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MedUni Vienna study questions school of thought for ruling out one-sided intubation

(Vienna, 25 Nov. 2010) Hundreds of thousands of endotracheal intubations are carried out worldwide every day. The right position of the endotracheal tube (ETT) is of decisive importance here and can be checked using various methods. A research group at MedUni Vienna has now discovered that the established school of thought for ruling out too deep intubation is not ideal and other methods should be preferred. These unexpected results were also recently published in the renowned British Medical Journal.

Even if intubations of the trachea are practically part of everyday medical practice, they are conducted by doctors from many different specialisations and with different levels of experience in airway management. Here checking the right position of the tube is one of the essential points in order to prevent complications and damage to the intubated patients.

With a too deep position of an ETT there is unilateral ventilation, usually of the right lung, for example. This can lead to a host of complications such as hyperinflation of the ventilated lung, underventilation of the unventilated lung (atelectasis formation) and, as a consequence, disturbance of the gas exchange with possible undersupply of oxygen for the body. In the worst case the hyperinflation of the ventilated lung can even cause a torn lung and the formation of a pneumothorax, a potentially life-threatening complication.

According to the established school of thought, the too deep position of the ETT in the mainstem bronchus of the right lung can be ruled out by listening to the lungs on both sides (auscultation). This view is now being questioned by the research work of the colleagues headed by Ass. Prof. Dr. Christian Sitzwohl.

In the cooperative study of the Department of Anaesthesia and General Intensive Care Medicine and the Department of Emergency Medicine at MedUni Vienna 160 patients were intubated for routine operations. Randomly 80 patients were intubated too deeply (one-sided on the right) while with 80 patients the ETT was inserted correctly in the trachea. Then an experienced anaesthetist and an anaesthetist in the first year of training had to determine the tube position independently of each other using one of four randomly selected tests. These tests were 1) the bilateral auscultation of the lungs, 2) observation and palpation of symmetrical chest movements, 3) reading the tube depth using the cm scale of the ETT or 4) a combination of all three methods. After the end of the test lasting for around five minutes the ETT was of course put in the correct place with all patients.

It became apparent that among the three individual tests the one with the highest “hit rate” was the tube depth (88%), followed by auscultation (65%) and observation (42.5%). The highest sensitivity for the correct diagnosis of the too deep tube position was achieved by the combination of all three tests (100%), but the difference to determination of the tube depth with a single method was not significant, however.

A probably more significant result was that the doctors with little experience in airway management missed too deep intubation by auscultation in 55% of cases. The probability of detecting a tube position on one side with auscultation increases significantly with experience, however. In contrast, the experience of the doctors was completely irrelevant for recognising an incorrect position using tube depth. So for those with little experience in airway management in particular tube depth seems to be a better procedure than auscultation for ruling out unilateral intubation. It was also demonstrated that the correct tube depth measured from the incisors is on average 21.5 cm for women and 23 cm for men.

In summary, the recommendation that auscultation is used as the method of choice to rule out unilateral intubation must be revised. Doctors with little experience in airway management in particular detect unilateral intubation with higher sensitivity simply by reading the tube depth. Tube positions deeper than 21.5 cm with women and 23 cm with men should be accepted only with the greatest care and after carrying out checks with all three tested methods.

The clarification of this important clinic question and its unexpected results has now also been published in the renowned British Medical Journal:

» Endobronchial intubation detected by insertion depth of endotracheal tube, bilateral auscultation, or observation of chest movements: randomised trial
Christian Sitzwohl, Angelika Langheinrich, Andreas Schober, Peter Krafft, Daniel I Sessler, Harald Herkner, Christopher Gonano, Christian Weinstabl, Stephan C Kettner
BMJ 2010; 341:c5943 doi: 10.1136/bmj.c5943

Short biography:
Ass. Prof. Dr. Christian Sitzwohl, born in 1966, received his doctorate in 1994 at the Medical University of Vienna and then by 2001 had completed his specialist training at the Department of Anaesthesia and General Intensive Care Medicine. Since 2010 he has been working as a senior physician at the Department of Anaesthesia and General Intensive Care Medicine at MedUni Vienna.
The other research focal points of Christian Sitzwohl include the themes “Value of cholinesterase in the course of intensive care as a predictor of the mortality/morbidity of an intensive care patient”, “renal protection in intensive care patients with rhabdomyolysis” and “physiological changes with hypothermia”.