Intermittent capnography during high-frequency jet ventilation for prolonged rigid bronchoscopy

BACKGROUND: Gas exchange during high-frequency jet ventilation (HFJV) for prolonged rigid bronchoscopy (RBS) is usually monitored by arterial blood gas analysis. Capnography of expired gases during brief HFJV discontinuation may be a reliable and noninvasive supplemental method. Capnography can be performed either for single breaths or with respiratory rate (RR) reduced to 10 x min(-1). The aim of this study was to demonstrate that capnography during short periods of HFJV discontinuation represents a reliable measure of PaCO2 during prolonged RBS. METHODS: We prospectively investigated 100 consecutive patients (75 male and 25 female) undergoing HFJV for RBS. HFJV was delivered through the rigid bronchoscope at the following settings: working pressure 1.2 bar, rate 100 x min(-1), FIO2 0.99, t(i)/t(tot)0.6. The light guiding channel ending at the distal tip of the rigid bronchoscope was used for gas sampling. Capnograms were assessed at 5 min intervals and compared to PaCO2 from arterial blood samples drawn simultaneously. The accuracy of single breath CO2 sampling was compared with sampling at RR=10 x min(-1). RESULTS: Mean duration of RBS was 30+/-21 min. A significant correlation between capnography (PetCO2) and arterial blood gas analysis (PaCO2) was observed, being r=0.90 for the RR= 10 x min(-1) method and r=0.91 for the single breath method. Mean difference between PaCO2 and PetCO2 was 0.37+/-0.2 kPa throughout the entire study period. No significant differences between single breath sampling or sampling at RR=10 x min(-1) were observed. CONCLUSION: Capnography performed during short periods of HFJV discontinuation reliably and noninvasively reflects PaCO2 during prolonged endoscopic procedures. Capnography during HFJV for RBS may reduce the frequency of arterial blood gas sampling, the duration of unmonitored intervals and costs.     

Hepatic resection using a water jet dissector

A newly-designed water jet dissector was used for hepatic resections in humans. To evaluate its usefulness, the water jet dissector was compared toan ultrasonic surgical aspirator in terms of average blood loss and time of operation. In hepatectomies on patients associated with liver cirrhosis, the average blood loss during hepatic resection using the water jet dissector was significantly smaller (P<0.05) than that with the ultrasonic surgical aspirator. However, in hepatectomies on patients without cirrhosis, the average blood loss during hepatic resection did not significantly differ between the two groups. Neither did the time of operation significantly differ between the two procedures in hepatectomies on patients with and without liver cirrhosis. No serious complications attributable to the use of the water jet dissector were encountered. The water jet dissector is thus considered to be a useful new device for use in the transection of the liver during hepatic resections.     

High-frequency jet ventilation using a helium–oxygen mixture

The physiological basis for the use of helium relates to the relationship described by Poiseuille. During turbulent gas flow, the factors determining the resistance to flow include the density of gas as well as the length and the radius of a tube. While it may not be possible to readily change the latter two, altering the density of the gas is possible by using helium instead of nitrogen. A helium-oxygen combination has been used most commonly to improve air exchange in patients with upper airway obstruction. Anecdotal reports also suggest the beneficial effects of helium during mechanical ventilation in patients with status asthmaticus, hyaline membrane disease, and other pulmonary parenchymal disorders. To date, the clinical reports have utilized helium only with conventional mechanical ventilation. We present a child whose progressive respiratory failure was treated by using high-frequency jet ventilation with a combination of helium and oxygen. The techniques for the delivery of helium and oxygen through the jet ventilator are discussed.     

Intravenous infusion of propofol for induction and maintenance of anaesthesia during endoscopic carbon dioxide laser ENT procedures with high frequency jet ventilation

Fourteen patients of ASA grades 1 3 were anaesthetised with continuous infusions of propofol and alfentanil for endoscopic carbon dioxide laser ENT microsurgery. Their lungs were ventilated with an oxygen-air mixture using a high frequency jet ventilator. Propofol was given at an initial rate of 120 μg/kg/minute for 10 minutes after a bolus dose of 2.6 mg/kg, and then at 80 fig μg/kg/minute. Alfentanil was given at a rate of 0.5 μg/kg/minute. Arterial pressure decreased significantly after the bolus dose. It increased significantly for a few minutes after laryngoscopy and returned to baseline values during maintenance of anaesthesia. Heart rate increased significantly during induction and until laryngoscopy was performed but it decreased below its initial value after 5 minutes of maintenance. Platelet count and the degree of aggregation did not change during infusion of propofol.     

