High-frequency positive-pressure ventilation (hfppv) during transthoracic resection of tracheal stenosis and during peroperative bronchoscopic examination

Tracheobronchoplasty in Japan

More than a century has passed since the first tracheoplasty was successfully performed by Eiselsberg in 1896. In that time, tracheobronchoplasty has developed with the extension of operative indications. This review focuses on who contributed to the development of this operation in Japan, and in what ways, with comparisons to results for these operations in the West. The headings include "Pioneers and colleagues", "Symbols and taxonomy", "Surgical anatomy", "Surgical diseases", "Anesthesia", "Surgical techniques", "Results", and "The present state". Although effort has been made to acknowledge various opinions, the convictions expressed herein are my own.

Anesthesia for airway surgery

Surgery of the upper airway requires diagnostic or therapeutic manipulation of the respiratory tree despite ongoing ventilation. Whether internal or external access to the conducting airway is required, anesthesiologist and surgeon, who must work together closely, share the airway. The anesthetic technique is influenced by the chosen mode of ventilation.

Tracheal resection and reconstruction

PURPOSE

To review the literature on tracheal and carinal resection and reconstruction, and to report the general approach to these patients, as well as the general guidelines for the safe administration of anesthesia. The airway management is extensively reviewed.

SOURCE

Articles obtained from a Medline search (1960 to October 1997; keywords: tracheal surgery, carinal surgery, airway management). Textbook literature including the bibliographies were also consulted.

PRINCIPAL FINDINGS

Benign or malignant tracheal and carinal pathology causing obstruction can be managed in several ways but resection and reconstruction are the treatment of choice for most patients with tracheal stenosis or tumour. Surgery of the trachea is a special endeavour where the airway is shared by the surgeon and the anesthesiologist. The principal anesthetic consideration is ventilation and oxygenation in the face of an open airway. Ventilation can be managed in different ways, including manual oxygen jet ventilation, high frequency jet ventilation, distal tracheal intubation, spontaneous ventilation, and cardiopulmonary bypass.

CONCLUSION

The management of anesthesia for tracheal surgery presents many challenges to the anesthesiologist. Knowledge of the various techniques for airway management is crucial. Meticulous planning and communication between the anesthesia and surgical teams are mandatory for the safe and successful outcome of surgery for patients undergoing this procedure.

Anesthesia for insertion of a Dumon stent in a patient with a large tracheo-esophageal fistula

PURPOSE

To present the anesthetic management for the insertion of a Dumon silicon stent to the trachea of a patient with a large tracheo-esophageal fistula. The aim of the stent insertion was to seal the fistula in order to prevent aspiration of esophageal content and subsequent pneumonitis.

CLINICAL FEATURES

A 45-yr-old man with a large tracheo-esophageal fistula was scheduled for the insertion of the Dumon stent. Since placement of the stent necessitates the insertion of a rigid bronchoscope, under general anesthesia, with its tip just proximal to the fistula, controlled ventilation was expected to be difficult to achieve because of the diversion of oxygen through the large fistula to the esophagus. We successfully ventilated the lungs, after the fistula was sealed using a large balloon which was inserted in the esophagus, and the stent insertion was completed uneventfully.

CONCLUSION

Anesthesia for procedures involving the central airway is challenging. This report describes a simple and practical method to facilitate ventilation by temporary seal of a tracheo-esophageal fistula using a modified esophageal balloon.

Anaesthesia for tracheal resection: report of 17 cases

PURPOSE

Laryngo-tracheal stenosis remains a major complication after prolonged intubation or tracheostomy. Surgical resection with end-to-end anastomosis carries the best long term prognosis. For the anaesthetist, however, this procedure represents a most challenging situation.

METHODS

Since 1993, we have used high frequency jet ventilation (HFJV) for tracheal resection. This paper describes the technique and the results of our series including 7 adults and 10 children.

RESULTS

There were no adverse haemodynamic or ventilatory consequences due to HFJV. Oxygenation was well maintained during the HFJV period. Sixteen of the 17 patients had a good outcome. Despite the good result of the resection-anastomosis, one child still suffers from an associated posterior glottic stenosis.

CONCLUSION

Since the introduction of HFJV for surgery of tracheal stenosis in our institution no complication of this ventilatory technique has occurred. It reduces the manipulation of the ventilation system and the period of apnea, thus decreasing the risk of hypoxaemia. The good access to the surgical field contributes to the success of resection-anastomoses in laryngo-tracheal stenosis.

Intraoperative management of distal tracheal rupture with selective bronchial intubation

Patients with tracheal rupture present a considerable challenge to the anesthesiologist. The most important aspect in anesthesiology in such cases is to maintain oxygenation and ventilation without compromising surgical repair. We report a case of a woman who suffered a chemical perforation of the carina and left bronchus after ingesting hydrochloric acid during a suicide attempt. We describe the intraoperative management strategies, with emphasis on the use of bilateral bronchial intubation to provide selective lung ventilation. Alternative modes of ventilation and the use of cardiopulmonary bypass are discussed.

