NLE Respiratory Nursing — Acute Respiratory Failure & ARDSDetailed Explanation

Acute Respiratory Failure: Definition and Types

Acute respiratory failure (ARF) occurs when the lungs can no longer maintain adequate gas exchange to meet the body's metabolic demands. It is defined by arterial blood gas (ABG) values rather than clinical appearance alone. There are two primary types: **Type I — Hypoxaemic Failure (Oxygenation Failure):** - Defined as PaO2 < 60 mmHg on room air. - The problem is the lung's inability to LOAD oxygen into the blood. - Think of the lung as a loading dock that cannot get oxygen onto the 'trucks' (red blood cells). - Common causes: Pneumonia, ARDS, pulmonary oedema, pulmonary embolism, atelectasis. - PaCO2 is often normal or even LOW (because the patient hyperventilates to compensate). **Type II — Hypercapnic Failure (Ventilation Failure):** - Defined as PaCO2 > 50 mmHg WITH pH < 7.35 (respiratory acidosis). - The problem is the lung/respiratory pump's inability to REMOVE carbon dioxide. - Think of a factory that cannot exhaust its waste gases — CO2 builds up. - Common causes: COPD exacerbation, opioid/sedative overdose, neuromuscular diseases (Guillain-Barré, myasthenia gravis), chest wall deformities, severe asthma (late stage). - Hypoxaemia is also present because CO2 displaces oxygen in the alveoli. **Why this distinction matters in the NLE:** The TYPE of failure determines your oxygen delivery strategy. Giving high-flow oxygen to a COPD patient (Type II) who relies on hypoxic drive can suppress their breathing stimulus — so controlled, low-flow O2 (targeting SpO2 88–92%) is used. For Type I, you give the highest FiO2 needed to correct hypoxaemia.

Pathophysiology of Respiratory Failure: V/Q Mismatch and Shunting

Understanding WHY oxygenation fails requires knowing the four main mechanisms. This is tested in the NLE and helps you understand ARDS and PE as well. **1. Ventilation-Perfusion (V/Q) Mismatch (Most Common Mechanism):** - Normal V/Q ratio = ~0.8 (ventilation and perfusion are well-matched) - V/Q MISMATCH occurs when some areas of the lung are ventilated but not perfused (dead space — as in PE: blood cannot reach the ventilated alveolus) OR perfused but not ventilated (shunt — as in pneumonia: blood passes unoxygenated alveoli) - Result: blood leaving the lung is poorly oxygenated - Responds to supplemental oxygen (except in pure shunt) **2. Intrapulmonary Shunt (True Shunt):** - Blood flows through the pulmonary capillaries but the alveoli are COMPLETELY COLLAPSED or FILLED with fluid - No opportunity for gas exchange at all - Classic in ARDS, severe pneumonia, pulmonary oedema - KEY FEATURE: DOES NOT RESPOND to supplemental oxygen — this explains the 'refractory hypoxaemia' of ARDS - Think of it as blood taking a 'detour' that bypasses all the oxygen **3. Diffusion Impairment:** - The alveolar-capillary membrane is thickened (fibrosis, pulmonary oedema) - Oxygen cannot diffuse across the thickened membrane efficiently - Seen in interstitial lung disease, early pulmonary oedema **4. Hypoventilation:** - Insufficient breathing to exchange gases — CO2 accumulates, O2 drops - Seen in Type II failure (opioid overdose, COPD, neuromuscular disease) - Responds well to increased ventilation (manual bagging, BiPAP, intubation) **Clinical Pearl:** The HALLMARK of ARDS is refractory hypoxaemia caused by SHUNTING — the hypoxaemia does NOT improve with O2 supplementation because the alveoli are flooded. This is the single most tested physiological fact about ARDS.

