Overventilation, Hypocarbia and Birth Injury*

In the time after birth, some infants may need help breathing through the use of machines. These machines must be set properly by a trained professional. If they are not, they will remove too much CO2 from the baby’s blood. This puts the baby at risk for brain damage, as CO2 levels that are too low prevent proper blood flow within the brain. This can cause tissue loss in the brain’s periventricular area, known as PVL. Overventilation can also cause lung tissue scarring or lung collapse.

Neonatal Respiration Injuries

Many newborns (especially preterm infants) require assisted ventilation at birth for conditions like apnea or respiratory failure. Despite its life-saving benefits, however, mechanical ventilation can cause serious damage if not managed properly. Brain damage, lung damage, and other complications may occur if the baby is over-oxygenated or over-ventilated. Throughout this page, our Detroit, Michigan birth injury attorneys will discuss everything you need to know about birth injury as it relates to overventilation and hypocarbia.

Overventilation occurs when a baby is given breaths that are so large and/or fast, it causes the baby to get rid of too much carbon dioxide (called hypocarbia). When a baby has abnormally low levels of carbon dioxide, it may cause permanent damage to the brain due to a lack of perfusion (cerebral blood flow) to critical areas of the brain. Hypocarbia and subsequent lack of perfusion has been associated with periventricular leukomalacia (involves the death of small areas of brain tissue around fluid-filled areas called ventricles; the damage forms “holes” in the brain), cerebral palsy, and hearing impairments.

Likewise, too much pressure from mechanical ventilation can cause lung problems such as a pnuemothorax or worsen bronchopulmonary dysplasia (an abnormal development of lung tissue in premature babies characterized by inflammation and scarring).

Medical Explanations

Causes of Overventilation

Overventilation occurs when the baby is getting help with some or all of its breathing. Common methods of assisted ventilation (breathing) include the following:

  • Mechanical ventilation.  When a baby needs help with breathing, she might be placed on a breathing machine, called a ventilator, which will either assist her breathing or completely breathe for her. Even though these machines display the volume of air being delivered to the baby’s lungs, as well as the pressure in the baby’s lungs, sometimes the medical team allows there to be a volume/pressure that is large enough to damage the baby’s lungs. The medical staff may set the volume of air/oxygen delivered to the baby high in order to decrease the carbon dioxide level in the baby’s blood. Volumes that are too high on the ventilator can cause lung damage that is similar to that of bagging. In addition, large volumes can cause a baby’s carbon dioxide level in the blood to fall below normal. When a baby has a continuously low carbon dioxide level (for a few hours or more), it can cause decreased blood flow (decreased perfusion) to the brain, thereby leading to brain damage and other injuries.
  • Bagging. This is when either a flexible tube is inserted into the baby’s trachea (windpipe) or the baby is given an oxygen mask and then a device, called a bag, is attached to the device. The bag is squeezed to force air or oxygen into the baby’s lungs. This is also known as positive pressure ventilation (PPV), or “bagging.”  Bagging is the method of breathing for a baby during an emergency situation, such as during CPR or while waiting to place the baby on a breathing machine (ventilator). Since bagging is done by hand, there really is no way to know how much air is being pushed into the baby’s delicate lungs. Thus the pressure or volume of air the baby’s lungs are getting usually is not known. Lungs can be seriously injured when too much volume / pressure is forced into them.

Overventilation and Infant Lung Injuries


This injury occurs when the volumes of air administered during ventilation are too large and create too much pressure in the baby’s lungs. The alveoli (the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place) become over-distended and rupture causing the lung to blow out. This results in holes in the lungs which allow air to leak through into the spaces around the lungs forming a pneumothorax. This build up of air prevents the lung from fully expanding. The longer this is left untreated, the more air there is that leaks into the space around the lung, which further restricts the ability of the lung to expand. This hinders the baby’s ability to breathe properly, which may causes oxygen levels to drop and carbon dioxide levels to increase in the long run. This decrease in the baby’s blood oxygen level can cause brain damage.

The pneumothorax also can compress the veins that bring blood to the heart. As a result, less blood fills the chambers of the heart, the output of the heart decreases, and the baby’s blood pressure decreases. This also can lead to serious problems and can cause a lack of blood flow to the brain, thereby increasing the chances of brain damage.

