[Giant lobar emphysema. The cause of a compressive hemithoracic opacity in a newborn infant]

In terms of human respiration, the act of expelling air, known as exhalation (or expiration), operates on the principle of pressure gradients. During expiration, the pressure within the lungs exceeds that of the surrounding atmosphere. Under normal conditions, quiet breathing involves passive exhalation and is free of muscular contractions. This is because the exhalation process is driven by the natural elastic recoil of the lungs and chest wall, both of which have an inherent tendency to...

Type I Respiratory Failure, or hypoxemic respiratory failure, occurs when the partial pressure of oxygen (PaO2) in arterial blood falls below 60 mmHg while breathing room air without a corresponding increase in arterial carbon dioxide levels (PaCO2). This condition highlights a significant impairment in the lungs' capacity to oxygenate the blood.
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:

A pneumothorax is a condition where air builds up in the space between the lung and the chest wall, causing the lung to collapse. This condition arises when air enters the space between the parietal and visceral pleura, disrupting the negative pressure essential for lung inflation. This can lead to a partial or complete collapse of the lung.
Pneumothorax can be even further classified as spontaneous, traumatic, and tension pneumothorax.

Pulmonary embolism (PE) occurs when a thrombus, fat or air embolus, amniotic fluid, or tumor tissue blocks one or more pulmonary arteries. These blockages originate in the venous system or the right side of the heart.EtiologyPE primarily arises from deep vein thrombosis (DVT) and other hypercoagulable states, such as inherited thrombophilias. Additional etiological factors include venous stasis, commonly seen in obesity, and endothelial injury from surgery and trauma. Less common causes include...

Atelectasis develops when alveoli lose their air and collapse inward. Because lung tissue is naturally elastic, these air sacs shrink rather than remaining open. Collapsed alveoli are no longer ventilated, reducing their role in gas exchange. Blood flow may continue in these regions, creating a ventilation–perfusion mismatch. Clinical findings include decreased breath sounds, dullness to percussion, reduced chest expansion, and decreased tactile fremitus as sound transmission through collapsed...

Emphysema, a major phenotype of chronic obstructive pulmonary disease (COPD), is characterized by irreversible destruction of alveolar walls and permanent enlargement of distal airspaces. Unlike chronic bronchitis, which primarily affects the airways, emphysema predominantly involves the lung parenchyma, where structural damage leads to airflow limitation.PathophysiologyIt most commonly results from prolonged exposure to cigarette smoke and other toxic gases, particularly cigarette smoke.