Ulnar length can predict optimal endotracheal tube depth

SAN JUAN, P.R.  – Measure twice, intubate once – good thinking alongside a pilot study that suggests a simple formula based on the length of a child’s ulna can accurately predict the optimal depth for endotracheal tube insertion. The formula could save time and spare children from unnecessary radiation, investigators said at the annual congress of the Society of Critical Care Medicine.

A study of 121 orally intubated children (median age, 35.7 months) in a pediatric and a cardiothoracic intensive care unit showed that the ulna could be accurately measured with digital calipers in children with varying body habitus, as well as those with neuromuscular disease, and that a simple formula based on the measurement provides a good estimate of the best tube insertion depth, said Dr. Anne Camerlengo, a fellow in pediatric critical care at Children’s Hospital Los Angeles, and her colleagues.

"While the chest radiograph is the gold standard for determining tube placement, several nonradiographic techniques have been described, including formulas based on the patient’s weight, height, or gestational age, or the endotracheal tube diameter. However, these formulas may be less accurate for our patients with scoliosis or neuromuscular diseases that affect their height, while ulnar length is a measure that’s preserved in this population," she said in a poster session.

To see whether they could derive an accurate predictive equation for determining optimal endotracheal tube depth – 2 cm above the carina of the trachea – the investigators used chest radiographs to measure the distance from the endotracheal tube to the carina in intubated children, and recorded their ulnar length, height, and depth of endotracheal tube insertion.

They determined the optimal tube depth to be the depth of insertion plus the distance from the tube to the carina, minus 2 cm. They then plotted the optimal tube position against ulnar length, and used linear regression to calculate the following predictive equation:

Depth of endotracheal tube insertion in centimeters equals 0.75 times the ulnar length in centimeters plus 4.4.

Dr. Camerlengo said that ulnar measurements are relatively easy to make, and that the only significant difficulty occurs with children who may be frightened by the appearance of the calipers with their pointed ends.

However, "given that most of these children are reasonably well sedated, there’s not usually an issue with cooperation or finding the bony landmarks. The ulnar length is particularly useful because the bony landmarks, even in our chubbier children, we are able to palpate deeply," she said.

The investigators need to collect additional data on nasally intubated patients before they can determine whether the formula can be applied to this population.

She said that they hope to expand the analysis to include subgroups based on patient age and the presence of neuromuscular disease, and emphasized that the formulas to determine the optimal depth for both oral and nasal endotracheal tubes will need to be confirmed in a validation study.

Dr. Alexandre T. Rotta, professor of pediatrics at Case Western Reserve University and chief of pediatric critical care at Rainbow Babies and Children’s Hospital, both in Cleveland, commented that the work is promising but needs to be put to the test.

"There has been a lot of work trying to look for the magic formula of how to place an endotracheal tube. I think that key now is to see whether this will be validated in real time. They validated the formula mathematically, so the question now is does it work for various patients under various conditions, and is it reproducible with my measurement versus her measurement," Dr. Rotta said in an interview.

He was not involved in the study, but comoderated the poster discussion session at which it was presented.

The study was internally funded. Dr. Camerlengo and Dr. Rotta each reported having no disclosures.

[email protected]

SAN JUAN, P.R.  – Measure twice, intubate once – good thinking alongside a pilot study that suggests a simple formula based on the length of a child’s ulna can accurately predict the optimal depth for endotracheal tube insertion. The formula could save time and spare children from unnecessary radiation, investigators said at the annual congress of the Society of Critical Care Medicine.

A study of 121 orally intubated children (median age, 35.7 months) in a pediatric and a cardiothoracic intensive care unit showed that the ulna could be accurately measured with digital calipers in children with varying body habitus, as well as those with neuromuscular disease, and that a simple formula based on the measurement provides a good estimate of the best tube insertion depth, said Dr. Anne Camerlengo, a fellow in pediatric critical care at Children’s Hospital Los Angeles, and her colleagues.

"While the chest radiograph is the gold standard for determining tube placement, several nonradiographic techniques have been described, including formulas based on the patient’s weight, height, or gestational age, or the endotracheal tube diameter. However, these formulas may be less accurate for our patients with scoliosis or neuromuscular diseases that affect their height, while ulnar length is a measure that’s preserved in this population," she said in a poster session.

To see whether they could derive an accurate predictive equation for determining optimal endotracheal tube depth – 2 cm above the carina of the trachea – the investigators used chest radiographs to measure the distance from the endotracheal tube to the carina in intubated children, and recorded their ulnar length, height, and depth of endotracheal tube insertion.

