Mechanical Ventilation study guide previews.

What happens includes clinicians increase respiratory rate for hypoxemia or add PEEP for hypercapnia.

Fix include Hypoxemia leading to increased FiO₂, increased PEEP, Hypercapnia leading to increased RR, increased VT (within lung-protective limits), This mistake underlies most ventilator mismanagement, Mistake #2: Over-Oxygenating Instead of Recruiting Lung, and FiO₂ is increased to 100% while PEEP remains low.

Fix include If FiO₂ > 60%, think PEEP, Use oxygen to buy time, not as a long-term solution, Mistake #3: Ignoring Plateau Pressure, and Peak pressures are followed, plateau pressures are not measured. Key threshold include Plateau pressure ≤ 30 cm H₂O. What happens includes tidal volumes are based on actual body weight.

After completing this study guide, you should be able to Average Volume Assured Pressure Support (AVAPS) is a mode of noninvasive ventilation that automatically adjusts inspiratory pressure support to achieve a target tidal volume. The ventilator continuously modifies inspiratory pressure support to achieve a clinician-selected tidal volume. Think of AVAPS as include "Pressure support ventilation with an automatic pressure adjustment system designed to maintain a target tidal volume.". As these variables change, tidal volume may fall despite unchanged pressure support.

Unlike CPAP, which delivers a single continuous pressure throughout the respiratory cycle, BPAP augments ventilation by increasing inspiratory pressure while maintaining expiratory pressure. The greater the pressure support, the greater the potential increase in tidal volume and carbon dioxide clearance. Patients with respiratory failure frequently generate substantial negative intrathoracic pressure in an attempt to maintain ventilation.

BPAP is the most commonly used form of noninvasive ventilation in emergency and critical care medicine. Reducing cardiac preload and afterload in heart failure. Average Volume Assured Pressure Support (AVAPS) is a BPAP mode that automatically adjusts inspiratory pressure to achieve a target tidal volume. Rather than delivering a fixed pressure support, AVAPS continuously modifies pressure support within clinician-defined limits to maintain a desired tidal volume. The ventilator then automatically adjusts inspiratory pressure as patient mechanics change.

The inspiratory includes expiratory (I:E) ratio defines how long the ventilator spends delivering a breath (inspiration) versus allowing passive exhalation (expiration). The I:E ratio is simply include Time in expiration.:2 (inspiration is half as long as expiration). Higher RR leading to less total cycle time leading to shorter expiratory time. Longer inspiratory time leading to shorter expiratory time. Lower inspiratory flow leading to longer inspiratory time. SHORTER EXPIRATORY TIME (e.g., 1:1 or inverse ratio).

Mechanical Ventilation Advanced: APRV introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Patient-ventilator dyssynchrony occurs when the timing or magnitude of ventilator assistance does not match the patient’s own respiratory efforts, leading to ineffective ventilation, increased work of breathing, or lung injury. Two important forms are double triggering and reverse triggering.

Two delivered breaths in rapid succession with minimal exhalation between them, often due to the patient’s inspiratory effort extending beyond the set inspiratory time. A ventilator-initiated breath that induces a reflex diaphragmatic contraction (“patient effort”) after the machine’s inspiratory phase, effectively the patient “following” the ventilator. The underlying physiology includes Patient inspiratory effort continues past the ventilator’s inspiratory time (Ti) and Flow or pressure returns to baseline but patient still “wants” to inhale, immediately triggering another breath.

Common Causes include Short Ti relative to patient’s neural inspiratory time (e.g., set Ti 0.8 s but patient needs 1.2 s), High drive (pain, anxiety, metabolic acidosis), and Insufficient flow in volume modes (patient “hungry” for flow - can sometimes also see flow starvation).

