PREOXYGENATION TECHNIQUES journal club new

Presented by- Dr Chhaya Singour
Moderator- Dr Nanish Sharma

INTRODUCTION
◾Preoxygenation - essential component of airway management
◾prolongs the period before the onset of hypoxaemia during
apnoea after induction of anaesthesia.
◾ allows the operator more time in the event of difficulty with
airway management.

EFFECTIVENESS
Effectiveness of preoxygenation is determined by its efficacy and
efficiency.
End-tidal oxygen concentration (EtO2) is increasingly viewed as
an unreliable marker of preoxygenation because it only assesses
efficacy rather than efficiency

METHODS
PROTOCOLAND REGISTERATION-
◾ systematic review was designed according to
recommended standards and reported per Preferred
Reporting Items for Systematic Reviews of Network Meta-
Analyses (PRISMANMA) guidelines. The review protocol
was prospectively registered on PROSPERO on May 17,
2022.

ELIGIBILITY CRITERIA-
◾data available on safe apnoea time; incidence of arterial
desaturation; lowest arterial oxygen saturation (SpO2) during
airway management; time to EtO2 of 90%; and arterial partial
pressure of carbon dioxide (PaCO2 ) and arterial partial
pressure of oxygen (PaO2 ) at the end of the preoxygenation.
◾Randomised to different preoxygenation techniques ( facemask;
HFNO) and methods ( supine vs head-up position or different
flow rates).

DATA COLLECTION-
STUDY DEMOGRAPHICS; PATIENT CHARACTERISTICS; INTERVENTION DETAILS;AND OUTCOMES OF INTEREST
.

OUTCOMES-
◾Primary outcome- safe apnoea time as measured by pulse
oximetry (i.e. time to arterial desaturation), most suitable metric
of effectiveness of preoxygenation.
◾Secondary outcome- incidence of arterial desaturation; lowest
SpO2 during airway management; time to EtO2 of 90%; and
PaCO2 and PaO2 at the end of the preoxygenation.

DATAANAL
YSIS
◾For continuous outcomes, mean (standard deviation [SD]) were
calculated. If median (inter-quartile range [IQR] [range]) was
presented, these were converted to mean (SD) using the Hozo
method.
◾ For categorical outcomes, the number of events and patients in
each arm, along with relative risk and standard error between
groups, were collected and analysed.

INTERVENTIONS
GROUPED preoxygenation techniques and their variations in nine different
individual interventions:
Supine position with facemask using tidal volume ventilation (TVV) and no pressure
support (FMsupine)
head-up position before apnoea, with facemask using TVV and no pressure support
(FMhead-up).
supine position with facemask using TVV and pressure support (continuous positive
airway pressure [CPAP], pressure support ventilation [PSV], PEEP) (Pssupine).
head-up position before apnoea, with facemask using TVV and pressure

◾supine position with facemask and patients
performing deep breaths with no pressure support
(DBsupine).
◾ head-up position before apnoea, with
facemask and deep breaths with no pressure support
(DBhead-up).
◾supine position with HFNO (HFNOsupine).
◾head-up position before apnoea, with HFNO (HFNOhead-
up).
◾head-up position with HFNO and with pressure support
(HFNOþPShead-up).

NETWORK META-ANALYSIS
◾The network analyses concomitantly considered the individual
preoxygenation techniques in the included studies for direct and
indirect comparisons, divided multi-arm studies into multiple
pairwise comparisons, taking one single- arm (one preoxygenation
technique) as the reference group, to which all the other groups
were compared.

PUBLICATION BIAS
◾ assessed for publication bias through comparison adjusted
funnel plots and assumed that studies comparing new
techniques with positive results are more likely to be
published.
◾Egger’s tests for funnel plot asymmetry were conducted.
◾threshold of significance was set at P<0.1.

PRIMARYAND SECONDARY OUTCOMES-

CONCLUSION
◾Preoxygenation of adults before induction of general anaesthesia was most
effective in terms of safe apnoea time when performed with high-flow nasal
oxygen with patients in the head-up position in comparison with facemask alone.
◾high-flow nasal oxygen in the head-up position is likely to be the most effective
technique to prolong safe apnoea time among those evaluated. Clinicians should
consider this technique and patient position in routine practice.

COMPLICATIONS
◾ No individual complication had sufficient data to perform network meta-analyses.
◾ Studies evaluated risk of gastric insufflation.
◾ They did not show relevant differences between interventions.
◾ There was no statistically significant inconsistency between direct and indirect evidence for
the primary outcome (i.e. safe apnoea time), incidence of desaturation, and PaO2 at the
end of preoxygenation.
◾ There was inconsistency in some comparisons for PaCO2 at the end of preoxygenation. The
number of comparisons available for incidence of severe desaturation, lowest SpO2, and
time to EtO2 of 90% were insufficient.

PREOXYGENATION
◾Eight deep breaths in 60 seconds are equivalent to three minutes
of tidal volume breathing of 100% oxygen.
◾Preoxygenation in a 25-degrees head-up position or ramping
position with the patient's head raised so that the ear is at the
level of the sternal notch helps to reduce dependent atelectasis,
improve ventilation/perfusion matching, decrease time to oxygen
desaturation during apnea, and improve the direct laryngoscopy
view, especially in obese patients.

◾In this way, the patient’s oxygen reserve in the
functional residual capacity is purged of nitrogen. Up
to 90% of the normal FRC of 2 L can be filled with
oxygen after preoxygenation.
◾Non invasive positive-pressure ventilation is another
technique that can improve preoxygenation,
especially in obese patients.

◾Assuming apatentair passageis present,oxygen insufflatedinto the pharynx
mayincreasetheduration ofapneatolerated bythepatient. Becauseoxygen
enters theblood from theFRC ataratefasterthan CO 2 leavestheblood,a
negativepressureisgeneratedinthealveolus, drawingoxygen into thelung
(apneicoxygenation).With aflow of 100% oxygen andapatentairway,arterial
saturation canbemaintainedfor a longer period despiteno ventilation,
permittingmultipleairway interventions should adifficultairwaybe
encountered.

WHY PREOXYGENATION IS ESSENTIAL?
◾A healthy adult, who is not obese, can be apneic for
approximately 9 minutes after preoxygenation before
significant desaturation occurs.
◾ Obesity, pregnancy, and other conditions that significantly
decrease functional residual capacity (FRC) or increase
oxygen consumption decrease the time to desaturation.

PREOXYGENATION TECHNIQUES journal club new

More Related Content

Similar to PREOXYGENATION TECHNIQUES journal club new

More from KavyaSamuthiravelu1

Recently uploaded

PREOXYGENATION TECHNIQUES journal club new