Nasopharyngeal Symptoms caused by Abnormal Inflation of the Endotracheal Tube in Patients undergoing Cervical Spine Surgery

E-mail: dralmoja@hotmail.com alvaro.montielj@imss.gob.mx ABSTRACT Background: Abnormal balloon inflation of the endotracheal tube can cause nasopharyngeal symptoms. The objective is to describe Signs and Symptoms caused by the Abnormal Insufflated Balloon of the Endotracheal Cannula on patients undergoing Cervical Spine Surgery under General Anesthesia. Methods: descriptive study, 39 patients underwent cervical spine surgery under general anesthesia, all of them were older than 18 years old and ASA I and II. The pressure balloon inflation of the endotracheal tube was measured by a manual manometer VBM Medizintechnik GmbH, measurements were made at the beginning of the procedure, and every hour during the transanesthetic period. The patients underwent a questionnaire about their symptoms on the recovery area and 24 hours after extubation. Results: 39 patients, 59% men, 41% women. Average age was 47, minimum 15 – maximum 77, SD 14.26 years old. The average pressure balloon inflation at the moment of intubation was 30.7 mmHg and at the moment of extubation was 29.07 mmHg. The symptoms presented on the Recovery Care Unit and at 24 hours were: pain, inflammation, dysphagia, foreign body sensation. Conclusion: The pressure balloon inflation of the endotracheal cannula is important, because a pressure greater than 30mmHg produce symptoms. Changes on the patient’s position produced variations on the balloon pressure; therefore, continuous monitorization of the pressure baloon must be done.


INTRODUCTION
The endotracheal intubation is a frequently employed technique in the operating room, it is used as a vital support measure to keep the airway safe and thereby ensure adequate tissue oxygenation (1).
The Endotracheal Cannula (EC) with high volume balloons are used to facilitate the connection between the patient and the mechanical fan, with its insufflation prevent leakages around the EC, therefore, ensuring adequate pressurization during positive pressure ventilation; however, hyperinflation of the endotracheal cannula balloon causes mucosal damage by restricting the capillary blood flow.The inappropriate filled of the balloon is associated with a high morbidity rate, either by overpressure or by lower pressure (2).
The tracheal capillary perfusion pressure has been estimated at 25 mmHg and has an inverse relationship to the pressure of the tracheal cannula balloon.Tracheal arterioles are located in the submucosa and oriented circumferentially forth between cartilages and longitudinally in the rear membranous portion (3).
The mucosa turns pale at 30mmHg and white at 37mmHg and the blood flow stops at 45mmHg.These findings suggest that blood flow is initially altered with balloon pressure levels of 22 mmHg and that complete occlusion of tracheal capillaries occurs at 37 mmHg (4).
The ischemic endpoint of the mucosa produced by high endotracheal cannula balloon consists on necrosis and infection, followed by scar formation and stenosis (5,6).Most are resolved spontaneously, however, some progress to laryngeal granulomas and stenosis secondary to healing (5,7).The complications as stenosis and tracheomalacia occur mainly under the first tracheal ring (6).The initial changes are functional, such as the diminished velocity or total interruption of the tracheal mucus (7).
The early changes includes flattening, fusion and erosion of respiratory epithelial cells, the ciliary function deteriorates or disappears as the irritation produced by the balloon of the tracheal cannula also produces constriction of the smooth muscle of the trachea (8).
The most frequent symptom after extubation is dysphonia and it has been reported in up to 80% of the patients, when persist, paralysis or vocal paresis occur secondary to recurrent

