Introduction: Airway patency is arguably the most important factor of the cardiopulmonary system. It is imperative that the bedside Respiratory Care Practitioner (RCP) can rapidly detect and treat airway emergencies. One tool for assisting the RCP in detecting airway displacements and obstructions is the use of capnography. At our institution capnography is routinely used for confirmation of tracheostomy placement following tube placement or tube changes. This case study presents the effectiveness of capnography for detecting a partial airway obstruction with the correct placement of the tracheostomy tube.
During the hospital stay, the patient progressed well in terms of respiratory weaning and able to tolerate aerosol trach collar (ATC) trials during the daytime and partial ventilator support over the night without any other acute issues.
On hospital day eight the patient developed respiratory distress during an ATC trial, in which the respiratory therapy team evaluated.
The RCP placed the patient back on the ventilator with the previous rest settings; Continuous Spontaneous Ventilation-Pressure Support, PEEP + 8.
After returning the patient to ventilator support, the machine started to pressure-overshoot and prematurely cycle the assisted breath. Exhaled tidal volume measurement's where extremely low. The tracheostomy tube was immediately assessed for patency by checking for obstruction with a suction catheter. The catheter passed freely. The ETCO2 monitor was placed inline between the tracheostomy tube and ventilator circuit for additional confirmation of airway patency. The ETCO2 waveform remained flat when placed inline indicating obstruction.
The patient was removed from the ventilator to further assess for correct tracheostomy position. During the disconnection from the ventilator the ETCO2 waveform was present (normal square waveform). After evaluating this finding it was assumed that the airway was patent and the patient was again placed on mechanical ventilation. Once again the ventilator prematurely cycled and the ETCO2 waveform was flat.
At this time the pulmonary team was called for a emergency bronchoscopy to evaluate the upper tracheostomy site and upper trachea. Bronchoscopy revealed granulomatous tissue distal of the tracheostomy tube.
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| Image 1: Granulomatous tissue distal of the tracheostomy tube |
At this point the patient was emergency transported to another facility for ENT intervention. At the time of transfer the patients medical condition was critical, but stable. The granulomatous tissue was treated surgically and removed.
Discussion: When evaluating airway patency in this patient by passing a suction catherter the device easily passed by displacing the granulomatous tissue, giving a false picture of patency. By including capnography into the assessment it reinforced that there was a issue with this patients airway & the necessity for emergency physician interaction. When the patient was on the ventilator the positive airway pressure and PEEP created airway obstruction by the “ball valve effect” indicated by the extremely low returned tidal volumes and the absence of a ETCO2 waveform. Once the patient was removed from the positive pressure, the ball valve effect was removed as indicated by the presence of the capnography waveform.
Discussion: When evaluating airway patency in this patient by passing a suction catherter the device easily passed by displacing the granulomatous tissue, giving a false picture of patency. By including capnography into the assessment it reinforced that there was a issue with this patients airway & the necessity for emergency physician interaction. When the patient was on the ventilator the positive airway pressure and PEEP created airway obstruction by the “ball valve effect” indicated by the extremely low returned tidal volumes and the absence of a ETCO2 waveform. Once the patient was removed from the positive pressure, the ball valve effect was removed as indicated by the presence of the capnography waveform.
