Two cases of barotrauma associated with transtracheal jet ventilation

Supraglottic jet oxygenation and ventilation decreased hypoxemia during gastrointestinal endoscopy under deep sedation at high altitudes: a randomized clinical trial

Background

Hypobaric hypoxia is common at high altitudes. Whether this exacerbates hypoxia during procedural sedation and whether hypoxia can be alleviated by the use of supraglottic jet oxygenation and ventilation (SJOV) are unknown. This study aimed to compare the incidence of hypoxia during gastrointestinal endoscopy under deep sedation at high altitudes with oxygen supply techniques using either a nasal cannula or SJOV.

Methods

This study was conducted from April 2022 to July 2022 in a tertiary hospital located 3650 m above sea level. Adult patients scheduled for routine gastrointestinal endoscopy under sedation were enrolled and randomized 1:1 to receive SJOV or a nasal cannula during sedation. Moderate hypoxia was the primary outcome, defined as an SPO2 of 75–89% for < 60 s. The secondary outcomes were respiratory-, cardiovascular-, and SJOV-related complications. The influence of characteristics regarding acclimatization to high altitudes (Tibetan ethnic group and erythrocytosis) on the occurrence of hypoxia was analyzed.

Results

None of the patients were lost to follow-up. A total of 72 patients were included in the analysis (36 patients in each group). There were 20 (27.8%) patients who experienced moderate hypoxia events. Significantly fewer hypoxic events occurred in the SJOV group than in the nasal cannula group [3 (8.3%) vs. 17 (47.2%), absolute risk difference (95% CI): − 38.9 (− 57.5, − 20.2) %, risk ratio (RR, 95% CI): 0.18 (0.06, 0.55), P < 0.001]. Significantly fewer patients in the SJOV group experienced mild hypoxia (P < 0.001) and severe hypoxia (P = 0.002). No serious adverse events occurred in either of the groups. The Tibetan ethnic group (P = 0.086) and erythrocytosis (P = 0.287) were not associated with the occurrence of hypoxia events.

Conclusions

The incidence of hypoxia was lower with SJOV than with nasal cannula in patients undergoing gastrointestinal endoscopy under deep sedation at high altitudes. The Tibetan ethnic group and erythrocytosis did not influence the occurrence of hypoxia.

Trial registration

This study was registered at ClinicalTrials.gov (NCT05304923) before enrollment by Dr. Yi Feng on 31/03/2022.

Ventilation strategies for front of neck airway rescue: an in silico study

BACKGROUND

During induction of general anaesthesia a 'cannot intubate, cannot oxygenate' (CICO) situation can arise, leading to severe hypoxaemia. Evidence is scarce to guide ventilation strategies for small-bore emergency front of neck airways that ensure effective oxygenation without risking lung damage and cardiovascular depression.

METHODS

Fifty virtual subjects were configured using a high-fidelity computational model of the cardiovascular and pulmonary systems. Each subject breathed 100% oxygen for 3 min and then became apnoeic, with an obstructed upper airway. When arterial haemoglobin oxygen saturation reached 40%, front of neck airway access was simulated with various configurations. We examined the effect of several ventilation strategies on re-oxygenation, pulmonary pressures, cardiovascular function, and oxygen delivery.

RESULTS

Re-oxygenation was achieved in all ventilation strategies. Smaller airway configurations led to dynamic hyperinflation for a wide range of ventilation strategies. This effect was absent in airways with larger internal diameter (≥3 mm). Intrapulmonary pressures increased quickly to supra-physiological values with the smallest airways, resulting in pronounced cardio-circulatory depression (cardiac output <3 L min^-1 and mean arterial pressure <60 mm Hg), impeding oxygen delivery (<600 ml min^-1). Limiting tidal volume (≤200 ml) and ventilatory frequency (≤8 bpm) for smaller diameter cannulas reduced dynamic hyperinflation and gas trapping, preventing cardiovascular depression.

CONCLUSIONS

Dynamic hyperinflation can be demonstrated for a wide range of front of neck airway cannulae when the upper airway is obstructed. When using small-bore cannulae in a CICO situation, ventilation strategies should be chosen that prevent gas trapping to prevent severe adverse events including cardio-circulatory depression.

Supraglottic jet oxygenation and ventilation reduces desaturation during bronchoscopy under moderate to deep sedation with propofol and remifentanil: A randomised controlled clinical trial

BACKGROUND

Hypoxaemia is frequently seen during flexible bronchoscopies that are done with a nasal approach under the traditional sedation with propofol. This study investigated the potential benefits of supraglottic jet oxygenation and ventilation (SJOV) using the Wei nasal jet tube (WNJ) in reducing hypoxaemia in patients undergoing bronchoscopy under moderate to deep intravenous sedation using a propofol, lidocaine and remifentanil cocktail.

OBJECTIVES

Our primary objective was to evaluate the efficacy and complications of SJOV via the WNJ during flexible bronchoscopy under moderate to heavy sedation with propofol and remifentanil.

DESIGN

A randomised controlled clinical trial.

