Monitoring, Ventilator Graphics & Patient Transport

Objectives — Monitor patient-ventilator system parameters; perform a ventilator system check; correct patient-ventilator dyssynchrony using ventilator graphics; determine procedures for transporting mechanically ventilated patients.

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Monitored Values

Pressures

Volumes

• Inhaled tidal volume (mandatory and spontaneous)
• Exhaled tidal volume (measured)
• Minute volume (mandatory + spontaneous)

Rates

• Mandatory rate
• Spontaneous rate
• Total rate

Pulmonary Mechanics

• Dynamic compliance
• Static compliance
• Airway resistance (RAW)
• MIP / MEP
• P0.1 (inspiratory pressure 100 ms after occlusion — weaning parameter)

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Peak Inspiratory Pressure (PIP)

PIP is affected by:

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Mean Airway Pressure (MAP / Paw)

• Normal: 5–10 cmH₂O
• Higher MAP = poorer oxygenation status and greater risk of adverse cardiac effects from positive pressure

Factors that increase MAP:

• PIP / tidal volume
• PEEP
• I-time / I:E ratio
• Respiratory rate
• Decreased compliance
• Increased RAW

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Plateau Pressure (Pplat)

Measured by programming an inspiratory hold ("inspiratory pause button").

• Represents pressure in the small airways and alveoli
• Always lower than PIP — because there is no flow during the hold, there is no RAW pressure component
• Target: < 30 cmH₂O (ARDS < 28 cmH₂O)

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Driving Pressure (ΔP)

Driving Pressure = Pplat − PEEP

The pressure required to deliver a tidal breath from the PEEP baseline to the plateau.

• Current literature: maintain < 15 cmH₂O

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Auto-PEEP (Intrinsic / Occult PEEP)

Gas trapped in alveoli at end-exhalation — abnormal and often undetected.

Causes

• Inadequate expiratory time (high RR, low PIFR)
• Obstructive disease (bronchoconstriction, secretions)
• Dynamic hyperinflation

Detecting Auto-PEEP

• Expiratory hold maneuver — direct measurement
• Flow-time scalar — flow does not return to zero before the next breath begins
• Flow-volume loop — flow does not return to baseline

Resolving Auto-PEEP

1. Bronchodilator therapy
2. Suction the airway
3. Increase the airway size if ETT is too small
4. Decrease I:E ratio (more time for exhalation):
   • Decrease rate
   • Increase PIFR (shortens I-time)
5. Allow spontaneous breathing — switch to CPAP
6. Disconnect from ventilator briefly
7. Measure PEEPi with expiratory hold button

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Pulmonary Mechanics

Dynamic Compliance

Cdyn = Vt / (PIP − PEEP)

Reflects both lung/chest compliance AND airway resistance (because flow is present).

Static Compliance

Cstat = Vt / (Pplat − PEEP)

Reflects only lung and chest wall compliance (no flow = no RAW contribution).

• Normal: 60–100 mL/cmH₂O
• Lower values indicate: ARDS, atelectasis, pneumothorax, pulmonary fibrosis, chest wall stiffness

Distinguishing RAW from Compliance Changes

"The Delta tells the story" — if only PIP rises (Pplat stays), it's a RAW problem. If both PIP and Pplat rise together, it's a compliance problem.

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Patient-Ventilator System Check

Definition

A documented evaluation of the mechanical ventilator and the patient's response to ventilatory support. Also called a "ventilator check."

When to Perform

• Scheduled basis — generally every 2 hours (institution-specific)
• Before obtaining blood samples for ABG analysis
• Before hemodynamic or bedside pulmonary function tests
• After any change in ventilator settings
• After acute deterioration in patient condition
• Any time ventilator performance is questionable

Objectives

• Document patient response at the time of the check
• Verify proper ventilator operation and patient connection
• Confirm alarms are set appropriately
• Confirm inspired gas is heated and humidified
• Measure FiO₂ with every change and at least every 24 hours
• Confirm settings match physician orders

Equipment Needed

• Stethoscope
• Universal precautions supplies
• Documentation paperwork
• Oxygen analyzer
• Cuff manometer

Procedure

1. Date and time, patient name and ID
2. Airway — size and position
3. Check circuit for condensation — empty as needed
4. Change expiratory filters as needed
5. Note date and time of last circuit change
6. Assess vital signs and breath sounds
7. Document all ventilator settings: mode, FiO₂, PEEP, Vt, RR, PIP limit, PS, PIFR and waveform, I:E ratio, sensitivity, humidifier temperature and water level
8. Document all measured values: PIP, Pplat, MAP, baseline, auto-PEEP, delivered Vt (inhaled and exhaled), minute volume (total and spontaneous)
9. Verify alarm settings and function
10. Assess patient-ventilator synchrony via graphics

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Ventilator Graphics

Purpose

Waveforms reflect the patient-ventilator interaction and allow the clinician to:

• Interpret ventilator and patient mechanics (compliance, RAW)
• Evaluate patient-ventilator synchrony
• Troubleshoot problems
• Fine-tune settings to reduce WOB

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Types of Waveforms

Scalars (Time-Based Waveforms)

Pressure-Time Scalar

• Y-axis: pressure (cmH₂O); X-axis: time (sec)
• Most common waveform in volume control
• Shows PIP, PEEP, and Pplat (during inspiratory hold)

Flow-Time Scalar

• Y-axis: flow (L/min); X-axis: time (sec)
• Inspiration above baseline; expiration below baseline
• Best for detecting auto-PEEP (flow does not return to zero) and bronchodilator response

Volume-Time Scalar

• Y-axis: volume (mL or L); X-axis: time (sec)
• If the tracing does not return to baseline → leak suspected

