Ventrain: an ejector ventilator for emergency use.

BACKGROUND: A small, flow-regulated, manually operated ventilator designed for ventilation through a narrow-bore transtracheal catheter (TTC) has become available (Ventrain, Dolphys Medical BV, Eindhoven, The Netherlands). It is driven by a predetermined flow of oxygen from a high-pressure source and facilitates expiration by suction. The aim of this bench study was to test the efficacy of this new ventilator. METHODS: The driving pressure, generated insufflation, and suction pressures and also the suction capacity of the Ventrain were measured at different oxygen flows. The minute volume achieved in an artificial lung through a TTC with an inner diameter (ID) of 2 mm was determined at different settings. RESULTS: Oxygen flows of 6-15 litre min(-1) resulted in driving pressures of 0.5-2.3 bar. Insufflation pressures, measured proximal to the TTC, ranged from 23 to 138 cm H(2)O. The maximal subatmospheric pressure build-up was -217 cm H(2)O. The suction capacity increased to a maximum of 12.4 litre min(-1) at an oxygen flow of 15 litre min(-1). At this flow, the achievable minute volume through the TTC ranged from 5.9 to 7.1 litres depending on the compliance of the artificial lung. CONCLUSIONS: The results of this bench study suggest that the Ventrain is capable of achieving a normal minute volume for an average adult through a 2 mm ID TTC. Further in vivo studies are needed to determine the value of the Ventrain as a portable emergency ventilator in a 'cannot intubate, cannot ventilate' situation.

Ventilation through a small-bore catheter: optimizing expiratory ventilation assistance.

BACKGROUND: Emergency ventilation through a small-bore transtracheal catheter can be lifesaving in a 'cannot intubate, cannot ventilate' situation. Ejectors, capable of creating suction by the Bernoulli principle, have been proposed to facilitate expiration through small-bore catheters. In this bench study, we compared a novel, purpose-built ventilation ejector (DE 5) with a previously proposed, modified industrial ejector (SBP 07). METHODS: The generated insufflation pressures, suction pressures in static and dynamic situations, and also suction capacities and entrainment ratios of the SBP 07 and the DE 5 were determined. The DE 5 was also tested in a lung simulator with a simulated complete upper airway obstruction. Inspiratory and expiratory times through a transtracheal catheter were measured at various flow rates and achievable minute volumes were calculated. RESULTS: In a static situation, the SBP 07 showed a more negative pressure build-up compared with the DE 5. However, in a dynamic situation, the DE 5 generated a more negative pressure, resulting in a higher suction capacity. Employment of the DE 5 at a flow rate of 18 litre min(-1) allowed a minute volume through the transtracheal catheter of up to 8.27 litre min(-1) at a compliance of 100 ml cm H(2)O(-1). The efficiency of the DE 5 depended on the flow rate of the driving gas and the compliance of the lung simulator. CONCLUSION: In laboratory tests, the DE 5 is an optimized ventilation ejector suitable for applying expiratory ventilation assistance. Further research may confirm the clinical applicability as a portable emergency ventilator for use with small-bore catheters.

Achieving an adequate minute volume through a 2 mm transtracheal catheter in simulated upper airway obstruction using a modified industrial ejector.

BACKGROUND: Needle cricothyrotomy and subsequent transtracheal jet ventilation (TTJV) is one of the last options to restore oxygenation while managing an airway emergency. However, in cases of complete upper airway obstruction, conventional TTJV is ineffective and dangerous. We transformed a small, industrial ejector into a simple, manual ventilator providing expiratory ventilation assistance (EVA). METHODS: An ejector pump was modified to allow both insufflation of oxygen and jet-assisted expiration through an attached 75 mm long transtracheal catheter (TTC) with an inner diameter (ID) of 2 mm by alternately occluding and releasing the gas outlet of the ejector pump. In a lung simulator, the modified ejector pump was tested at different compliances and resistances. Inspiration and expiration times were measured and achievable minute volumes (MVs) were calculated to determine the effect of EVA. RESULTS: The modified ejector pump shortened the expiration time and an MV up to 6.6 litre min(-1) could be achieved through a 2 mm ID TTC in a simulated obstructed airway. CONCLUSIONS: The principle of ejector-based EVA seems promising and deserves further evaluation.

A bench study of ventilation via two self-assembled jet devices and the Oxygen Flow Modulator in simulated upper airway obstruction.

