Table of contents
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Airflow Limitation
Taken from JAMA rational clinical exam series:
- Physiology:
- Airflow limitation resting airway diameter is abnormally small. This leads to a decrease in tethering forces Airflow limitation can occur due to a variety of reasons:
- Emphysema: the lung parenchyma is destroyed. This causes a decrease in the tethering forces that keep the airway open.
- Asthma: smooth muscle around the area is hyperreactive to stimuli.
- Chronic bronchitis: Increased mucous production in the airways leading to decreased airway diameter.
- It is significantly more difficult to empty lungs than to fill them due to natural physiologic decrease in airway diameter on expiration. This leads to air trapping and hyperinflation.
- Airflow limitation resting airway diameter is abnormally small. This leads to a decrease in tethering forces Airflow limitation can occur due to a variety of reasons:
- History:
- Background Info
- Exposure to sigarette smoke (≥70 pack-yrs LR+ 8.0, never smoked LR- 0.16)
- UPDATE: >40 pak years of smoking is a single best historical feature.
- Length of smoking works as least as well as pack years (studied).
- Occupational & Environmental pollutants.
- Personal/family history of atopic diseases.
- Age: (AL is not part of normal aging process!!, but age is proxy for toxin/smoke exposure).
- Exposure to sigarette smoke (≥70 pack-yrs LR+ 8.0, never smoked LR- 0.16)
- Symptoms:
- Wheezing, coughing, sputum production.
- Sputum production ≥1/4 cup (LR+ 4)
- Wheeze (LR+ 3.8)
- (No symptom useful for ruling-in or ruling-out).
- Chronic bronchitis: sputum production for at least 3 consecutive months in at least 2 years.
- Wheezing, coughing, sputum production.
- Background Info
- Exam:
- Inspection
- Cough? (intermittent, poor k=0.29)
- Look for A-P diameter (very specific, esp in children Sp 99%)
- Vital signs:
- Pulsus Paradoxus (Sn 45%, Sp 88% - most sensitive 2nd to Match test)
- During tidal breathing, BP cuff inflated above systolic. Slowly deflate until hear sound only during expiration, continue to deflate until hear during inspiration.
- Expiration BP > Inspiration BP
- ≥15mmHg differnece = positive.
- Pulsus Paradoxus (Sn 45%, Sp 88% - most sensitive 2nd to Match test)
- Palpation
- Palpate cardiac apex (in hyperinflation apex shifts centrally). (LR 4.6 specific, not sensitive, useful if present)
- Either cannot palpate or palpate centrally in subxiphoid.
- Palpate cardiac apex (in hyperinflation apex shifts centrally). (LR 4.6 specific, not sensitive, useful if present)
- Percussion
- Hyperresonance? (very precise, and quite accurate. LR+ 4.8 LR-0.73, Sn 32% Sp94%. one of most sensitive tests).
- Diaphragmatic Excursion (normal 5-6cm, decreased in COPD)
- Auscultation
- Auscultate bilaterally over lower, middle, and upper lung fields posteriorly, anteriorly, and along mid-axillary line.
- Types of sounds:
- Wheezing - high pitched musical tones during expiration. (most precise, Sn 15%, Sp 99.6%, rules in if heard!)
- Rhonchi - Lower pitched wheeze
- Intensity of breath sounds (scoring systems are poor). (less precise k=0.30-0.63)
- Measures of airflow:
- Forced Expiratory Time:
- Take deep breath and forcefully exhale until no more air can be expelled. (keep mouth + glottis open as if yawning).
- Listen over larynx or trachea with stethoscope the duration of airflow (measure with stopwatch, record to 0.1s).
- Can do multiple measurements and average
- Results:
- <6 seconds --> decrease in likelihood of AL (LR+ 0.45)
- 6-9s --> great increase in likelihood of AL (LR+ 2.7)
- 9s --> FEV1/FVC of 70%, a level that dx an airflow limitation. (LR+ 4.8)
- Match test
- Hold burning match at 10cm from pt's widely opened mouth. If match is still burning w/ forced expiration --> positive.
- DO NOT DO if patient is on O2.
- Peak Flow Meter:
- Only useful in assessing response to therapy.
- Studies: only improved accuracy of clinical exam for 1 of 4 MDs studied. Was equivalent to auscultating a wheeze.
- Forced Expiratory Time:
- Inspection
Does this patient have clubbing?
- Conditions associated:
- Neoplastic intrathoracic:
- Bronchogenic carcinoma
- Malignant mesothelioma
- Pleural Fibroma
- Mestastatic osteogenic sarcoma
- Suppurative intrathoracic disease
- Lung Abscess
- Bronchiectasis
- Cystic Fibrosis
- Empyema
- Chronic cavitary mycobacterial or fungal infection
- Diffuse pulmonary disease
- IPF
- Asbestosis
- Pulmonary AV malformations
- CV Disease
- Cyanotic congenital heart disease
- Infective endocarditis
- Arterial graft sepsis
- Brachial AV fistula
- Hemiplegic stroke
- GI
- IBD
- Celiac Disease
- Hepatobiliary Disease
- Cirrhosis (particularly biliary and juvenile)
- Metabolic
- Thyroid acropachy
- Neoplastic intrathoracic:
- How to measure clubbing:
- 1. General Appearance
- 2. Nailfold angles (normal nail comes out at 160°, but in clubbing it is 180° or more.
- 3. Phalangeal Depth Ratio (Normal Distalphalangeal finger depth DPD < interphalangeal depth (IPD)
- Normal DPD < IPD
- Clubbing DPD >IPD
- 4. Schamroth Sign (Diamond)
- Very little clinical testing of this.
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