Pulmonary Flashcards
How Is Obstructive Sleep Apnea (OSA) Defined?
○ According to the American Academy of Sleep Medicine, OSA is a breathing disorder characterized by narrowing of the upper airway that impairs normal ventilation during sleep.
○ Recurrent episodes of complete upper airway obstruction (apnea) or partial upper airway obstruction (hypopnea) may occur.
○ The number of these episodes occurring per hour, the apnea-hypopnea index (AHI), determines the severity of the condition.
Is There Any Difference Between OSA and OSA Syndrome?
○ OSA resulting in excessive daytime sleepiness (hypersomnolence) is known as OSA syndrome.
○ It is associated with systemic hypertension, pulmonary hypertension, coronary artery disease, atrial fibrillation, cerebrovascular disease, and diabetes mellitus type 2
How Is Severity of OSA Classified?
○ OSA is classified according to the number of apneas and/or hypopneas per hour of sleep observed during a sleep study.
○ This frequency is called the apnea-hypopnea index (AHI).
○ Scoring is outlined in Table 13.1.
○ Apnea is defined as cessation of air flow for 10 seconds.
○ Hypopnea is a reduction of air flow (≥30%) for 10 seconds.
What Is the Prevalence of OSA in the General Population? How Does the Prevalence Change in the Presence of Obesity?
○ Prevalence of OSA in the general population is approximately 10–20% .
○ In the obese population, the prevalence of OSA is increased markedly especially in those undergoing bariatric surgery where the prevalence of OSA approaches 70%.
○ OSA is undiagnosed, and subsequently untreated, in many patients, including those who are scheduled for surgery
What Are the Risk Factors
for the Development of OSA?
- Obesity.
- Advancing age – risk for development of OSA increases
from the third decade and peaks in 60–80-year-olds. - Males are more prone than females [9].
- Medical conditions – congestive heart disease, renal
failure, COPD, hypothyroidism, and polycystic ovarian
disease are some medical disorders that are associated
with an increased incidence of OSA. - Smoking – this is controversial. While the association is
plausible, the evidence is less than conclusive [10]. - Craniofacial abnormalities – more of a concern with chil-
dren, e.g., adenotonsillar hypertrophy, cleft lip/palate, and
abnormalities of the mandible or maxilla.
How Is OSA Diagnosed?
For a diagnosis of OSA, the American Academy of Sleep Medicine’s International Classification of Sleep Disorders (3rd edition) [11] requires either:
1. Signs and symptoms (e.g., associated sleepiness, insomnia, fatigue, snoring, observed apnea) or an associated medical or psychiatric disorder (e.g., hypertension, atrial
fibrillation, coronary artery disease, congestive heart failure, stroke, diabetes, mood disorder) coupled with an AHI of 5
or
2. AHI ≥ 15
○ The gold standard for measurement of AHI is a Level 1 sleep study (full-night polysomnography). This requires considerable resources including the attendance of a trained technician overnight in a sleep laboratory.
○ Level 1 studies capture multiple points of data: EEG (minimum of three channels), air flow, chin muscle tone, leg movement, eye movement, heart rate and rhythm, oxygen saturation, and chest and abdominal movement.
○ The technician observes live video feed of the subject and comments contemporaneously on the data being recorded.
○ Level 1 sleep studies provide a comprehensive assessment of changes occurring
during sleep.
○ Level 2 studies capture similar data to Level 1 studies but without the presence of a technician.
○ Level 3 studies use portable monitors which the patient can take home; they usually record at least three channels of data: oxygen saturation, air flow, and respiratory effort. ○ There are no EEG data to determine sleep or arousal. According to the American
Academy of Sleep Medicine Clinical Practice Guidelines, a Level 3 study (termed in the guideline “home sleep apnea testing”) is appropriate for the diagnosis of uncomplicated
adult patients thought to be at risk of moderate to severe sleep apnea.
○ Level 1 studies are recommended for those with “significant cardiorespiratory disease, potential respiratory muscle weakness due to a neuromuscular condition, awake hypoventilation or suspicion of sleep-related hypoventilation, chronic opioid medication use, history of stroke, or severe insomnia.”
