End-tidal PCO2 monitoring via nasal cannulae in pediatric patients: Accuracy and sources of error

Objective. To assess the correlation and accuracy of end-tidal PCO₂ (PetCO₂) sampled via nasal cannulae in pediatric patients by comparison to the criterion standard PaCO₂, and to identify sources of error during PetCO₂ monitoring via nasal cannulae.Methods. PetCO₂ was monitored continuously by sampling end-tidal gas through nasal cannulae that had been designed and manufactured for this purpose in spontaneously breathing children undergoing conscious or deep sedation during either cardiac catheterization (n = 43) or critical care (n = 54). When both the capnographic wave form and the PetCO₂ value had been stable for at least 10 minutes, the PetCO₂ value was recorded while blood was drawn from an indwelling arterial line for PaCO₂ measurement. The effects of age, weight, respiratory rate, oxygen delivery system, airway obstruction, mouth breathing, and cyanotic heart disease were evaluated by linear regression analysis and calculation of absolute bias (PaCO₂-PetCO₂).Results. Mouth breathing, airway obstruction, oxygen delivery through the ipsilateral nasal cannula, and cyanotic heart disease adversely affected accuracy. In patients without those factors, PetCO₂ correlated well with PaCO₂ (R² = 0.994), and absolute bias was 3.0 ± 1.8 mmHg.Conclusions. Several factors — some controllable and all recognizable — affect the accuracy of PetCO₂ monitored via nasal cannulae in pediatric patients. When these factors are not present, PetCO₂ correlates well with PaCO₂ and appears to be a useful monitor of ventilatory status during conscious or deep sedation.     

Prospective,randomized comparison of two supplemental oxygen methods during gastroscopy with propofol mono-sedation in obese patients

BACKGROUNDHypoxemia is a common complication in obese patients during gastroscopy with sedation. The Wei nasal jet tube (WNJT) is a new special nasopharyngeal airway with the ability to provide supraglottic jet ventilation and oxygen insufflation via its built-in wall channels. The aim of this study was to compare the efficacy and safety of the WNJT vs a nasal cannula for supplemental oxygen during gastroscopy with propofol mono-sedation in obese patients.AIMTo compare the efficacy and safety of the WNJT vs a nasal cannula for supplemental oxygen during gastroscopy with propofol mono-sedation in obese patients.METHODSA total of 103 obese patients with a body mass index of 30 kg/m² or more undergoing elective gastroscopy under propofol mono-sedation were randomly assigned to receive supplemental oxygen at 5 L/min through either a WNJT (WNJT group, n = 51) or a nasal cannula (nasal cannula group, n = 52). The lowest pulse oxygen saturation (SpO₂) and mild and severe hypoxemia during gastroscopy were recorded. The primary outcome was the incidence of hypoxemia.RESULTSThe lowest SpO₂ during gastroscopy with propofol mono-sedation was significantly increased in the WNJT group compared with the nasal cannula group. The incidence of mild hypoxemia and total incidence of hypoxemia were significantly lower in the WNJT group than in the nasal cannula group. Other than a higher incidence of epistaxis in the WNJT group, the occurrence of adverse events was similar between the devices. While neither device demonstrated a statistically significant difference in satisfaction among patients, the WNJT did result in improved satisfaction among anesthetists and physicians.CONCLUSIONDuring gastroscopy with propofol mono-sedation in obese patients, the WNJT, when compared with a nasal cannula for supplemental oxygen, can significantly reduce the occurrence of hypoxemia and improve both arterial oxygenation and satisfaction among anesthetists and physicians. The use of the WNJT may, however, lead to epistaxis in a few patients. In view of this clinically acceptable risk-benefit ratio, the WNJT may be recommended as an alternative tool for supplemental oxygen for the prevention of hypoxemia during gastroscopy with propofol mono-sedation in obese patients.     

