Touch & gestures
Consumer touch design assumes a person holding a device, looking at it, with clean bare hands, giving it their attention. A clinical surface is a cart being pushed, a wall display two metres away, a tablet operated through nitrile at arm's length, and a screen that gets leaned on.
Every gesture has an equivalent single-pointer control that is visible without performing the gesture. A gesture may be a shortcut. It may never be the way a function is discovered, and it may never be the only way a function is reached.
And, separately: no gesture acknowledges, silences or dismisses an alarm.
Why gestures are treated as a hazard here
A gesture has three properties that are fine in a consumer application and are not fine on a medical device.
- It is invisible. Nothing on screen says the gesture exists. A user who does not already know cannot find it, and a user who half-knows it will try variants.
- It is performed, not selected. Between deciding and acting there is a physical motion that can be interrupted, mis-tracked, or produced by something other than a finger — a sleeve, a palm, a cable, a bedrail.
- It has no target. A button occupies a place you can point at and describe to a colleague over the phone. "Swipe left on it" is not a location.
None of that argues against gestures as accelerators for people who use a device all day. It argues that a gesture cannot carry the primary path to anything, which is what SC 2.5.1 requires and what this page extends to alarms specifically.
Targets
| Context | Minimum target | Why |
|---|---|---|
| Baseline, any touch surface | 44 × 44 px | SC 2.5.8 requires 24 px; this system requires 44 px because none of its contexts are the calm seated one that 24 px assumes. |
| Gloved operation | 56 × 56 px | A gloved fingertip has a larger, less certain contact patch and worse proprioception. The user cannot feel the edge of the target. |
| Destructive or irreversible | 56 × 56 px, and separated | At least 12 px of dead space from any neighbouring control, and never adjacent to the control a user reaches for most. |
| Wall-mounted or across-room | Scaled by distance | Governed by Scaling & density. A target is sized for the reach distance it is actually used at, not the one it was designed at. |
Spacing matters more than size. Two 56 px targets touching each other are worse than two 44 px targets with a gap, because the failure mode of a large target is hitting its neighbour. Dead space is a control in its own right.
Permitted, and on what terms
| Gesture | Permitted for | Required equivalent |
|---|---|---|
| Tap | Everything. This is the primary input. | — |
| Scroll / pan | Moving a viewport | Visible scrollbar, and keyboard paging |
| Pinch to zoom | Zooming an image or a chart | Visible zoom controls with stated magnification — the value must be readable as a number, not inferred from the picture |
| Drag | Reordering, adjusting a boundary or a limit | A typed or stepped input for the same value — SC 2.5.7. A dragged value is also never committed on release without confirmation. |
| Long press | Revealing a secondary menu | A visible control that opens the same menu |
| Swipe | Paging between whole views | Visible previous/next controls |
Prohibited
- No gesture acknowledges, silences or dismisses an alarm. IEC 60601-1-8 expects a deliberate operator action; a swipe is exactly the motion a sleeve, a palm or a wiped-down screen produces. Acknowledgement is a targeted press on a labelled control, per Acknowledge & escalate — which also forbids doing it to more than one alarm at a time, and a swipe across a list is the most natural bulk-acknowledge gesture there is.
- No swipe-to-delete, swipe-to-dismiss or swipe-to-complete on clinical items. These make a destructive act out of an ambiguous motion, and place it exactly where a scroll goes wrong.
- No gesture is the only route to a function. SC 2.5.1, and the discoverability problem above.
- No path-based or multi-point gesture is required — no two-finger rotate, no three-finger anything, no shape tracing. SC 2.5.1 again, and they are unavailable to anyone using a head pointer, a stylus, or one hand.
- Nothing acts on touch-down. Actions fire on release, over the target, so a touch that started wrong can be dragged away and abandoned — SC 2.5.2. This is the single cheapest protection against accidental activation and it costs nothing.
- No shake, tilt or device-motion trigger. A device on a moving cart is being shaken continuously.
- No hover-dependent behaviour on any surface. Already required by Interaction & states; restated because touch is where it is violated.
Accidental input
Clinical screens are touched by things that are not trying to operate them. A palm resting while writing, a forearm leaning during a procedure, a cleaning wipe, a patient reaching past, a bedrail lowered against a cart-mounted display.
- Palm and large-contact rejection where the platform provides it, and target placement that assumes it does not — nothing consequential within a hand's width of the bottom edge, where a resting palm lands.
- No consequential control in a screen-edge gesture zone. The operating system owns those edges and will sometimes win, producing a control that works until the day it does not.
