Prone Positioning Protocol for ARDS: 4-Phase Checklist Guide

Mechanical ventilation requires individualized programming based on patient pathology: for patients without pulmonary disease, use tidal volumes of 8 ml/kg ideal body weight with PEEP of 5 cm H2O; for ARDS patients, apply lung-protective ventilation with tidal volumes of 6 ml/kg and PEEP titrated using the ARDSNet table (PEEP-FiO2 combinations) while monitoring driving pressure (should be <12-15 cm H2O); for obstructive lung disease, reduce respiratory rate and tidal volume to prevent air trapping and auto-PEEP; and for patients with pulmonary embolism, avoid high PEEP as it can worsen right ventricular function.

This comprehensive introduction establishes the foundational philosophy of lung-protective ventilation. The lecture argues that all patients deserve equal quality care regardless of hospital location. There are fundamentally two ventilator strategies: one for lung injury and one for obstructive disease. Even patients without apparent lung injury benefit from lung-protective approaches. The ARDSnet study group developed evidence-based strategies showing mortality reduction. Assist control mode is recommended as the default setting. Tidal volume should be 6-8 cc/kg based on ideal body weight, not actual weight, treating injured lungs as 'baby lungs' that cannot handle normal volumes. Inspiratory flow rate controls delivery speed and patient comfort—low rates cause distress while high rates (60-80 LPM) improve comfort. These settings are functionally separated: tidal volume equals lung protection, flow rate equals comfort.

Protective mechanical ventilation aims to minimize ventilator-induced lung injury (VILI) by using low tidal volumes (6-8 ml/kg of predicted body weight), maintaining low plateau pressures (preferably <16 cm H2O intraoperatively), and keeping driving pressure (difference between plateau pressure and PEEP) as low as possible. The lung is heterogeneous with dependent regions (gravity-dependent, prone to atelectasis) and non-dependent regions (prone to overdistension), so ventilation strategies must balance preventing alveolar collapse while avoiding excessive stretch. Evidence shows that higher tidal volumes and driving pressures correlate with increased postoperative pulmonary complications and mortality.

For patients requiring mechanical ventilation, lung protective strategies include: (1) Low tidal volume ventilation (6 mL/kg predicted body weight); (2) Limit plateau pressure below 30 cm H2O to prevent alveolar damage; (3) Use pressure control modes; (4) Consider neuromuscular blockade; (5) Optimize PEEP settings based on oxygenation needs. These approaches minimize ventilator-induced lung injury while maintaining adequate gas exchange.

Mechanical ventilation should follow lung protective strategies to prevent ventilator-induced lung injury, including low tidal volume ventilation (4-8 ml/kg predicted body weight), plateau pressure less than 30 cm H2O, driving pressure less than 15 cm H2O, and individualized PEEP settings (8-14 cm H2O for ARDS patients), with mode selection tailored to patient conditions such as ARDS, COPD, or neuroprotective ventilation.

Gravity affects both ventilation and perfusion in the lungs. In an upright position, gravity causes more blood to pool in the lower (basal) regions, increasing perfusion at the base. Similarly, ventilation is greater at the base because alveoli are less expanded and can receive more air. Both ventilation and perfusion decrease toward the apex (top) of the lungs. Ventilation decreases from the base to the apex (82% at base to 24% at apex). Perfusion decreases more dramatically (1.29 L/min at base to 0.1 L/min at apex). The V/Q ratio increases from the base to the apex (0.6 at base to 3.0 at apex). The pleura consists of two layers: the visceral pleura (inner layer) that adheres to the lung surface, and the parietal pleura (outer layer) that lines the chest wall. Pleural pressure is negative (subatmospheric) throughout the pleural cavity. At the apex, pleural pressure is approximately -10 cm H2O, while at the base it is approximately -2.5 cm H2O. Transpulmonary pressure is the pressure difference between alveolar pressure and pleural pressure. At the apex, this equals +10 cm H2O, indicating more inflated alveoli. At the base, this equals +2.5 cm H2O, indicating less inflated alveoli. Pulmonary capillary perfusion decreases from the base to the apex. V/Q mismatch occurs when ventilation and perfusion are not proportionally matched. At the base, high perfusion relative to ventilation can lead to shunting. At the apex, high ventilation relative to perfusion can lead to dead space.

