Question

After assisting with bronchoalveolar lavage and lung biopsy on a mechanically ventilated patient, the respiratory therapist notes the activation of a high pressure alarm. Peak inspiratory pressure has increased from 32 cm H2O before the procedure to 45 cm H2O after the procedure. Possible causes for the increased pressure include

1. bronchospasm.
2. pneumothorax.
3. pulmonary hemorrhage.

Answer 1

Increased airway resistance can result in more negative intrapleural pressure during inhalation due to the body working harder against resistance. A puncture to the thoracic cavity interrupts the negative pressure needed for lung expansion, leading to a pneumothorax which impairs breathing. The option (2) is correct.

Step-by-step explanation:

Increased airway resistance can affect intrapleural pressure during inhalation by making it more negative if the body works harder to draw air in against the resistance. This is because inhalation is an active process that requires the diaphragm to contract and create a negative pressure within the pleural space to allow air to flow into the lungs. If airway resistance is increased, for instance, due to bronchospasm, there is more negative pressure required to inhale the same volume of air, potentially leading to higher intrapleural pressures (more negative).

A puncture to the thoracic cavity, such as from a knife wound, can drastically alter the ability to inhale by causing a pneumothorax, where air enters the pleural space. This disrupts the normal negative pressure that is necessary for lung expansion during inhalation. Instead of creating a negative pressure that helps draw air into the lungs, the breach in the thoracic wall equalizes the intrapleural and atmospheric pressures, preventing the lungs from expanding properly and resulting in impaired breathing. Therefore, option (2) is correct.