Airway management and anesthesia in neonates, infants and children during endolaryngotracheal surgery

BACKGROUND: Endolaryngotracheal surgery in neonates, infants and children poses a big challenge for both anesthesiologist and surgeon. The narrowness of the airways and the great variability of the pathological lesions necessitate close collaboration between the surgical and the anesthesia team to provide optimal operating conditions and ensure adequate ventilation and oxygenation. METHODS: Sixty-two anesthetic records of endolaryngotracheal surgical procedures in neonates, infants and children with ASA physical status 1-3 were analyzed retrospectively. Anesthesia was administered as total intravenous anesthesia; propofol supplemented with remifentanil. Ventilation was performed as supraglottic, superimposed high-frequency jet ventilation via jet laryngoscope with integrated jet nozzles. RESULTS: Age was 58.93 (SD 35.40) months, range 3 weeks to 14 years; body weight 17.83 (SD 8.79) kg, range 2.4-50 kg. The capillary pCO(2) 5 min after the start of the surgical procedure (n = 62) was 40.01 (SD 7.71) mmHg and after 20 min (n = 24) 41.77 (SD 7.12) mmHg. No hypoxemia (oxygen saturation <90%) developed. All patients were hemodynamically stable during jet ventilation. Barotrauma or gas insufflation in the stomach did not occur. No perioperative tracheostomy was necessary. Laryngospasm occurred in one child during emergence from anesthesia. Four infants received postoperative conventional respirator therapy in the ICU overnight. CONCLUSIONS: Supraglottic superimposed high-/low-frequency jet ventilation via jet laryngoscopes with integrated jet nozzles is a minimally invasive ventilation technique for neonates, infants and children in endolaryngotracheal surgery, which allows an unimpaired operating field for the surgeon especially in LASER surgery.     

One lung anaesthesia

Ten patients about to undergo left-sided thoracotomy for carcinoma of the lung were entered into a crossover trial to compare cardiovascular and respiratory function during high frequency jet ventilation and conventional mechanical ventilation for one lung anaesthesia. All patients were anaesthetised with a standard technique using double lumen tubes and placed in the lateral position with the left chest open. The results showed no significant differences with regard to ventilation sequence but one lung high frequency jet ventilation gave higher values than one lung conventional ventilation for shunt (p less than 0.01) and positive end expiratory pressure (p less than 0.05) and lower peak inflation pressure values (p less than 0.01). There were no significant differences in cardiac output, pulmonary capillary wedge pressure, arterial carbon dioxide or available oxygen. Surgical conditions were satisfactory during both methods of ventilation and satisfactory gas exchange occurred. It was, however, more difficult to assess adequacy of ventilation during high frequency jet ventilation and the routine use of this method of ventilation is not recommended during one lung anaesthesia.     

Effect of high-frequency jet ventilation on heart rate variability

We investigated the effects of high-frequency jet ventilation (HFJV) on heart rate variability in nine patients during fentanyl (10μg·kg⁻¹) anesthesia using power spectral density analysis. ECG and arterial pressure were recorded during intermittent positive pressure ventilation (IPPV) (tidal volume 8 ml·kg⁻¹, respiratory rate 0.25 Hz) and during HFJV [5 Hz, 2.5 kg·(cm²)⁻¹]. The R-R interval time series obtained were analyzed by the autoregressive method, and low-frequency (LF) (0.05–0.15 Hz) power and high-frequency (HF) (0.20–0.50 Hz) power from R-R interval spectra were used for statistical comparison. LF power did not change during IPPV and HFJV (108.8±41.6 ms² vs 105.8±22.4 ms², mean±SE). HF power was detected during IPPV (65.1±14.3 ms²); however, it was not detected during HFJV. Plasma levels of norepinephrine and epinephrine were significantly higher during HFJV than during IPPV. The mean R-R interval, arterial pressure, and arterial blood gas data did not differ between IPPV and HFJV. These data indicate that, during fentanyl anesthesia, HFJV influences mainly the respiratory frequency fluctuation of heart rate variability, and they suggest that alteration of breathing patterns caused by HFJV might be involved, as well as elevated sympathetic neural outflow to the heart.     

Effects of changes in frequency and inspiratory time on arterial oxygenation and CO2 elimination during high-frequency jet ventilation in a child with laryngotracheal papillomata

An 11-yr-old female without any pulmonary disorders underwent laser resections of laryngotracheal tumors using high-frequency jet ventilation (HFJV) 6 times over a period of 17 months at our institute. In this series of surgeries, we studied the effects on PaO2 and PaCO2 during HFJV of changes of either frequency or inspiratory time. Increasing the frequency from 100 to 400/min decreased the PaO2 and increased the PaCO2. Decreasing the inspiratory time from 30% to 20% increased the PaCO2, although it did not affect the PaO2. All the procedures were uneventfully carried out without critically impairing gas exchange during HFJV. In this patient with normal lung function, CO2 elimination during HFJV appeared to be facilitated by either decreasing the frequency or increasing the inspiratory time. Arterial oxygen tension during HFJV was higher at lower frequencies.     

