Perianesthesia Nurses Association of British ColumbiaCathy Hanley, RN, BSNNovember 6, 2010

Capnography in the PACU: Theory and Clinical Applications

of end tidal C02 Monitoring

Objectives Review of physiology, ventilation vs

oxygenation Identify normal and abnormal etC02 values

and waveforms and appropriate clinical interventions

Discuss current applications of capnography in the PACU and beyond

Discuss current standards and recommendations

Review of capnography case studies

Brief History of Capnography

Used in anesthesia since the 1970s

Canadian Anesthesiologists’ Society requires it in the OR

New recommendations and standards expanding utilization

Capnography = Solutions for all Intubated and Non-Intubated patients

Capnography can be used in all areas of the hospital

Peds.

GI

MRI

Med-

Surg

EP/ Cath

Pain Mgmt

ORPACUICU

Capnography outside of the OR

Overview of Capnography

Capnography is the non-invasive, continuous measurement of CO2 concentration at the airway

Capnography provides three important parameters:• Respiratory rate detected

from the actual airflow

• Waveform tracing for every breath

• Numeric etCO2 value • Normal range 35-45 mmHg

Obtaining an Accurate Respiratory Rate

Manual Counting• Measures: • Chest or air movement

• Based on observation or auscultation that may be restricted by patient movement, draping or technique

Impedance (ECG Leads)• Measures:• Attempt to breathe• Chest movement

• Based on measuring respiratory effort or any other sufficient movement of the chest

etCO2

• Measures: • Actual exhaled breath at

airway

• Hypoventilation and No Breath detected immediately!

• Most accurate RR, even when you are not in the room!

Two separate physiologic processes

• The process of getting O2 into the body

Oxygenation• The process of

eliminating CO2 from the body

Ventilation

Respiratory Cycle = Oxygenation and Ventilation

Capnography• Measures etCO2• Reflects

ventilation• Hypoventilation

& apnea detected immediately

Pulse Oximetry• Measures SpO2• Reflects

oxygenation• Values lag with

hypoventilation & apnea, several to many minutes

http://www.covidien.com

Important Measurements

The Relationship between PaCO2 and etCO2

etCO2 normal range is 35 - 45 mmHg

Under normal ventilation and perfusion conditions, the PaCO2 & etCO2 will be very close

– 2 – 5 mmHg with normal physiology

Ideally, every alveolus is involved in air exchange (ventilation) and has blood flowing past it (perfusion), but in reality, ventilation and perfusion are never fully matched, even in the normal lung

Ventilation-Perfusion Mismatch There is inappropriate matching

of ventilation and perfusion when:

– “Dead space” is being ventilated with no perfusion

• Since no gas exchange occurs, air coming out is the same as air going in (no CO2)

– Unventilated areas of lung are being perfused (“Shunt”)

• Effect on etCO2 may be small but oxygenation may decrease greatly

Dead Space Ventilation

Physiologic– conducting airways

and unperfused alveoli

Mechanical– breathing circuits

Disease states leading to this include:– Severe hypotension– Pulmonary

embolism– Emphysema– Bronchopulmonary

dysplasia– Cardiac arrest

Bronchial intubation

Increased secretions

Mucus plugging

Bronchospasm

Atelectasis

Ventilation-perfusion mismatch

Summary - EtCO2 vs. PaCO2

End tidal CO2 (EtCO2) = noninvasive measurement of CO2 at the end of expiration

EtCO2 allows trending of PaCO2 - a clinical estimate of the PaCO2, when ventilation and perfusion are appropriately matched

Wide gradient is diagnostic of a ventilation-perfusion mismatch

EtCO2 monitoring allows for a breath by breath assessment of ventilation.

Why use etC02 in the PACU ?

Accurately monitors effective ventilation, giving a true airway respiratory rate

• Early warning of : Hypoventilation Apnea Obstruction

Provides easy and accurate airway monitoring for intubated or non-intubated patients

– Promotes better ventilation assessment resulting in timely interventions

– Titrate sedation and pain medication

Why use etC02 in the PACU? Indicator of Malignant Hyperthermia Use with patient with history of respiratory compromise,

such as asthma or COPD to monitor trend and need for breathing treatments and response to treatment

Endotracheal tube placement Monitoring during weaning Decrease frequency of arterial blood gases Use with non-invasive ventilation (NIV)

Case Study: Microstream Capnography in the PACU:Submitted by: Larry Myers RRTCottonwood HospitalMurray, Utah

Profile A 31-year-old female s/p abdominal

hysterectomy 6 months prior to admission is admitted with right lower quadrant pain. The patient underwent a bilateral salpingo-oophorectomy and lysis of adhesions on this admission. On post-op day one she became hypotensive and had a substantial decrease in her hematocrit. The patient was returned to the OR for an exploratory laparotomy.

Case Study in PACU Clinical Situation: When the patient was returned to the PACU, she was extubated and

became acutely hypoxic on a non-rebreather mask. The patient was in profound distress, drowsy, lethargic, but arousable and able to converse with c/o severe abdominal and chest pain.

