脑电双频指数监测在重症加强治疗病房机械通气患者镇静中的应用

目的探讨脑电双频指数(BIS)实时监测在重症加强治疗病房(ICU)机械通气患者镇静中应用的可行性。方法选取30例术后机械通气患者,静脉注射咪唑安定或异丙酚达到合理镇静,采用盲法对患者每隔5min分别记录1次Ramsay镇静分级评分及BIS。比较Ram say镇静分级评分对应BIS中位数的总体差异,分析BIS结果与Ram say镇静分级评分的相关性。计算BIS的敏感度和约登(Youden)指数,确定BIS监测的敏感度和特异度。结果随镇静深度的加深,BIS明显降低,Ramsay分级评分对应的BIS中位数之间差异有显著性(P<0.01);BIS与Ram say分级评分呈负相关(r=-0.794,P<0.01);Ram say分级评分2~5分(为合理镇静)时对应的BIS中位数的95%可信区间(参考值范围)为61~84;当BIS值为81时,BIS监测从镇静合理到镇静不足的Youden指数和敏感度最高;Ram say分级评分为6分(为镇静过度)时对应的BIS中位数的95%可信区间为48~58。结论BIS监测与Ram say镇静分级具有良好的相关性,能实时、客观地监测ICU机械通气患者的镇静状态,并指导镇静治疗。     

Helmet noninvasive ventilation for weaning from mechanical ventilation

We saw a patient who presented with carbon dioxide narcosis and acute respiratory failure due to an exacerbation of chronic obstructive pulmonary disease. We intubated and 12 hours later he had recovered consciousness and could cooperate with noninvasive ventilation, at which point we extubated and used a helmet to provide noninvasive positive-pressure ventilation in assist/control mode, and then during the ventilator-weaning process, pressure support, and finally continuous positive airway pressure. The patient had no complications from the helmet, and he was discharged from intensive care 48 hours after helmet ventilation was initiated. Helmet noninvasive ventilation is a potentially valuable ventilator-weaning method for certain patients.     

Noninvasive Doppler blood pressure monitoring in the monoplace hyperbaric chamber

We describe a noninvasive method of monitoring blood pressure in the monoplace hyperbaric chamber. A standard blood pressure cuff was placed on the patient's arm. A Doppler probe, linked to an ultrasonic Doppler flow detector outside the chamber, was secured over the patient's radial artery. Cuff inflation tubing and the Doppler probe wires were passed into the chamber by modifying a standard disposable hyperbaric intravenous pass-through. Blood pressure readings were determined by inflating and slowly deflating the cuff from outside the chamber while observing the sphygmomanometer within the chamber and listening for the first audible flow signal from the Doppler detector, corresponding to the systolic blood pressure. To minimize the risk of fire in the oxygen-filled monoplace hyperbaric chamber, the patient, Doppler detector, and chamber were grounded. Doppler readings obtained from nine normal subjects whose arterial pressures were being measured with indwelling radial arterial catheters (approved as part of another study by the hospital's Investigational Review Board) compare closely with the subject's blood pressures measured with this noninvasive method: 114±7.6 mm Hg (mean±1 SD) compared to 112±8.1 mm Hg, respectively (n=92 measurements in 8 subjects). We conclude that this noninvasive method of monitoring blood pressure within the monoplace hyperbaric chamber is accurate and suitable for monoplace clinical purposes.This study was supported by a grant from the Deseret Foundation of the LDS Hospital, Salt Lake City, UT.We wish to thank the subjects who volunteered for this investigation, and we appreciate the help of Pam Evans, RRT, and the rest of the hyperbaric staff who assisted in the data collection.     

New strategies for mechanical ventilation. Lung protective ventilation

Although research is ongoing, and there are no definitive data to mandate the final answer to the question of which ventilation strategies result in the most optimal outcomes, the consensus of clinicians today suggests that we limit FIO2 to nontoxic levels, limit ventilating pressures and volumes, and use PEEP levels adequate to recruit alveoli and prevent tidal collapse. The critical care nurse must remain vigilant in his or her review of current literature to maintain knowledge of the current recommendations for optimal MV strategies.     

