ATI LPN
Introduction of Respiratory System NCLEX Questions PN Questions
Question 1 of 5
In the presence of active surfactants, all of the following are expected to decrease EXCEPT?
Correct Answer: B
Rationale: Surfactant lowers alveolar surface tension (C) from 30 dynes/cm to 5, reducing collapse tendency (A) and work of breathing. Lung compliance (B) increases (normal 0.2 L/cm H2O to 0.5), not decreases, as expansion eases. In 300 million alveoli, surfactant's dipalmitoylphosphatidylcholine stabilizes, countering Laplace's law (P = 2T/r). B's rise unlike A's or D's fall enhances ventilation efficiency, per physiology (Q29).
Question 2 of 5
If dead space is one third of the tidal volume and arterial PCO2 is 45 mmHg, what is the mixed expired PCO2?
Correct Answer: B
Rationale: Mixed expired PCO2 (PECO2) is 30 mmHg. If Vd = Vt/3, then Va = 2Vt/3. Bohr's equation: Vd/Vt = (PaCO2 - PECO2) / PaCO2. Given PaCO2 = 45 mmHg, Vd/Vt = 1/3 → 1/3 = (45 - PECO2) / 45 → PECO2 = 45 - 15 = 30 mmHg. PECO2 reflects alveolar (40 mmHg) and dead space (0 mmHg) mix. B's 30 unlike A's 20 or D's 45 fits 1/3 dead space dilution, per gas mixing physiology (Q12).
Question 3 of 5
Which of the following is not correct regarding exhalation (expiration)?
Correct Answer: D
Rationale: Exhalation doesn't start with expiratory muscle relaxation. Passive expiration (A) uses lung recoil (C, true, -5 cm H2O intrapleural). Active expiration (B) engages muscles (e.g., abdominals). D's trigger relaxation fits inspiration's end; expiration begins when inspiratory muscles (diaphragm) relax, raising pressure (+1 mmHg). COPD hinders expiration (E, true, Q65). D's error unlike A's norm misaligns timing, per physiology.
Question 4 of 5
In primary atypical (presumably viral) pneumonia the most common of the following blood findings is:
Correct Answer: C
Rationale: Cold agglutination (C) is the most common blood finding in primary atypical pneumonia, often viral (e.g., Mycoplasma pneumoniae). This autoimmune reaction antibodies clump RBCs at low temperatures reflects infection-induced immune activation, detectable in 50-70% of cases. Leucocytosis (A) suits bacterial pneumonia, not viral, where counts are normal or low. Sheep RBC agglutination (B) isn't standard; cold agglutinins are specific. Secondary anemia (D) may occur late, not primarily. Latex fixation tests rheumatoid factor, unrelated here. Cold agglutinins, peaking in week 2-3, aid diagnosis when sputum or x-rays are inconclusive, distinguishing atypical from bacterial pneumonia in clinical hematology.
Question 5 of 5
Which of the following is not generally a cause of a pleural exudate:
Correct Answer: A
Rationale: Congestive heart failure (A) causes transudative, not exudative, pleural effusion fluid from hydrostatic pressure (e.g., left heart failure) has low protein (<3 g/dL), not inflammation-driven. Bacterial pneumonia (B), malignancy (C), myocardial infarction (D e.g., Dressler's), and influenza A (E post-viral) produce exudates high protein (>3 g/dL), often bloody or purulent, from capillary leak or infection. CHF's transudate contrasts with exudative etiologies, key in Light's criteria (e.g., pleural/serum protein ratio), guiding thoracentesis interpretation in chest nursing.