Loops

Pressure-Volume (P/V) Loop

• Controlled breaths move counter-clockwise
• Used to: adjust Vt, set PEEP via opening pressure (~15 cmH₂O), detect compliance changes

Flow-Volume (F/V) Loop

• Good for detecting auto-PEEP and small airway obstruction
• Resembles an FVC loop but reversed and not forced

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Using Graphics to Troubleshoot

Flow Starvation (PIFR Too Low)

• Sign: pressure-time scalar shows a downward dip during inspiration (patient demand exceeds flow delivery)
• Cause: PIFR set too low for patient's inspiratory demand
• Fix: increase PIFR

Peak Flow Too High

• Sign: very sharp pressure rise and short I-time; flow-time scalar returns to zero quickly
• Fix: decrease PIFR or increase I-time

Setting and Adjusting Tidal Volume via P/V Curve

• Normal P/V curve is S-shaped with an upper inflection point (over-distension) and lower inflection point (recruitment)
• Set Vt below the upper inflection point to avoid overdistension
• Pplat < 30 cmH₂O

Setting PEEP via P/V Curve

• Opening pressure (lower inflection point) ≈ 15 cmH₂O
• Set PEEP just above the opening pressure to prevent cyclic alveolar collapse

Detecting Increased Airway Resistance

Use the "delta" (PIP − Pplat):

Causes: secretions in airway, condensation in circuit, bronchospasm, full HME or filter

Treatment: suction, clear circuit water, bronchodilator

Detecting Decreased Compliance

Both PIP and Pplat rise proportionally — the delta stays the same.

Common causes: atelectasis, pulmonary edema, ARDS, pneumonia, pneumothorax

Treatment: increase PEEP, treat underlying cause

Detecting Leaks

• Detected on any waveform that includes volume (V-T scalar, F/V loop, P/V loop)
• V-Time scalar best — tracing does not return to baseline at end-exhalation

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Intra-Hospital Transport

Transportation of mechanically ventilated patients for diagnostic or therapeutic procedures:

• CT scan
• MRI
• Angiography

Includes preparation, movement to and from, and time spent at the destination.

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Inter-Hospital Transport Distance Guidelines

Goal: Improve survivability and decrease mortality.

Indications

Transport should only be undertaken after careful evaluation of the risk-benefit ratio.

Literature suggests nearly two-thirds of all transports for diagnostic studies fail to affect patient care.

Contraindications to Transport

• Cannot adequately oxygenate and ventilate during transport
• Cannot maintain acceptable hemodynamics
• Cannot adequately monitor patient status
• Cannot maintain airway control
• Transport team not fully assembled

Hazards of Transport

• Hyperventilation during manual ventilation → respiratory alkalosis
• Disconnection from ventilatory support
• Accidental extubation
• Loss of oxygen supply → hypoxemia
• Loss of PEEP/CPAP → hypoxemia
• Position changes → hypotension, hypercarbia, hypoxemia
• Equipment failure
• Inadvertent IV disconnection

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Transport Equipment

General

• Airway management supplies (check function before transport)
• Portable oxygen source
• Self-inflating bag and mask
• Portable monitor: ECG, HR, SpO₂, blood pressure
• Portable cardiac monitor / defibrillator
• Infusion pumps
• Appropriate pharmacologic agents (ALS)

Transport Ventilator Requirements

Power source: pneumatic only, or pneumatic + electronic.
Circuit: single-limb with exhalation valve, exhalation port, and PEEP valve.

Calculating Tank Duration

Tank Duration (min) = (Tank PSI × Tank Factor) / Minute Volume (L/min)

Tank Duration (hr) = Tank Duration (min) / 60

Note: Not all ventilators are 100% efficient — some gas drives internal circuitry and is not delivered to the patient.

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Transport Monitoring

Continuous:

• ECG and heart rate
• Blood pressure (arterial line preferred)
• Pulse oximetry
• Airway pressures (if transport ventilator used)

Periodic:

• Non-invasive blood pressure
• Respiratory rate
• Tidal volume

Selected patients may also need:

• Capnography (EtCO₂)
• Intra-arterial blood pressure
• Pulmonary artery pressure
• Intracranial pressure

Goal: provide the same level of monitoring during transport as the patient had in the ICU.

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Transport Team

• Registered Nurse
• Respiratory Therapist
• Physician — not mandatory, but should accompany unstable patients
• At least one member proficient in airway management
• At least one member must be an ACLS provider
• All members share responsibility for patient safety

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CCATT — Critical Care Air Transport Team

Mission

Maintain the ICU standard of care while moving the patient to more specialized care.

Training Location: Wright-Patterson AFB, Cincinnati, Ohio

Team Members

• Critical Care Physician (ideally)
• Critical Care Nurse
• Respiratory Therapist

CCATT Equipment

• 3 × Transport ventilators
• Infusion pumps (trained on specific pump during CCATT training)
• Portable suction
• Transport monitor / defibrillator
• Airway kit
• SMEED — platform for mounting all equipment to the litter
• I/O kit
• Medicine kit (sedation lockbox)
• iStat (portable ABG / blood analyzer)

Aircraft

• KC-135
• C-130

Gas Supply Options

• Portable liquid oxygen (most common)
• Aircraft oxygen supply
• Compressed oxygen cylinders with air compressor
• Oxygen blenders (neonatal transports)
• Oxygen concentrators

Aircraft-Specific Hazards

Effects of Altitude

As altitude increases, atmospheric pressure decreases and gas volume expands (Boyle's Law).

• Use Wright's spirometer to verify tidal volume in flight — volume delivered may differ from ground settings
• ETT cuff: expands during ascent (risk of tracheal injury) and deflates during descent (risk of aspiration)
  • Check and adjust cuff pressure before and after takeoff and landing