ARDS: Pathophysiology, Recognition, and Nursing Management

Acute Respiratory Distress Syndrome (ARDS) is a life-threatening condition requiring ICU-level care and is a high-priority NLE topic. Memorize its hallmarks and management principles. **Definition and Triggers:** ARDS is a SEVERE, ACUTE, DIFFUSE INFLAMMATORY LUNG INJURY. It is triggered by an initial insult — most commonly SEPSIS (the #1 cause), but also aspiration of gastric contents, trauma, pancreatitis, near-drowning, massive blood transfusion, and inhalation injury. **Pathophysiology (Step by Step):** 1. Trigger event (e.g., sepsis, aspiration) causes systemic/local inflammation 2. Inflammatory mediators (cytokines, neutrophils) damage the ALVEOLAR-CAPILLARY MEMBRANE 3. The membrane becomes LEAKY — protein-rich fluid floods the alveoli (non-cardiogenic pulmonary oedema) 4. SURFACTANT is destroyed → alveoli collapse (atelectasis) 5. Lung compliance DROPS drastically ('stiff lungs') — the patient works extremely hard to breathe 6. Massive intrapulmonary SHUNTING → REFRACTORY HYPOXAEMIA **Berlin Definition (2012) — Remember for NLE:** - Onset: Within 7 days of known clinical insult OR new/worsening respiratory symptoms - Bilateral opacities on chest X-ray not fully explained by effusions, collapse, or nodules - Respiratory failure NOT fully explained by cardiac failure or fluid overload (non-cardiogenic) - PaO2/FiO2 ratio: Mild = 200–300 mmHg; Moderate = 100–200 mmHg; Severe <100 mmHg **Clinical Manifestations:** - RAPID onset of SEVERE DYSPNOEA (hours to days after the trigger) - TACHYPNOEA with accessory muscle use - REFRACTORY HYPOXAEMIA — SpO2 does not improve with O2 (the HALLMARK) - BILATERAL CRACKLES on auscultation - Anxiety, restlessness, confusion (hypoxia effects on the brain) - Chest X-ray: DIFFUSE BILATERAL 'WHITE-OUT' OR 'GROUND GLASS' INFILTRATES - ABG: EARLY = Respiratory Alkalosis (hyperventilating) → LATE = Respiratory Acidosis (exhaustion) **Nursing Management (Priority Order):** 1. AIRWAY & OXYGENATION FIRST — nearly ALL ARDS patients require INTUBATION and MECHANICAL VENTILATION with PEEP 2. PEEP (Positive End-Expiratory Pressure): Keeps alveoli open at end-expiration, recruits collapsed alveoli, REDUCES SHUNTING, improves oxygenation — THE CORNERSTONE of ARDS ventilation 3. LUNG-PROTECTIVE VENTILATION: Low tidal volume (~6 mL/kg predicted body weight) to PREVENT VOLUTRAUMA and BAROTRAUMA 4. PRONE POSITIONING: Placing the patient face-down improves V/Q matching by redistributing blood flow to better-ventilated dorsal lung regions 5. TREAT THE UNDERLYING CAUSE (antibiotics for sepsis, etc.) 6. FLUID MANAGEMENT: Conservative fluids to prevent worsening pulmonary oedema 7. PREVENT COMPLICATIONS: VAP bundle, DVT prophylaxis, stress ulcer prophylaxis, skin care **Key Nursing Diagnoses (NANDA-I):** - Impaired Gas Exchange r/t alveolar-capillary membrane damage - Ineffective Breathing Pattern r/t decreased lung compliance - Risk for Infection r/t invasive mechanical ventilation - Anxiety r/t dyspnoea and inability to communicate

