Airway Stenosis-Related Increase of Pulmonary Pressure During High-Frequency Jet Ventilation Depends on Injector’s Position

Anesthesia for interventional pulmonology procedures: a review of advanced diagnostic and therapeutic bronchoscopy

PURPOSE

Interventional pulmonology is a growing subspecialty of pulmonary medicine with flexible and rigid bronchoscopies increasingly used by interventional pulmonologists for advanced diagnostic and therapeutic purposes. This review discusses different technical aspects of anesthesia for interventional pulmonary procedures with an emphasis placed on pharmacologic combinations, airway management, ventilation techniques, and common complications.

SOURCE

Relevant medical literature was identified by searching the PubMed and Google Scholar databases for publications on different anesthesia topics applicable to interventional pulmonary procedures. Cited literature included case reports, original research articles, review articles, meta-analyses, guidelines, and official society statements.

PRINCIPAL FINDINGS

Interventional pulmonology is a rapidly growing area of medicine. Anesthesiologists need to be familiar with different considerations required for every procedure, particularly as airway access is a shared responsibility with pulmonologists. Depending on the individual case characteristics, a different selection of airway method, ventilation mode, and pharmacologic combination may be required. Most commonly, airways are managed with supraglottic devices or endotracheal tubes. Nevertheless, patients with central airway obstruction or tracheal stenosis may require rigid bronchoscopy and jet ventilation. Although anesthetic approaches may vary depending on factors such as the length, complexity, and acuity of the procedure, the majority of patients are anesthetized using a total intravenous anesthetic technique.

CONCLUSIONS

It is fundamental for the anesthesia provider to be updated on interventional pulmonology procedures in this rapidly growing area of medicine.

Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation

BACKGROUND

Both superimposed high-frequency jet ventilation (SHFJV) and single-frequency (high-frequency) jet ventilation (HFJV) have been used with success for airway surgery, but SHFJV has been found to provide higher lung volumes and better gas exchange than HFJV in unobstructed airways. The authors systematically compared the ventilation efficacy of SHFJV and HFJV at different ventilation frequencies in a model of tracheal obstruction and describe the frequency and obstruction dependence of SHFJV efficacy.

METHODS

Ten anesthetized animals (weight 25 to 31.5 kg) were alternately ventilated with SHFJV and HFJV at a set of different fHF from 50 to 600 min. Obstruction was created by insertion of interchangeable stents with ID 2 to 8 mm into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded, and blood gases were analyzed repeatedly.

RESULTS

SHFJV provided greater than 1.6 times higher end-expiratory chest wall volume than HFJV, and tidal volume (VT) was always greater than 200 ml with SHFJV. Increase of fHF from 50 to 600 min during HFJV resulted in a more than 30-fold VT decrease from 112 ml (97 to 130 ml) to negligible values and resulted in severe hypoxia and hypercapnia. During SHFJV, stent ID reduction from 8 to 2 mm increased end-expiratory chest wall volume by up to 3 times from approximately 100 to 300 ml and decreased VT by up to 4.2 times from approximately 470 to 110 ml. Oxygenation and ventilation were acceptable for 4 mm ID or more, but hypercapnia occurred with the 2 mm stent.

CONCLUSION

In this in vivo porcine model of variable severe tracheal stenosis, SHFJV effectively increased lung volumes and maintained gas exchange and may be advantageous in severe airway obstruction.

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.