NLE Respiratory Nursing — Acute Respiratory Failure & ARDSSummary

Type I respiratory failure is characterized by inadequate oxygenation, defined as PaO2 <60 mmHg on room air, with normal or low PaCO2. The primary problem is a failure of the lungs to load oxygen into the bloodstream. Common causes include pneumonia, ARDS, pulmonary oedema, atelectasis, and pulmonary embolism. The underlying mechanisms involve ventilation–perfusion (V/Q) mismatch, intrapulmonary shunting (blood bypassing ventilated alveoli), diffusion impairment across the alveolar-capillary membrane, or low inspired oxygen. In the Philippine healthcare context, Type I failure is frequently encountered in patients with severe pneumonia (a leading cause of hospitalization in resource-limited settings), acute coronary syndrome with pulmonary oedema, and sepsis-related ARDS. Nursing management prioritizes high-concentration oxygen delivery (e.g., non-rebreather mask delivering 80–95% FiO2) while investigating and treating the underlying cause.

Type II respiratory failure involves inadequate ventilation—a failure to eliminate CO2. It is defined as PaCO2 >50 mmHg with pH <7.35 (respiratory acidosis). The problem is not oxygenation but the pumping and moving of air—alveolar ventilation is insufficient to blow off CO2. Common causes include COPD exacerbations, drug overdose (especially opioids), neuromuscular diseases (myasthenia gravis, Guillain-Barré syndrome), chest-wall deformities, and decreased respiratory drive from sedation or CNS depression. In Philippine clinical settings, COPD exacerbations (often triggered by air pollution in urban areas) and opioid overdose are increasingly common Type II failure scenarios. The pathophysiology involves hypoventilation—fewer breaths per minute, shallower tidal volumes, or both—such that CO2 produced by metabolism accumulates faster than it is eliminated. As CO2 rises, it becomes a CNS depressant (CO2 narcosis), further reducing the drive to breathe, creating a vicious cycle.

ARDS is a severe, acute, diffuse inflammatory lung injury characterized by bilateral pulmonary infiltrates and refractory hypoxaemia—hypoxaemia that does NOT improve with supplemental oxygen. This refractoriness is the defining feature and reflects intrapulmonary shunting so severe that high FiO2 cannot overcome it. ARDS is triggered by direct lung injury (aspiration, near-drowning, inhalation injury, contusion) or systemic inflammatory insults (sepsis, severe pancreatitis, massive transfusion, major trauma). Sepsis is the most common trigger in Philippine hospitals. The trigger causes diffuse damage to the alveolar-capillary membrane, increasing permeability. Protein-rich fluid floods the alveoli (non-cardiogenic pulmonary oedema), and surfactant is washed away and inactivated. Without surfactant, surface tension increases, alveoli collapse (atelectasis), and lung compliance plummets—the lungs become 'stiff,' requiring high pressures to ventilate. Hypoxaemia worsens, and the work of breathing skyrockets. Patients typically deteriorate over 12–48 hours after the inciting event. The oedema is non-cardiogenic—the pulmonary capillary wedge pressure (PCWP) is normal, distinguishing ARDS from cardiogenic pulmonary oedema.

PEEP is a cornerstone of ARDS management. Normally, after exhalation, airway pressure returns to zero. With PEEP, positive pressure is maintained at the end of expiration, preventing alveoli from collapsing. PEEP 'recruits' collapsed alveoli—reopening them—and keeps them open throughout the breath cycle. This improves oxygenation by reducing shunting and increasing ventilated lung volume. In ARDS, typical PEEP is 5–15 cm H2O (higher in severe disease). However, excessive PEEP has downsides: it increases intrathoracic pressure, which reduces venous return and can cause hypotension; it also risks barotrauma (ventilator-induced lung injury) if alveoli overdistend. The balance is critical. Modern ARDS management uses 'optimal PEEP' titration—the level that maximizes oxygenation while minimizing haemodynamic compromise and overdistension risk. Many Philippine ICUs now employ lung-recruitment manoeuvres (sustained pressure increases) followed by PEEP titration to find the individual patient's best PEEP level.