If only a small portion of the baby’s lung is collapsed, the physician may simply monitor the condition of the pneumothorax with a series of chest X-rays until the air is completely absorbed and the lung has re-expanded. A larger area of collapse may require that a needle or chest tube is inserted to remove the air. Surgery is the next option if a chest tube is unsuccessful.

Complications from a pneumothorax can cause serious damage and death, especially if the pneumothorax goes unnoticed. Signs and symptoms of a pneumothorax include:

  • Bluish color of the skin
  • Rapid heart rate
  • Diminished breath sounds on the affected side of the lung
  • Decreased blood pressure
  • The windpipe is shifted away from the affected lung
  • Sudden deterioration in the condition of the baby

Bronchopulmonary Dysplasia (BPD)

This is a common defect of the lungs among premature babies. It is characterized by scarring on the lungs, primarily from the immaturity of the lung tissue. BPD is typically diagnosed when a premature infant has been on ventilation /oxygen therapy long-term – more than 28 days. It is not known what causes this serious condition, however, mechanical over ventilation is known to worsen the condition due to increased pressure exerted on the lungs.

Low Carbon Dioxide Levels and Infant Brain Damage

When a baby is on a ventilator and is over ventilated because the machine is giving her breaths that are too large (and perhaps too fast), the carbon dioxide level in the blood may decrease below normal. When there is an abnormally low carbon dioxide level in the blood for too long (5 or 6 hours or more), blood flow to the brain is decreased (decreased perfusion) and permanent brain damage can occur as a result.

A baby that is receiving mechanical ventilation will likely have an umbilical artery catheter (UAC), which makes it easy to draw blood and monitor the oxygen and carbon dioxide levels in the blood. A sign of over ventilation is a carbon dioxide level that is below normal. A low carbon dioxide level that is due to over ventilation can be corrected by decreasing the volume of air given to the baby, as well as by decreasing the amount of breaths the baby is given by the ventilator.

Overventilation, Infant Brain Damage and Birth Injury

Periventricular leukomalacia (PVL)

This is the death of the white matter of the brain due to softening of brain tissue. It is a risk in premature babies and is caused by a lack of oxygen or blood flow to the periventricular area of the brain, which results in the death or loss of brain tissue.

The periventricular area is the area around the spaces in the brain called ventricles. These are critical areas as they contain nerve fibers that carry messages from the brain to the muscles. Babies with PVL are at risk for motor disorders, delayed mental development, coordination problems, and vision and hearing impairments. PVL may be accompanied by a hemorrhage or bleeding in the periventricular-intraventricular area (the area around and inside the ventricles), and can lead to cerebral palsy. The disorder is diagnosed by ultrasound of the head.

  • Cerebral palsy
  • Hypoxic ischemic encephalopathy (HIE)
  • Intraventricular hemorrhage
  • Cognition development disorder (below normal intellectual functioning)
  • Auditory deficits

Risk Factors for Overventilation Injuries

All babies that need help breathing are at risk for over ventilation injuries. Babies with the following problems are at risk:

  • Asphyxia: This is when a baby’s brain and other organs do not get enough oxygen before, during or just after birth.
  • Meconium aspiration syndrome: This is when a baby has problems caused by inhaling meconium, which comes from the baby’s first stool.
  • Respiratory distress syndrome
  • Premature birth

Babies who have lung injury prior to being over ventilated, or whose lungs are not fully developed, are the most susceptible to over ventilation lung injury.

Signs of Brain Damage from Overventilation

Signs of brain damage include the following:

  • Bluish skin
  • Muscle tone is poor or reflexes are weak
  • Low heart rate
  • Evidence of neurological problems, including coma and seizure
  • Multi-system organ dysfunction

Tests used to diagnose brain damage:

  • CT (computed tomography) scan
  • MRI (magnetic resonance imaging) scan
  • EKG (electrocardiogram)
  • Blood glucose levels
  • EEG (electroencephalogram)
  • Ultrasound
  • Evoked potential test
  • Echocardiogram

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