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Check a Pulse! When to Question SpO2, NIBP

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In conventional pulse oximetry, the incoming red and infrared signals are received from the photodetector. In many of the newer oximeters, the signals are digitized. – PowerPoint PPT presentation

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Title: Check a Pulse! When to Question SpO2, NIBP


1
Check a Pulse! When to Question SpO2, NIBP
EtCO2 Readings
Mike McEvoy, PhD, RN, CCRN, NRP Senior Staff RN
Cardiothoracic Surgical ICUs Albany Medical
College Albany, New York Chair Resuscitation
Committee Albany Medical Center EMS Coordinator
Saratoga County, New York EMS Editor Fire
Engineering magazine
2
Learning Objectives
  • Upon completion of the presentation the
    participant will
  • Recall two common sources of user error in
    non-invasive vital sign measurement
  • Discuss the methodology used to obtain a
    non-invasive blood pressure reading
  • State one response of a pulse oximeter when
    unable to detect a pulse
  • Talk Code 711

3
Case 1 - Desaturation
  • While charting
  • SpO2 alarms 74
  • Patient in no distress, good color
  • Repositioning sensor yields same 74 sat
  • ABG shows 98 sat

4
Well appearing patient, 74 SpO2
  • Why me?

5
Case 2 O2 Sat Out Of Nowhere
  • Patient discharged 2 hours ago
  • Mysterious waveform and 100 sat

6
Model of Light Absorption At Measurement Site
Without Motion
7
Model of Light Absorption At Measurement Site
With Motion
8
Influence of Perfusion on Accuracy of
Conventional Pulse Oximetry During Motion
Good Perfusion (Conventional PO)
SpaO298
SpO293
SpvO288
Poor Perfusion (Conventional PO)
SpaO298
SpO274
SpvO250
9
Conventional Pulse Oximetry Algorithm
Digitized, Filtered Normalized
R IR
  • 3 options during motion or low perfusion
  • Freeze last good value
  • Lengthen averaging cycle
  • Zero out

10
Next Generation Pulse Oximetry
11
Next Generation Pulse Oximetry
12
Masimo SET Signal Extraction Technology
Masimo SET Parallel Engines
SET Parallel Engines
13
A Solution for Patient Motion Discrete
Saturation Transform (DST)
In the presence of motion, SET separates the
venous and arterial saturation values resulting
in accurate saturation readings without false
alarms (compared to conventional oximetry that
averages the values to produce a reading)
Conventional Pulse Oximetry
14
Certainty
15
Case 3 Smoke Inhalation
  • ED Triage Desk
  • 35 yo male presents with diff breathing
  • States, My furnace exploded.
  • Soot in mouth/nares
  • O2 sat 98

16
Carbon Monoxide (CO)
  • Gas
  • Colorless
  • Odorless
  • Tasteless
  • Nonirritating
  • Physical Properties
  • Vapor Density 0.97
  • LEL/UEL 12.5 74
  • IDLH 1200 ppm

17
Limitations of Pulse Oximetry
Conventional pulse oximetry can not distinguish
between COHb, and O2Hb
From Conventional Pulse Oximeter
SpCO-SpO2 Gap The fractional difference between
actual SaO2 and display of SpO2
(2 wavelength oximetry) in presence of
carboxyhemoglobin
From invasive CO-Oximeter Blood Sample
Blood
Barker SJ, Tremper KK. The Effect of Carbon
Monoxide Inhalation on Pulse Oximetry and
Transcutaneous PO2. Anesthesiology 1987
66677-679
18
CO The Leading Cause of Poisoning Deaths
  • 30-50 of CO-exposed patients presenting to
    Emergency Departments are misdiagnosed

Barker MD, et al. J Pediatr. 19881233-43 Barret
L, et al. Clin Toxicol. 198523309-13 Grace TW,
et al. JAMA. 19812461698-700
19
Pulse CO-oximetry
20
Hgb Signatures CO, Met, Hgb
21
14,438 Patient Brown University Study
  • Partridge and Jay (Rhode Island Hospital, Brown
    University Medical School), assessed carbon
    monoxide (CO) levels of 10,856 ED patients
  • 11 unsuspected cases of CO Toxicity (COT) were
    discovered. Overall mean SpCO was 3.60
  • Occult COT was 4 in 10,000 during cold, 1 in
    10,000 during warm months
  • They concluded unsuspected COT may be identified
    using noninvasive COHb screening and the
    prevalence of COT may be higher than previously
    recognized

Non-Invasive Pulse CO-Oximetry Screening in the
Emergency Department Identifies Occult Carbon
Monoxide Toxicity. Suner S, Partridge R, Sucov
A, Valente J, Chee K, Hughes A, Jay G. J Emerg
Med 2008 Department of Emergency Medicine, Rhode
Island Hospital, Brown Medical School,
Providence, RI.
22
Pulse Oximetry
  • Problems
  • Accuracy
  • Motion artifact
  • Dyshemoglobins

23
Case 4 Which Pressure Is Right?
  • 78 yo trauma patient ? BP
  • A-line 70/42 (50)
  • NIBP 90/50 (52)

24
Blood Pressure Monitoring
Direct
Indirect
vs
Pressure
Flow
25
Errors in BP Measurement
  • Cuff Size
  • Too large ? BP
  • Too small ? BP
  • 2/3 extremity length
  • Mid Heart Level
  • Higher ? BP
  • Lower ? BP
  • Best sitting, arm _at_ side

26
How does NIBP work?
  • Measures flow (pulsatile)
  • Determines HR and MAP
  • By formula, calculates SBP and DBP
  • Subject to same interferences as auscultated BP
  • Important to confirm HR (if wrong, SBP and DBP
    wrong)

27
Mean Arterial Pressure (MAP)
  • A clinical parameter useful in assessing
    perfusion
  • Represents the average pressure within the
    arterial system throughout the cardiac cycle
  • MAP 2 (diastolic) systolic
  • 3
  • 2/3 time in diastole only when HR 70

28
  • 150
  • 90
  • 60

29
Waveform Capnography
  • Available for spontaneously breathing and for
    intubated patients

30
Case 5 Bad Day in OR
  • 37 yo male cholecystectomy
  • No significant PMH, smooth induction
  • Shortly after incision, EtCO2 gradually declines
  • Manual BVM with good compliance chest rise
  • ???

31
Circulation
The heart and lungs are inextricably linked
together
32
Cardiac Arrest!
  • Little O2 delivery or consumption
  • Little CO2 production or venous return

33
CO2 Clearance Reflects Perfusion
In other words CO2 production is largely
dependent on oxygen consumption!
34
Case 6 Misplaced ETT?
  • Cardiac arrest on med-surg floor
  • CRNA intubates without difficulty, visualizes
    tube pass through cords
  • EtCO2 circuit connected flatline
  • ???

35
Circuit Connector
36
Case 7 EtCO2 ? PaCO2
  • Post CABG patient EtCO2 drops to 6
  • ABG PaCO2 48 mmHg
  • Why?

37
Another Cause of Low EtCO2
  • Profound metabolic acidosis
  • pH 6.93

38
Questions?
  • Slides available at www.mikemcevoy.com
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