESULTS: In healthy subjects, internal oblique and rectus abdominis thickening fraction correlated with pressure generated during expiratory efforts (P < .001). In patients being ventilated, abdominal muscle thickness and thickening fraction were feasible to measure in all patients, and reproducibility was moderately acceptable. During a failed spontaneous breathing trial, thickening fraction of transversus abdominis and internal oblique increased substantially from baseline (13.2% [95% CI, 0.9-24.8] and 7.2% [95% CI, 2.2-13.2], respectively). The combined thickening fraction of transversus abdominis, internal oblique, and rectus abdominis measured during cough was associated with an increased risk of reintubation or reconnection to the ventilator following attempted liberation (OR, 2.1; 95% CI, 1.1-4.4 per 10% decrease in thickening fraction). INTERPRETATION: Abdominal muscle thickening on ultrasound was correlated to the airway pressure generated by expiratory efforts. In patients who were mechanically ventilated, abdominal muscle ultrasound measurements are feasible and moderately reproducible. Among patients who passed a spontaneous breathing trial, reduced abdominal muscle thickening during cough was associated with a high risk of liberation failure. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT03567564; URL: www.clinicaltrials.gov.

Assessing Diaphragmatic Function.

The diaphragm is vulnerable to injury during mechanical ventilation, and diaphragm dysfunction is both a marker of severity of illness and a predictor of poor patient outcome in the ICU. A combination of factors can result in diaphragm weakness. Both insufficient and excessive diaphragmatic contractile effort can cause atrophy or injury, and recent evidence suggests that targeting an appropriate amount of diaphragm activity during mechanical ventilation has the potential to mitigate diaphragm dysfunction. Several monitoring tools can be used to assess diaphragm activity and function during mechanical ventilation, including pressure-derived parameters, electromyography, and ultrasound. This review details these techniques and presents the rationale for a diaphragm-protective ventilation strategy.