Pulmonary Embolism (PE): Recognition, Diagnostics, and Management

Pulmonary embolism is a sudden, life-threatening obstruction of the pulmonary vasculature — most commonly by a thrombus that originated in the deep veins of the legs (DVT) and traveled to the lungs. It is one of the most preventable causes of in-hospital death in the Philippines and worldwide. **Pathophysiology:** - A clot (thrombus) forms in a deep vein — usually the legs or pelvis - The thrombus dislodges, travels through the right heart, and lodges in a pulmonary artery - The blocked artery creates DEAD SPACE (ventilated lung with no blood flow) - Reflex bronchoconstriction and vasoconstriction worsen the V/Q mismatch - MASSIVE PE: Obstructs >50% of pulmonary circulation → acute right heart failure → obstructive shock → cardiac arrest **Virchow's Triad — Risk Factors for Thrombosis (HIGH-YIELD):** 1. VENOUS STASIS: Prolonged immobility, bed rest, long airplane/bus rides, post-surgical patients, obesity 2. HYPERCOAGULABILITY: Cancer, pregnancy, oral contraceptives, dehydration, inherited clotting disorders, polycythaemia 3. ENDOTHELIAL INJURY: Surgery, trauma, central venous catheters, infection **Clinical Manifestations:** - CLASSIC SUDDEN ONSET: DYSPNOEA (#1 most common symptom), PLEURITIC CHEST PAIN (sharp, worsens with inspiration), TACHYPNOEA, TACHYCARDIA - 'SENSE OF IMPENDING DOOM' or profound anxiety — classic NLE descriptor - Haemoptysis (blood-streaked sputum) - Low-grade fever - MASSIVE PE: Hypotension, syncope, cyanosis, severe right heart strain → emergency! - DVT signs (often coexisting): Unilateral calf swelling, warmth, redness, tenderness (Homan's sign — unreliable but sometimes tested) **Diagnostics:** - CTPA (CT Pulmonary Angiography) = GOLD STANDARD confirmatory test - D-DIMER: Sensitive but NOT specific. NORMAL D-dimer RULES OUT PE in low-risk patients. High D-dimer does NOT confirm PE. - ABG: Hypoxaemia + Respiratory ALKALOSIS (low PaCO2 from hyperventilation) — classic pattern - CXR: Often normal; may show Hampton's hump (wedge-shaped opacity) or Westermark sign (oligaemia) - ECG: Usually shows sinus TACHYCARDIA; the classic 'S1Q3T3' pattern is uncommon - Ventilation-Perfusion (V/Q) SCAN: Alternative if CTPA contraindicated (e.g., renal failure) **Nursing Management Priority Order:** 1. OXYGEN immediately (non-rebreather or intubation if severe) 2. ELEVATE HEAD OF BED to ease breathing 3. STAY WITH THE PATIENT — reassure, monitor continuously 4. IV ACCESS and hemodynamic monitoring 5. Prepare for ANTICOAGULATION (treatment of choice) 6. THROMBOLYTICS (e.g., alteplase) ONLY for MASSIVE PE with haemodynamic instability 7. IVC FILTER if anticoagulation is contraindicated **PE PREVENTION — Heavily Tested in the NLE:** - EARLY AMBULATION post-surgery - COMPRESSION STOCKINGS (thromboembolic deterrent / TED stockings) - INTERMITTENT PNEUMATIC COMPRESSION (IPC) devices - PROPHYLACTIC ANTICOAGULATION (e.g., enoxaparin) in high-risk patients - LEG EXERCISES for immobilised patients - ADEQUATE HYDRATION

Anticoagulation Pharmacology: Heparin, Warfarin, LMWH, and DOACs

Anticoagulation pharmacology is among the MOST TESTED drug categories in the NLE. You must know each drug's monitoring parameter, therapeutic range, antidote, and key patient teaching points. **1. Unfractionated Heparin (UFH) — IV or Subcutaneous:** - MECHANISM: Activates antithrombin III → inhibits thrombin and Factor Xa - ONSET: Immediate (given IV for acute PE/DVT) - MONITORING: aPTT (activated partial thromboplastin time) — TARGET: 1.5–2.5x the control value (typically 60–100 seconds) - ANTIDOTE: PROTAMINE SULFATE (neutralizes heparin immediately) - KEY COMPLICATION: HEPARIN-INDUCED THROMBOCYTOPENIA (HIT) — paradoxical THROMBOSIS (not just low platelets). Monitor PLATELET COUNT every 1–3 days. If HIT suspected, STOP heparin IMMEDIATELY. - NLE Pearl: 'Monitor aPTT, antidote = protamine, watch for HIT' **2. Low-Molecular-Weight Heparin (LMWH) — Enoxaparin (Clexane), Dalteparin:** - Subcutaneous injection, more predictable dosing - NO ROUTINE MONITORING required (no aPTT needed) — this is a KEY DIFFERENCE from UFH - Anti-Xa levels can be checked in special populations (renal failure, pregnancy, extreme weight) - ANTIDOTE: Protamine sulfate (partially reverses, ~60% effective) - More convenient for outpatient prophylaxis and bridge therapy - Inject into the ABDOMEN (anterolateral abdominal wall), rotate sites, do NOT rub after injection **3. Warfarin (Coumadin) — Oral:** - MECHANISM: Inhibits Vitamin K-dependent clotting factors (II, VII, IX, X — '1972') - DELAYED ONSET: Takes 3–5 days to reach therapeutic effect → must OVERLAP with heparin for at least 5 days and until INR is therapeutic for ≥24 hours - MONITORING: PT/INR — TARGET for PE/DVT: INR 2.0–3.0 - ANTIDOTE: VITAMIN K (oral or IV for reversal); Fresh Frozen Plasma (FFP) for emergency reversal - KEY INTERACTIONS: Many drug interactions (aspirin, NSAIDs, antibiotics increase bleeding risk); dietary Vitamin K interaction — leafy greens (kangkong, malunggay, pechay) decrease warfarin effect - PATIENT TEACHING: Take at the SAME TIME each day; keep Vitamin K intake CONSISTENT (do not suddenly increase/decrease green leafy vegetable intake); report any unusual bleeding; regular INR monitoring; use soft toothbrush and electric razor **4. Direct Oral Anticoagulants (DOACs):** - Rivaroxaban (Xarelto), Apixaban (Eliquis) — Direct Factor Xa inhibitors - Dabigatran (Pradaxa) — Direct thrombin inhibitor - FIXED DOSING, NO ROUTINE MONITORING — major advantage - Specific reversal agents: Dabigatran → IDARUCIZUMAB (Praxbind); Rivaroxaban/Apixaban → Andexanet alfa - Increasingly used in the Philippines for long-term DVT/PE treatment **UNIVERSAL BLEEDING PRECAUTIONS — Teach ALL Anticoagulated Patients:** - Watch for: unusual bruising, prolonged bleeding from cuts, blood in urine (haematuria), dark/tarry stools (melaena), coffee-ground vomit (haematemesis), severe headache (intracranial bleed) - Use a SOFT-BRISTLE TOOTHBRUSH and ELECTRIC RAZOR - Avoid contact sports and activities with fall risk - Carry an anticoagulant alert card/ID - Do NOT take aspirin or NSAIDs without physician approval