Sp02: 82%pH: 7.22PaC02: 64.9mmHgHCO3: 25.5mEq/LPa02: 53mmHgSa02: 81%RR: 40bpmHR: 130bpmBP: 107/48

Clinical Situation

At this point anesthesia was preparing to reintubate. A suggestion was made to use etC02 with an oral/nasal cannula and place the patient on a high flow 02 delivery system with an Fi02 of 1.0 and monitor the patient closely.

The patient was rushed to the Radiology Department for a CT angiogram where a pulmonary embolus was ruled out.

Initial values:etC02: 62mmHgSp02: High 80’s

Over the next 2 hours, etC02 fell to 44mmHg and Sp02 increased to 98%.

Discussion The continuous monitoring of EtCO2 and SpO2 when measured in concert but evaluated independently allowed this patient to be safely observed and avoid reintubation and mechanical ventilation. It is also interesting to note, retrospectively, an expensive procedure to rule out PE may have been avoided with a better understanding of the relationship between arterial and end-tidal CO2. The probability of a PE in this case was low with a measured EtCO2 of 62 mmHg and a correlating PaCO2 of 64.9 mmHg. One would expect a wider gradient in the presence of significant dead space ventilation.

PACU, Post-op PCA, Med/Surg Floors

Post operative patients on Patient Controlled Analgesia (PCA) - often starts in PACU

Bariatric Patients/Obstructive Sleep Apnea(OSA) high risk patients

Awareness building regarding the need for monitoring ventilation/breathing on general floors

– Patient sentinel events/deaths– Recent professional statements (APSF, ISMP)

Great need for more education on Oxygenation vs. Ventilation for nurses in non-acute areas

Compelling Recent Research

“During analgesia and anesthesia, cases of respiratory depression were 28 times as likely to be detected if they were monitored by capnography as those that were not”

University of Alabama – Birmingham, Waugh, Epps, Khodneva - meta-analysis presented at the Society of Technology in Anesthesia International Congress, January, 2008

Capnography monitoring in patients receiving patient controlled analgesia (PCA)

Patient safety with Patient Controlled Analgesia (PCA)

Patient Controlled Analgesia (PCA) aids patients in balancing effective pain control with sedation

The risk of patient harm due to medication errors with PCA pumps is 3.5-times the risk of harm to a patient from any other type of medication administration error

2004 more deaths with PCA than with all other IV infusions combined

Due to oversedation and respiratory depression with PCA delivery

Sullivan M, Phillips MS, Schneider P. Patient-controlled analgesia pumps. USP Quality Review 2004;81:1-3. Available on the web at: http://www.usp.org/ pdf/patientSafety/qr812004-09-01.pdf.

PCA Issues List PCA by proxy Drug product mix-ups Device design flaws Inadequate patient/family education Practice issues including pump

misprogramming Inadequate monitoring

ISMP Medication Safety Newsletter, July 10, 2003 Vol 8, no.14

Currently, no monitoring during PCA therapy at most hospitals Post operative surgical units where there is no centralized

monitoring Large units making proximity to patient impossible Vital signs are typically every 4 hours Sometimes spot checking with pulse oximetry Nurse to patient ratio can be 1:6 – 1:10

How Ventilation Deteriorates when Administering Opioids

Opioids Depress the Brain’s signals to the Respiratory Muscles

Respiratory

Depression and

Eventual Failure

CO2 Build-up

Decreased LOC

Hypoventilation

•Decreased RR And Depth

•CO2 accumulates

CO2 Production CO2 Removal

CO2 production must equal CO2 removal

Case scenario

16 yr-old Billy falls off his skateboard and sustains a left femur fracture. He is now post-op from ORIF and is in the PACU extubated. He rates his pain at a 10 on 0-10 scale and has been given multiple doses of IV Morphine and is now on a PCA pump for pain.

Case scenario

Later that evening on the med-surg floor, after hours of poor pain control, Billy falls asleep

Afraid Billy will soon wake up and again be in severe pain, Billy’s mother repeatedly presses his morphine PCA button while he is asleep

He subsequently stops breathing and is resuscitated, but suffers hypoxic brain injury

Obstructive Sleep Apnea Sleep apnea is the most widely known sleep disorder

besides insomnia Believed to be under-reported 18-40 million people have sleep apnea

– Effects 2% of middle-aged females– Effects 4% of middle-aged males

More common in men It is estimated that nearly 80% of men and 93% of

women with moderate to severe sleep apnea are undiagnosedPractice Guidelines for the Perioperative Management of Patients with Obstructive

Sleep Apnea, Anesthesiology 2006; 104:1081–93

Sleep Diagnosis and Therapy ♦ Vol 3 No 5 September-October 2008

Mechanism of OSA…a vicious patternMuscles of

the pharynx relax

during deep sleep

Airway obstruction

Hypoxemia &

Hypercarbia

Acidosis activates

respiratory centers in the CNS

Stimulates and arouses patient to ventilate

Survival Mechanism

A more vicious pattern…with sedationMuscles of

the pharynx relax

during deep sleep

Airway obstruction

Hypoxemia &

Hypercarbia

Acidosis activates

respiratory centers in the CNS

Does not ventilate

Opiates & sedatives inhibit arousal mechanisms

Respiratory Arrest Without Intervention

PCA Case Scenario #2

60 year old female with morbid obesity and history of intractable low back pain

X-rays demonstrated severe bone-on-bone changes in both knee and hip areas

Placed on PCA continuous infusion with PCA demand dose

Placed on continuous SpO2 and EtCO2 monitoring

PCA Case Scenario #2 cont.

