High altitude pulmonary edema (HAPE) typically shows up in otherwise healthy patients after rapid ascent (e.g., mountain-climbing) with subsequent coughing, tachycardia, hypoxemia, and fatigue. These symptoms are often attributed to overexertion or dehydration, but it’s important to recognize the underlying physiology. At its core, altitude exposes the lung to hypoxia…
Silicosis is a chronic, progressive, fibrotic lung disease resulting from prolonged inhalation of respirable crystalline silica particles encountered by individuals working in sandblasting, mining, glass manufacturing, foundry operations, etc. Once inhaled, silica particles deposit deeply within the alveoli, triggering alveolar macrophages to release pro-inflammatory cytokines, thereby inciting persistent inflammation and…
B-lines are a vertical “comet-tail” artifact seen on lung ultrasound. They represent interstitial edema or increased lung water in thickened subpleural interlobular septa. In other words, B-lines represent fluid in the lungs (e.g., pulmonary edema, heart failure, etc.). When performing lung ultrasound, I use a high-frequency linear probe and begin…
A “miliary pattern” on chest x-ray (CXR) is a distinctive finding characterized by numerous small (1-4 mm) nodules, typically uniform in size and distributed throughout both lung fields, resembling millet seeds – hence the term “miliary.” Miliary patterns are most commonly associated with the hematogenous spread of diseases, including infection…
Unilateral cardiogenic pulmonary edema (CPE) accounts for ~2% of pulmonary edema cases and is classically caused by posterior papillary muscle rupture, resulting in acute, severe, eccentric mitral regurgitation. Flow is directed specifically to the right-sided pulmonary veins. This, in turn, overwhelms the lymphatic capacity of the right lung and results…
Permissive hypercapnia (PHC) is a deliberate and controlled elevation in carbon dioxide (CO2) during mechanical ventilation to limit over-distention of the lung and ventilator-induced lung injury (VILI) by reducing inspiratory pressures. This can often lead to a PaCO2 of 50-80 mmHg depending on the patient and situational factors with acute…
Artificial manual breathing unit (“Ambu”) bags are seen throughout healthcare to facilitate mask ventilation or ventilation through an indwelling endotracheal/tracheostomy tube. Pictured is an adult Ambu® SPUR® II resuscitator bag. Based on the manufacturer’s specifications, this Ambu bag has a resuscitator (“bag”) volume of ~1547 mL (~600 mL delivered with…
Driving pressure (Pdriving) is related to tidal volume (VT) and the respiratory system’s static compliance (Crs). At the bedside, Pdriving = plateau pressure (Pplat, determined by an inspiratory hold maneuver) minus PEEP. Based on the boxed equation in the diagram and assuming all other variables remain constant, increasing VT or…
In a conventional spontaneous/timed (S/T) mode, one directly sets an inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) to address issues with ventilation and oxygenation, respectively. Remember, pressure support = IPAP – EPAP. In contrast, average volume assured pressure support (AVAPS) is a mode with variable pressure…
Saddle pulmonary embolism (SPE) is a severe and life-threatening condition when a blood clot (embolus) becomes lodged in the main pulmonary artery, blocking blood flow to both lungs. The term “saddle” refers to the shape of the clot, which straddles the bifurcation of the pulmonary artery, resembling a saddle. The…