Gas movement during jet ventilation

By examining flows in the expiratory limb of a bias flow circuit, it is possible to measure tidal, entrained and spilt volumes during jet ventilation. Using this method on a canine model, tidal volume fell and minute volume rose when the respiratory rate rose from 12 to 200 breaths/min. The changes were compatible with a convective model of gas movement. Entrained volume remained a constant fraction of tidal volume and spilt volume fell as a fraction of jet volume as respiratory rate increased.     

Gas flow distribution in distal high frequency jet ventilation and lung thorax compliance

To investigate the influence of changes in thorax and lung compliance on ventilation during distal High Frequency Jet Ventilation (HFJV), similar ventilator settings were compared before and after changing the compliance in two groups of anaesthetized mongrel dogs. Each period of distal HFJV was preceded by adequate Intermittent Positive Pressure Ventilation (IPPV) to assure a start with baseline values. In Group 1 (n = 7), thorax compliance was changed by chest strapping, while in Group 2 (n = 7) lung compliance was changed by inducing acute lung injury by injection of oleic acid into the right atrium. Gas flow distribution in the ventilatory circuit during distal HFJV was determined before and after the changes in compliance were induced. Comparing similar ventilator settings during distal HFJV in the same dog, a decrease in lung or thorax compliance led to changes in gas flow distribution in the ventilatory circuit. Entrainment was decreased and bypass increased with a negative effect on the gas volume entering the lungs and on gas exchange. The results indicate that distal HFJV should be regarded as pressure-limited ventilation.     

高频喷射通气对重度烧伤合并吸入性损伤患者早期的呼吸支持

目的　观察高频喷射通气 (highfrequencyjetventilation ,HFJV)对重度烧伤合并吸入性损伤患者早期的治疗作用。　方法　 2 0例重度烧伤 (TBSA 79.6 %± 2 9.3% )并吸入性损伤患者 ,其中 19例行气管切开手术 ,1例经鼻插管。为防低氧血症 ,所有患者均应用HFJV ,观察通气前和通气后 11d内血气、呼吸率和脉搏等指标的变化。　结果　气管切开时间为伤后 (2 .7± 2 .4 )d ,HFJV时间为伤后(4.4 0± 2 .9)d。HFJV后 1～ 3d ,PaO2 显著高于通气前水平 (P <0 .0 1) ,随后HFJV 1周 ,PaO2 仍维持在较高水平。在整个通气期间 ,PaCO2 、呼吸率和脉搏率均无明显变化。结论　在重度烧伤合并吸入性损伤早期 ,HFJV有利于氧合作用的改善而无明显副作用 ,是一较为适用的呼吸支持方式     

Jet ventilation for anterior paediatric scoliosis surgery

Single-lung anaesthesia for thoracotomy is usually achieved with endobronchial intubation, a double-lumen tube or an endobronchial blocker. High-frequency jet ventilation (HFJV) is seldom described for thoracotomy in children, although it is used for both laryngology procedures in the operating room and as a ventilation mode in intensive care. HFJV was used in three children, aged 10-12 years, who presented for scoliosis correction involving thoracotomy. The jet ventilation catheter was passed through a tracheal tube to reduce the risk of outflow obstruction and allow a smooth conversion to intermittent positive-pressure ventilation when required. Mean airway pressures measured at the tip of the HFJV catheter were at or below 4 cmH2O. Surgical opening of the nondependent lung pleura resulted in sufficient collapse of the pulmonary parenchyma with the patient in the lateral decubitus position for the surgical procedure. Arterial blood gas analyses performed during thoracotomy were within normal limits, with no CO2 retention. HFJV is an alternative ventilation strategy for thoracotomy in children because of its unique ability to deliver small tidal volumes at low mean airway pressures via a narrow catheter.     

