Invention and Pilot Study of the Efficacy and Safety of the SUPRAtube Device in Continuous Supraglottic Aspiration for Intubated and Mechanically Ventilated Patients

Abstract

Background: Bronchoaspiration of content that accumulates in the supraglottic area (eg, saliva, gastroesophageal reflux) is a risk factor for ventilator-associated pneumonia. A continuous supraglottic suction system may decrease the risk of bronchoaspiration in these patients.

Objective: (1) Constructing a conceptual model and functional prototype of a continuous supraglottic suction device for use in humans; (2) defining functional characteristics in ex vivo swine head models; and (3) evaluating its efficacy and safety in mechanically ventilated patients.

Methods: Study conducted in three phases. First phase: definition of distances and diameters of the triangle determined by dental arch, posterior oropharynx and vallecula, and diameter of the oropharynx in axial projection; and identification of the declining area of supraglottic suction. Second phase: design engineering and functional prototype evaluated in ex vivo models. Third phase: evaluation of device use in terms of safety and efficacy in ventilated patients.

Results: We obtained a final functional model of the SUPRAtube device injected into PVC for medical use. Device effectiveness in in vitro simulation showed a high and fast suction capacity of liquid and thick volumes. Study of swine heads allowed to validate the shape, size and functional fenestration of the device. Study in intubated and mechanically ventilated patients showed a high supraglottic suction capacity and the absence of local adverse events during 72 (7-240) hours of continuous operation.

Conclusion: Our study describes the process of conceptualization, design and production of a practical, safe, low-cost continuous supraglottic suction device without representing antibiotic pressure, which appears to be a new complementary preventive strategy for the standard management of intubated and mechanically ventilated patients.

Keywords: SUPRAtube; bronchoaspiration; endotracheal tube; gastroesophageal reflux; mechanical ventilation; supraglottic suction.

Figure 1

(A) Example of the usual technique of suction of oropharyngeal content in intubated patients. Representative figure of the most common respiratory therapy technique to aspirate the content of secretions, gastroesophageal reflux and saliva accumulated in the nasopharyngeal territory of intubated and mechanically ventilated patients. The suction is not continuous but intermittent and totally dependent on the health professional. The suction tube in general is semi-rigid. Aspiration is carried out through the connection to a wall vacuum or portable source. The professional therapist must occlude the proximal leak to achieve suction when inserting the probe into the mouth and releasing it to avoid traumatic adhesion to the oropharyngeal tissue. (B) Representative image of the radiological studies of the oropharyngeal area. Representative figure of the CT images with which the fundamental anthropometric studies were started to determine the internal length of the device (defined as the distance from a reference line at the level of the dental arch (A) to a line at the level of the vallecula (B), and the size of the functional end (thimble) of the SUPRAtube device). Multiple anatomical reference relationships were used to define the fundamental morphological characteristics of the device and the location in the nadir zones. The mean values of the reference distances and their dispersion (SD) are described in the body of the document.

Figure 2

(A) Conceptual model of the SUPRAtube device. (A) shows the conceptual model of the oropharyngeal suction device in terms of the morphological requirements of being tubular, with multiple foramina arranged in several quadrants and having a length proportional to the nadir zone of the oropharynx. The tip of the conceptual model is represented by the white square. This conceptual model was evaluated in life-size human manikins (b) with orotracheal intubation, in order to perform the simulated analysis of the positioning in the nadir area (red rectangle) in mechanically ventilated patients. (B) Representative image of the radiological studies of the oropharyngeal area. Representative figure of the CT images with which the fundamental anthropometric studies were started to determine the internal length of the device (defined as the distance from a reference line at the level of the dental arch (A) to a line at the level of the vallecula (B), and the size of the functional end (thimble) of the SUPRAtube device). Multiple anatomical reference relationships were used to define the fundamental morphological characteristics of the device and the location in the nadir zones. The mean values of the reference distances and their dispersion (SD) are described in the body of the document.

Figure 3

Evaluation of the functional model of the supratube device in animal model ex vivo of porcine HEADS. (A) exemplifies experiments designed to simulate acute high volume fluid accumulation in the oropharyngeal area of porcine heads. It was assumed that this type of experimentation would allow evaluating the mechanical behavior of the device in the face of the imposed vacuum and in intimate contact with rhino-oropharyngeal structures. (A) shows the moment of instillation of liquid marked with methylene blue at the level of the oropharynx, while (B) shows the type of experiments performed on rhinopharynx. For more technical details, please refer to the text.

Figure 4

Assembly of wall vacuum, collector vessel, bottle-trap and SUPRAtube. For the different studies, a general assembly was used that included the wall vacuum (VacuTron^®, not shown), (A) the SUPRAtube device with generic tubing, (B) collecting vessel and (C) a volumetric calibrated trap flask, all of them translucent in order to visualize the liquid content that could eventually be obtained through aspiration once the SUPRAtube started its operation. All the elements were disposable, sterile and complying with all safety standards for patients.

Figure 5

Assembly of wall vacuum, collector vessel, bottle-trap and SUPRAtube. Representative figure of the SUPRAtube continuous suction system in the assembly form and in full operation in two patients, in which the volume of oropharyngeal content that was obtained acutely (flask-trap) at the time of its insertion is clearly evidenced and start of suction, even with the patient in a semi-recumbent position.

Figure 6

(A) Representative figure of the industrial design drawings of the SUPRAtube. The intention of taking the SUPRAtube device to the molding, injection, clinical validation and future commercialization process has required all the necessary plans being designed in accordance with current regulations. These design drawings are also necessary to file the patent application. For more details on the respective plans, please contact the principal investigator. (B) Specialized 3D graphic design of the end of the SUPRAtube and the fastening system to the orotracheal tube. The SUPRAtube, at its distal end which is inserted into the oropharynx, has the appearance shown in (a). The number of foramina in opposite quadrants and at the end of the device is clearly observed, a design that was validated as the most appropriate to allow high suction capacity but minimal risk of secondary adhesion and trauma. (b) Shows the fastening system designed to fix the SUPRAtube to the orotracheal tube, with ease of releasing and repositioning it by means of an opening and closing tab.

Figure 7

Videoendoscopic view of supraglottic anatomic area using fiber endoscopy in a patient with orotracheal tube and supratube. Representative figure of the type of endoscopic vision that allowed evaluating the positioning of the SUPRAtube end (A) in patients with orotracheal tube (B) and mechanical ventilation. In the case, it can be seen how the medial SUPRAtube foramina remain permeable and functional for aspiration in the event that respiratory secretions, gastric content or saliva accumulate.

Figure 8

Evaluation of the volume–time relationships of suctioning using the supratube device in laboratory conditions. One of the most attractive points of the SUPRAtube design is its high suction capacity, denoted in this figure as the two-dimensional ratio of the aspirated volume (abscissa, in mL) per unit of time (ordinate, in sec.). This type of approach allowed us to emulate the most dramatic conditions of fluid accumulation in the mouth, as can occur in cases of emesis, epistaxis or upper gastrointestinal bleeding. These evidences allowed us to consider the current SUPRAtube design valid and efficient. For more details, please refer to the text.