10.4 Step 4 Prototyping: Mock-Ups, Simulation & Iterative Evaluation

Step 4 Prototyping: Mock-Ups, Simulation & Iterative Evaluation

Core Principle: In Evidence-Based Design, a prototype is not a promotional showroom—it is an empirical laboratory. Mock-ups within Step 4 of CHD's eight-step process bridge design concepts and hypotheses with constructed reality, utilizing physical mock-ups, scripted clinical simulations, and human factors ergonomics to discover latent safety hazards, eliminate costly change orders, and optimize clinical workflows before concrete is poured.

Traditional healthcare architecture historically relied on two-dimensional blueprints and static three-dimensional renderings, presenting plans to clinical leadership for sign-off. However, clinical end-users—such as bedside nurses, surgeons, respiratory therapists, and environmental services technicians—cannot reliably evaluate complex three-dimensional ergonomics, dynamic workflow clearances, medical gas reach distances, or sightline obstructions from paper drawings. Consequently, critical design errors were frequently discovered only after the facility was constructed, necessitating expensive field change orders or permanently compromising clinical safety.

In the Evidence-Based Design (EBD) process described by The Center for Health Design (CHD), constructing mock-ups is one of the tasks within Step 4: Create and innovate evidence-based design concepts.

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Prototyping in the CHD 8-Step EBD Process

To see where prototyping fits, review The Center for Health Design's eight steps:

1. Define evidence-based goals and objectives
2. Find sources for relevant evidence
3. Critically interpret relevant evidence
4. Create and innovate evidence-based design concepts ← mock-ups and simulation happen here
5. Develop a hypothesis
6. Collect baseline performance measures
7. Monitor implementation of design and construction
8. Measure post-occupancy performance results

EDAC Study Guide 3 lists constructing mock-ups among the schematic design tasks, alongside annotating diagrams, documenting assumptions, updating hypotheses, testing design concepts, and selecting the best options (Section 10.3). The steps are iterative: mock-up findings can prompt new hypotheses or a return to the evidence.

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Hierarchical Typologies of Mock-Ups

Evidence-based prototyping is not a one-time event; it is an iterative continuum that progresses from rapid, inexpensive low-fidelity models to fully operational, high-fidelity environments.

Hierarchy of Prototyping Typologies

┌─────────────────────────────────────────────────────────────────────────┐
│ 1. Low-Fidelity Mock-Up (Schematic Design - SD)                         │
│ • Foam-core / Cardboard / Floor tape                                   │
│ • Rapid, low-cost ($)                                                   │
│ • Tests gross spatial volumes, bed orientation, door swings, clearances │
└───────────────────────────────────┬─────────────────────────────────────┘
                                    │ Iterative Feedback Loop
                                    ▼
┌─────────────────────────────────────────────────────────────────────────┐
│ 2. Mid-Fidelity Modular Mock-Up (Early Design Development - DD)         │
│ • Plywood framing / Modular casework / Adjustable rails                 │
│ • Moderate cost ($$)                                                    │
│ • Tests casework heights, reach zones, preliminary equipment layouts    │
└───────────────────────────────────┬─────────────────────────────────────┘
                                    │ Iterative Feedback Loop
                                    ▼
┌─────────────────────────────────────────────────────────────────────────┐
│ 3. High-Fidelity Fully Operational Mock-Up (Mid-to-Late DD)              │
│ • 1:1 Scale exact materials / Welded vinyl / Functional medical gases   │
│ • Working ceiling lifts / Realistic lighting scenes / Full equipment    │
│ • Substantial investment ($$$)                                          │
│ • Conducts scripted clinical simulations (Code Blue, Bariatric Transfer)│
└─────────────────────────────────────────────────────────────────────────┘

1. Low-Fidelity Rapid Mock-Ups (Schematic Design)

Constructed during the Schematic Design (SD) phase inside an empty warehouse or hospital basement, low-fidelity mock-ups utilize inexpensive materials such as corrugated cardboard, foam-core sheets, 2x4 lumber framing, and colored floor tape:

• Primary Purpose: Evaluate macro-spatial geometries, gross square footage, door swings, structural column encroachments, and bulk clearances.
• Operational Advantage: Exceptional flexibility. If an emergency physician notes that the trauma bay doorway impedes two passing stretchers, or a nurse realizes a bathroom door will strike the bed, the wall can be cut with a utility knife, relocated, retaped, and retested in 15 minutes at zero construction cost.

