Establishing a definitive airway is crucial during the management of critically ill patients. Both in-hospital and out-of-hospital providers routinely use cuffed endotracheal tubes with just a syringe to achieve an ‘appropriate’ seal without measuring cuff pressure. However, several studies have shown that both over-inflated (pressure >30 cmH2O) and under-inflated (pressure <20 cmH2O) cuffs are associated with worse outcomes (Delorenzo et al, 2021).
The tracheal mucosa, with an estimated capillary perfusion pressure of 35–40 cmH2O, can begin to develop ischaemia within just 15 minutes if the endotracheal cuff pressure exceeds 30 cmH2O2. To avoid the detrimental effects of over-inflation, several techniques and devices have been developed to assess intra-cuff pressure, such as commercial manometers, palpation techniques, and minimal occlusive volume assessments (Klonner et al, 2023). Among these, only the commercial manometer has proven to be effective in establishing optimal cuff pressure and seal (Delorenzo et al, 2021; Klonner et al, 2023).
Commercial manometers present disadvantages, including high cost, which limits their availability between hospital, emergency medical services (EMS), and helicopter emergency medical serices (HEMS). This results in pressure measurements only at departure and arrival at the hospital. Additionally, these devices are designed for static settings and do not provide continuous monitoring during transport, where movement and altitude changes can affect cuff pressure (Springer et al, 2016; Delorenzo et al, 2021).
The authors consider that for intubated patient transport, it is imperative to have a continuous monitoring of the cuffed tube to balance over-cuffed pressure and under-cuffed pressure resulting from altitude variations. Hence, a craft device is proposed for continuous monitoring of cuffed tubes during patient transport. The custom device uses an aneroid pressure manometer (measuring in mmHg), three-way stopcock, and a three-way stopcock with extension. To assemble, an aneroid pressure manometer was connected to a superior female port of three-way stopcock and its male port connected to the lateral female port of the three-way stopcock with extension (Figure 1). The extension allows for continuous connection between the tracheal tube pilot line and the crafted device (i.e. continuous cuff pressure monitoring), positioning the manometer near the patient's head. Additionally, it is disposable, reducing infection risk compared to that with reusable commercial devices.
Crafted device for continuous monitoring of cuffed tube pressure
The authors evaluated the proposed device in controlled scenarios. First, the custom device was connected to the tracheal tube pilot line, and a 20 ml syringe was used to inflate the cuff to 18 mmHg. Literature suggests a cuff pressure between 20–30 cmH2O (i.e. 15–22 mmHg). Therefore, the authors targeted 18 mmHg (near 25 cmH2O) in this test, which was verified using an AG-Cuffill on the superior three-way stopcock female port. Once the target pressure was achieved, the female lateral three-way stopcock port connected to the syringe was locked, and the cuffed tube was exposed to pressure changes.
The device's capabilities were verified by submerging the cuffed tube underwater to simulate atmospheric pressure changes, demonstrating continuous pressure variations throughout the dives. Later, the device was subjected to altitude (i.e. pressure) variations from 2850 meters above sea level (m.a.s.l.) to 1890 m.a.s.l. (i.e. over 3000 feet). In this test, the device also successfully measured all pressure variations continuously (Figure 2). Hence, the custom device demonstrated its usefulness for continuous monitoring of the cuffed tube, which may be comparable to the pressure changes expected during the monitoring of intubated patient transport (Figure 3). A patient's transport involves many factors that may affect pressure readings, such as vibration and laryngospasm. Therefore, further assessment in real patients is needed to evaluate the device's accuracy and impact on patient outcomes.
Crafted device subjected to pressure variation test
Application of crafted device to simulated intubated patient
In terms of HEMS feasibility, the proposed device offers significant advantages. It addresses the challenges posed by altitude changes during air transport, which can cause significant fluctuations in cuff pressure. The device's ability to provide continuous monitoring ensures that these fluctuations are detected and managed promptly, potentially reducing the risk of complications such as tracheal mucosal damage. Additionally, its compact size (15x5 centimeters) and light weight (138.9 grams) make it easy to store in the airway management bag, ensuring it is readily accessible during transport. The low cost and ease of assembly also enhance its feasibility for widespread adoption in various EMS and HEMS settings, ensuring that even resource-limited operations can benefit from continuous cuff pressure monitoring.
The authors hypothesise that continuous monitoring and control of intra-cuff pressure along patient transport (i.e. maintain intra-cuff pressure between 20–30 cmH2O or 15–22 mmHg) may reduce the detrimental effects of over-cuffed pressure and under-cuffed pressure on patient outcomes. However, prospective studies are needed to confirm or refute this hypothesis.