In managing an obstructed upper airway, an emergency transtracheal ventilation device needs to function as a bidirectional airway, allowing both insufflation of oxygen and egress of gas. The aim of the present study was to determine the capability of two self-assembled, three-way stopcock based jet devices and the Oxygen Flow Modulator to function as a bidirectional airway in conjunction with a small lumen catheter. For each device the effective pressures at the catheter's tip during the expiratory phase and the achievable minute volumes were determined in a laboratory set-up. Using the three-way stopcock based jet devices, changing the connection position of the transtracheal catheter from the in-line port to the side port of the three-way stopcock resulted in a decrease of expiratory pressure at the catheter's tip from a dangerous mean (SD) of 71.1 (0.08) cmH(2)O to -14.71 (0.05) cmH(2)O. Yet this negative expiratory pressure did not facilitate the egress of gas. All devices tested impeded the expiratory outflow and hence decreased the achievable minute volume. This decrease in minute volume was smallest with the Oxygen Flow Modulator.

Anaesthetic management of the airway in The Netherlands: a postal survey.

BACKGROUND AND OBJECTIVE: A postal survey was conducted in order to investigate current practice in airway management amongst Dutch anaesthetists and to investigate the role of recent training and the role of an 'Access to the Airway' airway management course. METHODS: A questionnaire containing 27 questions was sent to all practising anaesthetists in The Netherlands. Questionnaires were returned anonymously and were analysed using the Pearson chi(2)-test (P < 0.05) with the SPSSR version 8.0 statistical software program. RESULTS: The response rate was 42%. Of the respondents, 78% claim often or always to assess the expected degree of difficulty in tracheal intubation as part of routine preoperative assessment. The American Society of Anesthesiologist's Difficult Airway Algorithm was used by 19% of respondents. A wide variety of airway management techniques is being used. In 36% of all general anaesthetics a laryngeal mask airway is used. In 1.1% of all general anaesthetics tracheal intubation is performed with the flexible fibrescope. CONCLUSIONS: Dutch anaesthetists, who commenced anaesthetic training after 1988, and those who attended the airway management course 'Access to the Airway' are significantly more likely to follow the American Society of Anesthesiologist's Difficult Airway Algorithm and to use adjunctive techniques for airway management.

A practical clinical approach to management of the difficult airway.

Difficult airway management represents a challenge in anaesthesia. In the last decades airway difficulty awareness has improved as a result of better anticipation and decision-making. Airway algorithms and protocols have a more prominent role in training and in clinical anaesthesia practice. In addition, several new instruments and therefore new techniques have been developed. These have improved possibilities for the clinician to secure the airway. Clinicians should become familiar with this equipment and techniques by using them on a regular basis in elective cases. The instruments available must be selected by the characteristics of the patient population, the local circumstances and the experience of the anaesthesiologist. The aim of this paper is to provide some practical guidelines with respect to airway difficulty predictors and airway instrument choice.

Doing better in the 1990s--but not by much.

American Dental Association and federal agency reports indicate that during the past fifteen years, 1) the number and size of dental establishments have continued to increase, and 2) the number of dental assistant and dental hygienist program enrollees have fluctuated but remain lower than in earlier years (particularly dental assistant enrollees). Despite a tighter market for dental auxiliaries and improving dental practitioner income, dental assistant wages in the 1980s did not maintain parity with the rates of inflation and barely outpaced the levels of inflation in the first half of the 1990s. Dental hygienists fared only slightly better in the '90s.

Long-term intrathecal administration of midazolam and clonidine.

OBJECTIVE: To determine the clinical usefulness of the long-term intrathecal administration of midazolam and clonidine in patients with refractory neurogenic and musculoskeletal pain. SETTING: Pain Centre, Academic Hospital Groningen, Groningen, The Netherlands. PATIENTS: Four patients with chronic benign neurogenic and musculoskeletal pain, not responding to conventional analgesic therapy. OUTCOME-MEASURES: Visual Analogue Score, Activities of Daily Living. RESULTS: The intrathecal administration of midazolam and clonidine produced almost immediate and nearly complete pain relief. Even with continuous use, tolerance seemed to be no problem, and side effects appear to be minimal. CONCLUSION: Intrathecal infusion of midazolam and clonidine produced promising results in four patients with refractory chronic benign pain. Further research will be necessary to determine the efficacy and the risk-to-benefit ratio of long-term administration of this combination.

Hyaluronidase in the management of pain due to post-laminectomy scar tissue.

We describe a 31-year-old male with a rebound radicular syndrome due to post-laminectomy scarring in the intervertebral foramen and epidural space. Repeated injection of hyaluronidase through the intervertebral foramen into the scar tissue resulted in periods of appreciably reduced pain and increasing duration. No untoward effects were seen.