There are different techniques that anesthesia professionals use during general anesthesia to evaluate endotracheal tube cuff pressure without using a manometer (a manometer is used only with the direct intracuff pressure technique).Such techniques are, for instance, the minimal occlusive volume technique, palpation technique, and minimal leak technique (Stewart, 2003). However, it is questionable whether those techniques provide adequate intracuff pressure measurement or not. There is no standard of practice for intracuff pressure measurement during general anesthesia, even though pressure should be maintained in the recommended interval of 20 to 30 centimeters of water (Trivedi, 2010). The manometer can be a device used during general anesthesia for establishing the endotracheal tube intracuff pressure.
Case report
A forty-three-year old male, who came to an emergency department after five days of abdominal pain in the right upper quadrant, persistent nausea and vomiting, was scheduled for laparoscopic cholecystectomy surgery under general anesthesia. The patient appeared to be a healthy individual, without any other symptoms than those previously mentioned. He was 180 centimeters (cm) tall, weighed 90 kilograms and had no previous medical or surgical history. The patient was informed about the procedure of general anesthesia using an endotracheal tube (ETT). Following the induction of anesthesia, orotracheal intubation was performed. After a size 7.5 polyvinyl chloride high volume low pressure cuff endotracheal tube was placed, the ETT cuff was inflated with air using the palpation technique. The pilot balloon was palpated as a gross indication of intracuff pressure. 9 millimeters (ml) of volume were injected via the pilot balloon. After confirming and establishing the airway by capnography and bilateral breath sounds, volume control (VC) ventilator settings were programmed.
Shortly after applying a tidal volume (VT) of 750 ml, positive end-expiratory pressure (PEEP) of 5 cm water (H2O) and oxygen flow rate of 2 liters (L), the high peak airway pressure of 38 cm H2O was observed. Consequently, the VT was decreased to 600 ml. However, the peak airway pressure remained elevated, at 36 cm H2O. The ventilator setting was then changed from VC to pressure control mode. The peak inspiratory pressure was set at 34 cm H2O, which was able to deliver the tidal volume of 680 ml; however, the high peak airway pressure of 36 cm H2O was still observed. The use of the direct intracuff pressure technique, which required using a manometer to assess intracuff pressure, was not possible in the operating room as no manometer was available. The minimal occlusive volume technique was used instead, as a secondary measurement, to inflate the ETT cuff. A volume of air was injected into the cuff, which eliminated an audible end-inspiratory leak with positive pressure ventilation. Using this technique, the volume of the ETT cuff was decreased from 9 ml to 4 ml. After adjusting the ETT cuff volume, the VC ventilator settings were applied once again, with VT of 750 ml, PEEP 5 cm H2O and oxygen flow rate of 2 L. At this time, the decreased peak airway pressure of 26 cm H2O was observed. The surgery proceeded after the correction of the ETT cuff volume, which subsequently decreased the peak airway pressure.
Discussion
Anesthesia professionals routinely manage cuffed endotracheal tubes. It has long been believed, without any verification based on data, that anesthesia professionals have the skills to determine optimal intracuff pressure clinically, by using such techniques as the minimal occlusive volume technique, palpation technique (finger estimation), and minimal leak technique (Trivedi 2010). However, according to a study published in the Indian Journal of Anesthesia in 2010, research showed that there were anesthesiologists with more than five years of experience, who were blinded by the nature of the study and still failed to inflate the polyvinyl chloride endotracheal cuff at the recommended pressure when using the palpation technique and minimal leak technique. The result showed that the average probability of 80% cases was falling outside of the recommended range of intracuff pressure (Trivedi, 2010).
While there are some techniques that anesthesia practitioners can use to inflate endotracheal tube cuffs, the principle of the endotracheal tube cuff is intended to provide a seal at enough pressure to prevent aspiration but not to obstruct blood flow in the trachea (Spiegel, 2010).
Endotracheal tube cuff overinflation is related to complications including cough, sore throat, hoarseness, and blood streaked expectorant postextubation period (Liu, 2010). Other complications can also occur, including necrosis, bleeding stenosis, tracheal rupture, and tracheoesophageal fistulae (Spiegel, 2010). Tracheal mucosal blood flow reduces markedly when the pressure reaches 30 cm H2O (Porritt, 2009). When the pressure in the ETT cuff reaches 50 cm H2O or above, mucosal damage and blood flow cease in 15 minutes (Porritt, 2009).
Despite the recommendation of maintaining endotracheal tube intracuff pressure between 20 cm and 30 cm H2O, there is no standard of practice established for how to measure and assess the intracuff pressure during general anesthesia (Trivedi, 2010).
Stewart, a nurse anesthetist, performed another study in 2003, using mostly the palpation technique to inflate the endotracheal tube cuff. The study concluded that there was no difference between different levels of anesthesia professionals in their ability to estimate endotracheal tube cuff pressures. The study showed that, in 70% of the cases, the intracuff pressure was either too high or too low (Stewart, 2003).
Endotracheal tube cuff underinflation can increase the risk of aspiration during general anesthesia (Liu, 2010).
Using a manometer, direct measurement of ETT cuff pressures can be performed to prevent overinflation and underinflation of the cuff, which can subsequently avoid complications (Porritt, 2009).
Although high volume and low pressure endotracheal tube cuffs are associated with fewer complications than high pressure and low volume endotracheal cuffs, these devices may cause serious tracheal injury if the optimal intra cuff pressure is exceeded (Abdallah 2011).
Direct intracuff pressure measurement techniques, which require using a manometer, directly assess the intracuff pressure via the pilot balloon, but are not widely available in the current anesthesia practice. “Because a specialized tool, a manometer, is required, this technique requires a cost outlay and is less convenient and is, therefore, not performed commonly by anesthetists. It is, however, recommended as an effective technique to prevent overinflation and underinflation of endotracheal tube cuffs” (Stewart, 2003). Proper control of ETT pressure using a manometer helped reduce ETT related postprocedural respiratory complications such as cough, sore throat, hoarseness, and blood-streaked expectoration, even in procedures of short duration (1-3hrs) (Liu 2010). Even though manometers are costly, they can provide more adequate intracuff pressure measurement than other techniques that were used over the years by anesthesia professionals.
References
Abdullah M, C. Endotracheal tubes cuffs. University of Kwazulu-Natal Department of Anesthetics 2011; 1-24
Liu J, Zhang X, Gong W, et al. Correlations between controlled endotracheal tube cuff pressure and postprocedural complications: a multicenter study. International Anesthesia Research Society. 2010; Web.
Porritt K. Evidence Summary Endotracheal tube: care. The Joanna Briggs Institute. 2009;
Stewart S, Secrest JA, Norwood BR, et al. A comparison of endotracheal tube cuff pressures using estimation techniques direct intracuff measurement. AANA. 2003; 71(6):443. Spiegel JE. Endotracheal tube cuffs: design and function. Anesthesiology News. 2010; 51-58
Trivedi L, Jha P, Bajiya R, et al. We should care more about intracuff pressure: the actual situation in government sector teaching hospital. Indian Journal of Anesthesia. 2010; 54(4): 314-317.