COVID-19 respiratory support in the emergency department setting

IntroductionSevere acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19), may result in severe complications, multiorgan dysfunction, acute respiratory failure, and death. SARS-CoV-2 is highly contagious and places healthcare workers at significant risk, especially during aerosol-generating procedures, including airway management.ObjectiveThis narrative review outlines the underlying respiratory pathophysiology of patients with COVID-19 and discusses approaches to airway management in the emergency department (ED) based on current literature.DiscussionPatients presenting with SARS-CoV-2 infection are at high risk for acute respiratory failure requiring airway management. Among hospitalized patients, 10–20% require intensive care unit admission, and 3–10% require intubation and mechanical ventilation. While providing respiratory support for these patients, proper infection control measures, including adherence to personal protective equipment policies, are necessary to prevent nosocomial transmission to healthcare workers. A structured approach to respiratory failure in these patients includes the use of exogenous oxygen via nasal cannula or non-rebreather, as well as titrated high-flow nasal cannula and non-invasive ventilation. This review offers several guiding principles and resources designed to be adapted in conjunction with local workplace policies for patients requiring respiratory support.ConclusionsWhile the fundamental principles of acute respiratory failure management are similar between COVID-19 and non-COVID-19 patients, there are some notable differences, including a focus on provider safety. This review provides an approach to airway management and respiratory support in the patient with COVID-19.     

Face mask leak with nasal cannula during noninvasive positive pressure ventilation: A randomized crossover trial

Background

Nasal cannula can achieve apneic oxygenation during emergency intubation. However, pre-procedure nasal cannula placement may be difficult in patients undergoing non-invasive positive pressure ventilation (NPPV) prior to intubation. Our objective was to compare mask leak during NPPV with versus without simultaneous application of nasal cannula. We hypothesized mask leak would be no worse with concomitant use of nasal cannula (non-inferiority design).

Use of high flow nasal cannula in critically ill infants, children, and adults: a critical review of the literature

Background

High flow nasal cannula (HFNC) systems utilize higher gas flow rates than standard nasal cannulae. The use of HFNC as a respiratory support modality is increasing in the infant, pediatric, and adult populations as an alternative to non-invasive positive pressure ventilation.

Objectives

This critical review aims to: (1) appraise available evidence with regard to the utility of HFNC in neonatal, pediatric, and adult patients; (2) review the physiology of HFNC; (3) describe available HFNC systems (online supplement); and (4) review ongoing and planned trials studying the utility of HFNC in various clinical settings.

Results

Clinical neonatal studies are limited to premature infants. Only a few pediatric studies have examined the use of HFNC, with most focusing on this modality for viral bronchiolitis. In critically ill adults, most studies have focused on acute respiratory parameters and short-term physiologic outcomes with limited investigations focusing on clinical outcomes such as duration of therapy and need for escalation of ventilatory support. Current evidence demonstrates that HFNC generates positive airway pressure in most circumstances; however, the predominant mechanism of action in relieving respiratory distress is not well established.

Conclusion

Current evidence suggests that HFNC is well tolerated and may be feasible in a subset of patients who require ventilatory support with non-invasive ventilation. However, HFNC has not been demonstrated to be equivalent or superior to non-invasive positive pressure ventilation, and further studies are needed to identify clinical indications for HFNC in patients with moderate to severe respiratory distress.     

A case series of paediatric high flow nasal cannula therapy

IntroductionHigh flow nasal cannula is an emerging treatment option in Paediatric Intensive Care Units for paediatric patients in acute respiratory distress. Yet there is a paucity of literature describing its clinical application in various presenting pathophysiologies.AimTo describe three cases with differing underlying pathophysiologies and their response to high flow nasal cannula oxygen therapy.MethodPatients admitted to the Paediatric Intensive Care Unit with bronchiolitis, asthma and cardiomyopathy, and treated with high flow nasal cannula therapy were searched in the Paediatric Intensive Care database. The most representative cases were chosen to review.ResultsOne infant and two children were reviewed. All were commenced on high flow nasal cannula therapy in the Paediatric Intensive Care Unit and all demonstrated an improvement in their work of breathing. There was also a substantial improvement in their haemodynamic status. No patient required escalation to other forms of respiratory therapy.ConclusionHigh flow nasal cannula therapy is a viable treatment option for a range of patients presenting to the Paediatric Intensive Care Unit with acute respiratory distress. More invasive methods of respiratory support may be avoided by the use of high flow nasal cannula therapy.     