Lung-protective ventilation (LPV) is the gold-standard approach to mechanical ventilation in ARDS, validated by landmark clinical trials. LPV uses low tidal volumes (approximately 6 mL/kg of predicted body weight, not actual body weight) and permissive hypercapnia—allowing PaCO2 to rise somewhat (up to 50–60 mmHg) to avoid overdistending alveoli. The rationale is that high tidal volumes cause volutrauma (overdistension of healthy alveoli), worsening lung injury. By using lower volumes, alveoli are protected from mechanical stress. Permissive hypercapnia is tolerated because a slightly elevated CO2 is less harmful than the lung damage from high volumes. Pressure-limited ventilation (plateau pressure <30 cm H2O) ensures alveolar overdistension is avoided. In Philippine hospitals implementing LPV, nurses must understand the ventilator settings, monitor plateau pressures, and recognize that a rising PaCO2 within safe limits is expected and acceptable—this represents lung protection, not failure.

Prone positioning (turning the patient face-down) is a simple, non-pharmacological intervention that improves oxygenation in moderate-to-severe ARDS. The mechanism involves improved ventilation–perfusion matching: in the prone position, dorsal (back) lung zones are more dependent (gravity-favoured for perfusion) and are better ventilated, improving the match between ventilation and blood flow. Prone positioning also recruits previously collapsed alveoli in dorsal zones and reduces compression of ventral (front) zones. Studies show significant oxygenation improvements; severe ARDS (P/F ratio <100—see diagnostic section) may benefit even more. Prone positioning sessions typically last 12–16 hours daily. Risks include loss of airway access, accidental line/tube displacement, pressure injury to the face, and increased monitoring complexity. In Philippine hospitals with limited staff, prone positioning requires careful planning and extra hands to execute safely without tube migration.

A pulmonary embolism is an obstruction of the pulmonary artery or a branch, usually caused by a thrombus that dislodges from a deep vein of the legs or pelvis (DVT) and travels through the right heart to lodge in the pulmonary circulation. Less commonly, the embolus is fat (from long-bone fractures), air, amniotic fluid, or tumour fragments. PE risk is elegantly explained by Virchow's triad: (1) Venous stasis—slowed blood flow, e.g., from prolonged immobility (bed rest, long travel), atrial fibrillation, or venous obstruction; (2) Hypercoagulability—a prothrombotic state, e.g., from cancer, pregnancy, oral contraceptives, dehydration, sepsis, or inherited thrombophilic disorders; (3) Endothelial injury—damage to the vein wall, e.g., from trauma, surgery, central venous catheters, or previous thrombosis. Most PE arise from the deep veins of the lower extremities; risk increases significantly post-operatively, in immobilized patients, and in those with cancer or recent long-haul flights. In the Philippine context, post-operative patients, long-distance drivers/passengers, and cancer patients are at high risk.

PE presents with a classic triad of sudden dyspnoea, pleuritic chest pain (worse with breathing), and tachycardia. Accompanying features include tachypnoea (rapid breathing), anxiety, and often a subjective sense of 'impending doom'—an existential dread that something is terribly wrong. Haemoptysis (coughing up blood) and low-grade fever may occur if pulmonary infarction develops. The severity of presentation depends on the size of the embolus and the patient's cardiopulmonary reserve. A massive PE obstructs a large portion of the pulmonary vasculature, causing acute right-heart strain (the right ventricle cannot pump blood into the obstructed pulmonary artery), right-sided heart failure, hypotension, syncope, cyanosis, and potentially cardiac arrest—this is PE in shock (haemodynamic instability). A smaller PE may cause only modest dyspnoea and tachycardia. The 'impending doom' symptom is highly specific for PE and should trigger immediate evaluation. Importantly, a patient with PE may have coexisting signs of DVT (unilateral calf swelling, warmth, tenderness, positive Homan's sign)—looking for DVT is part of the PE assessment.