The management of tracheal rupture using bilateral bronchial intubation

The management of a patient who required positive pressure ventilation following pharyngolaryngo-oesophagectomy during which tracheal injury was sustained is described. Ventilation with a tracheal tube resulted in a massive pneumoperitoneum. Bilateral bronchial intubation was employed with success.

Carinal resection with two high-frequency jet ventilation delivery systems

A 76-yr-old man underwent carinal resection for squamous cell carcinoma through the right posterolateral thoracotomy approach. Ventilation was maintained by the use of two high-frequency jet ventilators, each attached to a separate catheter during the time of resection and reconstruction of the tracheal carina. These catheters were introduced through the endotracheal tube and positioned into the left and right main bronchi at the beginning of the tracheal resection. Then, conventional ventilation was replaced by high-frequency jet ventilation (HFJV) with different ventilatory variables for each lung. During two-lung jet ventilation there was good oxygenation, normocapnia and no cardiovascular complications. The principle advantage of using two separate high-frequency ventilators is that it allows for maximum ventilatory efficiency with lungs of different compliance.

The effective tracheal diameter that causes air trapping during jet ventilation

Jet ventilation consists of injection of gas at high flow rates through a small-diameter tracheal catheter. Air trapping (increase in end-expiratory lung volume) can occur during jet ventilation if the diameter of the trachea proximal to the tracheal catheter tip is too small (at least at one point in the trachea) to permit complete exhalation of the tidal volume around the tracheal catheter (ie, through the effective tracheal diameter). A mechanical lung model was used to determine the critical effective tracheal diameter at which air trapping starts to occur during jet ventilation. The experiment allowed derivation of a multivariable equation, namely: [formula: see text] to express the tidal volume produced by jet ventilation (y) as a function of gas flow rate (C), jet injection time (D), lung compliance (B), upper airway resistance (A), and effective tracheal diameter (E). As A to D increased and E decreased, y increased. More importantly, exhalation time was measured over the full range of values for A to E, and it was found that for every possible combination of values for A to D, there was always a unique critical effective tracheal diameter, 4.0 to 4.5 mm, that began to cause a very large increase in expiratory time (and with a sufficiently rapid respiratory rate [greater than 12 beats/min in this experiment], air trapping). Thus, when lung/jet ventilation factors tend to promote entry of jetted gas into the lungs (increased A to D, decreased E), even a small tidal volume has difficulty exiting the lung, if E is smaller than 4.5 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Modified jet ventilation during total laryngectomy: a prospective study using pulse oximetry and a pressure regulator

A method of jet ventilation during total laryngectomy is described. During the construction of the terminal tracheostomy, a small metal tube is used, instead of the traditional tracheostomy tube, to provide intermittent jet ventilation down the distal trachea. A pressure regulator is also employed to choose a driving pressure best suited to the chest and lung compliance of each patient. Excellent surgical access for tracheo-cutaneous anastomosis is achieved. Satisfactory ventilation during the jet period is also confirmed by unaltered PaCO2 and increased PaO2 levels. The use of pulse oximetry as a non-invasive and continuous monitor of arterial oxygenation is a simple alternative to arterial blood sampling.

In what respect does high frequency positive pressure ventilation differ from conventional ventilation?

The original rationale for HFPPV was that under certain conditions adequate alveolar ventilation could be achieved with high ventilatory frequencies and small tidal volumes. It was theorized further that increased ventilatory frequencies and low tidal volumes would decrease the airway pressures, barotrauma, and cardiovascular and other systemic consequences seen with conventional mechanical ventilation. The first clinical applications of HFPPV were in bronchoscopy and laryngoscopy for diagnostic and/or therapeutic purposes. Apart from these endoscopic applications, volume-controlled HFPPV has been compared with conventional ventilation in upper abdominal surgery and coronary artery bypass grafting. The possible advantages of HFPPV over conventional volume-controlled ventilation in the intensive care setting are still unclear. Provided that the mean lung volumes are similar, oxygenation in acute respiratory failure is similar with both ventilation methods. Although the role of HFPPV in the management of pulmonary diseases still remains to be clarified, it does provide effective ventilation in selected types of patients needing ventilatory support. New modes of pressure-controlled ventilation have not resolved all clinical problems in severe ARDS and/or acute respiratory failure. The search for means of optimal ventilatory support with minimal complications must continue, as conventional ventilation does not always offer the best treatment.

One lung anaesthesia. Cardiovascular and respiratory function compared during conventional ventilation and high frequency jet ventilation

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.

Combined unilateral high frequency jet ventilation and contralateral intermittent positive pressure ventilation

The anaesthetic management of a patient who required right lower lobectomy for bronchial carcinoma associated with emphysema, pneumoconiosis and a previous thoracoplasty for pulmonary tuberculosis, is described. A technique of unilateral high frequency jet ventilation plus conventional intermittent positive pressure ventilation to the contralateral lung was used.