改良鼻咽通气道用于阻塞性睡眠呼吸暂停综合征患者无痛胃镜检查的临床效果观察

目的 评价改良鼻咽通气道机械通气预防阻塞性睡眠呼吸暂停综合征（OSAS）患者无痛胃镜检查术中缺氧的效果。方法 将90例行无痛胃镜检查术的OSAS患者随机分为3组：鼻导管吸氧组（C组）、改良鼻咽通气道吸氧组（N组）和鼻咽通气道机械通气组（M组）。C组经鼻导管吸纯氧5 L/min;N组置入改良鼻咽通气道,并吸纯氧5 L/min;M组置入改良鼻咽通气道,并连接麻醉机行机械通气。主要观察指标为术中缺氧的发生情况;次要观察指标为：亚临床呼吸抑制和重度缺氧发生情况,缺氧事件处理措施（抬下颌、面罩加压通气和气管插管机械通气）使用情况,术中和术后体动、呛咳、鼻出血、咽痛和口腔干燥等不良反应发生情况,麻醉医师、操作医师和患者的满意度评分。结果 与C组比较,N组缺氧发生率降低（P <0.05）,M组缺氧发生率、亚临床呼吸抑制发生率、抬下颌使用率和呛咳发生率均降低,胃镜医师和麻醉医师满意度升高（均P <0.05）。与N组比较,M组缺氧发生率降低（P <0.05）。3组患者体动、鼻出血、咽痛和口腔干燥发生率比较,差异均无统计学意义（P> 0.05）。结论 改良鼻咽通气道机械通气可有效降...     

Monitoring End-Tidal Carbon Dioxide Levels of Deeply Sedated MRI Pediatric Patients During the Recovery Period

Safe and effective sedation for the pediatric patient while undergoing magnetic resonance imaging (MRI) is essential. Monitoring of the pediatric patient is essential not only during the MRI procedure, but also during the recovery period after the examination. Capnography, which measures end-tidal carbon dioxide (ETCO₂), is a routine part of anesthesia practice for general anesthesia that also works well for the sedated patient in the imaging department. This study assessed the use of ETCO₂ in the recovery area to monitor the pediatric patient after being sedated with intravenous (IV) pentobarbital while in the MRI scanner. The results of this study showed that ETCO₂ levels remained within the clinical normal range throughout the recovery period for pediatric patients sedated with IV pentobarbital.     

Using a high‐flow respiratory system (Vapotherm®) within a high dependency setting

Background: Vapotherm 2000i^® is a non‐invasive high‐flow respiratory support system used mainly in the treatment of type 1 respiratory failure. It uses a mixture of oxygen and air to deliver a set concentration via nasal cannula (or tracheostomy mask). The advantage of this system is the high humidity achieved using the integral heated water system. The system has been used in neonatal practice as a replacement for conventional continuous positive airway pressure (CPAP) but there is little published research within the adult setting about its use. Aim: This study discusses the indications for the use of this non‐invasive high‐flow respiratory support system, the system set up, the benefits and complications of the system. Audit design: An audit of 72 patients was undertaken within the Surgical High Dependency Unit that collected data on the types of patient receiving the therapy, its effectiveness and patient experience. Audit findings: The audit demonstrated reduced respiratory rate and improvement in oxygenation for treated patients. Conclusion: A non‐invasive high‐flow respiratory support system can be effective at improving oxygenation in hypoxic patients. Patients were generally satisfied with the system and the system seems suitable for use in an adult surgical high dependency setting.     