○ Level 3 studies provide reasonable diagnostic accuracy compared to Level 1 studies in adult patients with a
high probability of OSA and no unstable comorbiditie
What Is Central Sleep Apnea (CSA)?
○ As distinct from OSA, an obstructive issue, CSA occurs as a consequence of lack of ventilatory drive. It accounts for <10% of patients referred for Level 1 sleep studies.
○ Examples include Cheyne-Stokes respiration (seen in patients with heart failure, dementia, and neuromuscular disorders) and the use of CNS depressants such as opioids, alcohol, and benzodiazepines.
○ OSA and CSA can be present in the same patient.
○ Level 1 studies are required to assess patients suspected to have CSA or combined OSA/CSA
How Is OSA Screened for Preoperatively?
○ A number of questionnaires and screening tools have been developed to identify patients at high risk of OSA. These screening tools tend to have higher sensitivity than specificity, i.e., a low score indicates that the patient is unlikely to have OSA, but a high score warrants further consideration for a sleep study.
1. STOP-Bang is a validated screening tool for pre-surgery patients (see Fig. 13.1). STOP is an acronym for Snoring, Tiredness, Observed apnea during sleep, and
high blood Pressure. Bang is an acronym for BMI > 35 kg m−2, Age > 50 years, Neck circumference >16 inches/40 cm, and male Gender.
- Patients with five or more positive responses are deemed to be high risk for OSA. It has a sensitivity of 93% and 100% for AHI > 15 and AHI > 30, respectively.
2. The Berlin questionnaire is comprised of questions on snoring, excessive daytime sleepiness, sleepiness while driving, hypertension, age, sex, and BMI. The questionnaire is meant to be self-administered and is not as straightforward as the STOP-Bang questionnaire, with a slightly reduced sensitivity of 87% for AHI > 30.
3. The Perioperative Sleep Apnea Prediction Score (P-SAP) was derived from an observational study of over 43,000 adult anesthesia cases.
○ Three demographic variables (age > 43 years, male sex, and obesity), three history
variables (snoring, diabetes mellitus type 2, and hypertension), and three airway measures (large neck circumference, Mallampati score 3 or 4, and reduced thyromental distance) were identified as independent predictors for a diagnosis of OSA.
What Percentage of Patients Who Screen
Positive for OSA with STOP-Bang Test
Positive with Sleep Studies?
A retrospective study by Guralnick et al. reported that, of 211
patients who screened high risk for OSA with STOP-Bang (≥5)
over a 2-year period, 2.5% did not have OSA, 16.1% had mild
OSA, 26.3% had moderate OSA, and 55.1% had severe OSA
on completion of a diagnostic polysomnogram
What Comorbidities Are Associated
with OSA?
• Cardiovascular complications, including hypertension,
coronary artery disease, arrhythmia, and stroke, are more
common in OSA [16, 17].
• Type 2 diabetes has been shown in a number of studies to
be independently associated with OSA [18, 19]. Several
possible explanations for this link have been posited,
including sympathetic activation, oxidative stress, inflam-
mation, and hypothalamic-pituitary-adrenal axis dysfunc-
tion [19].
• Pulmonary hypertension has been shown to occur to vary-
ing degrees in 20–40% of OSA patients in the absence of
other known cardiopulmonary disorders. Pulmonary
artery pressure (PAP) responds well to CPAP treatment in
these patients [20]. However, the elevation in PAP appears
to be mild (mean PAP of 20–30 mm Hg), similar to that
seen in COPD patients with pulmonary hypertension.
• Gastroesophageal reflux disease (GERD) is frequently
seen in OSA patients
How Can the OSA Patient Be Optimized
Preoperatively?
• Associated comorbidities should be assessed and
optimized.
• Compliance with preoperative use of CPAP, as prescribed,
should be emphasized.
• Consideration should be given to commencement of
CPAP therapy preoperatively in the newly diagnosed
OSA patient, particularly when OSA is severe.
• There is insufficient evidence to recommend weight loss
as a means of preoperative optimization
What Are the Perioperative Complications
of OSA?
• Cardiovascular complications
– OSA increases the risk of myocardial ischemia and infarction, arrhythmias, pulmonary embolism, and cardiac arrest. A large meta-analysis of 13 studies with almost 4000 patients demonstrated that the risk of a postoperative cardiac event was over twice as high in OSA patients [22].