Insertion of intratracheal stents. Anaesthetic management using high frequency jet ventilation or cardiopulmonary bypass

The case histories of two patients who required the insertion of intratracheal stents are presented. The peroperative anaesthetic management of one case included the use of high frequency jet ventilation of the lungs; in the other case, partial cardiopulmonary bypass was used. The advantages and disadvantages of these two methods are discussed.

Surgical management of tracheal tumours

The annual incidence of primary tracheal tumours in Sweden is less than 1 per million population. Five cases of malignant tracheal neoplasm treated with segmental resection and primary reconstruction are described. Exploration and mobilization of the trachea were performed via right thoracotomy. Suprahyoid laryngeal release was also done in two cases, using a cervicomediastinal approach. The length of resected segment in these cases was 6 and 7 cm. High-frequency positive-pressure ventilation was used in four of the five cases and greatly facilitated the operation. Recovery was uneventful. Adenoid cystic carcinoma was too extensive for extirpation in one case, but 4 months after radiotherapy a 7 cm tracheal segment with residual tumour was removed; 3 years later the patient is well. There was no stenosis or other late complication and no local recurrence in the long-term survivors. No vocal paralysis occurred. The two patients with laryngeal release had remarkably little and transitory dysphagia. Technical problems are discussed and conclusions are presented.

High-frequency jet ventilation in major airway or pulmonary disruption

High-frequency jet ventilation is an experimental method of mechanical support, which achieves satisfactory alveolar ventilation and oxygenation at low peak-inspiratory pressures of 5 to 8 cm H2O and low end-expiratory pressures of 3 to 5 cm H2O. This characteristic was used to advantage in 23 patients with cancer, 12 of whom had tracheal or bronchial disruption complicated by pneumonia. Eight patients who could not be supported by conventional means were salvaged. Barotrauma complicated the very high peak airway pressures required to ventilate 8 of 11 patients with respiratory failure associated with diffuse interstitial pneumonia or pulmonary fibrosis. There were only 2 survivors despite temporary normalization of arterial blood gas values in 7 patients. Earlier use of high-frequency jet ventilation in patients with poor compliance may prevent pulmonary disruption in addition to deleterious hemodynamic and systemic effects of conventional high-pressure ventilation. Other applications under study include the role of jet ventilation in resection of the trachea or carina, and in major airway trauma.

Clinical evaluation of high-frequency positive-pressure ventilation (HFPPV) in laryngoscoy under general anaesthesia

A technique for automatic ventilation during laryngoscopy under general anaesthesia was evaluated in a lung model and in 5 patients (3--57 y) submitted for routine laryngoscopy. this technique has been given the name laryngoscopic HFPPV and utilizes an insufflation frequency (f) of 60 per min and a relative insufflation time (t%) of 22%. Ventilation is given via a nasotracheal insufflation catheter. Laryngoscopic HFPPV permits laryngeal surgery with a virtually unobstructed surgical field under complete muscular relaxation. The alveolar ventilation of the patient may be controlled by adjustment of the pressure of the anaesthetic gas mixture and there is no air entrainment through the larynx during insufflation. This makes possible use of O2/N2O mixtures and the oxygenation of the patient may be controlled by adjustment of the oxygen concentration of the anaesthetic gas mixture. As there is a continuous upward has flow through the larynx, blood or pieces of loose tissue are not sucked down into the trachea. A simple ventilation nomogram for clinical use is proposed. Adequately used, this nomogram guarantees safe ventilation during laryngoscopic HFPPV. An Fio2 of 0.3--0.4 gives adequate arterial oxygenation.

Physiologic evaluation of the HFPPV pneumatic valve principle and PEEP. An experimental study

In experiments in dogs the ventilatory and circulatory conditions prevailing with the ventilatory pattern in high-frequency positive-pressure ventilation (HFPPV) were investigated with use of a pneumatic valve principle and a ventilator system of an "open" character. Keeping the gas input constant the importance of insufflation frequency and insufflation time and the reactions to various levels of positive end-expiratory pressure (PEEP) were investigated in terms of changes in arterial pH, Pco2 and Po2. With the volumes of delivered gas kept constant, an increasing insufflation frequency from 60 to 100 per min gave a parallel decrease in tidal volume accompanied by lower maximum intratracheal pressures and a significant decrease in alveolar ventilation. Also taking into account the possibilities of inducing a suppression of the spontaneous respiration, higher ventilatory frequencies than 60 per min do now seem to introduce any further advantages. Including the associated effects on cardiac output and venous admixture, the cardio-pulmonary and circulatory parameters studied did not show any substantial changes with PEEP levels below 7.5--10 cm H2O. Thus the level of PEEP, which often is part of the ventilatory pattern in HFPPV, does not seem to have any untoward influence on the circulation (stroke volume, cardiac output, total peripheral vascular resistance) and oxygen transport (arterial oxygen content and oxygen flux) in normovolaemic dogs.