Journal of Clinical Monitoring and Computing 2015 end of year summary: anesthesia

Clinical monitoring is an essential part of the profession of anesthesiology. It would therefore be impossible to review all articles published in the Journal of Clinical Monitoring and Computing that are relevant to anesthesia. Because other reviews will address monitoring of the respiratory and cardiovascular system, the current review will limit itself to topics uniquely related to anesthesia. The topics are organized according to the chronological order in which an anesthetic proceeds: secure the airway; ventilate and deliver anesthetic gases; monitor vital organ function and anesthetic depth; and ensure analgesia during/after emergence from anesthesia (locoregional anesthesia and pain control).     

Pupillary reflex dilation in response to incremental nociceptive stimuli in patients receiving intravenous ketamine

Pupillometry is a non-invasive monitoring technique, which allows dynamic pupillary diameter measurement by an infrared camera. Pupillary diameter increases in response to nociceptive stimuli. In patients anesthetized with propofol or volatile agents, the magnitude of this pupillary dilation is related to the intensity of the stimulus. Pupillary response to nociceptive stimuli has never been studied under ketamine anesthesia. Our objective was to describe pupillary reflex dilation after calibrated tetanic stimulations in patients receiving intravenous ketamine. After written consent, 24 patients of our pediatric burn care unit were included. They received an oral morphine premedication (0.3 mg kg^?1) 1 h before their scheduled daily dressing change. Just before the procedure, they received 1 mg kg^?1 of intravenous ketamine. Two minutes after this bolus, tetanic stimulations of incremental intensities were performed on the arm of each patient (5–10–20–30–40–60 mA, 60 s interval between stimulations). Pupillary diameter, heart rate and movements were recorded before and after each stimulation. Tetanic stimulations were associated with changes in pupillary diameter and heart rate. The magnitude of these changes was significantly influenced by the intensity of stimulation (ANOVA for repeated measures, p?<?0.001). Movement was associated with a 32% increase in diameter (ROC curves, AUC 0.758) with 65% sensitivity and 77% specificity. In children, pupillary reflex dilation to nociceptive stimuli persists under deep sedation obtained with 1 mg kg^?1 of intravenous ketamine combined with a 0.3 mg kg^?1 oral morphine premedication, and its magnitude depends on the intensity of the stimulation. Our results confirm that pupillometry could be a relevant way to monitor nociception in anaesthetised subjects, including those receiving ketamine. Trial registration clinicaltrials.gov, NCT 02648412     

Les lunettes nasales à haut débit : nouvelle modalité d’oxygénothérapie ou nouvel outil de ventilation non invasive en réanimation pédiatrique ?

High flow nasal cannula (HFNC) is a new mode of respiratory support. In pediatrics, administration through nasal cannula of heated and humidified gas at rates >2 L/min improves oxygen delivery, dead space washing, and mucociliary clearance, compared with conventional oxygenation devices. HNFC generates positive pharyngeal pressure and may improve breathing work. HNFC could thus be considered as a device between high concentration mask and continuous positive airway pressure (CPAP). Tolerance is excellent and implementation simple. HFNC has been suggested as an interesting tool for the management of moderate to severe bronchiolitis. Experience in neonates and adults may encourage considering other indications, like respiratory support following extubation and management of mild asthma. Like any respiratory support, initiating HFNC requires close monitoring in a pediatrician intensive care unit.     

Accuracy of capnography with a 30 foot nasal cannula for monitoring respiratory rate and end-tidal CO2 in children

We tested the accuracy of a low flow (50 cc/min) sidestream capnographysystem equipped with an experimental 30-foot nasal cannula to monitor ventilatory status in children. End-tidal CO₂ and respiratory rate, both at room air and in the presence of supplemental oxygen, were recorded simultaneously from the experimental 30-foot nasal cannula and the standard, FDA approved, 10-foot nasal cannula. The 30-foot nasal cannula was as accurate as the 10-foot nasal cannula in measuring respiratory rate and end-tidal CO₂ in children. When supplemental oxygen was delivered by facemask, there was no dilutional effect on the respiratory rate or end-tidal CO₂ recorded with either the 10-foot or 30-foot nasal cannulas inplace. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of carboxyhemoglobin half-life in patients with carbon monoxide toxicity treated with high flow nasal cannula oxygen therapy