Mechanical Ventilation: Basics, Alarms, and Nursing Care

Mechanical ventilation supports or replaces spontaneous breathing when a patient cannot maintain adequate gas exchange independently. For the NLE, focus on ventilator alarm interpretation, nursing care of the ventilated patient, and VAP prevention. **Key Ventilator Settings (Know These for the NLE):** **PEEP (Positive End-Expiratory Pressure):** - Positive pressure maintained at the END OF EXPIRATION - KEEPS ALVEOLI OPEN between breaths → recruits collapsed alveoli → reduces shunting → improves oxygenation - The CORNERSTONE of ARDS ventilation - Too much PEEP → DECREASES VENOUS RETURN to the heart → decreased cardiac output → HYPOTENSION; also risks BAROTRAUMA **FiO2 (Fraction of Inspired Oxygen):** - The percentage of oxygen delivered by the ventilator - WEAN FiO2 to the LOWEST level that maintains adequate SpO2 (to prevent oxygen toxicity) - Target SpO2 ≥ 92–95% in most patients (88–92% in COPD) **Tidal Volume (VT):** - Volume of air delivered per breath - Standard: 6–8 mL/kg ideal/predicted body weight - In ARDS: LOW TIDAL VOLUME (~6 mL/kg) to prevent volutrauma and barotrauma (lung-protective) **Modes of Ventilation:** - Assist-Control (AC): Ventilator delivers a breath with every patient effort AND at set rate if patient does not breathe; most supportive - SIMV (Synchronized Intermittent Mandatory Ventilation): Set number of mandatory breaths; patient breathes spontaneously in between - Pressure Support Ventilation (PSV): Patient triggers all breaths; ventilator provides pressure support; used during WEANING **VENTILATOR ALARMS — Critical for the NLE:** **HIGH PRESSURE ALARM (pressure required to deliver breath is too high):** - Causes: SECRETIONS/mucus plug (most common), KINKED tubing, patient BITING the ETT, patient FIGHTING the ventilator (dyssynchrony), BRONCHOSPASM, PNEUMOTHORAX - ACTION: ASSESS the patient first → SUCTION if secretions suspected → check tubing for kinks → provide sedation/analgesia if patient fighting vent → notify physician - If unable to resolve quickly: DISCONNECT and MANUALLY VENTILATE with a bag-valve-mask and call for help **LOW PRESSURE ALARM (circuit pressure drops below set threshold):** - Causes: DISCONNECTION from the circuit, LEAK in the circuit, ETT CUFF DEFLATION or DISLODGEMENT - ACTION: CHECK ALL CONNECTIONS immediately → check ETT cuff pressure → check for extubation → manually ventilate if needed **NURSING CARE OF THE MECHANICALLY VENTILATED PATIENT:** 1. VERIFY ETT PLACEMENT: Bilateral equal breath sounds, capnography (end-tidal CO2), CXR (tip 2–3 cm above carina); note and mark the cm marking at the lips/teeth 2. SECURE THE ETT: Use commercial ETT holder or tape; prevent accidental extubation 3. KEEP BAG-VALVE-MASK AT BEDSIDE ALWAYS — for emergency manual ventilation 4. SUCTION ONLY AS NEEDED (not on a routine schedule); HYPEROXYGENATE (100% O2) before suctioning; limit each pass to ~10–15 seconds; rotate suction catheter; document secretion character 5. VAP PREVENTION BUNDLE: - HEAD OF BED 30–45° (most important preventive measure) - DAILY SEDATION INTERRUPTION (Sedation Holiday) and readiness-to-wean assessment - ORAL CARE with CHLORHEXIDINE gluconate every 4–6 hours - DVT PROPHYLAXIS (compression stockings, LMWH) - STRESS ULCER PROPHYLAXIS (proton pump inhibitors, H2 blockers) 6. COMMUNICATION: Provide alternative communication methods (alphabet board, writing pad, eye blinks for yes/no); the patient CANNOT SPEAK with an ETT 7. SEDATION AND ANALGESIA: Titrate to comfort and ventilator synchrony; ANALGESIA-FIRST approach (pain before sedation) 8. ORAL AND SKIN CARE: Meticulous mouth care; prevent pressure injuries from immobility and proning