Focus includes ineffective triggering - definition, pathophysiology, waveform recognition, contributing factors, and management. Ventilator dyssynchrony occurs when the patient’s respiratory efforts are not appropriately matched by the ventilator. This can result in increased work of breathing, discomfort, sedation needs, and potentially worse outcomes. Ineffective (or missed) triggering happens when the patient initiates an inspiratory effort that fails to trigger a ventilator-assisted breath. The patient wants to inhale, but the ventilator doesn't "see" it.

As a result, the patient's effort is wasted. Ventilators detect a breath based on include drop in airway pressure (e.g., 1-2 cm H₂O below baseline) and drop in baseline flow (e.g., 1-3 L/min below baseline).

Ineffective triggering occurs when include The patient effort is too weak to meet the trigger threshold, Auto-PEEP creates a pressure barrier (intrinsic PEEP must be overcome), Ventilator settings are insensitive (e.g., flow trigger too high), and Muscle weakness or sedation/paralysis reduces effort.

This study guide summarizes the foundational ventilator settings commonly used in volume control and pressure control modes. It is written to stand alone as an educational resource for early trainees and advanced providers.

PEEP is the constant pressure maintained in the lungs at the end of expiration. It prevents alveolar collapse, recruits lung units, and improves oxygenation. Typical settings are 5-20 cm H₂O, with 5 being minimal support. Increasing PEEP is particularly useful for hypoxemia.

FiO₂ is the percentage of oxygen delivered with each breath. Room air at sea level is 21%. On a ventilator, FiO₂ can be set from 21-100%. Higher FiO₂ improves oxygenation, though prolonged use of 100% oxygen can cause toxicity. Clinicians often aim to use the lowest FiO₂ that maintains adequate oxygen saturation.

By the end of this chapter, we should be able to Distinguish oxygenation failure from ventilation failure at the bedside.

Mechanical ventilation is a supportive therapy, not a definitive treatment. Its role is to temporarily replace or assist the work of breathing while the underlying disease process is identified and treated. Understanding why we ventilate patients helps frame appropriate goals and expectations.

At the bedside, patients generally require invasive ventilation for one or more of the following reasons Failure of oxygenation - inadequate arterial oxygen levels despite supplemental oxygen, Failure of ventilation - inadequate removal of carbon dioxide resulting in respiratory acidosis, Excessive work of breathing - impending respiratory muscle fatigue that risks rapid decompensation, and Inability to protect the airway - altered mental status, severe intoxication, or loss of protective reflexes.

Mechanical Ventilation Basics: How To Present Mechanical Ventilation On Rounds introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Mechanical Ventilation Basics: Modes, Settings, Alarms, Troubleshooting introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Mechanical Ventilation Basics introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

PEEP • FiO₂ • Respiratory Rate • Tidal Volume • Inspiratory Pressure. The percentage of oxygen delivered to the patient. Start high (e.g., 100%) in critically ill patients. Pressure maintained in the lungs at end expiration.

Obstructive lung diseases (primarily COPD and asthma) are characterized by increased airway resistance and prolonged expiratory time. When mechanically ventilated, these patients are at high risk of air trapping and dynamic hyperinflation, which can lead to auto-PEEP, barotrauma, and hemodynamic compromise.

Avoid overdistension; lower tidal volumes may be needed if plateau pressures rise. Lower rate allows longer exhalation and prevents breath stacking. Use higher inspiratory flow to deliver the breath faster, shortening inspiratory time and allowing more time to exhale.

Key Interpretation include High PIP, normal Pplat = high airway resistance (typical in asthma/COPD), High PIP and high Pplat = reduced lung compliance (concern for overdistension), The Major Risk, and Auto-PEEP (intrinsic PEEP) occurs when there is incomplete exhalation before the next breath starts-air trapping. This raises intrathoracic pressure and can cause.

Mechanical Ventilation in Obstructive Lung Disease introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Positive End-Expiratory Pressure (PEEP) is the pressure maintained in the lungs at the end of expiration during mechanical ventilation. Key idea include PEEP prevents alveolar collapse and improves oxygenation - but at the cost of increased intrathoracic pressure. Without PEEP include Repeated alveolar collapse and reopening occurs. Leads to worsening lung injury and impaired oxygenation.