They determined the optimal tube depth to be the depth of insertion plus the distance from the tube to the carina, minus 2 cm. They then plotted the optimal tube position against ulnar length, and used linear regression to calculate the following predictive equation:

Depth of endotracheal tube insertion in centimeters equals 0.75 times the ulnar length in centimeters plus 4.4.

Dr. Camerlengo said that ulnar measurements are relatively easy to make, and that the only significant difficulty occurs with children who may be frightened by the appearance of the calipers with their pointed ends.

However, "given that most of these children are reasonably well sedated, there’s not usually an issue with cooperation or finding the bony landmarks. The ulnar length is particularly useful because the bony landmarks, even in our chubbier children, we are able to palpate deeply," she said.

The investigators need to collect additional data on nasally intubated patients before they can determine whether the formula can be applied to this population.

She said that they hope to expand the analysis to include subgroups based on patient age and the presence of neuromuscular disease, and emphasized that the formulas to determine the optimal depth for both oral and nasal endotracheal tubes will need to be confirmed in a validation study.

Dr. Alexandre T. Rotta, professor of pediatrics at Case Western Reserve University and chief of pediatric critical care at Rainbow Babies and Children’s Hospital, both in Cleveland, commented that the work is promising but needs to be put to the test.

"There has been a lot of work trying to look for the magic formula of how to place an endotracheal tube. I think that key now is to see whether this will be validated in real time. They validated the formula mathematically, so the question now is does it work for various patients under various conditions, and is it reproducible with my measurement versus her measurement," Dr. Rotta said in an interview.

He was not involved in the study, but comoderated the poster discussion session at which it was presented.

The study was internally funded. Dr. Camerlengo and Dr. Rotta each reported having no disclosures.

[email protected]

SAN JUAN, P.R.  – Measure twice, intubate once – good thinking alongside a pilot study that suggests a simple formula based on the length of a child’s ulna can accurately predict the optimal depth for endotracheal tube insertion. The formula could save time and spare children from unnecessary radiation, investigators said at the annual congress of the Society of Critical Care Medicine.

A study of 121 orally intubated children (median age, 35.7 months) in a pediatric and a cardiothoracic intensive care unit showed that the ulna could be accurately measured with digital calipers in children with varying body habitus, as well as those with neuromuscular disease, and that a simple formula based on the measurement provides a good estimate of the best tube insertion depth, said Dr. Anne Camerlengo, a fellow in pediatric critical care at Children’s Hospital Los Angeles, and her colleagues.

"While the chest radiograph is the gold standard for determining tube placement, several nonradiographic techniques have been described, including formulas based on the patient’s weight, height, or gestational age, or the endotracheal tube diameter. However, these formulas may be less accurate for our patients with scoliosis or neuromuscular diseases that affect their height, while ulnar length is a measure that’s preserved in this population," she said in a poster session.

To see whether they could derive an accurate predictive equation for determining optimal endotracheal tube depth – 2 cm above the carina of the trachea – the investigators used chest radiographs to measure the distance from the endotracheal tube to the carina in intubated children, and recorded their ulnar length, height, and depth of endotracheal tube insertion.

They determined the optimal tube depth to be the depth of insertion plus the distance from the tube to the carina, minus 2 cm. They then plotted the optimal tube position against ulnar length, and used linear regression to calculate the following predictive equation:

Depth of endotracheal tube insertion in centimeters equals 0.75 times the ulnar length in centimeters plus 4.4.

Dr. Camerlengo said that ulnar measurements are relatively easy to make, and that the only significant difficulty occurs with children who may be frightened by the appearance of the calipers with their pointed ends.

However, "given that most of these children are reasonably well sedated, there’s not usually an issue with cooperation or finding the bony landmarks. The ulnar length is particularly useful because the bony landmarks, even in our chubbier children, we are able to palpate deeply," she said.

The investigators need to collect additional data on nasally intubated patients before they can determine whether the formula can be applied to this population.

She said that they hope to expand the analysis to include subgroups based on patient age and the presence of neuromuscular disease, and emphasized that the formulas to determine the optimal depth for both oral and nasal endotracheal tubes will need to be confirmed in a validation study.

Dr. Alexandre T. Rotta, professor of pediatrics at Case Western Reserve University and chief of pediatric critical care at Rainbow Babies and Children’s Hospital, both in Cleveland, commented that the work is promising but needs to be put to the test.

"There has been a lot of work trying to look for the magic formula of how to place an endotracheal tube. I think that key now is to see whether this will be validated in real time. They validated the formula mathematically, so the question now is does it work for various patients under various conditions, and is it reproducible with my measurement versus her measurement," Dr. Rotta said in an interview.

He was not involved in the study, but comoderated the poster discussion session at which it was presented.

The study was internally funded. Dr. Camerlengo and Dr. Rotta each reported having no disclosures.

[email protected]