Methods and apparatus for reducing tracheal infection using subglottic ...

[54] METHODS AND APPARATUS FOR

REDUCING TRACHEAL INFECTION USING
SUBGLOTTIC IRRIGATION, DRAINAGE
AND SERVOREGULATION OF
ENDOTRACHEAL TUBE CUFF PRESSURE

[75] Inventor: Jeffrey I. Joseph, Penn Valley, Pa.

[73] Assignee: Thomas Jefferson University,

Philadelphia, Pa.

[21] Appl. No.: 204,481 [22] Filed: Mar. 2, 1994

[51] Int. CI.6 A61M 15/00

[52] U.S. CI 128/207.15; 128/202.22

[58] Field of Search 128/202.22,207.15,

128/207.14, 205.23

[56] References Cited

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OTHER PUBLICATIONS

Morris, et al., "An Electropneumatic Instrument For Measuring And Controlling The Pressures In The Cuffs Of Tracheal Tubes: 'The Cardiff Cuff Controller'," J. Med. Eng. &Tech., vol. 9, No. 5 (Sep./Oct. 1985), pp. 229-230. Cobley, et al., "Endobronchial Cuff Pressures," British J. Anesthesia, 70:576-78 (1993).

Willis, et al., "Tracheal Tube Cuff Pressure: Clinical Use Of The Cardiff Cuff Controller," Anaesthesia, 43:312-14 (1988).

(List continued on next page.)

Primary Examiner—Aaron J. Lewis

Attorney, Agent, or Firm—Woodcock Washburn Kurtz

Mackiewicz & Norris

[57] ABSTRACT

An integrated system providing a mechanical and chemical barrier against the spread of infected secretions into the distal trachea is disclosed. An endotracheal tube used for patient airway management and provides a means to conveniently irrigate and drain the subglottic region below the vocal cords and above an inflated cuff. The subglottic region accumulates liquid secretions that may channel past an inflated endotracheal tube cuff, providing the necessary bacterial inoculum leading to bronchitis and nosocomial pneumonia. An irrigation channel delivers liquids such as saline or antibiotic and antifungal medications for mucosal hydration, and bactericidal action against infected subglottic secretions. An outer sleeve surrounding the endotracheal tube forms a suction lumen for removing the secretions. The tapered and compliant nature of this sleeve at body temperature allows a large suction channel without the need to greatly enlarge the outside diameter of the endotracheal tube at the vocal cord level. Electronic and mechanical controls provide regulated volume infusion and regulated suction. In addition, cuff pressure is servoregulated to the lowest pressure that provides a tracheal seal and rapid adjustment of cuff pressure so that peak airway pressures are attenuated, thus preserving mucosal perfusion. Pneumonia and patient mortality are thus prevented.

3 Claims, 1 Drawing Sheet

OTHER PUBLICATIONS

Spray, et al., "Aspiration Pneumonia: Incidence of Aspiration with Endotracheal Tubes," Am. J. Surg., 131:701-03 (Jun. 1976).

Mahul, et al., "Prevention of nosocomial pneumonia in intubated patients: respective role of mechanical subglottic secretions drainage and stress ulcer prophylaxis," Intensive Care Med., 18:20-25 (1992).

Tracheal intubation is used in respiratory medicine to deliver or remove a fluid to the airways of a patient. Tracheal intubation with an endotracheal tube is commonly used 15 during general anesthesia and when critically ill patients require airway protection and mechanical ventilation. Tracheal tubes include those used in tracheostomies as well as endotracheal tubes. Under certain conditions of long term ventilation, a tracheostomy tube is inserted through a sur- 2Q gical opening through the neck. An endotracheal tube is inserted into the trachea through either the mouth or nose (nasotracheal tube). Tracheal tubes are used for ventilation, and removal of secretions. Typically, endotracheal tubes are disposable plastic tubes, easily placed through the mouth or 2J nose, that guarantee a patent conduit for the delivery of respiratory gases. A seal between the outer wall of the tracheal tube and the inner lining of the trachea (the tracheal mucosa) must be formed. Most endotracheal tubes (except those for small children) provide a very compliant, thin 3Q walled inflatable cuff that forms a seal with the proximal tracheal rings. This seal allows for positive pressure ventilation at normal airway pressures with minimal leakage. The seal thus provides a closed circuit for ventilation and also prevents aspiration of pharyngeal contents into the respira- 35 tory tract. This seal is usually formed by inflating a pressurized cuff that surrounds the tracheal tube. The pressure in the cuff must be adequate to form a seal, but it is known that over-pressurization will cause tracheal trauma including hemorrhage, ulcers, perforation and strictures. The main 4Q cause of trauma is the loss of blood flow (ischemia) and resultant necrosis of the tracheal lining.