Nasopharyngeal Symptoms caused by Abnormal Inflation of the Endotracheal Tube in Patients undergoing Cervical Spine Surgery
laryngeal nerve compression by the endotracheal cannula balloon over the thyroid cartilage or the placement just below or adjacent to the vocal cord.Dysphagia and sore throat occur in half of patients after extubation.The more time the patient is under intubation the more the laryngeal damage occurs (11).
The cough and sore throat are common symptoms and their incidence is as high as 30% and 55% respectively.The probable causes may include mechanical compression by the endotracheal cannula balloon or physic-chemical stimulation of the tubes additives (12).
However, correlation between the mucosal damage degree and the severity of symptoms is unknown because symptoms are always subjective (11).It has been suggested that sore throat incidence and blood-streaked expectoration, increased after longer intubation as well as sore throat incidence, even more with intubation longer than 180 minutes.It possible means that pressure and time are two important variables on morbidity after endotracheal intubation (11)(12).
The first used endotracheal cannula balloons were of low volume and high pressure.Nowadays, the standard is a great diameter, high volume and low pressure balloon, which transmits less pressure with more uniform distribution over the tracheal wall, therefore, less possibility of causing injuries.
At present, high volume and low pressure endotracheal balloons are made as an attempt to decrease complications secondary to them, trying to maintain lower transmitted pressure.However, complications attributed to endotracheal cannula balloons are still frequent (13).
In 1977 Nordin on a study conducted on rabbits, observed that when endotracheal cannula balloon inflated pressure exceeded 25 mmHg, mucosal ischemia presented and that lesions are directly related to the cuff pressure, finding damage almost in all of those pressures higher than100 mmHg.He suggests that is more relevant the pressure level on the mucosa than the intubation time on the etiology of tracheal morbidity (14).Seegovin and Hasselt in 1984, on a human study rated the capillary blood flow in the tracheal mucosa through endoscopic technique, they observed the capillary blood flow compromised at pressures higher than 30 H2O cm and a complete obstruction at pressures higher than 50 H2O cm (15).
Carrol and Grenvik measured the pressure within the cuff through an aneroid manometer, at this moment an electronic, digital, instrument called P-V Gauge exists, which easily adapts to the endotracheal cannula cuff and has great accuracy on its measures, with a variation of ± 1 H2O cm (11).
As morbidity has been documented for overpressure, problems due to deflation have been attributed as well.Tobin and Grenvik in 1984 mentioned the oropharynx of the patients as the principal source of microorganisms responsible for nosocomial pneumonia, entry facilitated by the presence of tracheostomies and endotracheal cannulas (16).The palpation method may contribute to overpressure, therefore, is inadequate.Listening to leakages is not either recommended.
The aim of this study is to identify clinical signs and symptoms caused by the abnormal inflation of the endotracheal cannula balloon on patients undergoing cervical spine surgery under general anesthesia, in the recovery care unit (RCU) and 24 hours later, as well as to identify abnormal inflation of the endotracheal cannula balloon as risk for each sign and symptom.

MATERIAL AND METHODS
Study type: cohort study, descriptive, performed in the High Specialty Medical Unit of the Orthopedics and Traumatology Hospital of the Mexican Institute of Social Security (IMSS), from January to December of 2014.Subjects: Scheduled patients for Cervical Spine Surgery who underwent General Anesthesia affiliated to IMSS were included, older than 18 years old, both genders, ASA (American Society of Anesthesiologists) I and II, endotracheal intubation with armed cannula, without steroids administration before or after the surgery and those who accepted to be included in the study through a filling of a consent informed letter.
Patients were excluded if they presented with tracheolaryngeal anatomic abnormalities, with more than three failed endotracheal intubation attempts or the anesthesiologist did not accept to participate in the study.
Methodology: patients were intubated with armed cannula, its diameter was selected based on the intern diameter, 8 mm cannula was used for adult men and 7 mm cannula for adult women.The anesthesiologist checked leakage absence around the endotracheal cannula and measure the inflated balloon pressure by a manual (VBM Medizintechnik Gmb) manometer.Initially the balloon was adjusted at a pressure of 29 mmHg or lower.Later measures of the inflated balloon were made, every hour during the transanesthetic period, in every repositioning of the patient and before the endotracheal cannula withdrawal.The symptoms were evaluated by direct interrogatory at the RCU as well as 24 hours after the procedure and the swelling caused by direct or indirect laryngoscopy.We established as normal a pressure of <29 mmHg for the endotracheal cannula balloon inflation and erythema or edema or both as swelling.
The variables were, age, gender, size and diameter of the cannula, inflation pressure of the cannula, patient position; the sample size was established by the investigator given by the total of patients during the time of the study.
Statistics: Descriptive statistics was performed with central trend measures and dispersion.Fischer test for relative risk (RR) for abnormal inflation of the endotracheal cannula balloon and the development of clinical signs and symptoms presented by the patients y X2 to demonstrate the hypothesis (difference of proportions) we considered statistics significance a value of p< 0.05.

