Fig 1.
= flow measured with pneumotachograph number 1,
= flow measured with pneumotachograph number 2, Paw 1 = pressure measured with pressure transducer number 1, Paw 2 = pressure measured with pressure transducer number 2. Arrows indicate the connection between Paw ports and flow meters to data logger. The location of the clamp into the endotracheal tube is shown. I = inspiration, E = expiration.
Fig 2.
The four steps of the experiment are shown.
A) Step 1, measurement of the endotracheal tube resistance before clamping; B) Step 2, inspiratory hold to detect air leaks in the entire set up; C) Step 3, endotracheal tube clamping, disconnection from the ventilator and measurement of airway pressure and flow over time; D) Step 4, measurement of the endotracheal tube resistance after clamping; Paw = airway pressure; t = time; = flow measured with pneumotachograph number 1 (as in Fig 1);
= flow measured with pneumotachograph number 2 (as in Fig 1); Paw 1 = pressure measured with pressure transducer number 1 (as in Fig 1); Paw 2 = pressure measured with pressure transducer number 2 (as in Fig 1). Horizontal blue thin arrows indicate the inspiratory (I) and expiratory (E) direction. Black arrowed lines show the connection between the data logger and the Paw ports (broken lines) and flow meters (continuous lines).
Fig 3.
Criteria for defining and quantifying leaks after clamping the endotracheal tube (ETT) and disconnecting the ventilator.
From top to bottom, records of flow, airway pressure (Paw) and volume during the clamping of the nasal tube with the plastic clamp over time. Flow, Paw and volume were recorded between the lung model and the ETT. The first blue arrow indicates the inspiratory direction. The second blue arrow (EEO) shows the expiratory hold, the red arrow indicates the time of ETT clamping and the third blue arrow shows the disconnection of the ventilator from the ETT and the lung model. Paw and volume tracings after the clamping are shown in the blue rectangle. It can be seen that the Paw dropped after the detachment of the ventilator. The ventilator was then reconnected and baseline ventilation resumed. EEO = end expiratory occlusion. C = ETT clamping. D = disconnection of the ventilator from ETT.
Fig 4.
Relationship between airway pressure and flow before and after clamping of a nasal, oral and reinforced tube with each clamp.
ECMO = extracorporeal membrane oxygenation.
Fig 5.
Airway pressure (Paw) decay and volume lost after 5 s following endotracheal tube clamping and set up disconnection.
Fig 6.
Airway pressure (Paw) decay and volume lost after 30 s following endotracheal tube clamping and set up disconnection.
Table 1.
Airway pressure decay and volume lost 5 seconds and 30 seconds after disconnecting the endotracheal tube clamped for the three kinds of endotracheal tube.
Table 2.
Airflow resistance of the endotracheal tube before and after clamping for different tubes and clamps.