SETTING

The 180th Hospital of People's Liberation Army, Quanzhou, China, from 1 June to 1 November 2019.

PATIENTS

A total of 280 patients aged ≥18 years with American Society of Anesthesiologists' physical status 1 to 3 undergoing flexible bronchoscopy were studied.

INTERVENTIONS

Patients were assigned randomly into one of two groups, a nasal cannula oxygenation (NCO) group (n = 140) using a nasal cannula to deliver oxygen (4 l min-1) or the SJOV group (n = 140) using a WNJ connected to a manual jet ventilator to provide SJOV at a driving pressure of 103 kPa, respiratory rate 20 min-1, FiO2 1.0 and inspiratory:expiratory (I:E) ratio 1:2.

MAIN OUTCOME MEASURES

The primary outcome was an incidence of desaturation (defined as SpO2 < 90%) during the procedure. Other adverse events related to the sedation or SJOV were also recorded.

RESULTS

Compared with the NCO group, the incidence of desaturation in the SJOV group was lower (NCO 37.0% vs. SJOV 13.1%) (P < 0.001). Patients in the SJOV group had a higher incidence of a dry mouth at 1 min (13.1% vs. 1.5%, P < 0.001) than at 30 min (1.5% vs. 0%, P = 0.159) or at 24 h (0% vs. 0%). There was no significant difference between the groups in respect of sore throat, subcutaneous emphysema or nasal bleeding.

CONCLUSIONS

SJOV via a WNJ during flexible bronchoscopy under moderate to deep sedation with propofol and remifentanil significantly reduces the incidence of desaturation when compared with regular oxygen supplementation via a nasal cannula. Patients in the SJOV group had an increased incidence of transient dry mouth.

TRIAL REGISTRATION

Registered at www.chictr.org.cn (ChiCTR1900023514).

Feasibility of Surgical Treatment for Laryngomalacia using Spontaneous Respiration Technique

Objectives.

In this study, we review our institutional experience with pediatric laryngomalacia (LM) and report our experiences of patients undergoing supraglottoplasty using the spontaneous respiration using intravenous anesthesia and high-flow nasal oxygen (STRIVE Hi) technique.

Methods.

The medical records of 29 children with LM who visited Seoul National University Hospital between January 2017 and March 2019 were retrospectively reviewed. Surgical management was performed using the STRIVE Hi technique. Intraoperative findings and postoperative surgical outcomes, including complications and changes in symptoms and weight, were analyzed.

Results.

Of the total study population of 29 subjects, 20 (68.9%) were female. The patients were divided according to the Onley classification as follows: type I (n=13, 44.8%), II (n=10, 34.5%), and III (n=6, 20.7%). Twenty-five patients (86.2%) had comorbidities. Seventeen patients (58.6%) underwent microlaryngobronchoscopy under STRIVE Hi anesthesia. Four patients with several desaturation events required rescue oxygenation by intermittent intubation and mask bagging during the STRIVE Hi technique. However, the procedure was completed in all patients without any severe adverse effects. Overall, 15 children (51.7%) underwent supraglottoplasty, of whom 14 (93.3%) showed symptom improvement, and their postoperative weight percentile significantly increased (P=0.026). One patient required tracheostomy immediately after supraglottoplasty due to associated neurological disease.

Conclusion.

The STRIVE Hi technique is feasible for supraglottoplasty in LM patients, while type III LM patients with micrognathia or glossoptosis may have a higher risk of requiring rescue oxygenation during the STRIVE Hi technique.

Pediatric airway surgery under spontaneous respiration using high-flow nasal oxygen

OBJECTIVES

In pediatric airway surgery, SponTaneous Respiration using IntraVEnous anesthesia and Hi-flow nasal oxygen (STRIVE Hi) has not been well explored. Here, we report our experience of using STRIVE Hi in endoscopic evaluations and surgeries of the pediatric airway.

METHODS

This retrospective review was based on 45 airway procedures conducted under STRIVE Hi, performed by a single surgeon at a single institute from May 2017 to September 2018. After induction of anesthesia, continuous infusion with propofol and remifentanil was provided to ensure an adequate level of anesthesia and supply of humidified oxygen via a nasal cannula. Monitoring was conducted using a transcutaneous CO₂ sensor and a pulse oximeter, and the oxygen reserve and bispectral indexes were measured. No muscle relaxant was administered.

RESULTS

The median age of the patients was 16.0 months (range: 1-215 months) and the median weight was 10.2 kg (range: 2.4-38.5 kg). The median duration of spontaneous respiration was min 40 (range: 10-140 min). The airway procedures included diagnostic microlaryngoscopy, tracheocutaneous fistula excision, balloon dilation, supraglottoplasty, laryngeal cleft repair, injection laryngoplasty, papilloma excision, and subglottic cyst removal. During these procedures, STRIVE Hi facilitated evaluation of dynamic obstruction of the airway and the immediate outcome of surgical treatment and provided a good surgical view. Intubation and the termination of spontaneous respiration were required in only five patients.