Background: Acute carbon monoxide poisoning is a common environmental emergency worldwide. Treatment options are limited to normobaric oxygen therapy with a nonrebreather face mask or endotracheal tube and hyperbaric oxygen. The aim of this study is to determine the half-life of carboxyhemoglobin (COHb) in adult patients admitted to the emergency department with acute carbon monoxide poisoning receiving high flow nasal cannula (HFNC) oxygen. Device tolerability and patient comfort with the high flow nasal cannula were also evaluated.

Methods: This study was conducted between January 2017 and February 2018 in two academic emergency departments. Venous blood samples were obtained at 10?minute intervals to determine the rate of elimination of COHb. Patient comfort was evaluated by a verbal numeric rating scale. The primary outcome was the determination of the half-life of COHb. The secondary outcome was device tolerability and patient comfort with the high flow nasal cannula oxygen delivery system.

Results: A total of 33 patients were enrolled in the study. The mean baseline COHb level of the patients was 22.5% (SD 8%). The mean half-life of carboxyhemoglobin was determined as 36.8?minutes (SD 9.26?min) with high flow nasal cannula oxygen. COHb levels were halved during the first 40?minutes in 22 (67%) of the study patients. Twenty of the patients receiving HFNC oxygen did not report intolerance or discomfort. Among the 11 patients who requested a change in the flow rate, the median verbal numeric rating score was 7. After decreasing the flow rate, the median verbal numeric rating score was 9.

Conclusion: High flow nasal cannula oxygen is an easy, safe, comfortable and effective method to reduce COHb. HFNC may be a promising alternative method if it is validated as effective in future studies with clinical outcomes.     

Reduced cardiac sympathetic autonomic tone after long-term nasal continuous positive airway pressure in obstructive sleep apnoea syndrome

The increased sympathetic activation that occurs in obstructive sleep apnoea (OSA) may play an important role in associated morbidity. We investigated the effect of long-term (3 month) nasal continuous positive airway pressure (CPAP) on the autonomic nervous system assessed by heart rate variability (HRV). Fourteen patients (12 men), mean age 61·4 ± 8·1 years, with OSA underwent continuous synchronized electrocardiographic and polysomnographic monitoring. The apnoea/hypopnoea index (AHI) decreased from 50·6 ± 13·7 to 2·2 ± 2·5 events h^?1 after CPAP. HRV analysis showed significant decreases in low frequency (LF; from 7·12 ± 1·06 to 6·22 ± 1·18 ln ms² Hz^?1; P<0·001), high frequency (HF; from 5·91 ± 0·87 to 5·62 ± 0·92 ln ms² Hz^?1; P<0·05) and LF/HF (from 1·21 ± 0·12 to 1·11 ± 0·15 ln ms² Hz^?1; P<0·001) when the patients were asleep. The decrease in LF/HF was prolonged into the daytime (from 1·33 ± 0·22 to 1·24 ± 0·21 ln ms² Hz^?1; P<0·001). Treatment of OSA by CPAP significantly reduced the parameters of cardiac sympathetic tone, a favourable effect.     

Correlations between capnographic waveforms and peak flow meter measurement in emergency department management of asthma

Background

The usual method for initial assessment of an acute asthma attack in the emergency room includes the use of peak flow measurement and clinical parameters. Both methods have their own disadvantages such as poor cooperation/effort from patients (peak flow meter) and lack of objective assessment (clinical parameters). We were looking into other methods for the initial asthma assessment, namely the use of capnography. The normal capnogram has an almost square wave pattern comprising phase 1, slope phase 2, plateau phase 3, phase 4 and angle α (between slopes 2 and 3). The changes in asthma include decrease in slope of phase 2, increase in slope 3 and opening of angle α.