Planning for successful home mechanical ventilation

Home mechanical ventilation has evolved to permit discharge of patients on portable negative or positive pressure mechanical ventilators. Assessment of the patient for home discharge is initiated by a multidisciplinary team. The nurse, physician, social worker, respiratory therapist, speech therapist, occupational therapist, home health nursing agency, durable medical equipment supplier, and caregivers constitute the team. The crucial links to a successful patient discharge are an involved family and a well-developed plan of care, although patient finances also are important. The nurse develops, coordinates, and implements the teaching plan over a period of 2 or more weeks. The home caregivers provide total care for the patient several days before discharge. The home health agency and the durable medical equipment supplier provide services which ease the transition of care from hospital to home. One alternative to home discharge is placement in an extended care facility.     

Closed-loop mechanical ventilation

Closed-loop mechanical ventilation encompasses a plethora of techniques, ranging from the very simple to the relatively complex. In the simplest form, closed-loop ventilation is the control of one output variable of the mechanical ventilator based on the measurement of an input variable. An example would be pressure support ventilation, in which flow (output) is constantly changing to maintain pressure (input) constant throughout inspiration. More complex forms of closed-loop ventilation involve measurement of multiple inputs (eg, compliance, oxygen saturation, respiratory rate) to control multiple outputs (eg, ventilator frequency, airway pressure, tidal volume). The latter type of control more closely mimics the ventilatory control and response of human physiology. This review discusses both currently available closed-loop ventilation techniques and those only available outside the United States, along with some cutting-edge techniques that have only limited use. The operation, theoretical advantages, and limitations of each technique are reviewed. When available, the literature supporting or refuting each technique will be reviewed, but, unfortunately, little has been published on certain techniques.     

Managing mechanical ventilation

Caring for ventilated patients isn't just for critical care nurses anymore. Here's what you need to know to keep your patient breathing easy.     

Home mechanical ventilation

Recently, interest in the use of mechanical ventilation outside the hospital setting has been increasing. Patients with various types of chronic respiratory failure may benefit from this approach. Evaluation for long-term mechanical ventilation necessitates assessment of the underlying disease process, the goals of the medical team, and the needs of the patient and family. Externally applied negative-pressure devices can provide adequate ventilation for many patients, particularly those with neuromuscular diseases. Positive-pressure ventilation by means of a tracheostomy provides greater control of the airway, allows adjustment of tidal volume and minute ventilation, and may be delivered by portable equipment. Ongoing care and support services in the home must be provided. A variety of mechanical devices and new techniques of ventilator support have made home mechanical ventilation a realistic option for long-term care.     

Documentation issues for mechanical ventilation in pressure-control modes

As hospitals begin to implement electronic medical records, the inadequacies of legacy paper charting systems will become more evident. One area of particular concern for respiratory therapists is the charting of mechanical ventilator settings. Our profession's lack of a standardized and generally accepted taxonomy for mechanical ventilation leaves us with a confusing array of terms related to ventilator settings. Such confusion makes database design impossible for information technology professionals and is a risk-management concern for clinicians. Of particular note is the complexity related to set airway pressures when using modes whose primary control variable is pressure (versus volume). We review the clinically relevant issues surrounding documentation of the patient-ventilator interactions related to airway pressure and provide suggestions for a standardized vocabulary.     

Incidence of ischemic brain lesions in hyperbaric chamber inside attendants

Concern is growing about the negative long-term effects of hyperbaric exposure on the central nervous system of divers. This study was conducted with magnetic resonance imaging (MRI) to evaluate attendants that work inside hyperbaric chambers (known as inside attendants) for hyperintense brain lesions. Ten inside attendants and 10 healthy nondiving subjects were included in the study. A questionnaire was used to obtain information about subjects’ medical history, hyperbaric exposure history, alcohol intake, and smoking habits. T1-weighted, T2-weighted, and fluid-attenuated inversion recovery images were acquired with a 1.5-T MRI device. A lesion was included in the count if it was hyperintense on both T2-weighted and fluid-attenuated inversion recovery images. Although MRI revealed 3 hyperintense brain lesions in 2 of 10 inside attendants and in none of the controls, the differences between groups were not statistically significant (P=.147). The number of brain lesions counted did not correlate with the age of the inside attendants (r=0.007;P=.978), the number of hyperbaric exposures (r=-0.203;P=.574), or the duration of work as an inside attendant (r=0.051; P=.890). Investigators found a correlation, however, between the number of cigarettes smoked in a day and the number of brain lesions identified (r=0.779;P < .01). An increased incidence of hyperintense brain lesions was not observed in inside attendants who had never experienced decompression sickness compared with nondiving controls. Additional multicenter epidemiologic studies are needed if the occupational safety of inside attendants is to be enhanced.