CONCLUSIONS

STRIVE Hi is an effective and feasible anesthesia option in pediatric airway surgery. It provides unobstructed surgical access and is applicable to a wide range of procedures.

Supraglottic jet oxygenation and ventilation enhances oxygenation during upper gastrointestinal endoscopy in patients sedated with propofol: a randomized multicentre clinical trial

Background

Hypoventilation is the main reason for hypoxia during upper gastrointestinal endoscopy procedures with sedation. The key to preventing hypoxia is to maintain normal ventilation during the procedure. We introduced supraglottic jet oxygenation and ventilation (SJOV) through a new Wei nasal jet tube (WNJ) to reduce the incidence of hypoxia in patients sedated with propofol during upper gastrointestinal endoscopy procedures.

Methods

In a multicentre, prospective randomized single-blinded study, 1781 outpatients undergoing routine upper gastrointestinal endoscopy who were sedated with propofol by an anaesthetist were randomized into the following three groups: the supplementary oxygen via nasal cannula group [nasal cannula oxygen: O 2 (2 litres min -1 ) was administered via a nasal cannula]; the supplementary oxygen via WNJ group [WNJ oxygen: O 2 (2 litres min -1 ) was administered through a WNJ]; and the SJOV via WNJ group (WNJ SJOV: SJOV was administered via WNJ) at three centres from March 2015 to July 2016. The primary outcome of interest was the incidence of hypoxia (peripheral oxygen saturation of 75-89%). Other adverse events were also recorded.

Results

Supraglottic jet oxygenation and ventilation decreased the incidence of hypoxia from 9 to 3% ( P <0.0001). No severe hypoxia occurred in the WNJ SJOV group, one instance occurred in the WNJ oxygen group, and two instances were observed in the nasal cannula oxygen supply control group. Supraglottic jet oxygenation and ventilation-related minor adverse events increased significantly within 1 min after the procedure but decreased 30 min later.

Conclusions

The use of SJOV during upper gastrointestinal endoscopy for patients who are sedated with propofol reduces the incidence of hypoxia, with minor and tolerable adverse events. Supraglottic jet oxygenation and ventilation has a favourable risk-to-benefit ratio and may improve patient safety.

Clinical trial registration

NCT02436018.

Cannula cricothyroidotomy and rescue oxygenation with the Rapid-O2™ oxygen insufflation device in the management of a can't intubate/can't oxygenate scenario

We describe the successful use of cannula cricothyroidotomy and the Rapid-O2™ oxygen insufflation device (Meditech Systems Ltd, Dorset, UK) for rescue of a can't intubate/can't oxygenate (CICO) scenario in a patient with severe airway haemorrhage post-debridement of laryngeal amyloidosis. This case highlights the practical utility of a cannula technique for CICO rescue when appropriate equipment is used and when institutional measures are taken to prepare for this rare anaesthetic crisis.

Ventrain: from theory to practice. Bridging until re-tracheostomy

Imminent upper airway obstruction due to life-threatening tracheal stenosis of any cause is challenging. A 77-year-old woman, with a history of temporal tracheostomy for prolonged mechanical ventilation, presented with life-threatening tracheal stenosis to the emergency department. After failed intubation with a 5.0 mm internal diameter endotracheal tube, the patient was ventilated via a tube exchanger using Ventrain. Ventrain is a manual ventilation device that, in addition to oxygen supply during inspiration, initiates expiration by actively removing gas from the lungs by suction. Despite the nearly obstructed airway the patient was adequately ventilated with 'permissive' hypercarbia of 50 mm Hg and Saturation of peripheral Oxygen (SpO₂) 95%-98% until surgical re-tracheostomy was performed. The haemodynamic stability of the patient indicated that the active expiration prevented intrapulmonary pressure build-up by air trapping and subsequent barotrauma and/or haemodynamic deterioration, which may well be observed during traditional jet ventilation especially in case of a completely obstructed airway.

Supraglottic jet oxygenation and ventilation-assisted fibre-optic bronchoscope intubation in patients with difficult airways

A difficult airway may lead to hypoxia and brain damage. The WEI Nasal Jet Tube (WNJ) is a new nasal pharyngeal tube that applies supraglottic jet oxygenation and ventilation (SJOV) for patients during tracheal intubation without the need for mask ventilation. We evaluated the effectiveness and safety of SJOV-assisted fibre-optic bronchoscopy (FOB) using the WNJ in the management of difficult tracheal intubations. A total of 50 adult patients with Cormack-Lehane grade ≥3 and general anesthesia with tracheal intubation were randomly assigned to either the laryngeal mask airway (LMA) or WNJ groups. The primary outcome was the percentage of patients with SpO₂ values lower than 94 % during intubation. The proportion of successful intubations, total time of intubation, and associated complications were also recorded. The percentage of patients with SpO₂ values lower than 94 % during intubation was significantly higher in the LMA group (25 % in the LMA vs. 0 % in the WNJ, P = 0.01). Although there were no statistically significant differences in the total success rates of intubation, the first-attempt success rate was significantly higher in the WNJ group (100 vs. 79.2 %, P = 0.02). The total time required for intubation with the WNJ was shorter than that of the LMA (73.4 vs. 99.5 s, P < 0.001), although the duration of fibre-optic intubation was similar. The incidence of complications was similar between the two groups. SJOV-assisted FOB using the WNJ improved oxygenation and successful tracheal intubation in the management of difficult airways. This technique can be used as an alternative approach to improve success and minimize hypoxia during difficult airway management.