• Respiratory complications
– OSA has been associated with difficult mask ventilation and intubation [23, 24]. This may be independent of BMI [25].
– Postoperative oxygen desaturation, respiratory failure requiring noninvasive or invasive ventilation, reintubation, acute respiratory distress syndrome (ARDS), and aspiration and bacterial pneumonia are seen with
increased frequency postoperatively in patients with OSA .
• Longer duration of stay
• Unanticipated ICU transfer
• Acute renal failure
• Delirium
What Circumstances May Exacerbate the Risk of Perioperative Complications Occurring in the OSA Patient?
○ Patients undergoing major surgery, general anesthesia, surgery requiring postoperative opioids, and those with higher grades of OSA may be at increased risk.
○ A scoring system developed by the American Society of Anesthesiologists (Table 13.2) can be useful in determining the overall risk of postoperative OSA-related complications, but it is not evidence-based or clinically validated
Is There Any Reason Why This Patient Should Not Have an Interscalene Brachial Plexus (ISBP) Block to Reduce Perioperative Opioid Use?
○ ISBP blockade, as a result of a concomitant phrenic nerve block, is associated with diaphragmatic hemiparesis, the incidence of which approaches 100%.
○ This is usually subclinical but may become problematic in the presence of chronic respiratory disease.
○ OSA patients with a predisposition toward postoperative hypoxia might be
considered at greater risk after ISBP block.
○ However, the benefit of avoidance or reduction of postoperative opioid analgesia must also be taken into account.
○ A large retrospective review of over 15,000 shoulder surgery patients who received ISBP blockade showed that the incidence of respiratory complications was similar in OSA and non-OSA populations. When particularly concerned about postoperative respiratory compromise, a low-volume block with a short-/medium-acting local anesthetic, e.g., lidocaine, can be injected as a bolus via an ISBP catheter followed by a continuous low-dose infusion.
○ This can be calibrated to the patient’s pain needs as tolerated.
What Factors Determine Whether Surgery
Should Be Performed on an Inpatient or
Outpatient Basis?
○ This decision must be individualized to each patient. Factors taken into consideration include OSA severity, invasiveness and nature of the surgery, presence of coexisting diseases, general versus regional anesthesia, postoperative opioid use, and patient age.
True/False
(a) The apnea-hypopnea index (AHI) is the number of episodes of complete or partial upper airway obstruction occurring per day.
(b) An AHI of 15–25 signifies severe sleep apnea.
(c) Males are more prone to OSA than females.
(d) OSA can be diagnosed with an AHI ≥ 15.
(e) Full-night polysomnography is never used in the diagnosis of OSA.
1a.F
1b.F
1c.T
1d.T
1e.F
- (a) The STOP-Bang screening tool is a highly sensitive
questionnaire for the diagnosis of OSA
(b) The STOP component of STOP-Bang is an acro-
nym for Snoring, Tiredness, Obesity, and high
blood Pressure
(c) CPAP therapy should not be commenced in newly
diagnosed OSA patients preoperatively.
(d) Pulmonary hypertension is seen in up to 40% of
OSA patients.
(e) Interscalene brachial plexus block is contraindicated
in OSA patients undergoing arthroscopic shoulder
surgery
2a.T
2b.F
2c.F
2d.T
2e.F
What Is COPD?
- COPD is a progressive inflammatory disease of the airways and/or alveoli.
- It is characterized by expired airflow limitation that arises because of chronic long-term exposure to smoke or occupational/environmental air pollution.
- Inhalation of smoke produced by combustible tobacco products is the key
risk factor in over 75% of cases. - Patients suffer from persistent respiratory symptoms, chronic and progressive dyspnea, which may be accompanied by cough and sputum production.
- The diagnosis of COPD is confirmed by spirometry (post-bronchodilator
FEV1/FVC < 0.7). - Due to the insidious nature of the disease, COPD-related symptoms, particularly dyspnea, are frequently underreported.
- Susceptibility to develop COPD is influenced by genetic factors, reduced intrauterine and childhood lung growth (low birth weight, prematurity, and exposure to smoke), and a history of airway hyperresponsiveness, particularly asthma
What Are the Pathophysiological Consequences of COPD?