Cuff pressures are typically set between 10-50 mm Hg. This range of pressures is relatively wide and for any particular patient the formation of a seal without creating an 45 ischemia will require holding the pressure in a much narrower range. Moreover, because tracheal tubes are used in a dynamic environment, the pressure required to maintain an adequate seal will vary. Finally, cuff pressure will vary due to the diffusion of nitrous oxide into the cuff. Thus, estab- 50 lishing a correct cuff pressure and correctly regulating the cuff to this pressure are both important. For example, during mechanical ventilation, the intracuff pressure must be low enough to allow tracheal capillary perfusion, thus reducing the risk of ischemia, while being high enough to prevent 55 either loss of tidal volume or significant aspiration.

The use of high volume, low pressure endotracheal tube cuffs starting in 1973 reduced the incidence of complications from prolonged tracheal intubation. This more compliant cuff design provides a satisfactory tracheal seal for positive 60 pressure ventilation associated with significantly lower cufftracheal mucosa contact pressure. Unfortunately, when lung compliance significantly decreases—as often occurs in critically ill ICU patients—high airway pressures are transmitted through the distal cuff surface during inspiration. Cuff- 65 tracheal mucosal contact pressures approach peak airway pressures as high as 50 mm Hg during each inspiration. This

contact pressure far exceeds tracheal mucosal perfusion pressure of 15 mm Hg and significant ischemic damage can occur, and in fact mucosal ischemic damage commonly occurs in observed patient populations. Endoscopic and biopsy studies suggest a high incidence of mucosal ulceration, cartilage infiltration with bacteria, and ultimately, scar formation with the development of clinically significant airway narrowing. Local mucosal defense mechanisms are inhibited during tissue ischemia, allowing bacteria to multiple and invade deeper structures.

An additional cause of cuff pressures that exceed mucosal perfusion pressure is brought about during nitrous oxide general anesthesia. Nitrous oxide diffuses into a cuff eighty times faster than nitrogen diffuses outward, producing a significant increase in cuff volume such that cuff pressures often exceed 60 mm Hg, and the above-described ischemia and deterioration of the mucosa result.

Others have recognized and proposed solutions to the problems associated with excessive cuff pressures during prolonged intubation. For example, U.S. Pat. No. 5,235, 973—Levinson discloses a system for monitoring and controlling cuff pressure that requires both an inflation line and a monitoring line connected to the cuff. The monitoring line is used to determine when additional pressure should be applied to the cuff, and is governed by the pressure in the inspiration line of the ventilator. However, this system raises cuff pressure with each inspiration to avoid loss of tidal volume without regard for cuff-mucosal perfusion pressure and thus cannot provide satisfactory pressure regulation. Another pressure control system is disclosed in U.S. Pat. No. 4,924,862—Levinson. In this system, pressure relief valves connect the cuff and a source of pressurized gas. A high pressure relief valve regulates cuff over-pressure, while a low pressure relief valve is controlled by a flow detector monitoring the cuff inflation line. A continuous flow in the cuff inflation line is indicative of a cuff leak. Cuff pressure regulation via mechanical valves is disclosed by U.S. Pat. Nos. 4,770,170 and 4,825,862 both to Sato et al. However, as well known to those of skill in the art, mechanical valves have performed poorly in clinical use.

One pressure regulation device known as the Cardiff Cuff Controller has been reported in the literature. See Morris et al., J. Med. Eng. & Tech., Vol. 9, No. 5 (SeptVOct. 1985) at pp. 229-30; Cobley et al., "Endobronchial Cuff Pressures," British J. Anesthesia, 70:576-78 (1993). This device regulates cuff pressure using an air reservoir and pump that connect to the cuff via a controlled valve. A relief valve is also provided to alleviate over-pressure conditions. Use of this device is also reported in the literature. See Willis et al., "Tracheal tube cuff pressure: Clinical use of the Cardiff Cuff Controller," Anethaesthesia 43:312-14 (1988); and Cobley et al., referenced immediately above.

As explained above, the prevalence of tracheal tubes, and in particular endotracheal tubes, has led to detrimental effects being observed, particularly when patients are intubated for a long period of time. For example, pulmonary complications are caused by aspiration during prolonged orotracheal intubation. The current use of high volume, low pressure cuffs alleviates this problem to a certain extent. See Spray et al., "Aspiration Pneumonia: Incidence of Aspiration with Endotracheal Tubes," Am. J. Surg. 131:701-03 (June, 1976). However, aspiration can and does occur even using a properly designed high volume, low pressure cuff inflated to and maintained at an appropriate pressure. Regurgitated gastric fluids and pharyngeal secretions that enter the proximal trachea often accumulate above the inflated cuff and may channel to soil the more distal trachea and lungs.