Supraglottic jet oxygenation and ventilation saved a patient with 'cannot intubate and cannot ventilate' emergency difficult airway

The emergency difficult airway with the ‘cannot intubate and cannot ventilate’ (CICV) situation contributes to a high percentage of anesthesia- and emergency medicine-related morbidity and mortality. A new technique of supraglottic jet oxygenation and ventilation (SJOV) via the nasal approach was successfully used in an emergency to save a patient with a CICV difficult airway from a catastrophic outcome.

Impact of oxygen sources on performance of the Ventrain(®) ventilation device in an in vitro set-up

BACKGROUND

The Ventrain(®) (Dolphys Medical, Eindhoven, The Netherlands) is a disposable handheld ventilation device allowing active inspiration and expiration through a transtracheal catheter. This study investigated Ventrain(®) 's performance when used with different clinical oxygen sources in an in vitro set-up.

METHODS

Three anesthesia oxygen sources (wall-mounted flowmeter, respirator oxygen outlet port, and anesthesia ventilator circuit) were used at gas flow rates of 6, 9, 12, and 15 l/min. First, the sources' driving pressures (DP), the insufflation pressure (IP), and the flow at the catheter tip were measured using a gas flow analyzer. Tidal volumes (VT) delivered by the Ventrain(®) were assessed by the ASL5000 test lung (respiratory rate: 15 min(-1), I:E = 1:1, compliance: 100 ml/cmH2O, resistance: 3.06 cmH2O/l/s).

RESULTS

VT ranged from 82 to 483 ml for inspiration and 82 to 419 ml for expiration. Measured IP, flow, and VT were less dependent on the set gas flow rate but more on the source's DP. With rising DP the IP, the flow at the catheter tip and consequently VT increased. At an approximate target I:E ratio of 1:1, the ratio of inspiratory to expiratory VT increased with higher DP and gas flow rates.

CONCLUSION

The oxygen sources resulted in clinically different IP, flows, and VT delivered by the Ventrain(®) at given gas flow rates. This needs to be considered in a clinical emergency situation. Integrating an adjustable pressure valve into Ventrain(®) to allow regulation of the lowest necessary IP would make its use safer.

Pulmonary effects of expiratory-assisted small-lumen ventilation during upper airway obstruction in pigs

Novel devices for small-lumen ventilation may enable effective inspiration and expiratory ventilation assistance despite airway obstruction. In this study, we investigated a porcine model of complete upper airway obstruction. After ethical approval, we randomly assigned 13 anaesthetised pigs either to small-lumen ventilation following airway obstruction (n = 8) for 30 min, or to volume-controlled ventilation (sham setting, n = 5). Small-lumen ventilation enabled adequate gas exchange over 30 min. One animal died as a result of a tension pneumothorax in this setting. Redistribution of ventilation from dorsal to central compartments and significant impairment of the distribution of ventilation/perfusion occurred. Histopathology demonstrated considerable lung injury, predominantly through differences in the dorsal dependent lung regions. Small-lumen ventilation maintained adequate gas exchange in a porcine airway obstruction model. The use of this technique for 30 min by inexperienced clinicians was associated with considerable end-expiratory collapse leading to lung injury, and may also carry the risk of severe injury.

Transtracheal ventilation with a novel ejector-based device (Ventrain) in open, partly obstructed, or totally closed upper airways in pigs

BACKGROUND

Transtracheal access and subsequent jet ventilation are among the last options in a 'cannot intubate-cannot oxygenate' scenario. These interventions may lead to hypercapnia, barotrauma, and haemodynamic failure in the event of an obstructed upper airway. The aim of the present study was to evaluate the efficacy and the haemodynamic effects of the Ventrain, a manually operated ventilation device that provides expiratory ventilation assistance. Transtracheal ventilation was carried out with the Ventrain in different airway scenarios in live pigs, and its performance was compared with a conventional jet ventilator.

METHODS

Pigs with open, partly obstructed, or completely closed upper airways were transtracheally ventilated either with the Ventrain or by conventional jet ventilation. Airway pressures, haemodynamic parameters, and blood gases obtained in the different settings were compared.

RESULTS

Mean (SD) alveolar minute ventilation as reflected by arterial partial pressure of CO2 was superior with the Ventrain in partly obstructed airways after 6 min in comparison with traditional manual jet ventilation [4.7 (0.19) compared with 7.1 (0.37) kPa], and this was also the case in all simulated airway conditions. At the same time, peak airway pressures were significantly lower and haemodynamic parameters were altered to a lesser extent with the Ventrain.