The ventilation to perfusion ratio (V/Q ratio) is the relationship between alveolar ventilation (4.2 L/min) and pulmonary perfusion (5 L/min), normally around 0.8. In an upright posture, gravity affects perfusion more than ventilation, causing the V/Q ratio to be higher at the lung apex (wasted ventilation) and lower at the base (physiological shunt). V/Q mismatch occurs in conditions like emphysema (low V/Q) and pulmonary embolism (high V/Q), impairing gas exchange efficiency.

The Ventilation-Perfusion (V/Q) ratio represents the relationship between alveolar ventilation and pulmonary perfusion, with a normal value of 0.8 (80%). Gravity causes natural physiological variation: the lung apex has a higher V/Q ratio (~3) due to decreased perfusion relative to ventilation, while the base has a lower V/Q ratio (~0.6) due to increased perfusion. A ventilation defect (e.g., emphysema) decreases the V/Q ratio and causes shunt-like physiology where blood passes through unventilated alveoli, while a perfusion defect (e.g., pulmonary embolism) increases the V/Q ratio and causes dead space physiology where ventilated alveoli receive no blood flow. The lung uniquely responds to hypoxia with vasoconstriction (unlike most organs that vasodilate), redirecting blood to better-ventilated areas. This principle is clinically applied in V/Q scans for diagnosing pulmonary embolism and understanding conditions like TB reactivation in the apex (where high V/Q ratio means less perfusion and fewer immune cells).

The ventilation-perfusion (V:Q) ratio describes the relationship between air reaching alveoli (ventilation) and blood flow to alveoli (perfusion) for efficient gas exchange; in upright position, gravity causes decreased perfusion at lung apex (creating wasted ventilation) and increased perfusion at lung base (creating wasted perfusion), resulting in an average V:Q ratio of 0.8, where perfusion exceeds ventilation, and diseases like pneumonia, COPD, and pulmonary embolism can further disrupt this balance causing various types of V:Q mismatches.

Alveolar pressure is the pressure inside the alveoli, which equals atmospheric pressure (0 cm H2O) at rest, becomes negative (-1 cm H2O) during inspiration to draw air in, and becomes positive (+1 cm H2O) during expiration to expel air; pleural pressure is the negative pressure in the pleural space caused by opposing elastic recoils of the lungs (tending to collapse) and chest wall (tending to expand), with gravity creating a vertical gradient from more negative at the apex (-10 cm H2O) to less negative at the base (-2.5 cm H2O), and during the respiratory cycle, pleural pressure drops to -7.5 cm H2O during inspiration and returns to -5 cm H2O during expiration, while alveolar pressure follows a complementary pattern.

Invasive lines are medical devices inserted into the body to administer fluids, drugs, drain contents, and monitor functions, with the four common vascular lines being peripheral venous catheter, central venous catheter, peripherally inserted central catheter (PICC), and arterial line. Proper care of these lines involves five key aspects: assessment (pain, redness, inflammation, discharge, patency, and insertion date), scrubbing the hub with chlorhexidine or 70% alcohol for 15 seconds followed by 15 seconds drying time, using transparent dressings for protection and visibility, employing closed system extensions to prevent dislodgment and contamination, and performing flushing and locking procedures to maintain patency and prevent complications. Central line care additionally requires CLABSI prevention bundles, while PICC line care follows the ALERT mnemonic (Assess, Line patency, Ensure closed system, Re-examine for discharge/redness/swelling, Time and date). Arterial line care includes square wave testing to assess waveform accuracy, with normal waveforms showing one to two oscillations after the square wave, while underdamped waveforms show more than two oscillations and overdamped waveforms show sluggish or no oscillations.

In intensive care, patients commonly have multiple lines and tubes including endotracheal tubes (ventilated at 22cm depth with cuff pressure maintained at 20-30cm H2O), inline suction systems, nasogastric tubes (purple-colored for IV safety), and central venous catheters (typically IJ lines with 1-5 lumens labeled with date/time and drug infusions); proper care involves regular cuff pressure checks, securement to prevent pressure damage, and collaborative management with ICU specialists.

This educational session covers the technical and practical management of central venous catheters (CVC) and arterial lines in intensive care settings. The arterial line is defined as arterial cannulation using a peripheral catheter, primarily for continuous blood pressure monitoring (systolic, diastolic, and mean arterial pressure) and arterial blood gas sampling. Proper interpretation of arterial waveforms requires understanding the six components: systolic upstroke, systolic peak, systolic decline, dicrotic notch, diastolic downstroke, and diastolic pressure. The square wave test (flush test) is essential for assessing line accuracy, with 15-20 oscillations indicating proper damping. The CVC is a thin, flexible tube inserted into a vein and advanced to the superior vena cava, with functions including central venous pressure monitoring, blood sampling, and medication administration. CVC care requires specific attention to fixation, permeabilization using the push-pause technique with 10ml syringes, and maintenance of a patent lumen. The session emphasizes that these devices should only be used for their intended purposes, with regular reassessment of necessity to prevent complications such as infections.