Aims

Our objective was to compare and assess the correlation between the changes in capnographic indices and peak flow measurement in non-intubated acute asthmatic patients attending the emergency room.

Methods

We carried out a prospective study in a university hospital emergency department (ED). One hundred and twenty eight patients with acute asthma were monitored with peak flow measurements and then had a nasal cannula attached for microstream sampling of expired carbon dioxide. The capnographic waveform was recorded onto a PC card for indices analysis. The patients were treated according to departmental protocols. After treatment, when they were adjudged well for discharge, a second set of results was obtained for peak flow measurements and capnographic waveform recording. The pre-treatment and post-treatment results were then compared with paired samples t-test analysis. Simple and canonical correlations were performed to determine correlations between the assessment methods. A p value of below 0.05 was taken to be significant.

Results

Peak flow measurements showed significant improvements post-treatment (p?p?p?p?=?0.35). Correlation studies done between the assessment methods and indices readings did not show strong correlations either between the measurements or the magnitude of change pre-treatment and post-treatment.

Conclusion

Peak flow measurements and capnographic waveform indices can indicate improvements in airway diameter in acute asthmatics in the ED. Even though the two assessment methods did not correlate statistically, capnographic waveform analysis presents several advantages in that it is effort independent and provides continuous monitoring of normal tidal respiration. They can be proposed for the monitoring of asthmatics in the ED.     

Ferumoxytol Does Not Impact Standardized Uptake Values on PET/MR Scans

Purpose

Tumor response assessments on positron emission tomography (PET)/magnetic resonance imaging (MRI) scans require correct quantification of radiotracer uptake in tumors and normal organs. Historically, MRI scans have been enhanced with gadolinium (Gd)-based contrast agents, which are now controversial due to brain deposition. Recently, ferumoxytol nanoparticles have been identified as an alternative to Gd-based contrast agents because they provide strong tissue enhancement on MR images but are not deposited in the brain. However, it is not known if the strong T1- and T2-contrast obtained with iron oxide nanoparticles such as ferumoxytol could affect MR-based attenuation correction of PET data. The purpose of our study was to investigate if ferumoxytol administration prior to a 2-deoxy-2-[¹⁸F]fluoro-d-glucose [¹⁸F]FDG PET/MR scan would change standardized uptake values (SUV) of normal organs.

Procedures

Thirty pediatric patients (6–18 years) with malignant tumors underwent [¹⁸F]FDG-PET/MR scans (dose 3 MBq/kg). Fifteen patients received an intravenous ferumoxytol injection (5 mg Fe/kg) prior to the [¹⁸F]FDG-PET/MR scans (group 1). Fifteen additional age- and sex-matched patients received unenhanced [¹⁸F]FDG-PET/MR scans (group 2). For attenuation correction of PET data, we used a Dixon-based gradient echo sequence (TR 4.2 ms, TE 1.1, 2.3 ms, FA 5), which accounted for soft tissue, lung, fat, and background air. We used a mixed linear effects model to compare the tissue MRI enhancement, quantified as the signal-to-noise ratio (SNR), as well as tissue radiotracer signal, quantified as SUVmean and SUVmax, between group 1 and group 2. Alpha was assumed at 0.05.

Results

The MRI enhancement of the blood and solid extra-cerebral organs, quantified as SNR, was significantly higher on ferumoxytol-enhanced MRI scans compared to unenhanced scans (p?<?0.001). However, SUVmean and SUVmax values, corrected based on the patients’ body weight or body surface area, were not significantly different between the two groups (p?>?0.05).

Conclusion

Ferumoxytol administration prior to a [¹⁸F]FDG PET/MR scan did not change standardized uptake values (SUV) of solid extra-cerebral organs. This is important, because it allows injection of ferumoxytol contrast prior to a PET/MRI procedure and, thereby, significantly accelerates image acquisition times.