2. Mid-Fidelity Modular Mock-Ups (Early Design Development)

Bridging SD and Design Development (DD), mid-fidelity mock-ups employ prefabricated modular panels, adjustable rail systems, and rough plywood millwork:

• Primary Purpose: Evaluate spatial heights, supply storage reach envelopes, counter depths, sink locations, and computer charting station orientations relative to patient sightlines.

3. High-Fidelity Fully Operational Mock-Up Rooms (Design Development)

Constructed during Design Development (DD), high-fidelity mock-ups are exact 1:1 physical replicas of key repeatable room typologies (such as acute care patient rooms, intensive care suites, operating rooms, and emergency trauma bays):

• Full Technical Functionality: Built with actual specified finishes—seamless welded sheet vinyl flooring with integral 6-inch coving, impact-resistant drywall, specified high-NRC acoustic ceilings, operational dynamic circadian lighting controls, plumbed handwashing sinks, and fully functional architectural headwalls or ceiling power columns equipped with active medical gases (oxygen, medical air, vacuum suction).
• Real Clinical Equipment Integration: Outfitted with authentic hospital beds, overhead ceiling lift tracks and motors, IV smart infusion pumps, physiological monitors, ventilators, and crash carts.
• Primary Purpose: Provide an authentic, immersive clinical testbed where multidisciplinary teams can run high-stress simulation scenarios to evaluate ergonomics, equipment collisions, and clinical safety.

Virtual Reality (VR) & 3D CAVE Environments

Virtual Reality (VR) head-mounted displays and Cave Automatic Virtual Environments (CAVEs) allow users to explore digital Building Information Models (BIM) in immersive 3D. While highly effective for visualizing unit-wide circulation sightlines, sun-angle glare across seasons, and finish color schemes, virtual reality cannot replace physical mock-ups. VR lacks tactile feedback, cannot simulate the real-world resistance of moving a 500-lb bariatric patient sling, and cannot capture the physical congestion of 10 clinicians managing tangled IV lines and oxygen hoses around a cardiac arrest patient.

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Interdisciplinary Simulation-Based Testing Protocols

The true power of a high-fidelity mock-up is realized when it is subjected to scripted clinical simulations. Rather than passive walkthroughs, multidisciplinary teams execute rigorous, standardized clinical emergency scenarios.

Code Blue Resuscitation Simulation Layout in High-Fidelity Mock-Up

                 Airway Physician / RT
                 ┌──────────────────┐
                 │   Head of Bed    │
    Defibrillator│   [Removed]      │Crash Cart
    ┌──────────┐ │                  │┌──────────┐
    │ Defib /  │ │  Patient Bed     ││ Medication│
    │ Oper. RN │ │                  ││ RN / RT  │
    └──────────┘ │  Chest Comp. RN  │└──────────┘
                 │  ┌────────────┐  │
                 │  │ (Bedside)  │  │
                 └──┴────────────┴──┘
                   IV / Infusion RN

    Code Leader ◄──────────────────► Chart Scribe RN
    (Foot of Bed Clearance)         (Doorway Sightline)

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Human Factors & Ergonomic Evaluation Methodologies

To ensure prototype testing produces objective, defensible data rather than subjective opinion, EBD researchers employ formal human factors and ergonomics (HFE) assessment methods:

1. Video Motion Tracking & Spaghetti Diagrams

High-definition overhead cameras record all personnel movements during simulated care events. Researchers map each clinician's movement pathways onto floor plans, creating spaghetti diagrams:

• Metrics Captured: Total cumulative walking distances (meters/feet), frequency of directional backtracking, wasted steps to fetch supplies, and physical collisions in high-traffic choke points.
• Design Impact: Comparing competing room designs (e.g., inboard bathroom vs. outboard bathroom) reveals which layout minimizes clinician travel and eliminates spatial bottlenecks during emergency care.

2. Wearable Eye-Tracking Technology

Clinicians wear lightweight eye-tracking glasses during simulations to record their visual gaze points and pupillary scan paths:

• Metrics Captured: Fixation duration, visual dwell time, and scan frequency on vital signs monitors, medication labels, alarm beacons, and elapsed-time clocks.
• Design Impact: Uncovers visual obstructions—such as ceiling-mounted IV poles or boom arms blocking the nurse's direct line of sight to cardiac telemetry monitors while administering critical medications.