This section details comprehensive post-intubation care protocols. The ICU bundle includes T (thromboprophylaxis), H (head of bed elevation >30°), U (ulcer prophylaxis with famotidine/pantoprazole), E (enteral feeding), G (glycemic control 140-180 mg/dL), S (sedation holiday for daily assessment), B (bowel regimen), I (indwelling line assessment), and D (antibiotic de-escalation). Daily chest X-rays verify endotracheal tube position (3-5 cm above carina) and line placements. Arterial blood gases provide complete metabolic and respiratory assessment, while venous blood gases estimate arterial pH by adding 0.05. Arterial lines are preferred for frequent monitoring to prevent radial artery trauma. These standardized protocols ensure comprehensive patient care and prevent complications.

When entering any ICU space, the first critical step is performing an environmental scan - standing still and assessing what is happening, identifying spaces, machines, and the patient. ICU spaces should be organized logically with screens positioned so all monitors are visible from the foot of the bed. The ventilator should be placed near the patient's head (typically on the left side), bed controls should be accessible, and gas cylinders should be positioned for easy access. When working in a new ICU unit, staff should spend time orienting themselves to the macro environment - knowing the location of the stockroom, bathroom, restroom, exit, and sluice room. Endotracheal tubes require proper securing devices that prevent pressure ulcers. Tracking tape is a temporary solution for emergency/EMS settings but should not be used in ICU environments. Proper tube holders distribute pressure over a larger area. All ET tube patients should have an inline suction adapter to prevent aerosolization during suctioning. The correct assembly order for ET tube circuits is: ET tube, inline suction adapter, viral filter (rated for appropriate tidal volume - adults need >250ml filters), then end-tidal CO2 adapter. Side-stream CO2 adapters take a sample to a separate monitoring device, while mainstream adapters measure directly inside the tube. During ventilator changes, end-tidal CO2 sampling must be placed outside the filter to prevent aerosolization. When changing ventilators, the tube should be clamped before disconnecting to prevent aerosolization and maintain PEEP. Normal nasal cannulas are designed for normal oxygen flows (up to 4-5 liters) and should not be used for high-flow oxygen delivery during outbreaks. A surgical mask should be placed over the patient's face even during normal nasal oxygenation to limit aerosolization. The safest position for staff is in front of the patient, not behind, as mask openings direct air escape backward. All infusion bags and tubing should be labeled with medication name and concentration. When multiple infusions are running, the maintenance fluid should be the fastest-flowing line and positioned at the back of the system. For any IV medication, three key parameters must be documented: concentration (mg/ml), desired dose (mg/kg/min), and infusion rate (ml/min). These are interrelated - doubling the concentration allows the same dose at a slower rate or double the dose at the same rate, which is important for fluid management. Arterial lines require a transducer that measures pressure at its specific location. The transducer must be positioned at the same height as the patient's heart (approximately the 4th intercostal space) to provide accurate readings. If the transducer is on the floor, it will read higher (blood pressure plus weight of blood above). If positioned above the heart, it will read lower. Arterial lines require regular flushing with heparinized saline to prevent clotting. The pressure bag must be pressurized above expected arterial pressure to ensure flushing flows into the patient rather than bleeding blood out. The line should be zeroed twice per shift by clamping both the patient and pressure bag, telling the monitor to zero, then opening clamps to verify accurate readings. Any air in an arterial line will cause false pressure readings. Ventricular fibrillation (VF) is a quivering heart rhythm that requires immediate defibrillation. The survival chance decreases by 10% for every 60 seconds of delay in defibrillation. Any critical care worker should recognize VF and immediately defibrillate after confirming no pulse and proper ECG attachment. Defibrillator pads must be placed as far apart as possible with the heart between them. Before defibrillation, the person operating the machine should visually confirm no one is touching the patient. A clear verbal announcement ('clear, clear, clear') is standard practice. After defibrillation, the immediate action is to start chest compressions. The bag-mask should remain on the ET tube during defibrillation (the plastic bag does not conduct energy). The defibrillator should not be checked for at least 2 minutes after the shock, as no useful information will be visible on the monitor that early.