14. Management in positive pressure ventilation.
14. Management in positive pressure ventilation.
The Tulip has been designed to be easily introducible, with an effective ventilatory seal that operates at 60mls volume under normal circumstances. This enables manual ventilation at +/-20cmH2O normally. This enables the Tulip to be used with intermittent positive pressure ventilators when required. Values greater than this require down regulation using the pressure release/regulation valve upon the anaesthetic circuit to prevent excessive gastric dilation at values greater than 20cmH2O ventilation pressure.
To effectively ventilate the Patient, it is important to consider the effects of high peak-pressures upon gastric dilation, post-operative vomiting and consequent aspiration. It is advised to use gentle ventilation patterns with a recommended value range of +/-20cmH2O, which is adequate to maintain the desired end tidal CO2 values in most elective Patients. If excessive ventilation pressures are required to maintain oxygenation and normocapnia, then it may be necessary to increase the Tulip’s cuff inflation volume, which in turn increases the mucosal barrier pressure, allowing ventilation pressures to be matched to requirements. It is important that these excess ventilation pressures are not maintained, and that plans for alternative airway management are considered at an early stage, namely endotracheal intubation with controlled ventilation to minimize any gastric dilation, and protect the Patient against any aspiration risk.
The Tulip can be inflated to withstand ventilation pressures in excess of 100cmH2O in mannequins, so almost any ventilating pressures may be generated with the Tulip in-situ, depending upon the volume (>60mls) and pressure (>60mmHg/80cmH2O) within the Tulips balloon-cuff. Clearly, this value is considered excessive for Human ventilation and requires down regulation to the normal values of +/-20cmH2O using the pressure-regulating valve on the anaesthetic breathing circuit. Cuff pressures may thus also be reduced when such high levels of ventilation pressure are not required by the user.
Neuromuscular paralysis is not required for the insertion of a Tulip, which is specifically beneficial in the Patient in whom airway control may be compromised. This is also beneficial if the anticipated spontaneously breathing anaesthetic requires modification to the relaxant technique. In this case the long acting relaxant may be given, and controlled ventilation instigated with ventilators without any manipulation of the Tulip in-situ, once in place and secured. The Tulip may be safely used in this scenario if there is no possibility of aspiration, such as the starved, elective Patient. In relaxant technique ventilation, peak ventilation pressures may rise excessively as the relaxant wears off, causing audible leaks and necessitating further doses of relaxant to reduce the resistance of the chest wall achat viagra montreal.
The Tulip is not designed to be used in conjunction with nasogastric tubes placed externally to the inflatable cuff, as the presence of the tube on the outside of the inflatable cuff undermines the oropharyngeal seal, making it possible for secretions to reach the posterior oropharyngeal wall in close proximity to the laryngeal inlet. The presence of the nasogastric tube may also undermine the oropharyngeal seal causing audible or non audible leaks, which may compromise effective ventilation of the Patient.
Such nasogastric tubes may however be passed through the breathing tube, as may bougeys, guide-wires and bronchoscopes.
Reversal of neuromuscular blockade may be conducted whilst the Tulip tube remains in place, as the sealed oropharynx enables ventilation management to be delivered with full control at all times, if the cuff remains inflated in the recommended fashion. The Tulip may therefore be left in place, the reversal given, and the Patient taken directly to recovery after the onset of regular, deep respiration without any further interference with the airway.
It is considered possible to perform more minor abdominal surgery using the Tulip, relaxant, controlled ventilation technique in those Patients considered to be of low aspiration risk. Overly obese patients, and those with a history of regurgitation or hiatus hernia, are considered unsuitable candidates for a Tulip.