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The Airway LedgerRespiratory device review

An independent trade magazine on single-use respiratory, anaesthesia and critical care devices

Respiratory, anaesthesia and critical care devices, explained

Respiratory care and anaesthesia devices, explained. Each guide covers how a device is built, where it sits in the circuit and what the clinician checks at the bedside.

Start with breathing circuitsBubble CPAP at the cot side

A clinical engineering bench with coiled clear breathing tubes, a Y-piece, filters and a water trap laid out under a bright lamp
The devices in these guides meet at the bedside: tubes, filters, traps and interfaces that carry and condition the gas a patient breathes.

Start with the sections

Three sections, from the circuit to the airway

Each section opens with an index of its guides. Pick the circuits and their condensate, the filters and humidifiers that condition the gas, or the interfaces that reach the patient.

  1. A clinical engineer's bench with coiled transparent corrugated breathing tubes, a Y-piece and a water trap laid out under a bright lamp.
    01

    Ventilation and Anaesthesia Circuits

    The tubes, connectors and traps that carry gas between the machine and the patient: ventilator and anaesthesia circuits, heated wire tubing and water traps, read against ISO 5367 and the 22 mm connector standard.

    4 guides inside

  2. A row of small cylindrical breathing circuit filters and a humidifier chamber on a clinical supply shelf.
    02

    Filters and Humidification

    The devices that clean and condition inspired gas: heat and moisture exchangers, bacterial and viral filters, and active heated humidification, with the tests and standards behind their stated figures.

    3 guides inside

  3. A neonatal nasal CPAP interface with short prongs and headgear resting on a clean cloth.
    03

    Airway and Oxygen Delivery

    The interfaces that reach the patient: CPAP, BiPAP and NIV masks, bubble CPAP for newborns, nebulizer kits for aerosol delivery, and catheter mounts with closed suction.

    4 guides inside

Section 1 of 3

Ventilation and Anaesthesia Circuits

The tubes, connectors and traps that carry gas between the machine and the patient: ventilator and anaesthesia circuits, heated wire tubing and water traps, read against ISO 5367 and the 22 mm connector standard.

  • A neonatal ventilator circuit with two slim limbs and a small Y-piece connected to a test lung on an ICU trolley.

    Ventilation and Anaesthesia Circuits

    Ventilator Breathing Circuits

    How adult, paediatric and neonatal ventilator breathing circuits differ in tube size, compliance, water traps and connections under ISO 5367.

    Adult, paediatric and neonatal limbs and why the size matters.

  • Close view of a corrugated heated wire breathing tube with water droplets collecting in its dependent loop.

    Ventilation and Anaesthesia Circuits

    Heated Wire Breathing Circuits

    Why heated wire circuits form condensation, how tube and room temperature interact, and the checks that keep rainout out of the airway.

    Warm the tube wall and the water stays in the gas.

  • An anaesthesia machine in an operating theatre with a circle system, soda lime canister and reservoir bag in view.

    Ventilation and Anaesthesia Circuits

    Anaesthesia Breathing Circuits

    How circle and Mapleson anaesthesia breathing systems work, what soda lime does, and how circuits are chosen for adult and paediatric cases.

    The circle system, its valves and the soda lime canister.

  • A transparent water trap on a ventilator circuit partly filled with clear condensate, held in a gloved hand.

    Ventilation and Anaesthesia Circuits

    Water Traps in Breathing Circuits

    What breathing circuit water traps collect, how double traps manage condensate, and how to empty and check them without breaking the circuit.

    Catch the condensate before it reaches the airway.

Open the Ventilation and Anaesthesia Circuits index

Section 2 of 3

Filters and Humidification

The devices that clean and condition inspired gas: heat and moisture exchangers, bacterial and viral filters, and active heated humidification, with the tests and standards behind their stated figures.

  • A hygroscopic heat and moisture exchanger filter held beside a ventilator Y-piece in a gloved hand.

    Filters and Humidification

    Heat and Moisture Exchanger Filters

    How HME filters recover heat and moisture, the hygroscopic, hydrophobic and combined types, and how tidal volume changes their efficiency.

    Passive humidification, and its limits at high tidal volume.

  • Two breathing circuit filters on a bench, one straight and one angled, with the pleated filter media visible.

    Filters and Humidification

    Bacteria and Viral Filters

    What bacterial and viral filters capture in a breathing circuit, how electrostatic media work, and where filters sit to protect patient and machine.

