1. Are we still hyperventilating cardiac arrest
patients in the UK? A simulation-based study
Dr Peter Sherren MBBS FRCA, Dr Asher Lewinsohn BSc MBBS (Hons) MRCS, Dr Dhuleep
(Hons)
Sanjay Wijayatilake BSc MBBS FRCA
Department of Anaesthesia & Intensive Care Medicine, Queen’s Hospital, Essex, England.
Queen’
Introduction Results Conclusions
• Despite all the research, education and • The difference between the mean minute • This study has demonstrated that healthcare
training that has gone into the field of CPR ventilation for the 97 participants (13.1 Lmin-1), professionals, despite agreed guidelines, are
during the last 50 years, survival rates and that of the preliminary instructor group (5.8 hyperventilating simulated cardiac arrest
remain bleak1. Lmin-1) was statistically significant (p= 0.02). patients.
• A significant problem is that what the • The sample population mean for the minute • Suboptimal ventilation was a problem across
medical community is being trained to do, is ventilation, respiratory rate and tidal volume all the backgrounds and specialties
not being replicated in clinical practice2,3. were 13.1 Lmin-1 (SD 7.3), 21.2 min-1 (SD 9.1) investigated; although doctors performed best
and 647 ml (SD 170) respectively. The here, they were still found to be
• It has long been established that excessive
corresponding 95% confidence intervals of the hyperventilating to an unacceptable level.
ventilation can have an adverse effect on
means are 11.6-14.6 Lmin-1, 19.4-23 min-1 and
survival4. The explanation for this deleterious • There may be scope for the use of paediatric
613-681 ml.
outcome is multi-factorial: ventilation in many (500ml) self inflating reservoir bags as a first
circumstances involves interruption of chest • These results exceed the Resuscitation line device. This simple measure may ensure
compression and thus reduced organ Council’s suggested minute ventilation of 5 delivery of more guideline consistent
perfusion; while positive pressure ventilation Lmin-1, respiratory rate of 10 min-1 and tidal ventilation6.
(IPPV) attenuates some of the beneficial volume of 500 ml.
effects of chest recoil and the negative
pressure thoracic pump. This, in combination
• Table 2 shows the results of the individual
groups within this study. The only statistically
References
with a direct increase in pulmonary vascular
significant difference between the four groups
resistance from IPPV, results in a reduction
was found when comparing minute ventilation 1. Eisenberg MS, Mengert TJ. Cardiac
of transpulmonary blood flow, left ventricular
(p= 0.03). resuscitation. N Engl J Med 2001;
end-diastolic pressure and can ultimately
Table 1 - Spread of specialties involved in the study 344:1304—1313.
result in impaired haemodynamic
effectiveness of CPR5. 2. Editorial Board. Advanced Life Support.
5th edition. The Resuscitation Council (UK)
• As a result of this we conducted a manikin-
2006; ISBN 1-903812-11-9: 29
based study to assess the quality of
ventilation delivered during simulated CPR, 3. Abella BS, Alvarado JP, Myklebust H et
in a large UK centre. al. Quality of cardiopulmonary resuscitation
during in-hospital cardiac arrest. JAMA.
2005 Jan 19;293(3):305-10.
4. O’Neill JF, Deakin CD. Do we
Methods hyperventilate cardiac arrest patients?
Resuscitation. 2007 Apr;73(1):82-5.
• A simulated cardiac arrest scenario was 5. Aufderheide TP, Lurie KG. Death by
undertaken by 97 participants from a range of hyperventilation: A common and life-
medical specialties (Table 1). threatening problem during
cardiopulmonary resuscitation. Crit Care
• Participants were asked to asynchronously Med 2004 Vol. 32, No. 9 (Suppl.)
ventilate a simulated adult cardiac arrest
patient for a period of 1 minute using a 1.6L 6. Nehme Z, Boyle MJ. Smaller self-inflating
self inflating bag. An intubated Laerdal bags produce greater guideline consistent
SimMan manikin was utilised for the purpose ventilation in simulated cardiopulmonary
of the simulation. During this time the mean resuscitation. BMC Emerg Med. 2009 Feb
tidal volume, minute ventilation and Table 2 - Comparison of data on ventilation parameters. 20;9:4.
respiratory rate were measured with the use
of a spirometer.
• Preliminary work carried out on a sample of
advanced life support instructors with
anaesthesia training, returned a mean minute
ventilation of 5.8 Lmin-1 (SD 3.9).
• A calculated sample size of 90 was required
to detect a 20% increase in the minute
ventilation (primary outcome) from the 5.8
Lmin-1 found in this instructor group ( level
of 0.05, with a 90% power). A p-value <0.05
was considered statistically significant.