Understanding the Impact of Obesity on Breathing and Sleep Scot
Jones, BA, RRT-ACCS, RCP
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Is Obesity a Problem? of adults in the United States, or 60
million people, are obese 30% From CDC.gov
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Is Obesity a Problem? Children worldwide are obese 22,000,000
From World Health Organization
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Is Obesity a Problem? From World Health Organization of
diabetes of ischemic heart disease certain cancers 58% 21% 8%
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Is Obesity a Problem? of United States medical costs may be
directly related to obesity 17% From CDC.gov
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Is Obesity a Problem? Yes.
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A Few Statements Poking fun? I think not. Respect the person,
analyze the behavior. Health professionals should have a (basic)
understanding of obesitys effects on how we deliver care.
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FACT or FICTION? Obese people tend to be lazier than people who
are thinner.
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FACT AND FICTION! Sedentary lifestyle practices do contribute
to obesity, but there are many people who are sedentary, but not
obese
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FACT or FICTION? Obese people eat too much.
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FACT AND FICTION! Overeating does contribute to obesity, but it
is more complicated than just that
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FACT or FICTION? Obese people are less intelligent
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FICTION! Obvious? Maybe not socially!
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FACT or FICTION? Obese people have control over their
weight
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FACT AND FICTION! Weight control is very complex. Calories In
Calories Out Weight
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Where are we heading? Understanding some terminology Lung
Mechanics Comorbidities Obesity Hypoventilation Syndrome Strategies
Socioeconomic considerations Critical care considerations
Noninvasive, airway, ventilatory, weaning/extubation
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How to Define Obesity
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Methods of Measurement Body Mass Index (BMI) - calculation
Hydrostatic weight Body calipers % Body Fat
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Body Mass Index Body Weight (kg) Height (m 2 ) FlawsStrengths
Indirect Measurement Doesnt take muscle into account Noninvasive
Simple and effective when used in context
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BMI NIH/NHLBI Table BMI < 18.5Below normal weight
19-24Normal weight 25-29Overweight 30-34Class I Obesity 35-39Class
II Obesity 40+Class III Obesity National Institutes of Health
(NIH), National Heart, Lung, and Blood Institute (NHLBI). The
practical guide: identification, evaluation, and treatment of
overweight and obesity in adults. Bethesda: National Institutes of
Health. 2000, NIH publication 00-4084.
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Lung Mechanics and Obesity
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Diaphragm is pushed upward Weight on chest wall restricts, and
prevents diaphragmatic excursion Adipose requires blood/oxygen
Increased risk of obstructed upper airway v
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Systemic Proinflammatory State Oversimplified: Proinflammatory
molecules lead to a number of metabolic and cardiovascular
complications of obesity, which may lead to airway inflammation
(think Asthma)
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Related Diseases and Disorders
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Obstructive Sleep Apnea From Washington.edu
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Classifying Severity Apnea Hypopnea Index (AHI) OSA SeverityOSA
Score 6-20Mild1 21-40Moderate2 > 41Severe3 Adapted from Gross,
JB, Bachenber, KL, and Benumof, JL, et al. Practice guidelines for
the perioperative management of patients with obstructive sleep
apnea. Anesthesiology 2006; 104:1081.
Obesity and OSA 1-SD increase in BMI = 4x increased risk for
OSA (Young, et. Al) BMI > 40 = 40-90% prevalence (Rajala, et.
Al) 10% change in body weight = 30% change in AHI BMI OSA
Prevalence
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Fat Distribution and OSA Male > Female Distribution (central
pattern around neck/trunk/abdominal) Schwartz, et al. Annals of the
ATS, Feb 2008
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Obesity Hypoventilation Syndrome
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Drive & Strength Respiratory Load Mechanisms of Ventilatory
Failure
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Drive & Strength Respiratory Load Mechanisms of Ventilatory
Failure Lung and Chest Wall Elastic Loads Lung CL Insp Threshold
Chest Wall Mechanics Supine Position Resistive Loads Upper AW
Obstruction Lower AW Obstruction Other Loads Increased CO2
Production Increased Deadspace
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Drive & Strength Respiratory Load Mechanisms of Ventilatory
Failure Decreased Drive Blunted drive in OHS Resp Depression (Meds)
Sleep Deprivation Hypothyroidism CNS disease Decreased Strength
Deconditioning and atrophy from acute illness Medications Metabolic
Disorders Myopathic Effects
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Apnea/Hypopnea Event PaCO2 pH PaCO2/pH return to baseline
OSA
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Apnea/Hypopnea Event PaCO2 pH PaCO2/pH fails to return Renal
Compensation HCO3 Depression of Ventilation OHS
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Strategic Considerations
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Meta-Analysis LOS / BMI are directly related statistically >
BMI may have a protective effect > LOS may be due to >
difficulty in dx and tx, not mobilizing pt as often > LOS = >
Mortality (long-term)
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BMI and Disease Risk
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Sociocultural Question #1 As a Health Professional, is it your
responsibility to be concerned with a patients weight?
