Search

Background: Nasopharyngeal tubes are useful in pediatric anesthesia for insufflating oxygen and anesthetics. During nasopharyngeal tube‐anesthesia, gas insufflation provides some positive oropharyngeal pressure that differs from the proximal airway pressure owing to the flow‐dependent pressure drop across the nasopharyngeal tube (ΔPNPT). Aims: This study aimed to investigate whether ΔPNPT could be used for calculating oropharyngeal pressure during nasopharyngeal tube‐assisted anesthesia. Methods: In a physical model of nasopharyngeal tube‐anesthesia, using Rohrer's equation, we calculated ΔPNPT for three nasopharyngeal tubes (3.5, 4.0, and 5.0 mm inner diameter) under oxygen and several sevoflurane in oxygen combinations in two ventilatory scenarios (continuous positive airway pressure and intermittent positive pressure ventilation). We then calculated oropharyngeal pressure as proximal airway pressure minus ΔPNPT. Calculated and measured oropharyngeal pressure couples of values were compared with the root mean square deviation to assess accuracy. We also investigated whether oropharyngeal pressure accuracy depends on the nasopharyngeal tube diameter, flow rate, gas composition, and leak size. Using ΔPNPT charts, we tested whether ΔPNPT calculation was feasible in clinical practice. Results: When we tested small‐diameter nasopharyngeal tubes at high‐flow or high‐peak inspiratory pressure, proximal airway pressure measurements markedly overestimated oropharyngeal pressure. Comparing measured and calculated maximum and minimum oropharyngeal pressure couples yielded root mean square deviations less than 0.5 cmH2O regardless of ventilatory modality, nasopharyngeal tube diameter, flow rate, gas composition, and leak size. Conclusion: During nasopharyngeal tube‐assisted anesthesia, proximal airway pressure readings on the anesthetic monitoring machine overestimate oropharyngeal pressure especially for smaller‐diameter nasopharyngeal tubes and higher flow, and to a lesser extent for large leaks. Given the importance of calculating oropharyngeal pressure in guiding nasopharyngeal tube ventilation in clinical practice, we propose an accurate calculation using Rohrer's equation method, or approximating oropharyngeal pressure from flow and pressure readings on the anesthetic machine using the ΔPNPT charts. [ABSTRACT FROM AUTHOR]

Although mechanical ventilation via an endotracheal tube has undoubtedly led to improvement in neonatal survival in the last 40 years, the prolonged use of this technique may predispose the infant to development of many possible complications including bronchopulmonary dysplasia. Avoiding mechanical ventilation is thought to be a critical goal, and different modes of noninvasive respiratory support beyond nasal continuous positive airway pressure, such as nasal intermittent positive pressure ventilation and synchronized nasal intermittent positive pressure ventilation, are also available and may reduce intubation rate. Several trials have demonstrated that the newer modes of noninvasive ventilation are more effective than nasal continuous positive airway pressure in reducing extubation failure and may also be more helpful as modes of primary support to treat respiratory distress syndrome after surfactant and for treatment of apnea of prematurity. With synchronized noninvasive ventilation, these benefits are more consistent, and different modes of synchronization have been reported. Although flow-triggering is the most common mode of synchronization, this technique is not reliable for noninvasive ventilation in neonates because it is affected by variable leaks at the mouth and nose. This review discusses the mechanisms of action, benefits and limitations of noninvasive ventilation, describes the different modes of synchronization and analyzes the technical characteristics, properties and clinical results of a flow-sensor expressly developed for synchronized noninvasive ventilation. [ABSTRACT FROM AUTHOR]

Background Apnoea, desaturations and bradycardias are common problems in preterm infants which can be treated with nasal continuous positive airway pressure (NCPAP) and nasal intermittent positive pressure ventilation (NIPPV). It is unclear whether synchronised NIPPV (SNIPPV) would be even more effective. Objective To assess the effects of flow-SNIPPV, NIPPV and NCPAP on the rate of desaturations and bradycardias in preterm infants and, secondarily, to evaluate their influence on pattern of breathing and gas exchange. Patients and methods Nineteen infants (mean gestational age at study 30 weeks, 9 boys) with apnoeic spells were enrolled in a randomised controlled trial with a cross-over design. They received flow-SNIPPV, NIPPV and NCPAP for 4 h each. All modes were provided by a nasal conventional ventilator able to provide synchronisation by a pneumotachograph. The primary outcome was the event rate of desaturations (≤80% arterial oxygen saturation) and bradycardias (≤80 bpm) per hour, obtained from cardiorespiratory recordings. The incidence of central apnoeas (≥10 s) as well as baseline heart rate, FiO2, SpO2, transcutaneous blood gases and respiratory rate were also evaluated. Results The median event rate per hour during flow-SNIPPV, NIPPV and NCPAP was 2.9, 6.1 and 5.9, respectively (p<0.001 and 0.009, compared with flow-SNIPPV). Central apnoeas per hour were 2.4, 6.3 and 5.4, respectively (p=0.001, for both compared with flow-SNIPPV), while no differences in any other parameter studied were recorded. Conclusions Flow-SNIPPV seems more effective than NIPPV and NCPAP in reducing the incidence of desaturations, bradycardias and central apnoea episodes in preterm infants. [ABSTRACT FROM AUTHOR]