Anticoagulation is the cornerstone of PE and DVT management, preventing thrombus propagation and new clot formation. Four main anticoagulant classes are used: (1) Unfractionated heparin (UFH)—intravenous, rapid onset, requires continuous monitoring via aPTT (activated partial thromboplastin time; target 1.5–2.5 times control), reversible with protamine sulfate. UFH is preferred in acute PE and in patients with renal failure (because it is not renally eliminated). Risk: heparin-induced thrombocytopenia (HIT)—a paradoxical prothrombotic state from antibodies against heparin-platelet complexes; monitor platelet count closely. (2) Low-molecular-weight heparin (LMWH, e.g., enoxaparin)—subcutaneous, more predictable pharmacokinetics, usually no routine monitoring (except in renal impairment or obesity), also reversed partly by protamine. LMWH is convenient for outpatient DVT prophylaxis and treatment. (3) Warfarin (a vitamin-K antagonist)—oral, delayed onset (several days), monitored via PT/INR (target 2.0–3.0 for PE/DVT). Warfarin has many drug interactions and requires consistent dietary vitamin-K intake (green leafy vegetables). Antidote: vitamin K (slow reversal) or fresh frozen plasma (immediate reversal). (4) Direct oral anticoagulants (DOACs)—e.g., rivaroxaban, apixaban, dabigatran—fixed dosing, no routine monitoring, rapidly acting. Dabigatran has a reversal agent (idarucizumab). DOACs are increasingly used because of convenience, though cost is high in Philippine settings.

Diagnosis of acute respiratory failure begins with ABG (arterial blood gas) analysis. The ABG provides PaO2, PaCO2, pH, bicarbonate (HCO3), and base excess—all essential for classifying the failure type and acid-base status. Type I failure: PaO2 <60 mmHg (on room air), normal or low PaCO2; Type II failure: PaCO2 >50 mmHg with pH <7.35. Pulse oximetry (SpO2) is continuous and useful but does not quantify CO2. Chest X-ray shows the cause (infiltrates in pneumonia/ARDS, opacification in pulmonary oedema, oligemia in PE). For ARDS specifically, bilateral infiltrates on CXR are required (in addition to refractory hypoxaemia). The P/F ratio—PaO2 divided by FiO2—grades ARDS severity: >300 = mild, 200–300 = moderate, <100 = severe. (Example: PaO2 65 mmHg on FiO2 0.6 → P/F ratio = 65 ÷ 0.6 = 108, indicating severe ARDS.) For PE diagnosis, CT pulmonary angiography (CTPA) is the gold standard—it directly visualizes the thrombus in the pulmonary arteries. D-dimer (a fibrin degradation product) is sensitive but not specific for PE; a normal D-dimer helps exclude PE in low-risk patients (negative predictive value ~95%), but an elevated D-dimer is non-specific (many conditions elevate it). ABG in PE typically shows hypoxaemia with hypocapnia (respiratory alkalosis from hyperventilation).

Recognizing the stage of hypoxaemia is crucial for early intervention. Early hypoxaemia (mild-to-moderate, PaO2 still 50–70 mmHg) causes restlessness, agitation, anxiety, inability to concentrate, tachypnoea, tachycardia, and hypertension—sympathetic activation. Importantly, restlessness and a change in mental status (confusion, irritability) are among the earliest and most specific signs of hypoxaemia and must never be dismissed as anxiety or agitation alone. Many nurses and physicians mistakenly attribute early hypoxaemia to psychiatric causes, delaying oxygen therapy. Late hypoxaemia (severe, PaO2 <50 mmHg) causes drowsiness, confusion, decreased level of consciousness, bradycardia (the heart tires), dysrhythmias, cyanosis, and eventually respiratory depression and arrest. Hypercapnia (CO2 retention) adds somnolence and drowsiness ('CO2 narcosis'). The key teaching point: if a previously well patient suddenly becomes restless or confused, think hypoxaemia first and check oxygen saturation—do not wait for cyanosis (a late sign).

Mechanical ventilation delivers breaths via an endotracheal tube (ETT) when spontaneous breathing is insufficient. Common modes include: (1) Assist-Control (AC)—the ventilator delivers a breath at a set rate; if the patient initiates a breath, the ventilator delivers a full tidal volume (assisted breath). This guarantees a minimum minute ventilation. (2) Synchronized Intermittent Mandatory Ventilation (SIMV)—the ventilator delivers mandatory breaths at a set rate, but allows the patient to take spontaneous breaths between them; spontaneous breaths are unassisted (lower pressure). SIMV is used to wean patients toward spontaneous breathing. (3) Pressure Support Ventilation (PSV)—the ventilator delivers pressure for each patient-initiated breath, assisting spontaneous breathing without a mandatory rate; the patient controls the rate. PSV is used late in weaning. Key parameters: tidal volume (mL/kg), respiratory rate (breaths/min), FiO2, and PEEP. Alarms alert to problems: high-pressure alarm (obstruction—suction, kinked tube, biting, bronchospasm) or low-pressure alarm (leak or disconnection). Nurse safety duties include confirming ETT placement (bilateral breath sounds, capnography, CXR), securing the tube, keeping the manual resuscitation (ambu) bag at the bedside, responding to alarms, suctioning only as needed, and hyperoxygenating before suctioning (to prevent hypoxaemia during suctioning).

