Final answer:
The estimated size of an uncuffed endotracheal (ET) tube for an average-sized 4-year-old child is likely between 4.0 and 5.0 mm internal diameter, which can be determined using a color-coded length-based tape. During intubation, air is supplied to the lungs via a squeezable bag connected to the ET tube.
Step-by-step explanation:
For elective intubation of an average-sized 4-year-old child with respiratory failure, a color-coded length-based tape is commonly used to estimate the appropriate size of an uncuffed endotracheal (ET) tube. Generally, a 4.0 to 5.0 mm internal diameter uncuffed ET tube is suitable for this age group, with the specific size depending on the individual child's size and anatomy. Estimation using the length-based tape matches the child's length to a color zone that suggests equipment sizes, including the ET tube size.
During intubation, a squeezable bag connected to the ET tube is often used to artificially supply air to the patient's lungs. If an individual were to manually supply air using a balloon, they would have to exert sufficient force to generate the necessary gauge pressure to aid breathing. For example, to create a gauge pressure of 4.00 cm water on a balloon with an effective area of 50.0 cm², a certain amount of force needs to be applied by the hands squeezing the balloon.