A home brewed low cost cuff inflator and pressure monitor.

Sir,

Endotracheal tube (ETT) cuff pressure management is an essential part of airway management in intubated and mechanically ventilated patients.

Cuff pressures in the intubated patients in hospitals and Intensive Care Units are often too high. Acceptable cuff pressures are best achieved when a cuff pressure manometer has been used. Obstruction to mucosal blood flow occurs at pressures above 30 cm H2O, with total occlusion of flow at 50 cm H2O.[1] Commercially available cuff inflators are costly. The use of this crucial equipment is neglected and is often not available in many hospitals or hospital areas of economically poor countries.

We have devised a cuff inflator and cuff pressure measuring device with readily available materials [Figure 1]. These include an airway low pressure manometer detached from an old unused Bird ventilator with a reading up to 100 cm H2O pressure. As an alternative, low cost commercially available low pressure monitor can also be made use of. Other spares include cuff inflating one-way valve cut from Foley's catheter, a 3-way connector and other easily available connectors. All the parts were bonded with the help of quick fix sealant and tested for air leak in a bowl of water. We tested the accuracy of the device by connecting it to mercury manometer and also commercially available Portex® cuff inflator which matched with the readings with an error as low as 2–3 cm H2O in the clinical range of 20–35 cm H2O. Keeping this small error into account we are practically using the device regularly both for ETT cuff and laryngeal mask airway (LMA) cuff. We have already used it in 80 cases to check the ETT cuff pressure and for inflating cuff of pro-seal LMA to the required pressure in 60 patients.

Figure 1

The assembled cuff inflator and cuff pressure monitor connected to endotracheal tube (a) and its calibration (b)

The incidence and severity of tracheal mucosal lesions increase with cuff pressure >30 cm H2O. It is revealed that the majority of cuff pressures exceeded safe pressure and required correction.[2] The pressure exerted on the trachea must be maintained within a range (25–30 cm H2O or 18–22 mmHg) to ensure perfusion to the tracheal capillaries without causing injury.[3] Only 27% of pressures were within 20–30 cm H2O; 27% exceeded 40 cm H2O. Hence, it is recommended that endotracheal cuff pressure be set and monitored with a manometer.[4] It is important to perform cuff pressure measurements at 6–12 hourly intervals and to use the correct method.

At the time of periodic pressure check while connecting any cuff inflator to the ETT valve, loss of cuff pressure of about 6.6 cm H2O can occur on an average needing reinflation to adjust for pressure loss.[5] However, our device has the advantage that it can be pre-pressurized with the help of 3-way connector of the assembly before pressure check which can prevent cuff pressure loss and deflation.

Our low cost cuff pressure inflator can be easily constructed and can be practically used. Innovative practice and translational research is an important aspect of higher education and postgraduate curriculum. It can be a useful as an aid in innovative teaching methodology to teach basic foundations in anaesthesiology by giving such projects to postgraduate students to imbibe spirit of creativity.