Define ctg file

You are here:. This section covers the following topics. Click to go directly to the topic. In the case of Advanced Turning, use Dynamic View to rotate the view so X points to the right and Y points up toward the top of the screen. Starting at the coordinate system origin, define the desired tool profile in the first quadrant. Only Arc and Line element types may be used to define the profile. Define the holder profile in the first quadrant in the same manner as the tool profile.

The holder profile should start and end at X0. The holder profile does not need to start at the same Y position as the tool profile end, and may actually overlap the tool profile, if desired. The tool preview window will display the CTG tool profile. Use Verification to verify a toolpath assigned to the tool associated with the CTG file. To display the tool holder, turn on the Show Holder option. Starting at the coordinate system origin, define the desired holder profile in the first quadrant.

The holder profile should have a general CCW direction, and it should end touching the Y axis at X 0. Using the User Event panel, insert a User Command element before the first element in the holder profile to signal to the system that the holder profile is to be translated along the tool axis to the appropriate position, as defined by the Length Preset. Specify the desired placement of the holder relative the parametrically defined tool by specifying a Length Preset distance.

If the tip of the holder was drawn starting at Y0. If the holder is to be placed at a specific distance from the tip of the tool, enter that distance into the Length Preset. Use Dynamic View to rotate the view so X points to the right and Y points up toward the top of the screen. Define the tool profile in the desired orientation relative the X and Y axes. The turning tool radius center should be placed at the origin position, and the profile should be closed and have a general CCW direction.

For fixed hole tools, place the tool tip at the origin position. Define the holder profile in the same manner as the tool profile, placing it in the desired orientation relative the X and Y axes.

Look at the CTG and assess what the average heart rate has been over the last 10 minutes, ignoring any accelerations or decelerations. A normal fetal heart rate is between bpm. Fetal tachycardia is defined as a baseline heart rate greater than bpm. Fetal bradycardia is defined as a baseline heart rate of less than bpm.

Severe prolonged bradycardia less than 80 bpm for more than 3 minutes indicates severe hypoxia. Causes of prolonged severe bradycardia include:. Baseline variability refers to the variation of fetal heart rate from one beat to the next. Variability occurs as a result of the interaction between the nervous system , chemoreceptors , baroreceptors and cardiac responsiveness. It is, therefore, a good indicator of how healthy a fetus is at that particular moment in time, as a healthy fetus will constantly be adapting its heart rate in response to changes in its environment.

To calculate variability you need to assess how much the peaks and troughs of the heart rate deviate from the baseline rate in bpm. Variability can be categorised as either reassuring , non-reassuring or abnormal. Reduced variability can be caused by any of the following: 2. Accelerations are an abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds.

Accelerations occurring alongside uterine contractions is a sign of a healthy fetus. The absence of accelerations with an otherwise normal CTG is of uncertain significance. Decelerations are an abrupt decrease in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds. The fetal heart rate is controlled by the autonomic and somatic nervous system.

In response to hypoxic stress, the fetus reduces its heart rate to preserve myocardial oxygenation and perfusion.

Unlike an adult, a fetus cannot increase its respiration depth and rate. This reduction in heart rate to reduce myocardial demand is referred to as a deceleration. Early decelerations start when the uterine contraction begins and recover when uterine contraction stops.

This is due to increased fetal intracranial pressure causing increased vagal tone. It therefore quickly resolves once the uterine contraction ends and intracranial pressure reduces.

This type of deceleration is, therefore, considered to be physiological and not pathological. Variable decelerations are observed as a rapid fall in baseline fetal heart rate with a variable recovery phase. All fetuses experience stress during the labour process, as a result of uterine contractions reducing fetal perfusion.

Whilst fetal stress is to be expected during labour, the challenge is to pick up pathological fetal distress. Variable decelerations are usually caused by umbilical cord compression. The mechanism is as follows: 1. The umbilical vein is often occluded first causing an acceleration of the fetal heart rate in response. Then the umbilical artery is occluded causing a subsequent rapid deceleration.

When pressure on the cord is reduced another acceleration occurs and then the baseline rate returns. The accelerations before and after a variable deceleration are known as the shoulders of deceleration. Their presence indicates the fetus is not yet hypoxic and is adapting to the reduced blood flow. Variable decelerations can sometimes resolve if the mother changes position.

The presence of persistent variable decelerations indicates the need for close monitoring. Variable decelerations without the shoulders are more worrying, as it suggests the fetus is becoming hypoxic.

Late decelerations begin at the peak of the uterine contraction and recover after the contraction ends. This type of deceleration indicates there is insufficient blood flow to the uterus and placenta. As a result, blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis. A prolonged deceleration is defined as a deceleration that lasts more than 2 minutes :. A sinusoidal CTG pattern is rare , however, if present it is very concerning as it is associated with high rates of fetal morbidity and mortality.

A sinusoidal pattern usually indicates one or more of the following:. Once you have assessed all aspects of the CTG you need to determine your overall impression. The overall impression can be described as either reassuring , suspicious or abnormal. Overall impression is determined by how many of the CTG features were either reassuring, non-reassuring or abnormal.

Regard the following as concerning characteristics of variable decelerations:. Clinical Examination. An Introduction to the Arclight. Eye Drops Overview.