3. Postural & Biomechanical Strain Analysis (RULA & REBA)

Ergonomists assess physical posture during tasks such as transferring patients, plugging equipment into headwalls, or accessing supply carts using validated postural scoring tools:

• RULA (Rapid Upper Limb Assessment): Evaluates biomechanical loading on the neck, trunk, and upper extremities (shoulders, arms, wrists).
• REBA (Rapid Entire Body Assessment): Evaluates full-body postural stress, dynamic lifting loads, and musculoskeletal injury risk.
• Design Impact: Identifies awkward trunk flexion, excessive reaching (>24 inches across beds), or dangerous twisting, leading to optimized heights for headwall medical gas outlets and monitor arms.

4. Cognitive Workload Scoring (NASA-TLX)

The NASA Task Load Index (NASA-TLX) is a standardized multidimensional assessment instrument that measures subjective cognitive workload across six subscales:

1. Mental Demand: How much mental and perceptual activity was required?
2. Physical Demand: How much physical activity was required?
3. Temporal Demand: How much time pressure was felt?
4. Performance: How successful was the participant in executing the task?
5. Effort: How hard did the participant have to work to achieve their level of performance?
6. Frustration Level: How irritated, stressed, or annoyed did the participant feel?

Clinicians complete the NASA-TLX immediately after simulated scenarios in competing room prototypes (for example, two headwall layouts), giving the team a structured comparison of perceived workload to weigh alongside observed performance.

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Uncovering Latent Safety Threats & Physical Design Conflicts

Prototyping routinely exposes critical latent safety threats—environmental hazards embedded in the design that would remain hidden until triggered by real-world clinical operations:

• Medical Gas & Cord Clashes: High-fidelity testing frequently discovers that medical gas outlets on the headwall are located directly behind patient bed frames or IV poles. Inserting flowmeters or suction canisters requires staff to contort over the patient, and heavy electrical cables cross paths of travel, creating severe tripping hazards.
• Ceiling Lift Disconnects: Mock-up simulations often reveal that a linear ceiling lift track terminates 3 feet short of the bathroom toilet. As a result, staff must manually unhook and pivot a vulnerable patient mid-transfer, dramatically increasing fall risk and caregiver back injuries. Discovering this allows the team to redesign the track as a continuous curved line directly into the toilet room.
• Bathroom Door Collisions & Patient Trapping: Inward-swinging bathroom doors are a serious hazard: if a patient collapses inside the bathroom, the body can block the door, delaying rescue. Mock-up trials test and validate alternative solutions, such as bidirectional rescue hinges, sliding pocket/barn doors with acoustic drop seals, or outward-swinging doors with emergency breakaway hardware.
• Hand Hygiene Sink Splash Radius: In simulations using fluorescent dye under UV blacklight, handwashing in poorly specified shallow sinks can show droplets landing about a meter or more from the sink, onto nearby clean counters, prompting splash guards or sink relocation.

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The Financial Business Case: The 1-10-100 Cost-of-Change Rule

Healthcare executives sometimes question the cost of building and testing high-fidelity mock-ups. EDAC study materials note that the time and money saved despite the initial cost of creating mock-ups is significant. The logic is often expressed as a cost-of-change curve (sometimes called a "1-10-100" rule of thumb): the later a problem is found, the more it costs to fix.

The Cost-of-Change Curve in Healthcare Facility Delivery

 Phase 1: Prototype / Mock-Up Phase ─────► Revise drawings / model (lowest cost)
 Phase 2: Active Construction Phase  ─────► Field change orders (higher cost)
 Phase 3: Post-Occupancy Phase       ─────► Retrofits in occupied rooms (highest cost)
 (Illustrative orders of magnitude; actual costs vary)

• Fixing an Error during Prototyping: If simulation reveals that medical gas outlets are 8 inches too low or an electrical conduit conflicts with a ceiling lift bracket, revising the digital CAD/BIM model costs a few hundred dollars in drafting time.
• Fixing an Error during Construction: If that same conflict is discovered after drywall and conduit rough-in during active construction, the contractor must issue formal Requests for Information (RFIs), demolish installed assemblies, re-route plumbing, patch drywall, and pay overtime labor, escalating into hundreds of thousands of dollars in cumulative change orders across a 250-bed tower.
• Fixing an Error Post-Occupancy: If the error is discovered after the hospital opens, remediating it requires shutting down operational, revenue-generating acute care beds, erecting dust barriers, venting negative air, paying premium containment contractors, and risking nosocomial fungal outbreaks (e.g., Aspergillus) among immunocompromised patients.

By catching mechanical, electrical, plumbing, and ergonomic conflicts before construction documents are finalized—and multiplying each fix across many identical rooms—mock-ups frequently pay for themselves while improving safety from opening day.