CONCLUSIONS

The results of this study suggest that the Ventrain device can ensure sufficient oxygenation and ventilation through a small-bore transtracheal catheter when the airway is open, partly obstructed, or completely closed. Minute ventilation and avoidance of high airway pressures were superior in comparison with traditional hand-triggered jet ventilation, particularly in the event of complete upper airway obstruction.

Rescue ventilation through a small-bore transtracheal cannula in severe hypoxic pigs using expiratory ventilation assistance

BACKGROUND

Suction-generated expiratory ventilation assistance (EVA) has been proposed as a way to facilitate bidirectional ventilation through a small-bore transtracheal cannula (TC). In this study, we investigated the efficiency of ventilation with EVA for restoring oxygenation and ventilation in a pig model of acute hypoxia.

METHODS

Six pigs (61-76 kg) were anesthetized and ventilated (intermittent positive pressure ventilation) via a cuffed endotracheal tube (ETT). Monitoring lines were placed, and a 75-mm long, 2-mm inner diameter TC was inserted. After the baseline recordings, the ventilator was disconnected. After 2 minutes of apnea, reoxygenation with EVA was initiated through the TC and continued for 15 minutes with the ETT occluded. In the second part of the study, the experiment was repeated with the ETT either partially obstructed or left open. Airway pressures and hemodynamic data were recorded, and arterial blood gases were measured. Descriptive statistical analysis was performed.

RESULTS

With a completely or partially obstructed upper airway, ventilation with EVA restored oxygenation to baseline levels in all animals within 20 seconds. In a completely obstructed airway, PaCO2 remained stable for 15 minutes. At lesser degrees of airway obstruction, the time to reoxygenation was delayed. Efficacy probably was limited when the airway was completely unobstructed, with 2 of 6 animals having a PaO2 <85 mm Hg even after 15 minutes of ventilation with EVA and a mean PaCO2 increased up to 90 mm Hg.

CONCLUSIONS

In severe hypoxic pigs, ventilation with EVA restored oxygenation quickly in case of a completely or partially obstructed upper airway. Reoxygenation and ventilation were less efficient when the upper airway was completely unobstructed.

Airway management of an unusual case of recurrent rhinoscleroma

Rhinoscleroma is a rare entity encountered in anesthesia practice. We discuss the management of a patient after its recurrence, involving the upper respiratory tract i.e. nasopharynx and oropharynx, which compromised the airway. The pateint was referred for anesthesia on three different occasions with different presentations owing to the recurrence of symptoms.The presence of an oropharyngeal membrane with a small opening made airway management a challenge. The patient was successfully managed on all three occasions. Imaging facilitated assessment and subsequent airway management.

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.

Anaesthesia for microlaryngeal and laser laryngeal surgery: impact of subglottic jet ventilation

OBJECTIVE

Over the past 20 years, jet ventilation techniques have been developed to enable safe and controlled microlaryngoscopy and the accurate treatment of laryngeal pathology. This study examined how advances in jet ventilation tube design have facilitated safe endolaryngeal surgery.

STUDY DESIGN

The study documented the development and use of the Jockjet subglottic jet ventilation tube system at the Prince of Wales Hospital, Sydney. The new system consisted of two components: a Teflon tube with an outer diameter of 4 mm at the larynx, and a companion ventilator. The facility for end-tidal carbon dioxide and distal airways pressure monitoring was incorporated via dedicated channels. The Venturi jet was produced via a covered tip to prevent trauma to the tracheal mucosa.

SETTING

The Prince of Wales and Sydney Children's Hospitals, incorporated with The University of New South Wales.

PATIENTS

From June 2002 to March 2008 inclusive, 1000 consecutive patients underwent microlaryngeal surgery at this institution. Subglottic jet ventilation, via the Jockjet tube, was employed for 332 patients.

MAIN OUTCOME MEASURES

Anaesthetic safety and intra-operative surgical access.

RESULTS

In all the 332 patients observed, surgical access was optimised and no adverse anaesthetic outcomes were encountered.

CONCLUSION

Subglottic jet ventilation facilitates safe airway management during microlaryngeal and laser laryngeal surgery.

Needle vs surgical cricothyroidotomy: a short cut to effective ventilation

Cricothyroidotomy can be performed using three techniques. This literature review seeks to determine which is more appropriate for use in prehospital can't intubate/can't ventilate scenarios where laryngeal mask airways prove ineffective. The common approach of inserting a 14-gauge cannula and using low-pressure ventilation via intermittent occlusion of an opening in oxygen tubing (15 l x min(-1) flow) results in ineffective ventilation within 60 s or less, depending on the degree of airway obstruction. In the absence of a high degree of upper airway obstruction, ventilation can be effective if the cannula is attached to a high pressure (45 psi) jet ventilator, but such devices are rare in UK prehospital practice. A self-inflating bag used with a cuffed tube inserted through a horizontal scalpel incision provides sustained adequate ventilation, has a relatively low complication rate compared to needle cricothyroidotomy and is a skill that can be easily taught to paramedics, nurses and doctors.