Ventilator-associated pneumonia is a serious complication of mechanical ventilation, caused by aspiration of contaminated oropharyngeal secretions into the lungs. VAP increases morbidity, mortality, length of ICU stay, and cost. Prevention is far superior to treatment. The evidence-based VAP prevention bundle (also called the 'bundle of care') includes: (1) **Head-of-bed elevation 30–45°**—this is the single most effective intervention, reducing aspiration by gravity. Supine or near-supine positioning dramatically increases VAP risk. (2) **Oral care with chlorhexidine**—antiseptic rinse reduces oropharyngeal bacterial colonization. (3) **Daily sedation interruption and spontaneous breathing trials (SBT)**—reducing sedation daily and assessing readiness to wean reduces unnecessary ventilation time. (4) **DVT prophylaxis**—compression stockings, intermittent pneumatic compression, or anticoagulation to prevent DVT/PE in immobile ventilated patients. (5) **Stress-ulcer prophylaxis**—H2 blockers or proton-pump inhibitors to prevent aspiration of gastric acid (stress ulceration is common in critical illness). Additional measures include subglottic suctioning (suction above the ETT cuff to remove secretions before they enter the lungs) and avoiding gastric overdistension. VAP typically develops >48 hours after intubation and presents with fever, purulent sputum, and new infiltrates on CXR.

NANDA-I nursing diagnoses provide a standardized framework for identifying patient problems and planning interventions. For acute respiratory failure and ARDS, common diagnoses include: (1) **Ineffective breathing pattern** (related to increased work of breathing, decreased respiratory muscle strength, or CNS depression) → manifested by dyspnoea, tachypnoea, use of accessory muscles, or irregular breathing. Interventions: position upright, provide oxygen, teach breathing techniques, monitor ABG. (2) **Ineffective airway clearance** (related to excessive secretions, weakness, or obtundation) → manifested by crackles, rhonchi, cough, or inability to clear secretions. Interventions: suction as needed, encourage cough, position to drain secretions, humidify air. (3) **Impaired gas exchange** (related to alveolar-capillary damage, shunting, or V/Q mismatch) → manifested by hypoxaemia, restlessness, or altered mental status. Interventions: deliver oxygen, monitor ABG/SpO2, position for optimal ventilation (including prone in ARDS), manage PEEP. (4) **Anxiety** (related to acute illness, hypoxaemia, or fear of dying) → manifested by restlessness, expressed fear, or vital sign elevation. Interventions: provide reassurance, explain procedures, teach relaxation, provide sedation if needed. (5) **Acute confusion** (related to hypoxaemia or hypercapnia) → manifested by disorientation, memory loss, or altered consciousness. Interventions: correct the underlying gas abnormality, reorient, ensure safety. For PE, **Risk for altered tissue perfusion** is relevant (risk of pulmonary, cardiac, or systemic hypoperfusion from the embolus).

Maslow's hierarchy of needs provides a framework for clinical prioritization. The hierarchy, from foundational to advanced, is: (1) **Physiological needs** (oxygen, food, water, sleep, shelter); (2) **Safety needs** (protection, stability); (3) **Love/belonging needs** (relationships); (4) **Esteem needs** (respect, recognition); (5) **Self-actualization** (personal growth). In acute respiratory failure and ARDS, the patient's most basic physiological needs—oxygen and breathing—are threatened; all other needs are secondary. Thus, the nurse's immediate priority is: **Assess airway patency, deliver oxygen, ensure adequate ventilation, and support the respiratory system.** Only after the patient is oxygenated and ventilating adequately can the nurse address safety concerns (e.g., fall prevention, tube security), psychological needs (anxiety reduction, communication with family), or higher-order needs. This principle applies to all emergency scenarios—ABC (airway, breathing, circulation) is the mnemonic expression of Maslow's physiological priority.