Reexpansion Pulmonary Edema Due to High-Frequency Jet Ventilation: Report of a Case

Barotrauma is well known to be a relatively common complication of high-frequency jet ventilation (HFJV); however, the occurrence of reexpansion pulmonary edema (REPE) is extremely rare. We report herein a case of REPE caused by difficulties encountered with anesthesia using HFJV during video-assisted thoracic surgery (VATS) for a spontaneous pneumothorax. We believe the rapid increase in pressure in the lung after degassing for VATS resulted in REPE as well as typical barotrauma. Received: August 27, 1999 / Accepted: July 25, 2000     

高频通气在气管隆突重建术中的应用

目的 评价高频通气应用于气管隆突重建术的可行性。方法 择期肺癌需行气管隆突重建术患者１０例,常规麻醉诱导,插入双腔气管导管,开胸新开健侧主支气管后行高频通气,呼吸频率（ＲＲ）１２０次／ｍｉｎ,呼吸比（１：Ｅ）１：２,驱动压力０．１５～０．２０ＭＰａ。连接一条高频喷射通气导管（内径３ｍｍ）,插入一侧主支气管内３ｃｍ,并在术前、单肺通气后１５ｍｉｎ、高频通气后５ｍｉｎ、１０ｍｉｎ、２０ｍｉｎ及再次单肺     

Air entrainment during high-frequency jet ventilation in a model of upper tracheal stenosis

BACKGROUND: Previous work has demonstrated that when high-frequency jet ventilation (HFJV) is applied above an airway stenosis, higher distal airway pressures are produced compared with when the same ventilation is delivered below the stenosis (BSV). This study aimed to investigate the mechanisms underlying this finding. METHODS: HFJV was applied to a model of laryngo-tracheal stenosis with the jet located above the stenosis (ASV), with a catheter passed through the stenosis (TSV) or with HFJV delivered by a side port BSV. For each configuration and over a range of diameters of stenosis (2.5-8.5 mm), distal tracheal pressures and delivered minute volume were measured and air entrainment estimated. Experiments were repeated using the same model with the addition of a simulated 'pharynx' around the stenosis. RESULTS: Distal airway pressures, minute volumes, and air entrainment were consistently higher during ASV compared with BSV and TSV. The presence of the 'pharynx' made no significant difference to airway pressures or air entrainment. Delivered minute volumes varied between ASV, TSV, and BSV, and were also dependent on the stenosis diameter. With ASV, there appeared to be a range of stenosis diameters (4.0-5.5 mm) which 'maximized' minute volumes. CONCLUSIONS: The results suggest that the high airway pressures generated during ASV are the consequence of air entrainment and this effect, although reduced slightly, is maintained in the presence of the model pharynx. In contrast to the previous work, no significant entrainment occurred during BSV. If applicable to patients, these data suggest that ASV HFJV should be avoided in small diameter stenoses, but provides more efficient gas delivery and greater distending pressures with larger stenoses. BSV HFJV produces lower distal pressures and more consistent oxygen concentrations of injected gas across a range of stenosis diameters.     

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.     

Tubeless combined high-frequency jet ventilation for laryngotracheal laser surgery in paediatric anaesthesia

BACKGROUND: High-frequency jet ventilation (HFJV) is an alternative ventilatory approach in airway surgery and for facilitating gas exchange in patients with pulmonary insufficiency. We have developed a new technique of combined HFJV utilising two superimposed jet streams. In this study we describe the application of tubeless supralaryngeal HFJV during laryngotracheal laser surgery in infants and children. METHODS: Tubeless combined HFJV characterised by the simultaneous supralaryngeal application of a low-frequency (LF) and a high-frequency (HF) jet stream was evaluated in a clinical study in 10 children undergoing elective laryngotracheal CO2 laser surgery. Additionally, pressure and flow characteristics were determined with the use of a paediatric test lung. HFJV was applied by means of a modified Kleinsasser laryngoscope with integrated metal injectors. In addition to pulse oximetry, monitoring of ECG, heart rate and blood pressure, supraglottic airway pressure was measured and arterial blood gases were analysed. RESULTS: Tubeless combined HFJV was used in 10 infants and children (mean age 4.6 yr, range 2 months-10 years) undergoing 17 consecutive endoscopic procedures with CO2 laser microsurgery of the larynx or the trachea under general anaesthesia.The mean duration of supralaryngeal HFJV was 46 min (range 15-75 min). Mean driving pressures of the HF and the LF jet streams were 0.75 bar and 0.95 bar, respectively. Inspiratory oxygen ratios were in the range 0.4-1.0. HFJV resulted in mean PaO2 and PaCO2 values of 19.7 kPa and 6.1 kPa, respectively. No complications during HFJV were observed. In the test lung, combined HFJV applied with driving pressures of 0.7-1.0 bar and 0.9-1.2 bar for HF and LF jet ventilation, respectively, resulted in maximum peak and baseline distal airway pressures of 17.6 cm H2O and 5.4 cm H2O, respectively. CONCLUSION: The application of the combined double frequency HFJV was effective in maintaining gas exchange in the presence of laryngeal or tracheal stenoses. It provided good visibility of anatomical structures and offered space for surgical manipulation, avoiding the use of combustible material inside the larynx or trachea.     