A new tracheal tube and methods to facilitate ventilation and placement in emergency airway management

The "jet endotracheal tube" (JET) has been designed to facilitate emergency intubation in apnoeic or paralyzed patients with a difficult airway. We investigated the efficiency of jet ventilation to maintain adequate oxygenation and ventilation using the initially designed JET, either with its distal tip positioned above vocal cord and pointed directly at or 45 degrees to the right of the vocal cord opening midline in 10 adult paralyzed pigs. The effectiveness of using end tidal carbon dioxide pressure (PetCO(2)), chest rise and breath sounds to facilitate tracheal placement of the JET blindly in a simulated difficult airway was studied. All complications of using the JET were noted. Jet ventilation with the distal tip of the JET pointed directly at, not 45 degrees to the right of vocal cord opening midline, provides adequate oxygenation and ventilation during intubation. In a simulated difficult airway, PetCO(2), chest rise and breath sounds were all effective methods to assist placement of the JET blindly, and the combination of all three methods works the best. No serious complications were detected with the use of the JET. Our results suggest that a correctly positioned JET guided by monitoring PetCO(2), chest rise and breath sound provides adequate oxygenation and ventilation during intubation in apnoeic pigs, and facilitates the intubation blindly in a simulated difficult airway. No serious complications were observed using the JET in this study. In patients requiring emergency intubation, a JET with PetCO(2) monitoring catheter and the instructions for use may be a useful addition to the airway management devices.

Percutaneous transtracheal emergency ventilation during respiratory arrest: comparison of the oxygen flow modulator with a hand-triggered emergency jet injector in an animal model

The oxygen flow modulator is a device for percutaneous transtracheal emergency ventilation. Simulating a respiratory arrest situation, we studied the effects of this device in comparison with a hand-triggered emergency jet injector during pulmonary resuscitation. Nine pigs were anesthetized and mechanically ventilated. After surgical exposure, an emergency transtracheal airway catheter was inserted into the trachea. Ventilation was stopped until SpO2 was below 70%. Each animal was subsequently randomly ventilated via the transtracheal airway catheter with either the hand-triggered emergency jet injector or the oxygen flow modulator. After 10 minutes, respiratory and hemodynamic parameters were recorded. Ventilation was stopped again until SpO2 reached 70%, and the animal was ventilated with the second device. With both devices, pulmonary resuscitation was successful. Whereas PaO2 differed not significantly between the two devices, PaCO2 was lower during percutaneous transtracheal ventilation with the hand-triggered emergency jet injector.

Surgical vs wire-guided cricothyroidotomy: a randomised crossover study of cuffed and uncuffed tracheal tube insertion

Using an airway mannequin and artificial lung model, we compared surgical cricothyroidotomy with a 6.0-mm cuffed Portex tracheostomy tube with wire-guided cricothyroidotomy using a 5.0-mm cuffed Melker or 6.0-mm uncuffed Melker tube. The trial was carried out by 27 anaesthetists using a randomised, crossover design. Surgical cricothyroidotomy proved significantly faster (mean (SD) time to first breath 44.3 (12.5) s for Portex surgical, 87.2 (21.6) s for cuffed Melker, 87.8 (19.2) s for uncuffed Melker, p < 0.001). With a standardised ventilator model, the cuffed tubes provided more effective ventilation (mean (SD) tidal volume 446 (41) ml Portex, 436 (52) ml cuffed Melker, 19 (5) ml uncuffed Melker, p < 0.001). Fourteen of the participants preferred the wire-guided system. We conclude that, in this model, a cuffed device is preferable when cricothyroidotomy is needed. In addition, the surgical method is quicker than a wire-guided approach.

Superimposed high-frequency jet ventilation (SHFJV) for endoscopic laryngotracheal surgery in more than 1500 patients

BACKGROUND

Superimposed high-frequency jet ventilation (SHFJV), which does not require any tracheal tubes or catheters, was developed specifically for use in laryngotracheal surgery. SHFJV uses two jet streams with different frequencies simultaneously and is applied in the supraglottic space using a jet laryngoscope and jet ventilator.

METHODS

Between 1990 and 2004, SHFJV was studied in 1515 consecutive patients (including 158 children requiring laryngotracheal surgery) prospectively. Ventilation was performed with an air/oxygen mixture and anaesthesia was administered i.v.

RESULTS

Adequate oxygenation and ventilation was achieved in 1512 patients. Arterial blood gas analyses (BGA) were performed between 1990 and 1994; thereafter BGA was only performed in patients with high-grade stenosis of the larynx/trachea or high-risk patients [n=623, mean Pa(O(2)) 133.8 (39.4) mm Hg and mean Pa(CO(2)) 42.3 (10.1) mm Hg]. There were no significant changes in Pa(O(2)) or Pa(CO(2)) during the entire period of SHFJV. No complications secondary to the ventilation technique were observed; in particular, no barotrauma occurred. Three patients required tracheal intubation. SHFJV was also successfully used for laser surgery (n=312). It proved to be a safe mode of ventilation without any complications such as airway fire, major haemorrhage, or aspiration of debris.