- The chronic inflammatory process induces
(1) obstructive bronchiolitis, a narrowing and obstruction of small airways
with gas trapping during expiration leading to hyperinflation;
(2) emphysematous change, destruction of lung parenchyma with minimal fibrosis, breakdown of elastin (loss of elastic recoil), and remodeled enlarged acinar units with a reduced blood/gas exchange interface;
(3) mucus hypersecretion in some but not all individuals; and
(4) pulmonary vascular bed destruction and hypoxic vasoconstriction leading over time to pulmonary hypertension and right ventricular dysfunction.
How Is the Severity of COPD Assessed?
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) (https://goldcopd.org/) provides a structured process for quantification of disease status incorporating the Refined ABCD assessment tool (Fig. 14.3) [1]. This involves the following:
1. Determining the FEV1, the key ongoing metric for severity of airflow limitation.
Grades of airflow limitation range in severity from 1 to 4:
(a) GOLD 1 (mild) individuals have an FEV1 ≥ 80% of predicted values.
(b) GOLD 2 (moderate) 50% ≤ FEV1 < 80% predicted.
(c) GOLD 3 (severe) 30% ≤ FEV1 < 50% predicted.
(d) GOLD 4 (very severe) FEV1 < 30% of predicted.
2. Eliciting a history of exacerbation episodes in the previous 12 months.
An exacerbation of COPD is defined as an “acute worsening of respiratory symptoms that results in additional therapy” [1]. Exacerbations can be considered:
(a) Mild/moderate (treated medically out of hospital)
(b) Severe (hospital emergency room treatment or admission)
A history of two mild/moderate exacerbations or one severe exacerbation in the last 12 months places the patient in the severe, as opposed to the moderate, exacerbation category in the GOLD assessment schema.
3. Assessing symptom severity.
- Dyspnea is the most common presenting symptom of COPD.
- A simple well-validated measure of COPD-related dyspnea is the Modified Medical Research Council (mMRC) Dyspnea Scale.
- This scale involves self-assessment of breathlessness severity experienced during physical activities ranging from strenuous exercise to dressing and undressing.
- A score of ≥2 in the mMRC places the patient in the higher-risk groupings according to the GOLD assessment schema. A weakness of mMRC is the focus on dyspnea solely, exclusive of cough and sputum production.
What Is the Utility of GOLD Grading
and Grouping in the Perioperative Period?
COPD is underdiagnosed and undertreated in the commu-
nity. Appropriate pharmacological interventions decrease
symptoms and the risk and severity of exacerbations, also
reducing perioperative morbidity and mortality. The GOLD assessment structure allows the application of appropriate
treatment algorithms tailored to the stage of the disease in
the individual patient.
Furthermore, there is emerging evidence that GOLD
grouping can be helpful in predicting perioperative
complications. Patients in high-risk GOLD groups (C and D)
have been shown to be a higher risk of postoperative
complications, especially infection and wound issues, than
those in low-risk GOLD groups (A and B)
What Coexisting Conditions Should One
Consider in a Patient with COPD?
Lung cancer, cardiovascular diseases (especially right-sided
heart failure and coronary artery disease), obstructive sleep
apnea, gastroesophageal reflux disease (GERD), and depres-
sion are all associated with COPD and are important causes
of morbidity and mortality in this population.
What Are the Current Recommendations for Maintenance Bronchodilator and Steroid Therapy in COPD?
○ The GOLD groupings are very helpful in guiding pharmaological therapy in COPD.
- For group A (few symptoms and mild exacerbation history), a SAB, taken as needed, is indicated.
- For group B (more symptoms but mild exacerbation history), a LAB is suggested.
- For group C (few symptoms and severe exacerbation history), single or dual LAB is recommended ± inhaled steroid (IS).
- For group D (more symptoms and severe exacerbation history), dual LAB with IS ± roflumilast (a PDE-4 inhibitor) ± macrolide antibiotic therapy is recommended.
What Are the Causes of Interstitial Lung
Disease?
Causes of ILD are categorized according to whether the
underlying cause is known or unknown. A common approach
to classification of ILD is outlined in Fig. 16.1 [1]. IPF is the
commonest ILD of unknown cause.