RESULTS
A total of 39 patients were included, 23 (59%) were men and 16 (41%) women, the average age was 47, minimum 15 -maximum 77, SD 14.36 years old; the average weight was 72.53 kilograms, minimum 46 -maximum 96, ± 10.88 kilograms, average size was 162.48 centimeters, minimum 140 -maximum 178, ± 9.96 centimeters.The average Body Mass Index (BMI) was 27.43, minimum 20.96 -maximum 35.20,SD 3.07 of which 8 (20.51%) patients had a BMI bigger than 30 and 31 (79.4%) less than or equal to 29.The average of the endotracheal cannula number used was 8, minimum 7 -maximum 9.5), SD 0.54 mm.In all patients an armed cannula was used, the balloon pressure during the surgical procedure is described below.(Table I)

DISCUSSION
Inadequate endotracheal cannula balloon inflation may compromise and alter laryngeal structures, secondary to the direct contact of the cannula with the airway structures, resulting in mucosal injuries which might be mild but annoyed to the patient.
Nowadays there are plenty of endotracheal cannulas varieties.
The high volume and low pressure cannulas are used to prevent gas leakage, pulmonary aspiration and tracheal injuries, as well as to decrease symptomatology on the patient undergoing general anesthesia.
However, at the moment of inflate a balloon above normal range, a greater pressure over the tracheal walls is directly caused.At a pressure of 40 H2O cm the tracheal mucosa and submucosa perfusion is deficient; there is loss of ciliary mucosa, ulceration and bleeding.Serious complications may be reached such as tracheal stenosis or tracheoesophagical fistula (15)(16).
The endotracheal cannula balloon pressure is not measured on a routine manner on the anesthetic procedures, which contributes to the appearance of symptoms that appear commonly on the immediate postoperative such as, dysphagia, sore throat, foreign body sensation, problems to speak, increased secretions, pain to swallow and hoarseness which commonly decreases in a maximum of 48 hours (24).However, because the pressure measurement is very simple to perform, this must be measure continuously to prevent injuries.
Our study origins from the necessity to acknowledge the signs and symptoms caused by the different inflation pressures on the endotracheal cannula balloon on the supine and prone position in which the patients are placed during cervical spine surgery.
With respect to gender, our population distribution was slightly higher in men (59%) compare to women (41%).It occurred more frequently on male patients on the RCU and at 24 hours later, this possibly related to the threshold and the anatomical oropharynx position which is more anterior and bigger in diameter than in women and the necessity to inflate with more volume the endotracheal cannula balloon.
However, the pain perception is influenced by complex interactions between biological variables (gonadal hormones, genetics, pain circuit and central nervous system variations) and psychological variables (depression, anxiety, culture, gender expectative role, social learning factors and importance given to pain).Big differences exist on these variables among individuals and from the viewpoint of gonadal hormones and pain, the variability is deep (16).

Table 1 :
Balloon pressure during surgery.

Table 4 :
Chi-Square values for inflation pressure of the balloon and the development of symptoms on the RCU and 24 hours later.

Table 2 :
Signs and symptoms in Recovery Care Unit and 24 hrs later.

Table 3 :
Relative Risk to developing signs and symptoms secondary to abnormal inflation of the endotracheal cannula balloon.