CONCLUSION

SHFJV is an advanced ventilation mode playing a pivotal role in the (open) ventilatory support/ventilation of patients with laryngotracheal stenosis. It is particularly indicated in cases of severe stenosis and offers optimal conditions for laryngotracheal surgery, including laser surgery and stent implantation techniques.

[Bilateral tension pneumothorax after retrieval of transtracheal jet ventilation catheter]

We report a bilateral tension pneumothorax which occurred in a 36-year-old man after high-frequency jet ventilation (HFJV) for panendoscopy. The patient had been treated with radiotherapy and chemotherapy two years ago for an oropharyngeal adenocarcinoma, and by surgery for a recurrence. The incident occurred after a cough episode triggered by the withdrawal of the Ravussin transtracheal catheter. We are discussing the risk factors and the mechanisms of pneumothorax during HFJV with special emphasis on trapping and lung fibrosis.

Measuring tracheal airway pressures during transtracheal jet ventilation: an observational study*

Tracheal airway pressures were measured via a transduced fibrescope during transtracheal jet ventilation in 10 patients. Ravussin transtracheal jet ventilation catheters were inserted under local anaesthesia. Following induction of general anaesthesia, tracheal airway pressures were measured at three anatomical levels during fibreoptic intubation. Overall pressure changes during transtracheal jet ventilation were small with the maximal pressure increase (13 mmHg) measured at the carina.

Comparing methods of administering high-frequency jet ventilation in a model of laryngotracheal stenosis

We administered high-frequency jet ventilation (HFJV) to a tracheal-lung model with connectors of internal diameter 2.5-8.5 mm to simulate ventilation through varying degrees of laryngotracheal stenosis. With reductions in diameter, end-expiratory pressure (EEP) and peak inspiratory pressure (PIP) increased. During supraglottic, translaryngeal, and transtracheal HFJV, respectively, EEP was > or =10 mm Hg at diameters narrower than 5.5, 4.0, and 3.5 cm, and PIP was >20 mm Hg at diameters narrower than 5.5, 3.5, and 3.0 cm. EEP and PIP were greater during supraglottic HFJV than during translaryngeal and transtracheal HFJV (P < 0.01). At diameters of <3.5 and 4.0 cm, respectively, PIP and EEP increased and were significantly greater (P < 0.01) during translaryngeal HFJV than during transtracheal HFJV. In a second experiment, the degree of ventilation and air entrainment was assessed by administering nitrous oxide 4 L/min to the model. Nitrous oxide concentrations were significantly (P < 0.01) smaller and nitrogen concentrations were significantly (P < 0.01) larger during supraglottic HFJV than either translaryngeal or transtracheal HFJV. The larger EEP and PIP associated with supraglottic HFJV may be attributable to increased ventilation and air entrainment compared with translaryngeal and transtracheal HFJV.

IMPLICATIONS

Ventilatory driving pressure during supraglottic high-frequency jet ventilation may be reduced to minimize high airway pressures and hence the potential for pulmonary barotrauma in patients with laryngotracheal stenosis.

Securing the child's airway in the emergency department

Airway management is an important aspect of pediatric emergency care. Prompt, effective airway access can mean the difference between a good outcome and disability or death. Optimal management requires an understanding of the differences between children and adults with respect to airway anatomy and physiology and response to medications to facilitate airway access. In most cases, the emergency physician is called to secure a child's airway with little forewarning. This review details a logical and practical approach to the uncomplicated pediatric airway. Emphasis is also placed on recognition of the difficult airway and methods to render the difficulty less daunting. Good judgment and the appropriate skills are the prerequisites for success.

Pneumomediastinum after dental surgery

A previously healthy woman presented with chest pain and cervical swelling several hours after undergoing surgical removal of third molar teeth. Mediastinal and subcutaneous emphysema was demonstrated by chest X-ray. Air had been introduced under the soft tissue flap by the high-speed turbine drill used to remove the alveolar bone, rather than the air/water syringe. Surgical handpieces that vent the air away from the surgical field should be used during such procedures. The mediastinal and subcutaneous air resolved after oxygen administration.

Pneumoperitoneum: a review of nonsurgical causes

OBJECTIVE

To review causes of nonsurgical pneumoperitoneum (NSP), identify nonsurgical etiologies, and guide conservative management where appropriate.

DATA SOURCE

We conducted a computerized MEDLINE database search from 1970 to 1999 by using key words pneumoperitoneum and benign, nonsurgical, spontaneous, iatrogenic, barotrauma, pneumatosis, diaphragmatic defects, free air, mechanical ventilation, gynecologic, and pelvic. We identified 482 articles by using these keywords and reviewed all articles. Additional articles were identified and selectively reviewed by using key words laparotomy, laparoscopy, and complications.

