Term of the Day

Alveolar Ventilation: The portion of tidal volume that actually reaches the alveoli of the lungs. During exhalation, part of this gas remains in the conducting airways and re-enters the alveoli with the next inhalation.

Case Study -- A Simple Case of Pneumonia?

O.K. ladies and gents, time to play Dr. House! We'll start with a relatively simple case of pneumonia...

Patient A presents to the emergency room with symptoms of pneumonia, including cough, dyspnea, and hemoptysis. X-ray confirms the presence of diffuse infiltrates in the right lung, and on physical examination, hypoventilation and hypotension are noted. The history reveals that, prior to the pneumonia, the patient had not experienced any respiratory symptoms of any kind. The patient did report, however, that he had been experiencing a mild, stabbing chest pain 10-15 seconds after swallowing food or liquids, and often found it difficult to swallow. He reported that if he "bore down" as if he were defecating, swallowing was usually easier. The problem was worse when he had to eat in a hurry, and he said food sometimes "went down the wrong pipe" producing coughing fits. He had been experiencing this for months, and had tried managing his own symptoms using Maalox, without any real success -- the problem seemed to be getting worse. He reported a particularly bad episode of regurgitation and coughing the day before his breathing problems started.

What kind of pneumonia does A have? Is pneumonia the real underlying problem here? If not, what is/are the likely diagnosis(es)? What test would you order next? What "sign" would you be looking for on this test?

Term of the Day

Cor Pulmonale: Right ventricular enlargement (hypertrophy, dilation, or both) secondary to pulmonary hypertension. Increased afterload (pressure in the pulmonary trunk) leads to chronic pressure overload in the right ventricle, thus increasing the work it must do. The right ventricle ultimately fails when pulmonary artery pressure equals systemic blood pressure.

Term of the Day

Hypersomnia Sleep Apnea (HSA) Syndrome: Periodic breathing and episodes of apnea (absence of air flow for at least 10 seconds during sleep) associated with stage I and II and REM sleep. Decreased arterial oxygen saturation leads to arousal, thus interrupting the sleep cycle and leading to sleep and REM deprivation. HSA syndrome is mainly the result of upper airway obstruction occurring during sleep. Patients may experience hundreds of episodes of apnea per night, which leads to extreme daytime sleepiness. Snorting and thrashing about during sleep are common, and some patients may experience sleepwalking or enuresis.

Term of the Day

Forced Vital Capacity: The maximum amount of air that can be forcefully and rapidly exhaled after a deep breath (maximal inspiration); approximately 5.0 L (5000mL) for an adult male (can be up to 7.0 L in well-trained athletes or as low as 3.0 L in an asthmatic).