Experience of improvised esophageal stethoscope over precordial stethoscope as effective monitoring tool in developing countries for intraoperative monitoring of children during general anaesthesia.

1. Experience of improvised esophageal stethoscope and precordial stethoscope as
effective monitoring tool in developing countries for intraoperative monitoring of
children during general anesthesia.
ABSTRCT
This prospective observational study was carried out to observe effectiveness of
improvised esophageal stethoscope over precordial stethoscope. During the study
esophageal stethoscope was used to monitor dynamic vital parameters of the children. It
has been observed that sometimes heart and breath sounds were not clearly audible by
precordial stethoscope due to loose contact and misplacement where as by improvised
stethoscope not only heart & breathe sounds but also added & transmitted sounds were
clearly audible. Precordial stethoscope needs frequent refixing and repositioning
interfering surgical team and sterility where esophageal stethoscope once it is fixed in
appropriate depth of insertion position does not change. By esophageal stethoscope even
muffle heart sounds can be audible which could minimize stress among anesthesiologists.
So, results of the study showed significant difference between precordial and improvised
esophageal stethoscope.
INTRODUCTION
Monitoring of the patient's ventilation and circulation remains of paramount importance
during anaesthesia. Simple mechanical devices such as the esophageal stethoscope
remain useful both when more sophisticated devices are available and in areas where
expensive electronic monitors are not available. Paediatric anaesthesia is a discipline
which has particularly utilized monitoring with a stethoscope, either esophageal or
external thoracic. Esophageal stethoscopy provides reliable and continuous
cardiopulmonary monitoring. The esophageal stethoscope may also provide specialized
information such as auditory signs of venous air embolism. The esophageal stethoscope
may also allow monitoring when a transthoracic stethoscope may not be practical due to
the surgical site.1,2,3

2. An esophageal stethoscope is a simple, versatile, inexpensive monitor that transfer a great
deal of information’s to the brain without expensive high technology.2
Esophageal
stethoscope is the best means of monitoring heart sounds, quality of heart tones, in some
cases dysrhythmias, murmurs, breath sounds, detect the onset of wheezing, identify
secretions that need to be removed by suction and also best means of early detection of
venous air embolism.4,5,6,7
An esophageal stethoscope still has a place and that the use of an endotracheal tube
placed in the oesophagus is a simple, inexpensive, readily available method which
requires minimal expertise to achieve.1,2,3
In developing countries simple, low cost and improvised device is safe, suitable and
useful due to unavailability and unaffordability of high cost devices.
MATERIALS AND METHODS
This prospective observational study was carried out in Dhaka Shishu Hospital among
100 children of ASA grade I & II scheduled for elective surgery under general
anaesthesia during the period of Dec 2011 to May 2012. Children with anatomic airway
abnormalities, tonsiller hypertrophy, adenoid hypertrophy, bleeding disorder, intracranial
hypertension, surgery in esophagus & trachea and porphyria were excluded from the
study. During pre-operative assessment height and weight of baby was documented.
Procedure was explained to the parents or guardian and informed consent was taken.
Children were instructed to fast 6 hours after normal meal and 2 hours after clear liquids
before operation. Sisters accompanied the children inside theater, a reliable intravenous
access was established and baseline vital parameters were recorded. Experiment was
carried out using an improvised esophageal stethoscope assembled by using pediatric
sthethoscope without bell & diaphragm and age appropriate sized cuffed endotracheal
tube. Lubricated esophageal stethoscope had been inserted through oropharyngeal route
into esophagus after administration of GA. Right before insertion of esophageal
stethoscope, stomach had been properly suctioned & decompressed and device inserted
up to a depth depending on age of the patient where heart and breath sounds were clearly

3. audible after inflating the cuff. During operation periodical suction of stomach was given
through endotracheal tube of esophageal stethoscope. Depth of insertion was also
estimated by height in inches divided by two. Quality of heart and breath sounds or any
other added sounds has been recorded during intraoperative period. At the end of
operation with proper suctioning esophageal stethoscope has been removed before
extubation.
RESULTS
A total 100 patients were included in this study. The study was conducted in Dhaka
Shishu Hospital from Dec 2011 to May 2012. The observations obtained in the study
have been summarized in tabular form (Table I- II ).
Table-I: Age & Sex distribution of children (n=100)
Age of the children (Average) Male Female
06 months 25 25
12 months 25 25
Total 50 50
Table-II: Height distribution of children
Age of children (Average) Weight (Average) Height (Average)
06 months 7.5 kgs 66.9 cms
12 months 9.8 kgs 75.2 cms
Sources: Oxford Medical Publications, 1989

4. Findings of the study has been summarized as follows:
• During intraoperative monitoring many a time it has been found that heart and
breath sounds were not clearly audible by thoracic precordial sthethoscope due to
loose contact or misplacement but in improvised esophageal stethoscope not only
heart and breath sounds are audible but also added & transmitted sounds were
clearly audible which helps to take appropriate measures in time.
• In thoracic precordial sthethoscope anesthesiologists need to refixed &
repositioned the sthethocope frequently, interfering surgical teams and
jeopardizing sterility of operations but in esophageal stethoscope once it is fixed
in appropriate depth of insertion, position remains as it was like endotracheal
tube.
• In esophageal stethoscope muffle heart sounds which is audible clearly where
peripheral pulse is very weak/ feeble and it minimizes the stress and anxiety
among anesthesiologists.
DISCUSSION
To compare the effectiveness and reliability between improvised esophageal stethoscope
and precordial stethoscope for intraoperative monitoring of children during general
anesthesia a study was conducted in Dhaka Shishu Hospital. Esophageal stethoscope
provides reliable and continuous cardiopulmonary monitoring. The esophageal
stethoscope may also provide specialized information such as auditory signs of venous air
embolism. The esophageal stethoscope also allow monitoring when
a transthoracic stethoscope may not be practical due to the surgical site.1,2,3
In the present
study it was observed that during intraoperative monitoring many a time heart and breath
sounds were not clearly audible by thoracic precordial sthethoscope due to loose contact
or misplacement but in improvised esophageal stethoscope not only heart and breath
sounds were audible but also added & transmitted sounds were clearly audible which
helps to take appropriate measures in time. The findings is very much consistent to
Chakraborty & Mathur study. The findings is also consistent with R N Westhorpe & C
Ball study which states that “following induction and intubation, the lubricated catheter is
gently inserted into the esophagus. By gentle rotation and an adjustment of catheter depth
the point of maximal intensity of heart sounds, murmurs or breath sounds maybe
determined.8,9,10”

