Domain: Healthcare — Human Physiology
Target concept: Effect of Breath Holding on Blood Oxygen Saturation

Video generation prompt: Connect the oximeter to the subject's finger and record the resting oxygen saturation. Then, have the subject hold their breath for 30 seconds and observe the changes in the oxygen saturation values.

Evaluation guide:
(i) Target concept: Peripheral oxygen saturation (SpO₂) is dynamically responsive to alveolar ventilation status; breath-holding induces progressive arterial desaturation that becomes detectable at the fingertip within roughly 20-30 seconds, reflecting both the physiological desaturation timeline and the several-second response lag inherent to finger pulse oximetry.
Minimum mechanism: Functional pulse oximeter must be correctly applied to perfused finger tissue; subject must suspend respiratory gas exchange for the full hold; photoplethysmographic signal must remain valid (no motion artifact) to yield an interpretable SpO₂ trend.
(ii)Storyline: [Frame sequence] 1. Static shot: oximeter clipped to finger, stable ≥95% value visible on screen. 2. Subject closes mouth and ceases breathing (no chest rise/fall) for a sustained ~30-second hold. 3. Oximeter screen updates to show a lower numeric value partway through or near the end of the hold; same device, same finger, no repositioning. 4. Value remains stable at the lower level until breath is released. Perspective: Fixed frontal/side view capturing both the finger-oximeter interface and screen display; no camera movement; full visibility of the oximeter screen and finger pad at all times.

Manual:
Experimental Procedure
1. Attach pulse oximeter securely to subject's index finger.
2. Wait for stable resting SpO₂ reading (displayed numerically on device).
3. Instruct subject to hold breath for 30 seconds.
4. Observe and record the SpO₂ value during and immediately after the breath-hold.
Observation of Experimental Phenomena
Resting SpO₂ displays ≥95%; during the 30-second breath-hold, the SpO₂ value begins to fall after a several-second lag (reflecting pulse-oximeter signal averaging and finger circulation time) and stabilizes at a lower numeric value (<95%).
Summary of Experimental Principles
Holding the breath halts alveolar gas exchange, so already-bound oxygen is progressively consumed while carbon dioxide accumulates, producing a measurable decline in arterial — and pulse-oximeter-measured peripheral — oxygen saturation. Because pulse oximeters average their signal over roughly 10-20 seconds and blood must recirculate from the lungs to the fingertip capillary bed, the displayed drop lags a few seconds behind the true onset of desaturation; a hold of at least ~25-30 seconds is therefore needed for the decrease to become clearly visible on the device.

Prompt Grounding rubric:
level_1: No pulse oximeter is visible anywhere in the frame; no human hand or finger appears; no breath-holding action (closed mouth, still chest) is depicted; and neither a resting nor a during-hold oxygen-saturation number is ever shown on any screen.
level_2: A pulse oximeter appears but is not clipped onto a finger, or a finger is shown with no oximeter attached; alternatively, the subject appears to hold their breath (mouth shut, no chest movement) but the oximeter screen never displays a numeric SpO₂ reading at any point.
level_3: The oximeter is clipped onto a finger and shows a resting SpO₂ reading before the hold begins; the subject's mouth stays closed with no visible chest or abdomen movement for a sustained period; however, the number on the oximeter screen never changes from its resting value anywhere in the clip.
level_4: The oximeter remains clipped to the same finger throughout; a resting SpO₂ reading (≥95%) is shown before the subject begins holding their breath; the subject's mouth stays closed with no visible inhalation or exhalation for a sustained interval consistent with roughly a 30-second hold; a second, lower SpO₂ number subsequently appears on the same screen, all of this occurring in one continuous, spatially coherent scene.
level_5: In addition to everything required for score 4, the oximeter screen legibly displays two distinct numbers in sequence (an initial reading ≥95% and a later reading <95%), both readable without cuts, freeze-frames, or overlay graphics splicing them together; the same finger and same device stay in unbroken contact from the first reading through the second.

Scientific and Causal Correctness rubric:
level_1: The displayed SpO₂ number shows no relationship to the breath-hold at all: it stays exactly the same, rises, or jumps erratically (e.g., up then down) regardless of whether the subject is holding their breath; or the oximeter shows a physiologically impossible reading (e.g., over 100% or under 50% with no clinical context).
level_2: The SpO₂ number changes, but in the wrong direction (e.g., it rises while the subject is visibly holding their breath), or the change happens before the hold starts or only after the subject has already resumed breathing; or the screen shows dashes/error symbols instead of a number during the hold.
level_3: The SpO₂ number decreases at some point in the video, but the decrease is not clearly linked to the breath-hold (for instance it drops while the subject can be seen breathing normally), or the oximeter shows only a single unchanging reading for the whole clip, or the finger's contact with the sensor pad is too ambiguous (loose clip, visible gap) to trust the reading.
level_4: The SpO₂ number decreases while the subject's mouth is visibly closed and the chest/abdomen show no breathing motion, with the drop appearing sometime during the roughly 30-second hold (a natural several-second lag before the reading responds is expected and acceptable) rather than being required at the very first instant of the hold; the oximeter clip stays seated on the fingertip with the sensor pad fully covered; no other visual cue contradicts the depicted physiology.
level_5: All requirements for score 4 are satisfied, plus the drop is unambiguous: two clearly legible, stable numbers appear in sequence on the same oximeter display (an initial reading and a strictly lower later reading), with no flicker, overlay, or on-screen distortion obscuring either number, and no extraneous text or device interferes with the oximeter's display at any point.

Spatiotemporal Consistency rubric:
level_1: The oximeter or the subject's finger disappears from view partway through the clip and then comes back with no visible motion connecting the two moments; the hand or device jumps to a noticeably different position or angle between shots with no motion shown connecting them; the room lighting switches abruptly (e.g., bright to dark) with no gradual change; the number on the oximeter screen replaces itself with a hard cut instead of any visible update.
level_2: The finger or the oximeter body visibly warps or changes shape; the clip is seen detaching from the finger and reattaching partway through the clip; the chest or abdomen is seen rising and falling (a breath) at some point during what is supposed to be the breath-hold; the displayed number disappears and a new number appears with no visible transition between the two.
level_3: The oximeter stays clipped in the same position on the same finger for the entire clip; the mouth remains closed with no breathing motion visible during the hold; the lighting on the hand and screen looks the same from the start of the clip to the end, with no sudden shift; the video shows no flickering or breaking-apart of the hand, device, or screen; ordinary hand stillness (an imperceptible natural tremor) is acceptable.
level_4: Beyond what is required for score 3, the finger and oximeter keep the same relative position and angle throughout: no sliding, twisting, or repositioning of the clip on the finger; the closed-mouth, no-breathing posture is maintained continuously across the entire hold with no visible breath at any point; when the SpO₂ number changes, it updates cleanly rather than being spliced or jump-cut in.
level_5: Beyond what is required for score 4, the hand's posture, the oximeter's angle, and the visibility of its screen stay constant throughout the clip with no visible shake or wobble; the numeric display can be read continuously with no strobing, doubling, or stutter of the digits; the background behind the hand does not change at any point in the clip.