Clinical Assessment: Early vs. Late Signs of Respiratory Failure

One of the most heavily tested NLE concepts is the ability to DISTINGUISH EARLY from LATE signs of respiratory compromise. Early recognition enables intervention before the patient deteriorates into respiratory arrest. **EARLY SIGNS OF HYPOXAEMIA (Act NOW — these are SUBTLE but critical):** - RESTLESSNESS, AGITATION, and ANXIETY — the brain is the first organ to react to low O2; an agitated patient is hypoxaemic until proven otherwise - CONFUSION or change in mental status (disorientation) - TACHYPNOEA (increased respiratory rate — body trying to get more O2) - TACHYCARDIA and HYPERTENSION (sympathetic nervous system activation) - Nasal flaring, accessory muscle use (intercostals, sternocleidomastoid) - Complaints of shortness of breath or 'air hunger' **LATE/OMINOUS SIGNS (Emergency — deterioration imminent):** - CYANOSIS — central (lips, tongue, mucosa); indicates severe hypoxaemia (PaO2 usually <50 mmHg) - BRADYCARDIA — the heart is failing from hypoxia; this is PRE-ARREST - DYSRHYTHMIAS — hypoxia causes cardiac irritability - HYPOTENSION — cardiovascular collapse - DECREASED LEVEL OF CONSCIOUSNESS — stupor, unresponsiveness - RESPIRATORY ARREST — cessation of spontaneous breathing - Agonal/gasping respirations **SIGNS OF HYPERCAPNIA (CO2 buildup — Type II failure):** - Headache (CO2 causes cerebral vasodilation) - Drowsiness, lethargy progressing to confusion - WARM, FLUSHED SKIN and BOUNDING PULSE (CO2 causes vasodilation) - CO2 NARCOSIS — profound CNS depression from extreme CO2 elevation **NLE TRICK QUESTION ALERT:** The NLE commonly asks 'Which is the EARLIEST sign of hypoxaemia?' The answer is always RESTLESSNESS or a CHANGE IN MENTAL STATUS — NOT cyanosis (which is late and unreliable). Do not be tricked by cyanosis as an early sign. **Nursing Assessment Priority in Respiratory Distress:** Using the NURSING PROCESS: 1. ASSESSMENT: Airway patency, respiratory rate/depth/effort, accessory muscle use, SpO2, auscultate breath sounds, mental status, ABG, vital signs 2. DIAGNOSIS: Impaired Gas Exchange; Ineffective Breathing Pattern; Anxiety 3. PLANNING: Priority = Physiological survival needs (Maslow Level 1) 4. IMPLEMENTATION: Airway first, then oxygenation, then treat cause 5. EVALUATION: Improved SpO2, RR normalizing, mental status improving

ABG INTERPRETATION: pH 7.30 = Acidosis; PaCO2 70 mmHg = elevated (respiratory cause); HCO3 32 mEq/L = elevated (chronic metabolic compensation, confirming chronic CO2 retention in COPD). This is PARTIALLY COMPENSATED RESPIRATORY ACIDOSIS with HYPERCAPNIA = TYPE II Respiratory Failure with chronic compensation. The elevated HCO3 confirms this COPD patient chronically retains CO2. This patient relies on the HYPOXIC DRIVE (low O2 level) as his primary stimulus to breathe because his brain's chemoreceptors are desensitized to high CO2. Giving HIGH-FLOW O2 (Option A) would eliminate the hypoxic drive → RESPIRATORY ARREST. The correct approach is CONTROLLED LOW-FLOW OXYGEN (24% FiO2 via Venturi mask) targeting SpO2 88–92% — enough to correct dangerous hypoxaemia without suppressing the drive to breathe. Option C (intubation) may be needed if pH continues to fall despite treatment, but controlled O2 is the immediate first step. Option D is wrong — bicarbonate is not indicated here.