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Sociocultural Question #2 As a Health Professional, is it your
responsibility to counsel patients on their weight status
(overweight or underweight)
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Sir, Youre Fat.
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A Few Cautions Most people are already aware that they are
obese Many people are sensitive about their weight Most people will
not (can not?) make major, sweeping changes Consider your own
motives and attitudes about people who are obese
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Dilemmas in Diagnostics Diagnostics become increasingly
difficult everything: The X-Ray CT Scanning Ultrasound Access for
blood-related lab tests Clinical confusion of multiple
comorbidities
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+
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The Airway Bergler, et al., 1997
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The Airway
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The Ideal Airway
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Airway Strategies Assess the physiology Proactive use of
difficult airway equipment Consider back-up plan what will you do
if you cannot intubate? Consider NOT using paralytics or heavy
sedation if possible Consider trial of noninvasive ventilation
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Nutrition Actual Body Weight may overestimate (Harris- Benedict
Equation) Consider Indirect Calorimetry Consider in context of
failure-to-wean
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The Nutrition Balance Caloric Restrictions Catabolic-induced
muscle loss impairs wound healing Weakens diaphragmatic muscles
delays ventilator weaning Moderate restriction may be okay
Excessive Calories Increases production of CO 2 which will increase
minute ventilation (tachypnea) -> failed SBT -> potential
delays in weaning
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Noninvasive vs. Invasive Treat OSA and OHS Pre-intubation PaO 2
higher with NPPV preparation. Futier, et. Al, Anesthesiology, Vol
114(6), 1354-1363 Post-extubation Support earlier extubation
attempts by extubating directly to NPPV
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To Trach or Not to Trach Unable to Wean, repeated intubations,
long- term needs CPAP failure with OSA BiPAP failure with OHS
(opportunity for ventilatory support at night)
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To Trach or Not to Trach Controlled environment (OR) Trach
changes may be a challenge Specialized trachs Early
Tracheostomy
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Positioning Consider Reverse Trendelenberg (sitting upward
while lying down)
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Early Mobility Laying in a hospital bed quickly results in
muscle wasting, and it is much more difficult to get it back once
it is gone Early mobilization is a key (yes, even if the patient is
in the ICU, and on a vent, and on high FIO2, and on high PEEP) Use
of adapted mobility equipment
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Ventilation Strategies What we know: High pressures hurt the
lungs Large volumes hurt the lungs There is a greater incidence of
later-onset ARDS in patients who are obese than there are in leaner
patients (Gong, et al.; Thorax. 2010;65(1):44-50)
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Ventilation Strategies The Big Question: Appropriate V T should
be set by: a.) Height b.) Weight c.) Waist circumference d.)
Whatever feels right How do we offset, then, the weight on the
chest?
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Ventilation Strategies Answer: Using Applied (or therapeutic)
PEEP Consider starting point of... +8 to +10 cmH 2 O +15? +20?
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Ventilator Pressures Lung Protective Strategy: Maintain Pplat
< 30 cmH2O Obese Patients: There can be a battle between
maintaining safe pressures and maintaining adequate ventilation.
Consideration: Watch pressures carefully: Consider measuring
transpulmonary pressures and maintaining < 35 cmH2O
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Weaning Considerations Adequate Support Provide adequate
hemodynamic support Consider tracheostomy with subsequent wean
Consider specialized unit and systemized approach Future direction
of weaning
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Medication Considerations Pain/Sedation + adipose storage =
prolonged period of recovery Significant concern of ventilatory
depression with adequate pain management (loss of airway!)
Medication administration by IBW, TBW, or DW?
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Obesity is not just a comorbidity. It is a disease.