5. To monitor heart and breathe sound, it has been mentioned in WHO manual that
continuous monitoring of heart rate and respiration is essential in small children in which
a precordial or oesophageal stethoscope suggested as invaluable tool for monitoring.17
In
our study it was clearly differentiated the effectiveness and reliability of two devices.
Esophageal stethoscope even muffle heart sounds were audible clearly where peripheral
pulse was very weak/feeble and it minimizes the stress and anxiety among
anesthesiologists where as precordial stethoscope was less effective as a monitoring tool.
In thoracic precordial sthethoscope anesthesiologists need to refixed & repositioned the
sthethocope frequently, interfering surgical teams and jeopardizing sterility of operations
but in esophageal stethoscope once it is fixed in appropriate depth of insertion, position
remains as it is like endotracheal tube.
Teaching about and routine use of a precordial or esophageal stethoscope was not
deemed essential by majority of existing residency programs. A reevaluation of this lack
of education appears warranted in light of the low cost and extra added patient vigilance
provided by the precordial or esophageal stethoscope.13,14,15,16
There was another study
where it has also been states that current anesthesia training may be fostering an
environment where providers overlook a valuable minimally invasive, and cost-effective
continuous monitor of patients' dynamic vital organ function.12
In the present
observational study it was suggested that although anesthesia provider is overlooking this
simple but effective device, though it couldn’t be enlisted into anesthesia curriculum but
this device is providing direct information to anesthesia providers without delay which is
inevitable in modern monitoring equipments because all monitoring equipment having
response time before providing information to anesthesia providers.
There were limitations of our study like tracheal tube is designed for trachea not for
esophagus, so stomach content might regurgitate back. To date there is no PVC tube
designed for esophagus with a blind tip for esophageal use. There is no such study that
inflation of cuff cause esophageal ischemia. There is lack of similar study to get data and
book pictures of improvised esophageal stethoscope which is consistent with Dr Agnes
Watson study.11
.

6. CONCLUSION
Improvised esophageal stethoscope is very simple to assemble, minimally invasive, cost
effective, and properly suitable for developing countries which provides continuous
monitoring of dynamic vital organ functions. The use of the stethoscope as a continuous
monitoring device has decreased among training institutions and most anaesthesiologists
feel it has been superseded by other monitoring equipments although the complications of
these monitoring devices were rare. The main factors limiting the use of stethoscope are
due to the presence of modern monitoring equipments such as pulse oximetry and
capnography.
References:
1. Chakroborty A, Mathur S. A simple technique for esophageal stethoscopy.
Anaesthesia and Intensive Care 2007;
2. Eckhardt K, Aseno S. The individually fitted earpiece. Letter to the editor. Update
in Anaesthesia 2002; 14:33.
3. Manecke Jr GR, Poppers PJ.Esophageal stethoscope placement depth: its effect
on heart and lung sound monitoring during general anesthesia. Anesth Analg
1998; 86:1276-1279.
4. Petty C. We do need precordial and esophageal stethoscopes. 1987,3:192-193
5. Mayer BW. Pediatric anesthesia; a guide to its administration; Philadelphia,
Lippincott, 1981:34-35
6. Karl E, Samuel A. Update in Anaesthesia 2002;14:13
7. Anaesthesia in the District Hospital. World Health Organisation 2001
8. McIntyre JWR. Stethoscopy during anaesthesia. Can J Anaesth 1997; 44:535-542.
9. Westhorpe R N, Ball C. Precordial and oesophageal stethoscopes. Anaesthesia
and Intensive Care 2008;
10. Smith C. An endo-esophageal stethoscope. Anesthesiology 1954; 15:566.

7. 11. Agnes W, Anil V. Survey of the use of oesophageal and precordial stethoscopes
in current paediatric anaesthetic practice 2001; 11:437-442
12. Richard C, Jeffrey S. Use of esophageal or precordial stethoscopes by anesthesia
providers: Are we listening to our patients? Journal of Clinical Anesthesia
1995,7:367-372
13. Alan Jay S. The Precordial/Esophageal Stethoscope-A Vigilance Monitor No
Longer Taught to Anesthesiology Residents. Anesthesiology 2001; 95:A524
14. Gregory GA: Monitoring During Surgery in PEDIATRIC ANESTHESIA, 2nd ed,
Gregory GA, ed, NY, Churchill Livingstone, 1989, pp 478.
15. Raemer DB: Monitoring Respiratory Function in PRINCIPLES AND PRACTICE
OF ANESTHESIOLOGY, Rogers MC, Tinker JH, Covino BC, Longnecker DE
eds, St Louis, Mosby Year Book, 1993, pp 783.
16. http://www.health.state.ny.us/ (Section 405.13).
17. WHO manual. Essential surgical care.