    What the filter captures, and where it sits to do it.

  • A heated humidifier base with a water chamber and a temperature probe on a ventilator stand.

    Filters and Humidification

    Humidification in Invasive Ventilation

    Active heated humidification against passive HMEs: target temperature, condensation risk and the checks that keep inspired gas conditioned.

    Active against passive, chosen per patient.

Open the Filters and Humidification index

The bench in pictures

Five views from the guides

Five photographs from the guides below, each with the page that explains the scene in full.

  • A neonatal ventilator circuit with two slim limbs and a small Y-piece connected to a test lung

    Field note 1

    Circuits sized to the patient

    Adult, paediatric and neonatal limbs differ in diameter and compliance, and in small patients that decides whether the set volume reaches the lungs.

  • A row of small cylindrical breathing circuit filters and a humidifier chamber on a clinical supply shelf

    Field note 2

    Filters that condition and clean

    An HME returns heat and moisture from the breath, and the same device often removes particles. Its efficiency falls as tidal volume rises.

  • An oronasal NIV mask and headgear laid on a hospital bed beside a tubing connector

    Field note 3

    The interface is the therapy

    Pressure that leaks around a mask does not reach the airway, so fit and leak are checked as carefully as the machine setting.

  • A transparent water trap on a ventilator circuit partly filled with clear condensate

    Field note 4

    Where the condensate goes

    Warm gas cools in the limb and gives up its water. A trap at the lowest point keeps that liquid out of the airway.

  • A small jet nebulizer chamber fitted into a ventilator circuit near the Y-piece, with mist inside

    Field note 5

    Getting the drug to the lung

    Nebulizer type, circuit position and bias flow decide how much of an aerosol dose actually reaches the patient.

Section 3 of 3

Airway and Oxygen Delivery

The interfaces that reach the patient: CPAP, BiPAP and NIV masks, bubble CPAP for newborns, nebulizer kits for aerosol delivery, and catheter mounts with closed suction.

  • An oronasal NIV mask and headgear laid on a hospital bed beside a tubing connector.

    Airway and Oxygen Delivery

    CPAP, BiPAP and NIV Masks

    How CPAP, BiPAP and NIV interfaces differ, what mask fit and leak mean for therapy, and how to judge an interface at the bedside.

    Seal, leak and skin: how an interface is judged.

  • A neonatal bubble CPAP setup with the expiratory limb submerged in a water bottle and small bubbles rising.

    Airway and Oxygen Delivery

    Bubble CPAP in Neonatal Care

    How bubble CPAP generates pressure through a water column, why the circuit must keep bubbling, and how humidification and prongs are managed.

    Pressure from a water column, and the checks it needs.

  • A small jet nebulizer chamber fitted into a ventilator circuit near the Y-piece, with mist inside.

    Airway and Oxygen Delivery

    Nebulizer Kits and Aerosol Delivery

    Jet, ultrasonic and vibrating mesh nebulizers, where to place a nebulizer in the circuit, and how bias flow and humidity change drug delivery.

    Placement and bias flow decide the dose.

  • A flexible catheter mount with a double swivel elbow attached to an endotracheal tube connector on a training manikin.

    Airway and Oxygen Delivery

    Catheter Mounts and Closed Suction

    What a catheter mount does between the circuit and the airway, how closed suction systems work, and how to keep the assembly light and swivel-free.

    Keep the circuit off the tube and suction in a sleeve.

Open the Airway and Oxygen Delivery index

Sources and standards

The documents behind these guides

The Airway Ledger writes from published material rather than from opinion. These are the standards, reviews and regulator pages the guides rely on, so you can read the originals for yourself.

  • External source

    ISO 5367:2023

    Anaesthetic and respiratory equipment, breathing sets and connectors: leakage, flow resistance and the designation of breathing tubes.

  • External source

    ISO 5367:2014

    The previous edition of the breathing sets standard, still cited by many product documents and regulatory summaries.

  • External source

    Bubble CPAP in Infants

    A clinical review of CPAP in neonates, including the physiology and the evidence for bubble CPAP in low resource settings.

  • External source

    FDA on reprocessed single-use devices

    How the United States regulator treats devices labelled for single use when a hospital or third party reprocesses them.

  • External source

    Humidification of ventilated patients

    A review comparing heated humidifiers with heat and moisture exchangers, their control systems and their limits.

  • External source

    HME humidification properties

    A modelling and measurement study of how much moisture different heat and moisture exchangers return per breath.