Airway Obstruction Caused by Sputa in Heat and Moisture Exchange Filter During Ventilation Using Supra-Laryngeal Mask Airway: A Case Report

Introduction: Supra-laryngeal mask airway (LMA) is widely accepted as an alternative to the tracheal tube. However, compared to the use of a tracheal tube, it may take longer to identify the many different causes of sudden respiratory distress. In particular, heat and moisture exchange filters are one of the most overlooked causes. Case presentation: The case was that of a 76-year-old male Japanese patient (161.9 cm, 66.5 kg) who underwent an open renal biopsy. He presented with chronic obstructive pulmonary disease, with a Hugh–Jones dyspnea score of 2. The patient did not discontinue smoking prior to the operation. Anesthesia was induced using propofol (100 mg), fentanyl (100 ?g), and remifentanil (0.3 ?g/kg/min). I-gel™ #4 was inserted following neuromuscular blockade with rocuronium (40 mg). Anesthesia was maintained with 3–6% desflurane under positive pressure ventilation. After induction in the left lateral and jackknife positions, the following ventilator settings were used: volume-controlled ventilation with tidal volumes of 450 mL, respiratory rate of 12 breaths per minute, an inspiratory: expiratory ratio of 1:2, and a positive end expiratory pressure of 5 cmH2O. With these settings, the peak inspiratory pressure was 16 cmH2O. Five minutes after initiating the operation, the peak inspiratory pressure steadily increased to 30 cmH2O. Although we administered rocuronium, the peak inspiratory pressure and end-tidal carbon dioxide concentration increased over time. When we disconnected the heat and moisture exchange filter and LMA, we noticed a large quantity of sputa. A suction catheter was passed down the LMA and the sputa was removed, but the LMA was not obstructed. The peak inspiratory pressure continued to increase with tidal volumes of only 20–30 mL. Despite a normal external appearance of the heat and moisture exchange filter, we replaced it with a new one. The ability to ventilate improved immediately and the SpO2 recovered from 92% to 100%. Conclusions

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Abstract 59: The Incidence Of Pulmonary Aspiration With Laryngeal Mask Airway Use During Cardiopulmonary Resuscitation And Positive Pressure Ventilation In Swine.

Circulation ◽

10.1161/circ.116.suppl_16.ii_935-c ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Brian Suffoletto ◽

James Menegazzi ◽

Eric Logue ◽

David Salcido

Keyword(s):

Laryngeal Mask Airway ◽

Cardiopulmonary Resuscitation ◽

Positive Pressure Ventilation ◽

Validation Cohort ◽

Pulmonary Aspiration ◽

Laryngeal Mask ◽

Positive Pressure ◽

Suction Catheter ◽

Chest Compressions ◽

Lung Expansion

Objective: Pulmonary aspiration of gastric contents occurs 20 –30% of the time during cardiopulmonary resuscitation (CPR) of cardiac arrest. This is due to loss of protective airway reflexes, pressure changes generated during CPR, and positive pressure ventilation (PPV). Even though the American Heart Association (AHA) has recommended the laryngeal mask airway (LMA) as an acceptable alternative airway for use by EMS personnel, concerns over the capacity of the device to protect from pulmonary aspiration remain. We sought to determine the incidence of aspiration after LMA placement, CPR and PPV. Methods: We conducted a prospective study on 16 consecutive post-experimental mixed-breed domestic swine of either sex (mean mass 25.7 ±1.4 kgs). A standard size-4 LMA was modified so that a vacuum catheter could be advanced into and past the LMA diaphragm. The LMA was placed into the hypopharynx and its position confirmed using End-tidal CO 2 and direct visualization of lung expansion. Fifteen milliliters of heparinized blood were instilled into the pharynx. After 5 PPVs with a mechanical ventilator, chest compressions were performed for 60s with asynchronous ventilations continuing at a rate of 12 per minute. After chest compressions, a suction catheter was inserted through the cuff and suction applied for approximately 1 minute. The catheter was removed and inspected for signs of blood. The LMA cuff was deflated and the LMA removed. The intima of the LMA diaphragm was inspected for signs of blood. In a validation cohort of 4 animals, the LMA was reinserted, a cricothyrotomy performed and 5 mL of blood instilled directly into the trachea. Results: There were 0/16 (95% CI=0 –17%) with a positive tests for the presence of blood in both the vacuum catheter and the intima of the LMA diaphragm. In the validation cohort, all four were positive for blood in both the vacuum catheter and the intima of the LMA diaphragm. Conclusions: In this simple model of regurgitation of after LMA placement, there was no sign of pulmonary aspiration, and no evidence that blood had passed beyond the seal created by the LMA cuff. Concerns over aspiration with LMA use may be unfounded. Future studies should determine the frequency of pulmonary aspiration after LMA placement in the clinical setting.

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