Soon after starting PCA, patient desaturated to SpO2 = 85%

Patient placed on 60% O2 aerosol mask and EtCO2 monitoring discontinued

PCA continuous discontinued, PCA demand dose continued

PCA Case Study #2 cont.

Following morning, patient appeared very lethargic and difficult to arouse

SpO2 in high 90s EtCO2 monitor reapplied on patient

with readings of 74 mmHg* indicating elevated CO2 level

Patient was transferred to ICU with diagnosis of obstructive sleep apnea complicated by obesity and PCA

*Normal EtCO2 = 35-45 mmHg

Normal Waveform

A-B: Baseline = no CO2 in breath, end of inhalation

B-C: Rapid rise in CO2

D-E: Inhalation

C-D: Alveolar plateau

D

D: End point of exhalation (EtCO2)

Anatomy of a Waveform

Sudden loss of waveform and EtCO2 to zero or near zero / no respiration detected

– Possible causes

• Intubated:

• Kinked or dislodged ETT

Abnormal waveforms – No Breath loss of waveform

Total airway obstruction Complete disconnect from ventilator Non-intubated:

Apnea Dislodged Capnoline

Absent alveolar plateau indicates incomplete alveolar emptying or loss of airway integrity

– Possible causes

Abnormal waveforms Loss of alveolar plateau

Intubated: Partial airway obstruction caused by

secretions Leak in the airway system Bronchospasm Endotracheal tube in the hypopharynx

Non-intubated: Head and neck position secretions

Classic Hypoventilation

Classic Hyperventilation

Gradual decrease in etCO2 with normal waveform indicates a decreasing CO2 production, or decreasing systemic or pulmonary perfusion

Abnormal waveforms - decreased etCO2

Hypothermia (decrease in metabolism)

Hyperventilation

Hypovolemia

Decreasing cardiac output

Capnography in Obstructive Lung Disease

– Waveform shape detects presence of bronchospasm

– etCO2 trends assess disease severity (e.g., asthma, emphysema)

– etCO2 trends gauge response to treatment (e.g., asthma, emphysema

Rise in baseline CO2 indicates rebreathing of CO2

Intubated patient– Addition of mechanical dead space

to ventilator circuit

– Technical errors in CO2 analyzer

Abnormal waveforms – rebreathing intubated and non-intubated

Non-intubated patient

Poor head & neck alignment

Draping at the airway

Insufficient flow to O2 mask

Shallow breathing that does not clear anatomical dead space

Abnormal Waveforms – What to do Assess patient Check sample line

position – reposition or check ET tube position

Check head/neck alignment, and open airway, suction if needed

Instruct patient to take a deep breath

If patient is not breathing and not responding, follow airway protocol

Movers and Shakers / Clinical Compass

‘The monitoring used in the PACU should be appropriate to the patient’s condition and a full range of monitoring devices should be available’.

Canadian Anesthesiologists’ Society, R. Merchant, et al Revised edition 2010

Institute for Safe Medication Practices (ISMP)

“Do not rely on pulse oximetry readings alone to detect opiate toxicity. Use capnography to detect respiratory changes caused by opiates, especially for patients who are at high risk (e.g., patients with sleep apnea, obese patients).”

– Establish guidelines for appropriate monitoring of patients who are receiving opiates, including frequent assessment of the quality of respirations (not just respiratory rate) and specific signs of oversedation.

ISMP Medication Safety Alert, February 22, 2007, Vol. 12, Issue 4

ASA (American Society of Anesthesiologists) Practice guidelines for the perioperative management of

patients with obstructive sleep apnea CO2 monitoring should be used during moderate or deep sedation for

patients with OSA. If moderate sedation is used, ventilation should be continuously monitored by capnography or another automated method if feasible because of the increased risk of undetected airway obstruction in these patients.

Postoperative Management:OSA patients should be monitored for a median of 3 hours longer than the non-OSA counterparts before discharge. Monitoring of OSA patients should continue for a median of 7 hours after the last episode of airway obstruction or hypoxemia.

Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep Apnea. Anesthesiology 2006 May;104(5):1081-93

Conclusion

Capnography for sedation/analgesia/postoperative monitoring:

– Accurately monitors RR– Monitors adequate ventilation– Monitors hypoventilation due to over-sedation more

effectively than pulse oximetry – Earliest indicator of apnea and obstruction– Adds additional level of safety providing caregiver

with objective information to make accurate assessments and timely interventions

Be Prepared. Be Proactive

Continuing Capnography Education

Oridion Knowledge Center: www.capnographyeducation.com

Three capnography courses available:– A Guide to Capnography during Procedural Sedation– A Guide to Capnography in the Management of the Critically

Ill– A Guide to Monitoring etCO2 during Opioid Delivery