     

Clinical Implementation of Magnetic Resonance Imaging Systems for Simulation and Planning of Pediatric Radiation Therapy

AimTo describe the clinical implementation and optimization of magnetic resonance imaging (MRI) systems installed in a radiation oncology department for dedicated use in radiotherapy (RT) simulation and treatment planning for pediatric patients.MethodsTwo wide-bore MRI systems were installed and commissioned in 2016. Patient setups, coil placements, and scan protocols were developed to image various anatomic sites in children. Patients with brain tumors were routinely imaged using a pair of flexible loop coils and a posterior receiver coil integrated into the patient couch. The integrated posterior coil and the flexible anterior torso coil supported by the coil bridge were used together when imaging the abdomen, pelvis, or spine. A three-dimensional acquisition was most often performed, given the benefit of high-resolution multiplanar reformation as well as elimination of B0-related distortions in the slice selection direction.ResultsWe performed 542 MRI studies (265 for planning and 277 for monitoring on-treatment tumor changes) on pediatric patients in the first year after system installation. Multisequence images of pediatric RT patients with ependymoma, medulloblastoma, craniopharyngioma, rhabdomyosarcoma, or Ewing sarcoma were shown to illustrate the image quality obtainable with optimized planning sequences.ConclusionsMagnetic resonance imaging (MRI) of pediatric patients in their treatment positions with setup devices in place can be performed with coil arrangements that include flexible coils. The resulting image quality is suitable for treatment planning and on-treatment monitoring. We provide optimized site-specific sequence parameters to support the continued improvement of MRI for pediatric RT planning.     

25例阿司匹林耐受不良三联征患者行鼻内镜鼻窦手术的护理

总结了25例阿司匹林耐受不良三联征患者全身麻醉下,行鼻内镜鼻窦手术的圈手术期护理经验.术前加强健康教育,术后重视气道监护、出血的观察,注意鼻喷激素药物的正确使用,加强对药物治疗效果和反应的观察,早期发现患者哮喘先兆,避免哮喘持续发作及全身过敏反应的发生,使患者鼻腔黏膜水肿短期内消退,促进鼻腔创面的愈合.本组术毕返回病房后,1h内有2例出现哮喘症状,因护理观察及时,治疗措施得当,哮喘症状均迅速缓解;1例因早期发现,采取了有效护理措施,避免了哮喘的发作.     

High flow nasal cannula: Influence of gas type and flow rate on airway pressure and CO2 clearance in adult nasal airway replicas

BackgroundHigh flow nasal cannula therapy is a form of respiratory support which delivers high flow rates of heated, humidified gas to the nares via specialized cannula. Two primary mechanisms of action attributed to the therapy are the provision of positive airway pressure as well as clearance of CO₂-rich exhaled gas from the upper airways.MethodsPhysiologically accurate nose-throat airway replicas were connected at the trachea to a lung simulator, where CO₂ was supplied to mimic the CO₂ content in exhaled gas. Cannula delivered either air, oxygen or heliox (80/20%volume helium/oxygen) to the replicas at flow rates ranging from 0 to 60 l/min. Five replicas and three cannulas were compared. Tracheal pressure and CO₂ concentration were continuously measured. The lung simulator provided breaths with tidal volume of 500 ml and frequency of 18 breaths/min. Additional clearance measurements were conducted for tidal volume and breathing frequency of 750 ml and 27 breaths/min, respectively.FindingsCannula flow rate was the dominant factor governing CO₂ concentration. Average CO₂ concentration decreased with increasing cannula flow rate, but above 30 L/min this effect was less pronounced. Tracheal positive end-expiratory pressure increased with flow rate and was lower for heliox than for air or oxygen. A predictive correlation was developed and used to predict positive end-expiratory pressure for a given cannula size as a function of supplied flow rate and occlusion of the nares.InterpretationCompared with administration of air or oxygen, administration of heliox is expected to result in similar CO₂ clearance from the upper airway, but markedly lower airway pressure.