STUDY SELECTION

We reviewed all case reports and reviews of NSP, defined as pneumoperitoneum that was successfully managed by observation and supportive care alone or that required a nondiagnostic laparotomy.

DATA SYNTHESIS

Each unique cause of nonsurgical pneumoperitoneum was recorded. When available, data on nondiagnostic exploratory laparotomies were noted. Case reports were organized by route of introduction of air into the abdominal cavity: abdominal, thoracic, gynecologic, and idiopathic.

CONCLUSIONS

Most cases of NSP occurred as a procedural complication or as a complication of medical intervention. The most common abdominal etiology of NSP was retained postoperative air (prevalence 25% to 60%). NSP occurred frequently after peritoneal dialysis catheter placement (prevalence 10% to 34%) and after gastrointestinal endoscopic procedures (prevalence 0.3% to 25%, varying by procedure). The most common thoracic causes included mechanical ventilation, cardiopulmonary resuscitation, and pneumothorax. One hundred ninety-six case reports of NSP were recorded, of which 45 involved surgical exploration without evidence of perforated viscus. The clinician should maintain a high index of suspicion for nonsurgical causes of pneumoperitoneum and should recognize that conservative management may be indicated in many cases.

Cricothyroidotomy and transtracheal high frequency jet ventilation for elective laryngeal surgery. An audit of 90 cases

We carried out an audit of needle cricothyroidotomy and transtracheal ventilation used during anaesthesia for elective endolaryngeal surgery. The data on 90 consecutive procedures was collected over two years. Patients were anaesthetized using a total intravenous technique. An intravenous cannula or Tuohy needle was placed through the cricothyroid membrane and the patient was ventilated via the cannula using high frequency jet ventilation. Technical details of the procedure and any perioperative complications were recorded. There were 12 complications in total. Only three of these were clearly related to the cricothyroid puncture, i.e., one minor bleed and two cases of limited local surgical emphysema. All complications were minor and resolved without sequelae.

Jet ventilation in upper airway obstruction: description and model lung testing of a new jetting device

Patients with critical upper airway stenosis require a tracheotomy for corrective surgery. We describe a new transtracheal device that permits safe ventilation of these patients without tracheotomy. It is based on a coaxial bicannular design that allows "push-pull" ventilation by jetting gas through the inner cannula and applying suction through the outer cannula. It further allows monitoring of airway pressure, tidal volume, and end-tidal CO2. The device was placed in the "trachea" of an artificial lung, and the preparation was made airtight by sealing the proximal end of the trachea. Tidal volumes and their associated pressures were measured simultaneously at different parts of the airway at several lung compliances and airway resistance settings while varying the jet and suction pressures. A large range of tidal volumes was achieved at safe airway pressures using clinically relevant airway resistance and lung compliance settings. Airway pressures measured through the device correlated well with pressures measured directly in the airways at the same time. Tidal volumes, measured through a Wright respirometer in the suction line, exceeded actual values at high suction settings and decreased below actual values at low suction settings. This new form of jet ventilation allowed efficient ventilation of the artificial lung with a totally occluded upper airway.

IMPLICATIONS

Tracheotomy is required for surgery to relieve stridor because gas forced into the trachea at high pressures through a percutaneously placed needle (jetting) cannot be exhaled quickly enough for respiration. We describe a device that allows jetting in the stridorous patient by actively assisting expiration, thereby eliminating the tracheotomy requirement.

Cervical osteomyelitis after percutaneous transtracheal ventilation and tracheotomy

BACKGROUND

Percutaneous transtracheal ventilation has proven useful in emergent airway management.

METHODS

A report of a case is presented. Results. A 42-year-old woman who developed laryngospasm required emergency airway intervention She developed massive subcutaneous emphysema and required emergent cricothyroidotomy which was immediately converted to a tracheotomy. Although she was quickly decanulated, she developed late cervical osteomyelitis which resolved with intravenous antibiotic therapy.

CONCLUSIONS

Cervical osteomyelitis has not been previously reported as a complication of percutaneous transtracheal ventilation or tracheotomy Contamination of the deep neck spaces facilitated by pressure dissection of the fascial planes may have led to this complication.

High-frequency jet ventilation--a review of its role in laryngology

High-frequency jet ventilation (HFJV) is a safe, effective anaesthetic technique with a low risk of aspiration which has not yet gained wide acceptance in laryngology. Following anaesthesia and muscular relaxation the patient is intubated with a size 7FG infant feeding catheter and ventilation is achieved by delivering small bursts of anaesthetic gas at high frequency. The mechanisms of gas exchange are thought to be little different from those of conventional ventilation. We have found HFJV to be of value in laryngoscopy, laryngo-tracheal reconstruction, tracheoplasty, bronchoscopy and tonsillectomy. The advantages include: (a) ease of intubation, especially in the presence of a supraglottic mass; (b) improved surgical access compared with a conventional endotracheal tube; and (c) protection of the airway by the inherent 'auto-PEEP' effect. Care must be taken to ensure that conditions allow adequate exhaust of expired gas. Humidification of inspired gas is essential during prolonged procedures.