This patient has ALL the hallmarks of ARDS: known trigger (aspiration), acute onset, bilateral CXR infiltrates, NON-CARDIOGENIC cause, and — most critically — REFRACTORY HYPOXAEMIA (PaO2 45 mmHg despite 100% O2). The ABG shows early respiratory alkalosis (pH 7.50, PaCO2 25 = hyperventilating compensatorily), which will progress to respiratory acidosis as she tires. Using MASLOW'S HIERARCHY, PHYSIOLOGICAL SURVIVAL needs (gas exchange/oxygenation) take absolute priority over safety (risk for aspiration — the aspiration already happened), psychological needs (anxiety), or other concerns. The PRIORITY NANDA-I nursing diagnosis is 'Impaired Gas Exchange' because the immediate threat to life is inadequate oxygenation. The priority intervention is immediate notification for intubation and mechanical ventilation with PEEP. Option A is secondary. Option C and D are lower priority in this acute situation.

CLINICAL PICTURE: Post-orthopaedic surgery (venous stasis + endothelial injury = Virchow's triad), sudden dyspnoea, PLEURITIC chest pain (worsens with breathing), tachycardia, tachypnoea, hypoxia, and the classic 'sense of impending doom' = PULMONARY EMBOLISM until proven otherwise. D-dimer is elevated — but remember, elevated D-dimer is SENSITIVE but NOT SPECIFIC (many conditions raise D-dimer). It does NOT confirm PE. To CONFIRM PE, the GOLD STANDARD is CTPA (CT Pulmonary Angiography), which directly visualizes thrombus in the pulmonary arteries. Option A (V/Q scan) is an alternative when CTPA is contraindicated (renal failure, contrast allergy) but not the first choice. Option B (CXR) is useful but not confirmatory — PE CXR is often normal. Option D (ECG) helps exclude MI and may show tachycardia but does not confirm PE. The nurse's role: apply O2, elevate HOB, notify physician, prepare for CTPA and IV heparin.

HEPARIN-INDUCED THROMBOCYTOPENIA (HIT) RECOGNITION: The clinical picture is classic HIT: (1) Platelet count drop >50% (from 210,000 to 88,000 = 58% drop) within 5–10 days of heparin initiation; (2) New thrombosis (lower extremity swelling) DESPITE anticoagulation — the paradox of HIT is CLOTTING not bleeding; (3) No other obvious cause for thrombocytopenia. HIT is a dangerous immune-mediated complication where heparin-antibody complexes ACTIVATE platelets → paradoxical THROMBOSIS (clotting). The IMMEDIATE priority is to STOP ALL HEPARIN (including heparin flushes and heparin-coated catheters) and notify the physician. Option A is DANGEROUS — more heparin worsens HIT. Option B is incorrect — a >50% platelet drop on heparin is NOT expected and requires action. Option D is wrong — restarting heparin at any dose is contraindicated in HIT. Alternative anticoagulants (argatroban, fondaparinux) are used instead. Protamine alone is not the solution here.

LOW PRESSURE ALARM ANALYSIS: The alarm indicates inadequate pressure in the circuit — the ventilator cannot deliver the set tidal volume because air is leaking somewhere. The nurse found the circuit intact but the ETT CUFF pressure is LOW (15 cmH2O vs. normal 20–30 cmH2O). A low cuff pressure means AIR IS LEAKING AROUND THE ETT CUFF — escaping into the oropharynx instead of going into the lungs. This also explains the dropping SpO2 (patient is not receiving adequate ventilation). The IMMEDIATE priority fix is to REINFLATE the ETT CUFF to 20–30 cmH2O to create an adequate seal. This directly corrects the leak and should resolve the alarm and SpO2 drop. Option A (silence alarm) is dangerous — never silence without fixing. Option B (increase FiO2) does not address the cause — if the tidal volume is leaking around the cuff, more O2 percentage will not help delivery. Option D is premature — the problem has been identified and can be fixed immediately. If inflating the cuff did not work, THEN disconnect and manually ventilate while calling for help.