ABGs Practice
A pt on a mechanical ventilator has the following ABG results: pH 7.28, PaCO2 52 mmHg, HCO3 29 mEq/L. What is the primary acid-base imbalance and compensation status?
Partially Compensated Respiratory Acidosis
Rationale: pH of 7.28 is acidotic (<7.35), PaCO2 of 52 is acidotic (>45), HCO3 of 29 is alkalotic (>26). So because the CO2 is acidotic as well as the pH, the pt is in Respiratory Acidosis, and because the HCO3 is slightly alkalotic it shows that the kidneys are beginning to compensate, but not fully because the pH is still abnormal. So we have respiratory acidosis with metabolic alkalosis compensation.
When inspecting a three-chamber wet suction chest drainage unit, which chamber acts as a one-way valve allowing air to escape the pleural space while preventing outside air from entering/
The water seal chamber
Rationale: The water seal chamber contains 2 cm of sterile water, acting as a one-way valve that allows air or fluid to evacuate the pleural space while sealing against atmospheric backflow.
Why is the insertion of an oropharyngeal airway strictly contraindicated in an alert or semi-conscious pt?
Because it triggers the gag reflex, risking vomiting and aspiration
Rationale: An oropharyngeal airway depresses the tongue and is only tolerated by unconscious or heavily sedated pts who lack an intact cough/gag reflex. Conscious pts require a nasopharyngeal airway.
In which ventilator mode is a pre-set tidal volume delivered for every breath, whether machine-triggered or patient-initiated, placing the pt at risk for respiratory alkalosis?
Volume Assist/Control (V-A/C)
Rationale: In V-A/C, the vent delivers a set tidal volume every time the pt initiates a breath, if the pt hyperventilates or breathes rapidly, every breath receives full volume, blowing off excessive CO2.
What is the cardinal, defining diagnostic sign of Acute Respiratory Distress Syndrome (ARDS)?
Refractory Hypoxemia
Rationale: Refractory hypoxemia is severe arterial hypoxemia (PaO2) that fails to improve even when high concentrations of supplemental oxygen (FiO2) are administered, caused by extensive intrapulmonary shunting.
An ICU pt with severe COPD displays the following ABGs: pH 7.36, PaCO2 58 mmHg, HCO3 33 mEq/L. How should the nurse document this acid-base diagnosis?
Fully Compensated Respiratory Acidosis
Rationale: The pH of 7.36 is normal (7.35-7.45), but leans towards acidotic. PaCO2 of 58 (>45) is acidotic, and HCO3 of 33 (>26) is alkalotic. Because the pH is normal and both PaCO2 and HCO3 are abnormal, we are fully compensated. And because the CO2 is the most abnormal, our primary problem is respiratory with metabolic alkalosis compensation.
During palpation around a patient's chest tube insertion site, the nurse notes a soft, puffy texture that feels like "rice krispies" or bubble wrap popping under the skin. What is this clinical finding?
Subcutaneous Emphysema
Rationale: Subcutaneous Emphysema occurs when air leaks from the pleural space or insertion site into the surrounding subcutaneous tissue, creating a characteristic crunchy, crackling sensation upon palpation.
Immediately following an emergency endotracheal intubation, what diagnostic test must be obtained to confirm that the ETT tip rests safely above the carine?
Chest X-Ray
Rationale: While bilateral breath sounds and end-tidal CO2 provide initial bedside verification, a CXR is the definitive diagnostic standard to ensure proper depth and avoid right mainstem bronchus intubation.
What does a high pressure ventilator alarm signify, and what are three common patient-related causes?
Obstruction caused by excess secretions, biting/kinking the ETT, or coughing/bucking the vent
Rationale: High pressure alarms indicates increased airway resistance or obstruction. The nurse checks for kinks in the tubing, suctions secretions, or addresses pt fighting the vent.
Differentiate between direct vs. indirect etiologies of ARDS, giving two examples of each.
Direct: Aspiration, Pneumonia, Near-drowning
Indirect: Sepsis, Severe trauma, Pancreatitis, Fat embolism
Rationale: Direct injuries directly damage alveolar tissue (e.g., aspiration, lung contusion). Indirect injuries stem from systemic inflammatory mediators traveling through the bloodstream to damage pulmonary capillaries (e.g., sepsis, acute pancreatitis)
A pt experiencing septic shock and acute respiratory failure exhibits: pH 7.15, PaCO2 62 mmHg, HCO3 14 mEq/L. What complex acid-base condition does this represent?
Mixed Respiratory and Metabolic Acidosis
Rationale: Both the CO2 of 62 and the HCO3 of 14 are acidotic as well as the pH.
What are the only clinical situations where a chest tube may be clamped momentarily?
1. Locating the source of an unexpected air leak
2. Quickly changing out a full chest drainage unit
Rationale: Routine clamping is strictly prohibited because obstructing the drainage tube traps air and rapidly causes a tension pneumothorax. Clamping must only occur momentarily with padded hemostats.
What are the earliest clinical manifestations of tissue hypoxia that alert the nurse to prioritize airway and oxygenation interventions?
