Usefulness of continuous oxygen insufflation into trachea for management of upper airway obstruction during anesthesia

Dynamic modulation of upper airway function during sleep: a novel single-breath method

To examine the dynamic modulation of upper airway (UA) function during sleep, we devised a novel approach to measuring the critical pressure (Pcrit) within a single breath in tracheostomized sleep apnea patients. We hypothesized that the UA continuously modulates airflow dynamics during transtracheal insufflation. In this study, we examine tidal pressure-flow relationships throughout the respiratory cycle to compare phasic differences in UA collapsibility between closure and reopening. Five apneic subjects (with tracheostomy) were recruited (2 men, 3 women; 18–50 yr; 20–35 kg/m2; apnea-hypopnea index >20) for this polysomnographic study. Outgoing airflow through the UA (face mask pneumotachograph) and tracheal pressure were recorded during brief transtracheal administration of insufflated airflow via a catheter. Pressure-flow relationships were generated from deflation (approaching Pcrit) and inflation (after Pcrit) of the UA during non-rapid eye movement sleep. During each breath, UA function was described by a pressure-flow relationship that defined the collapsibility (Pcrit) and upstream resistance (Rus). UA characteristics were examined in the presence and absence of complete UA occlusion. We demonstrated that Pcrit and Rus changed dynamically throughout the respiratory cycle. The UA closing pressure (4.4 ± 2.0 cmH2O) was significantly lower than the opening pressure (10.8 ± 2.4 cmH2O). Rus was higher for deflation (18.1 ± 2.4 cmH2O·l−1·s) than during inflation (7.5 ± 1.9 cmH2O·l−1·s) of the UA. Preventing occlusion decreases UA pressure-flow loop hysteresis by ∼4 cmH2O. These findings indicate that UA collapsibility varies dynamically throughout the respiratory cycle and that both local mechanical and neuromuscular factors may be responsible for this dynamic modulation of UA function during sleep.

Low-Flow Transtracheal Rescue Insufflation of Oxygen After Profound Desaturation

BACKGROUND

The objective of this study was to determine whether low-flow transtracheal insufflation of oxygen (TRIO) could rescue an animal from profound desaturation. This temporizing maneuver could be useful during cannot-intubate or -ventilate scenarios by resolving hypoxia without the morbidity associated with more invasive procedures.

METHODS

Seven swine for a total of 12 runs were studied. Animals were pharmacologically anesthetized, paralyzed, and mechanically ventilated with room air. After disconnection from the ventilator and desaturation to an Spo2 < 50%, low-flow TRIO (2 L/min) was administered for 1 hour.

RESULTS

All animals survived and Spo2 increased to greater than 90% in 23 seconds on average. Pao2 (mean, 183 mm Hg) remained elevated throughout the study. Hemodynamic stability was maintained for at least 15 minutes.

CONCLUSION

Low-flow TRIO rescued animals from profound hypoxia and maintained oxygenation for at least 1 hour. Low-flow TRIO did not prevent hypercarbia with its subsequent sympathetic activation.

Multidisciplinary management of life-threatening tracheal obstruction

Life-threatening obstruction of the lower trachea is rare, and protocols for treating severe narrowing of the tracheal lumen are scant. We describe our management to provide safe airway control in a severely dyspnoeic patient with unilateral vocal cord paralysis and a 1mm opening of the lower trachea.

[Preoxygenation and upper airway patency control]

During preoperative assessment, risk factors of upper airway obstruction should be evaluated: respiratory insufficiency, low O(2) reserve, preoxygenation failure or difficult face mask ventilation. In healthy subjects, spontaneous breathing O(2) for 3 min is the reference method. Apnoea duration is longer after preoxygenation than after denitrogenation, even if FEO(2) and SpO(2) do not change during the two last minutes of preoxygenation. The apnea time is longer after 3 min spontaneous breathing than after four deep breaths for 1 min in most of the literature. Maximal breathing during 2 min can produce values comparable to those obtained with tidal volume breathing for 3 min. FEO(2) monitoring is helpful in the assessment of preoxygenation quality: In case of oxygenation impairment during anaesthesia induction, algorithm use is helpful. Because desperate emergencies will occur in association with anaesthesia, every location should have the immediate availability of Fastrach and trans tracheal ventilation. Every anaesthesiologist should be familiar with and well practised in a variety of airway management techniques. Teaching programs are organised in order to develop anaesthesiologist sensitisation and skill.

Ventilating with tracheal gas insufflation and periodic tracheal occlusion during sleep and wakefulness

INTRODUCTION

The current invasive and noninvasive methods for delivering long-term ventilatory support rely on cumbersome patient interfaces that may interfere with upper airway function. To overcome these limitations, a novel system was developed to ventilate conscious, spontaneously breathing dogs through a self-contained cuffed cannula that was used for tracheal gas insufflation (TGI) and periodic tracheal occlusion (PTO). We hypothesized that TGI + PTO would provide greater ventilatory support than would TGI alone and that its effect would be more pronounced during sleep than wakefulness.

METHODS

Chronically tracheostomized dogs were monitored for sleep (ie, EEG, electro- oculogram, and nuchal electromyogram) and breathing (ie, tracheal pressure [Ptr] and upper airway flow via snout mask). A thin transtracheal cannula housed within a cuffed tracheostomy tube was used for TGI and PTO monitoring. E, gas exchange, and breathing patterns were examined during sleep and wakefulness at baseline (ie, no TGI) and during the application of TGI alone (at 5, 10, and 15 L/min) and the application of TGI + PTO.

RESULTS

Compared to baseline breathing without TGI, TGI at 5, 10, and 15 L/min decreased minute ventilation without influencing PaCO(2). In contrast, TGI + PTO led to progressive increases in ventilation, positive Ptr swings, and decreases in PaCO(2) as the flow rate was increased during sleep and wakefulness. Moreover, spontaneous breathing efforts ceased during TGI + PTO at flow rates of 10 and 15 L/min during wakefulness, and at all flow rates during sleep.

CONCLUSIONS

The findings indicate that TGI + PTO can fully support ventilation in a spontaneously breathing canine model during sleep and wakefulness. Its streamlined interface could ultimately prove to be clinically significant, once technical concerns are addressed.