Intrapulmonary Shunting and Pneumonia Overview

Intrapulmonary Shunting

• Intrapulmonary shunting is a form of V/Q mismatch where blood reaches the arterial system without participating in gas exchange
• This occurs when blood passes through a portion of the lung that is not ventilated
• When intrapulmonary shunting exists, supplemental oxygen alone is ineffective
• The goal is to keep the arterial hemoglobin oxygen saturation greater than 90%
• Supplemental oxygen is effective in treating hypoxemia because of alveolar hypoventilation and V/Q mismatching
• PEEP helps open collapsed alveoli, stabilize flooded alveoli, and increases FRC
• PEEP decreases intrapulmonary shunting
• ECMO is similar to cardiopulmonary bypass where blood is removed from the body, pumped through a membrane oxygenator, where CO2 is removed and O2 is added, and returned to the body

Pneumonia

• Pneumonia is an acute inflammation of the lung parenchyma caused by an infectious agent which leads to alveolar consolidation
• The classifications of pneumonia include community-acquired pneumonia (CAP), nosocomial pneumonia (HAP), and ventilator-associated pneumonia (VAP)
• Contributing factors to the development of CAP include impaired swallowing, altered mental status, chronic obstructive pulmonary disease, and comorbid conditions such as diabetes, malignancy, and coronary artery disease
• Impaired swallowing and altered mental status result in increased exposure to various pathogens from the aspiration of oropharyngeal secretions
• HAP pathogens include Escherichia coli, H.influenzae, methicillin-sensitive S.aureus, S.pneumoniae, P.aeruginosa, Acinetobacter baumannii, methicillin-resistant S.aureus, Klebsiella spp., and Enterobacter spp.

Aspiration Lung Disorder

• Aspiration is the inhalation of foreign material, usually food or gastric secretions, into the lungs
• The aspiration of acid (pH less than 2.5) produces the most severe pulmonary reaction because of extensive pulmonary damage
• Aspiration of acid can cause severe hypoxemia, hypercapnia, and acidosis
• The aspiration of nonacid liquid (pH greater than 2.5) is similar to acid liquid aspiration initially, but minimal structural damage occurs
• Intrapulmonary shunting and V/Q mismatching usually start to reverse within 4 hours, and hypoxemia clears within 24 hours

Management of Aspiration Lung Disorder

• When aspiration is witnessed, immediate treatment is instituted to secure the airway and minimize pulmonary damage
• The patient’s head is turned to the side, and the oral cavity and upper airway are suctioned to remove gastric contents
• Direct visualization by bronchoscopy removes large particulate aspirate and confirms an unwitnessed aspiration
• Bronchoalveolar lavage is not recommended because it disseminates aspirate and increases damage
• Altering the patient's consciousness may be the result of deficits in awareness, arousal, or both
• The four discrete disorders of consciousness are (1) coma, (2) vegetative state, (3) minimally conscious state, and (4) locked-in syndrome
• Coma is characterized by the absence of both wakefulness and awareness

This quiz covers key concepts related to intrapulmonary shunting and pneumonia, including the mechanisms of gas exchange and treatments for hypoxemia. It addresses the implications of ventilation-perfusion mismatch and the classifications of pneumonia. Test your understanding of these critical pulmonary concepts.