Restlessness, agitation, anxiety, tachycardia
Rationale: CNS changes (restlessness, apprehension) and sympathetic compensation (tachycardia) represent early hypoxia. Severe signs like cyanosis and bradycardia occur late in respiratory collapse.
If a ventilator's low-pressure alarm sounds and the nurse finds that the pt is completely disconnected from the circuit, what is the immediate nursing action is reconnecting fails?
Rationale: Whenever ventilator alarms cannot be immediately resolved or equipment malfunction is suspected, the nurse must manually ventilate the pt to ensure continuous gas exchange.
In which stage of ARDS (occurring after 10 days of lung injury) does progressive destruction of alveoli and severe decrease in lung compliance occur?
Stage 4: The Fibrotic Stage
Rationale: ARDS progresses through Stage 1 (Initial), Stage 2 (Exudative), Stage 3 (Proliferative, 2–10 days), and Stage 4 (Fibrotic, >10 days), where healthy tissue is replaced by dense fibrotic tissue, creating severe ventilation difficulties.
An ICU patient with severe, persistent diarrhea presents with the following arterial blood gas panel: pH 7.30, PaCO2 30 mmHg, HCO3 16 mEq/L. Name this acid-base diagnosis and compensation level.
Partially Compensated Metabolic Acidosis
Rationale: the pH of 7.30 is acidotic, the PaCO2 of 30 is alkalotic, and the HCO3 of 16 is acidotic. Because everything is abnormal, we have partial compensation, and since the HCO3 is acidotic with the pH, we have metabolic acidosis, with respiratory alkalosis compensation.
A confused pt accidentally pulls their pleural chest tube completely out of their chest wall. What is the nurse's immediate priority action?
Applying a sterile occlusive dressing taped on three sides over the insertion site
Rationale: Taping an occlusive dressing on 3 sides creates a flutter valve effect, allowing trapped air to escape during expiration while preventing atmospheric air from being sucked back in during inspiration.
What is the primary clinical goal when titrating oxygen settings on a ventilator, and why is an FiO2 > 60% for longer than 24 hours dangerous?
Minimizing FiO2 to a non-toxic level (<60%) to prevent oxygen toxicity
Rationale: Sustained exposure to high FiO2 (>60% for more than 24 hours) damages alveolar-capillary membranes, leading to tracheobronchitis, absorption atelectasis, and tissue inflammation.
What is a major cardiovascular complication that can result from applying high levels of Positive End-Expiratory Pressure (PEEP)?
Decreased cardiac output and severe hypotension
Rationale: High PEEP increases intrathoracic pressure, which compresses the vena cava, decreases venous return to the heart, lowers preload, and drops cardiac output and systemic blood pressure.
What are four key components of the Ventilator Care Bundle implemented to prevent Ventilator-Associated Pneumonia (VAP)?
1) Head of bed elevated 30°–45°
2) Daily sedation vacations & readiness to wean
3) Peptic ulcer disease prophylaxis
4) DVT prophylaxis (plus oral care q2h)
Routine morning lab work for a patient with chronic severe COPD reveals: pH 7.37, PaCO2 56 mmHg, HCO3 32 mEq/L. Name this acid-base diagnosis and compensation level.
Fully Compensated Respiratory Acidosis
Rationale: The pH has returned to normal range but is leaning acidotic, the PaCO2 of 56 is acidotic, the HCO3 of 32 is alkalotic. So because the pH has returned to normal, we are fully compensated, and since the CO2 is acidotic, the pt is in respiratory acidosis with metabolic alkalosis compensation.
How does the nurse distinguish between an expected finding versus an unexpected abnormality in the air leak chamber?
Fluctuation/Tidaling with respiration is expected, while continuous rapid bubbling indicated an air leak
Rationale: intermittent bubbling or tidaling (moving up and down with breathing) is expected as air evacuated or pleural pressure shifts. Continuous, constant bubbling signs a structural air leak in the system or pt connection.
A pt with end-stage COPD experiences acute exacerbation. Why must supplemental oxygen be titrated cautiously to maintain SpO2 between 88-92%?
To avoid suppressing their hypoxic drive for breathing
Rationale: Patients with chronic hypercapnia rely on low blood oxygen levels rather than CO2 levels to stimulate breathing so over-oxygenating them can cause hypoventilation and severe CO2 retention.
What is the cardinal nursing safety rule before administering a neuromuscular blocking agent (NMBA) like cisatracurium or vecuronium, and what is the target Train-of-Four (TOF) response?
ALWAYS sedating the patient first, and targeting 2 out of 4 twitches on Train-of-Four?
Rationale: Paralytics provide zero analgesia or sedation; paralyzing an awake patient causes extreme psychological trauma. TOF monitoring uses a peripheral nerve stimulator to verify 2/4 twitches for optimal neuromuscular blockade.
During a Spontaneous Breathing Trial (SBT), what are three specific clinical criteria that require the nurse to immediately abort the trial and return the patient to full ventilator support?
Respiratory Rate > 35, SaO2 < 90%, Tidal Volume < 5 mL/kg, HR > 20% from baseline or BP > 180/90 mmHg
Rationale: Signs of severe respiratory fatigue, hemodynamic instability, or dysrhythmias indicate that the patient is failing the weaning trial and must be returned to supportive settings immediately.