Alan Hall
2/3/09
Case 1: Mr. Jackson’s Broken Hip, Objective 11
Learning Objective: Define and summarize causes of wheezing. Review the physical properties of airflow through a tube. Briefly assess the impact of Mr. Jackson’s
cardiopulmonary status on gas exchange.
Wheezing:
 Wheeze- an adventitious sound that is continuous and musical and lasts longer than 250 msec, typically high-pitched
o Produced by vibrations of airway walls and turbulent airflow in partially obstructed airways of all sizes
 Inspiratory and polyphonic wheezes are more common with larger airway obstruction
o Stridor- specific inspiratory wheeze, loudest over central airways
 Expiratory and monophonic wheezes are more common with smaller airway obstruction
o Often accompanied by prolonged expiration
Causes of Wheezing:
Extrathoracic Upper Airway
Intrathoracic Upper Airway
Lower Airway Obstruction
Obstruction
Obstruction
1. Postnasal Drip
1. Tracheal Stenosis
1. Asthma
2. Hypertrophied Tonsils
2. Foreign Body Aspiration
2. COPD
3. Laryngeal Edema
3. Tumors
3. Pulmonary Edema
4. Retropharyngeal Abscess
4. Intrathoracic Goiter
4. Pulmonary Embolism
5. Obesity
5. Right sided aortic arch
5. Bronchitis
6. Bilateral Vocal Cord Paralysis
6. Bronchiectasis
7. Tumors
Physical Properties of Airflow through a Tube:
 Poiseuille’s Law (for laminar flow)
o Flow = ∆P(πr4/8nl)
(P = pressure, r = radius, l = distance, n = viscosity)
th
o Radius is raised to 4 power, so small changes in radius can cause large direct changes in flow
 Example: If an airway is narrowed from 4 to 2 cm then airflow is reduced from 256 to 16 ml/min
o Can be very important in obstructive lung diseases like asthma/COPD, where this narrowing can lead to wheezing
 With airway intubation, the length of the tube and radius of the tube are important
o As length increases, airflow decreases by the same factor + same radius changes as above
Relevance to Case:
 Poiseuille’s Law helps explain how small changes in airway radii can lead to large flow changes, which in Mr. Jackson’s case
helps explain how the airway obstruction from his COPD can lead to wheezing + prolonged expiration
 Mr. Jackson was intubated in OR, and Poiseuille’s Law is especially useful in thinking about flow in regards to length and radii
of endotracheal tubes
Cardiopulmonary Status on Gas Exchange in Mr. Jackson:
 ABG: pH=7.36 (N), PaCO2=49 (H), PaO2=65 (L), HCO3=32 (H)
o pH is normal, PaCO2 is elevated -> respiratory acidosis (R.A.)
 With chronic respiratory acidosis, HCO3 should increase 3.5meq/L for every 10 mmHg increase in PCO2
 HCO3 should only be ~27.5 (24 + 3.5), so there must be another disorder present- two options below
1. Acute alveolar hyperventilation superimposed on chronic ventilatory failure (COPD causing compensated chronic R.A.)
 Superimposed hyperventillation after trauma (with RR of 24)would help blow off some CO2, lowering PaCO2,
causing pH to increase to normal range, while HCO3 remains elevated
2. or Mixed: primary compensated chronic R.A. (COPD) and secondary metabolic alkalosis
 Metabolic alkalosis- possible hypovolemic contraction alkalosis- elderly after fall, along with Furosemide use
 Hypoxemia and hypercarbia can be explained by COPD – with airway inflammation, increased mucus production, alveolar
destruction, and increased lung compliance that can all affect gas exchange
References:
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Irwin RS, Barnes PJ, Hollingsworth H. Diagnosis of wheezing illnesses other than asthma in adults. UptoDate.com (Sept. 2009).
Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL, Loscalzo J. Harrison's principles of internal medicine (17th ed.). New York: McGraw-Hill Medical Publishing Division. 2009.
Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. Saunders 7 ed. 2004.
Loudon R, Murphy RLH. Lung sounds. Am Rev Respir Dis 1984; 130:663.
Richardson DR, Randall DC, Speck DF. Cardiopulmonary Physiology, Second Edition. Hayes-Barton 2nd ed. 2005.
U.S. Public Health Service National Heart, Lung and Blood Institute. Global Initiative for Chronic Obstructive Lung Disease: Global Strategy for the Diagnosis, Management, and Prevention of
Chronic Obstructive Pulmonary Disease, 2004. www.goldcopd.com. Last updated: 2009.