Assessment of the tricuspid valve: a comparison of four transesophageal echocardiographic windows

OBJECTIVE: Tricuspid valve annular dilation is associated with persistent tricuspid valve regurgitation (TR) after cardiac surgery. The purpose of this study is to compare assessment of the tricuspid valve annulus from 4 different echocardiographic windows. DESIGN: Prospective study. SETTING: Single tertiary care hospital. PATIENTS: Twenty patients undergoing cardiac surgery, including right atriotomy. METHODS: Measurements of the tricuspid valve annular diameter during ventricular diastole (TVADd) and of TR jet dimensions, obtained from 3 different transesophageal and 1 transgastric echocardiographic window, were compared with each other and with that measured by the surgeon during cardiopulmonary bypass. Data were compared using correlation statistics, bias analysis, and analysis of variance for repeated measures. RESULTS: TVAD measured by the surgeon both agreed and correlated best with TVADd measured from the transgastric right ventricular inflow/outflow window (r = 0.98; mean bias 0.04 cm). The proximal TR jet widths and TR jet lengths were larger when measured from midesophageal 4-chamber and midesophageal right ventricular inflow/outflow windows compared with other windows (p < 0.01). CONCLUSION: TVADd was more accurately measured from transgastric windows, whereas the measurements of the TR jet were greater from esophageal windows. These data support imaging from multiple windows to obtain a more comprehensive assessment of the tricuspid valve anatomy and function.     

Effects of helium on high frequency jet ventilation in model of airway stenosis

Background. The addition of helium to the inspired gas may facilitateventilation in the presence of clinically evident upper airwayobstruction. However, there are no data on the effects of usinga helium–oxygen mixture during high frequency jet ventilation(HFJV) in upper airway obstruction. Methods. HFJV at a frequency of 150 min^–1 (driving pressure2 bar, inspiratory time 30%) was applied to a trachea–lungmodel to simulate ventilation through varying degrees of fixedlaryngotracheal stenosis (2.5–8.5 mm). HFJV was deliveredfrom above, through and below the level of stenosis to simulatesupraglottic, transglottic and infraglottic administration.Measurements of distal tracheal pressures were repeated foreach route at steady state for each stenosis diameter usingboth 100% oxygen and helium–oxygen (50% oxygen, 50% helium).The output of the ventilator was measured during operation onoxygen and helium–oxygen. Results. Peak, mean and end-expiratory pressures were greaterduring simulated supraglottic HFJV than during transglotticand infraglottic HFJV, and pressures increased markedly as thediameter of the stenosis decreased for all routes of ventilation(P<0.001). Generated pressures during HFJV using helium–oxygenand 100% oxygen were very similar overall, although reductionsin pressures were observed during ventilation with helium–oxygenvia the transglottic and transtracheal routes at stenosis diameters<4 mm (P<0.05). However, HFJV with the helium–oxygenmixture increased the delivered gas volumes by     

Experimental model of laryngotracheal stenosis in infants: effects of different high-frequency jet ventilation patterns on pulmonary parameters

Background: Supraglottic high‐frequency jet ventilation (HFJV) in laryngotracheal surgery in infants with modified jet laryngoscopes offers the surgeon an unimpaired operating field. However, supraglottic HFJV is associated with the development of high airway pressures, inadvertent positive end‐expiratory pressure (PEEP) levels, and barotrauma. Methods: We investigated the total lung volumes (TLV) and tidal volume variations at peak inspiratory pressure levels (PIP) and at PEEP levels along with the pulmonary pressures (PIP and PEEP) during two conventional methods of supraglottic HFJV in an infant trachea–lung model without stenosis and with different degrees of stenosis. Results: With augmentation of the driving pressure in the experiment without stenosis, the TLV plus the pulmonary pressures increased. With narrowing of the stenosis, TLV reduced at PIP level and increased at PEEP level. Volume shifts were significantly higher during superimposed HFJV compared with monofrequent HFJV at equivalent stenosis diameter (P < 0.05) except for the setting with 0.3 bar driving pressure (P > 0.05). The pulmonary PIP was in none of the test series higher than 20 mbar, and the pulmonary PEEP did not exceed 14 mbar. Conclusions: The results from our experimental model support the safe and effective clinical use of supraglottic HFJV in infants with tracheal stenosis. Moderate driving pressures provide acceptable pulmonary pressures in normal compliant lungs.