- Repeat suppression. Two activations of the same control within a few hundred milliseconds are one activation. A bumped cart produces doubles.
- A cleaning mode on any surface that is wiped down between patients — because the alternative is that the surface is cleaned while live, and every rule on this page is then being tested by a cloth.
The surfaces this system targets
| Surface | What changes |
|---|---|
| Cart or bedside display | Moving, bumped, viewed standing and off-axis, operated by whoever is nearest. Assume interruption between any two actions. |
| Wall or ceiling display | Often not touched at all. Nothing may require touch to be understood; everything needed at a glance is legible at the room's longest sightline. |
| Tablet in gloves | Larger targets, no precision, no fine drag, and frequently one-handed while the other hand is occupied or non-sterile. |
| Sterile field, indirect operation | Operated by a colleague on instruction. Every control must be nameable out loud — which is another reason a gesture cannot be a primary path. |
| Personal phone | Small, one-handed, in poor light, possibly by a patient or carer. Controls sit in thumb reach, and Lay-facing content governs the words. |
Outcomes of use
What this contributes to, in the terms of Usability & context of use. These are attributes believed to contribute to an outcome; the outcome itself is settled by observing real use in a specified context, not by this page.
- Effectiveness — the intended action is the one that happens. Most touch failures on a clinical surface are not the user's mistake; they are a target that was too small, too close to its neighbour, or activated by something that was not a finger.
- Efficiency — worse on paper, since gestures are faster than visible controls for anyone who knows them. The trade is deliberate: this system optimises for the person who does not use the device every day, and for the day the regular user is interrupted.
- Satisfaction — a surface that does not do things nobody asked for. A single accidental dismissal costs more trust than a dozen extra taps.
Do's and don'ts
— a labelled 56 px control on the alarm itself.
Deliberate, targeted, nameable over the phone, and impossible to produce with a sleeve.
Swipe the alarm away.
The motion a cleaning cloth makes, applied to the one control that must record a person's deliberate decision.
Pinch to zoom, with ×2.4 shown and zoom controls beside it.
The gesture is a shortcut over a visible control, and the magnification is a readable number rather than something inferred from the picture.
Pinch to zoom. No indicator, no controls.
Nothing on screen says zoom exists or what it is currently set to — so nothing says the image is not at native scale.
Drag the limit to 92, then Confirm 92 bpm.
The drag proposes; a targeted press commits. The value is also typeable, per SC 2.5.7.
Drag the limit to 92. Applied on release.
A safety limit set by where a finger happened to leave the glass, on a cart that may have moved during the drag.
Fires on release, over the target.
A touch that landed wrong can be dragged off and abandoned — SC 2.5.2, and free.
Fires on touch-down, for responsiveness.
Every brush, lean and bump is now a committed action, and there is no moment in which the user can change their mind.
Clinical safety notes
Trace these in your risk file (ISO 14971) and usability engineering file (IEC 62366-1). Contact and cleaning assumptions belong in the same file as the cleaning instructions.
- No gesture acknowledges, silences or dismisses an alarm. Mitigates: an alarm cleared by a sleeve, a cloth or a scroll, with a record saying a person decided.
- Every gesture has a visible single-pointer equivalent. Mitigates: a function reachable only by users who already know it exists.
- Actions fire on release, over the target. Mitigates: accidental activation by contact that was never an attempt to act.
- 44 px baseline, 56 px gloved and destructive, with enforced dead space. Mitigates: the adjacent-control error, which is the dominant touch failure in gloved use.
- Dragged values propose; a separate press commits. Mitigates: a safety limit set by where a finger left a moving screen.
- No swipe-to-delete or swipe-to-dismiss on clinical items. Mitigates: a destructive act triggered by an ambiguous motion in the same place as scrolling.
- Repeat suppression and edge-zone avoidance. Mitigates: double activation from a bumped cart, and controls that collide with operating-system gestures.
- A cleaning mode exists on any wiped surface. Mitigates: a live interface being operated by a cloth.
Related
- Affordance & perceivability — the general rule this page applies: a control exists only if every reader who can operate it can perceive it.
- Interaction & states — hover carries nothing, and what focus does on a touch surface.
- Spacing — the dead space between targets, as a scale rather than a per-screen decision.
- Scaling & density — target size as a function of viewing and reach distance.
- Accessibility — the success criteria this page leans on, and what they require beyond touch.
- Acknowledge & escalate — what a deliberate operator action has to be.
- Therapy control & dosing — the strictest case: a control that changes what a device does to a body.