Type I and Type II respiratory failures represent opposite gas-exchange problems. Type I (hypoxaemic) reflects inadequate oxygenation—lungs are failing to load oxygen (e.g., pneumonia blocks gas exchange, shunting in ARDS prevents oxygen loading). Type II (hypercapnic) reflects inadequate ventilation—the respiratory pump is failing to move air and blow off CO2 (e.g., weak muscles, CNS depression, high airway resistance). A patient may have both (Type III failure, 'combined'), but understanding the distinction is critical for treatment: Type I needs oxygen and lung recruitment; Type II needs ventilatory support (BiPAP, mechanical ventilation) to increase minute ventilation. Nurses must recognize which type to avoid dangerous mismanagement (e.g., high oxygen in a COPD patient with Type II failure can worsen ventilation).

ARDS is a subset of Type I (hypoxaemic) respiratory failure, but with a defining feature: refractory hypoxaemia. Mild-to-moderate Type I failures (e.g., pneumonia with PaO2 60–80 mmHg on supplemental oxygen) usually respond to oxygen therapy and treatment of the cause. ARDS, by contrast, shows severe hypoxaemia that worsens or does not improve despite high FiO2—this refractoriness reflects profound intrapulmonary shunting (blood bypassing ventilated lung). Thus, ARDS is Type I failure at its most severe, requiring mechanical ventilation with PEEP to recruit collapsed alveoli. Nurses assess for this progression: if a patient with pneumonia fails to oxygenate despite high-flow oxygen and develops bilateral infiltrates and required intubation, ARDS should be suspected. Recognizing ARDS early changes the management paradigm from antibiotics alone to antibiotics plus mechanical ventilation optimization.

ARDS's core pathophysiology is alveolar collapse (atelectasis) due to surfactant loss and increased surface tension. PEEP directly addresses this by applying positive pressure at the end of expiration, mechanically holding alveoli open and preventing their collapse. Without PEEP, alveoli would collapse with each exhalation, requiring enormous effort to re-inflate on the next breath (like blowing up a straw)—this is why ARDS lungs are so 'stiff.' PEEP restores a physiological 'resting tone' to alveoli, keeping them recruited and dramatically improving oxygenation. Thus, PEEP is not just a ventilator setting; it is the cornerstone of ARDS management, directly treating the pathophysiology. Nurses who understand this mechanism grasp why PEEP is non-negotiable in ARDS and why accidental PEEP loss (circuit disconnection) causes rapid desaturation.

Virchow's triad (stasis, hypercoagulability, endothelial injury) elegantly explains all PE risk factors and guides prevention. Every patient risk factor fits one of these three categories: immobility = stasis; cancer/pregnancy = hypercoagulability; surgery/trauma = injury. Prevention strategies address each: early mobilization (combats stasis), anticoagulation prophylaxis (combats hypercoagulability), and careful vascular access/vein preservation (prevents injury). Understanding the triad allows nurses to quickly assess a post-operative patient (stasis + injury high; give anticoagulation + compression + mobilize early) or a cancer patient (hypercoagulability high; give anticoagulation prophylaxis). The triad also explains why PE often clusters after certain events (e.g., long-haul flights = stasis in immobile patient; surgery = stasis + injury; cancer diagnosis = hypercoagulability)—knowing the trigger helps nurses recognize at-risk patients.

The four anticoagulant classes differ in onset, duration, monitoring requirements, and reversals—understanding these differences prevents dosing errors and bleeding complications. UFH requires aPTT monitoring (therapeutic window is narrow); LMWH requires minimal monitoring (more predictable); warfarin requires INR monitoring (due to drug/diet interactions); DOACs require no routine monitoring (fixed dosing). This relationship is crucial: a nurse who forgets to monitor aPTT in a UFH patient risks overdosing (causing bleeding) or underdosing (allowing clot progression). Conversely, knowing that DOACs are fixed-dose reduces the monitoring burden but shifts responsibility to patient education (adherence, timing). Reversal agents also differ: protamine for heparin, vitamin K for warfarin (slow), idarucizumab for dabigatran (fast). These distinctions are high-yield exam topics and critical for safe anticoagulation in PE/DVT care.