Goal includes deliver a clear, concise, and clinically relevant ventilator summary during ICU presentations. Pressure to keep alveoli open at end expiration.

A pressure support spontaneous breathing trial allows the patient to breathe independently while the ventilator provides a small amount of positive pressure during inspiration. The ventilator only provides a preset pressure boost during inspiration. Core idea includes spontaneous breathing with minimal inspiratory assistance. During PSV include The patient generates negative pressure to trigger the ventilator and The ventilator delivers a fixed inspiratory pressure. Inspiratory flow decreases naturally and cycles off when flow falls.

This reduces the effort required from respiratory muscles. A CPAP spontaneous breathing trial allows completely spontaneous breathing while maintaining a continuous baseline airway pressure throughout the respiratory cycle.

A spontaneous breathing trial (SBT) is the gold-standard bedside assessment to determine whether a patient can be safely liberated from mechanical ventilation. It evaluates the patient’s ability to breathe without significant ventilatory support, simulating post-extubation conditions. Timing includes usually after resolution of the underlying illness, hemodynamic stability, and adequate oxygenation/ventilation (lots of varying practice patterns). Prerequisites include FiO₂ ≤ 60% and PEEP ≤ 10 cm H₂O (general targets, may vary by patient), Hemodynamic stability (minimal/no vasopressors), Adequate mental status (can protect airway), and Manageable secretions.

Methods include Patient breathes through endotracheal tube with supplemental O₂ but no ventilator assistance, Pressure Support Ventilation (PSV): Most common in ICUs. Ventilator provides minimal support (PS 5-8 cm H₂O, PEEP 5 cm H₂O) to overcome endotracheal tube resistance, Continuous pressure applied but no pressure support, Multicenter RCT (≈1,000 patients) comparing pressure-support SBTs vs T-piece SBTs before extubation, and Pressure-support trials were associated with lower extubation failure rates than T-piece, especially in high-risk patients (older age, COPD, cardiac disease).

Rationale includes the endotracheal tube adds resistance; small pressure support helps approximate normal post-extubation conditions. Typical settings includes pS 5-8 cm H₂O, PEEP 5 cm H₂O, FiO₂ ≤ 60%. Provides a balance between realism and patient comfort. Clinical markers of success during an SBT HR < 120-140, SBP 90-180, minimal vasopressor needs and SpO₂ ≥ 90%, PaO₂/FiO₂ > 150-200. Tolerable work of breathing (no diaphoresis, accessory muscle use, paradoxical breathing).

VentilatorA machine that delivers gas (usually air or oxygen) into the lungs under positive pressure to assist or replace spontaneous breathing. Positive Pressure VentilationDelivery of gas to the lungs by pushing air in under pressure; exhalation occurs passively when pressure is released. Respiratory Rate (RR)Number of breaths delivered by the ventilator per minute. Positive End-Expiratory Pressure (PEEP)The pressure maintained in the airways at end expiration to prevent alveolar collapse; typical settings are 5-10 cm H₂O.

Plateau Pressure (Pplat)Pressure measured during an inspiratory pause (no flow); estimates alveolar pressure and lung compliance. ComplianceChange in volume per change in pressure (ΔV/ΔP);. Delivers mandatory breaths synchronized to patient effort; allows spontaneous breaths in between. Patient-triggered and cycled breaths supported to a set pressure level. High baseline pressure with intermittent releases to facilitate ventilation. Inspiratory-to-Expiratory Ratio (I:E Ratio)Ratio of time spent in inspiration versus expiration (e.g., 1:2, 1:1.5). Flow RateThe speed at which gas is delivered during inspiration (L/min).

Trigger SensitivityThreshold (pressure or flow) that determines how easily the patient can initiate a ventilator breath. Rise Time (Pressurization Time)Time taken for the ventilator to reach set inspiratory pressure in pressure-targeted modes.