Tidal volume and airway pressure under percutaneous transtracheal ventilation without a jet ventilator: comparison of high-flow oxygen ventilation and manual ventilation in complete and incomplete upper airway obstruction models

Three Cases of Transtracheal Catheter Oxygenation for Postoperative Dyspnoea with Pituitary-Dependent Hyperadrenocorticism in Dogs Treated by Surgery

Transsphenoidal surgery (TSS) is a curative treatment for pituitary-dependent hyperadrenocorticism, and its use in dogs has recently increased. One of the most serious postoperative complications of TSS is dyspnoea. We report three cases where transtracheal catheter oxygen therapy prevented death from respiratory distress secondary to enlarged soft palate after TSS.

Management of haematoma after thyroid surgery: systematic review and multidisciplinary consensus guidelines from the Difficult Airway Society, the British Association of Endocrine and Thyroid Surgeons and the British Association of Otorhinolaryngology, Head and Neck Surgery

Haematoma after thyroid surgery can lead to airway obstruction and death. We therefore developed guidelines to improve the safety of peri‐operative care of patients undergoing thyroid surgery. We conducted a systematic review to inform recommendations, with expert consensus used in the absence of high‐quality evidence, and a Delphi study was used to ratify recommendations. We highlight the importance of multidisciplinary team management and make recommendations in key areas including: monitoring; recognition; post‐thyroid surgery emergency box; management of suspected haematoma following thyroid surgery; cognitive aids; post‐haematoma evacuation care; day‐case thyroid surgery; training; consent and pre‐operative communication; postoperative communication; and institutional policies. The guidelines support a multidisciplinary approach to the management of suspected haematoma following thyroid surgery through oxygenation and evaluation; haematoma evacuation; and tracheal intubation. They have been produced with materials to support implementation. While these guidelines are specific to thyroid surgery, the principles may apply to other forms of neck surgery. These guidelines and recommendations provided are the first in this area and it is hoped they will support multidisciplinary team working, improving care and outcomes for patients having thyroid surgery.

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.

Manual volume delivery via Frova Intubating Introducer: a bench research study

PURPOSE

Oxygen delivery through a Frova Intubating Introducer may be life-saving, and gas flow characteristics through this device have been described. Nevertheless, the feasibility of using a self-inflating resuscitation bag to deliver air or oxygen through this device has not been assessed. We compared volumes of air delivered and peak pressures generated with normal and maximal bimanual compression of a self-inflating resuscitation bag connected to a 70 cm Frova Intubating Introducer.

METHODS

In this bench research study, the proximal end of the 14-F Frova Intubating Introducer was connected to the self-inflating resuscitation bag, and the distal end was connected to a flow analyzer fitted with an adult test lung. Thirty-five anesthesia health care providers (staff/trainees) squeezed the self-inflating resuscitation bag with three normal and three maximal bimanual compressions. Endpoints of interest included the delivered volume of air and generated peak pressure.

RESULTS

Normal bimanual compression resulted in a smaller mean (standard deviation) volume of air and peak pressure compared with maximal bimanual compression [554 (131) vs 955 mL (121); mean difference - 400.4; 95% confidence interval [CI], - 441.8 to - 359.0; P < 0.001; and 22.0 (3.4) vs 41.8 cmH₂O (13.3); mean difference - 19.7; 95% CI, - 23.5 to - 15.9; P < 0.001, respectively].

CONCLUSION

Clinically useful, life-sustaining volumes of air can be delivered using normal and maximal bimanual compression of a self-inflating resuscitation bag connected to a 70 cm Frova Intubating Introducer.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT02786355); registered 27 January, 2016.

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.