Ventilation modes reflect a progression from full ventilatory support toward spontaneous breathing, mirroring the patient's recovery. Assist-Control (AC) is the most supportive—every breath is assisted, guaranteeing minute ventilation. As the patient improves, the ventilator is switched to SIMV, where mandatory breaths decrease and the patient takes more spontaneous (unassisted) breaths, gradually assuming responsibility for ventilation. Finally, Pressure Support Ventilation (PSV) assists spontaneous breathing lightly, allowing the patient to control rate and depth while getting respiratory muscle support. The transition from AC → SIMV → PSV → spontaneous (extubation) represents the patient's improving respiratory competence. Nurses must recognize this progression and advocate for weaning trials (discontinuing sedation daily, assessing readiness) to avoid prolonging mechanical ventilation. Delayed weaning increases VAP risk, delirium, and ICU stay duration.

ABG values tell a story of the respiratory system's state. PaO2 <60 mmHg signals hypoxaemia (Type I failure or very severe Type II); PaCO2 >50 mmHg signals hypoventilation (Type II failure). pH <7.35 with elevated PaCO2 = respiratory acidosis (ventilation failure); pH >7.45 with low PaCO2 = respiratory alkalosis (hyperventilation, often from hypoxaemia driving increased breathing). Rising PaCO2 over time in ARDS suggests either patient tiring (worsening prognosis) or—if in the context of protective ventilation—intended permissive hypercapnia (acceptable). A patient with normal or low PaCO2 despite low PaO2 is typically hyperventilating (respiratory alkalosis), trying to correct hypoxaemia; if PaCO2 is high with hypoxaemia, the patient is tiring (ominous sign). Serial ABGs track trends and guide management: worsening oxygenation despite increasing FiO2 suggests ARDS, requiring mechanical ventilation; rising CO2 with falling pH suggests Type II failure, requiring ventilatory support. Nurses who understand these relationships can interpret ABGs and recognize critical changes.

Hypoxaemia and hypercapnia produce overlapping but distinguishable clinical pictures. Hypoxaemia (low O2) causes restlessness, anxiety, tachycardia, hypertension, agitation—sympathetic activation in response to tissue hypoxia. Hypercapnia (high CO2) causes headache, somnolence, drowsiness, confusion, flushed warm skin, bounding pulse—CO2 is a CNS depressant and cerebral vasodilator. A patient with both (common in ARDS with CO2 retention) shows features of both: restlessness initially (hypoxaemia driving sympathetic response) that may progress to drowsiness and confusion (hypercapnia and fatigue setting in). Recognizing which predominates guides treatment: if restlessness is the main sign, oxygenation is the priority; if drowsiness dominates, ventilatory support (to blow off CO2) is urgent. Understanding these distinct syndromes prevents misattribution (e.g., mistaking restlessness for anxiety when it reflects hypoxaemia).

Both PEEP and prone positioning recruit collapsed alveoli, improving oxygenation in ARDS, but via different mechanisms. PEEP applies continuous positive pressure to hold alveoli open. Prone positioning redistributes perfusion to dorsal (back) lung zones that are better ventilated when prone, improving V/Q matching. Together, they are synergistic: prone positioning in the context of optimized PEEP may achieve even greater oxygenation improvement than either alone. Nurses coordinating ARDS care often see orders for both interventions; understanding their complementary roles—PEEP recruits and holds, prone positioning optimizes perfusion-ventilation distribution—clarifies why both are used and why the combined effect is powerful. Modern ARDS bundles often include: optimized PEEP, lung-protective ventilation, AND prone positioning for moderate-to-severe disease.

VAP results from aspiration of contaminated oropharyngeal secretions; preventing it requires a multi-pronged approach. Head-of-bed elevation reduces aspiration by gravity. Oral care reduces the bacterial burden in the oropharynx, so less virulent inoculum is aspirated. Sedation interruption and weaning reduce unnecessary ventilation time. DVT prophylaxis prevents thromboembolic complications (another ICU complication). Stress-ulcer prophylaxis prevents gastric bleed and gastric acid aspiration. These interventions are distinct but integrated—no single intervention alone is sufficient; the bundle is effective. Nurses implement the bundle as a routine care protocol, not as individual 'nice-to-have' measures. Hospitals with strong VAP prevention bundles show dramatically lower VAP rates and outcomes. This concept reinforces that critical-care nursing is multidimensional: you cannot just focus on ventilator management; you must address all aspects of the ventilated patient's physiology.