Regulation of Ventilation, Ventilation/Perfusion Ratio, and Transport

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Regulation of Ventilation, Ventilation/Perfusion
Ratio, and Transport
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Objectives

• Review how the body regulates normal ventilation.
• Explain how feedback systems of the body can
  influence ventilation.
• Discuss the V/Q ratio and how it influences the
  body.
• Identify the role of red blood cells and
  hemoglobin in oxygen transport.

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Introduction

• Understanding how the body ventilates and
  oxygenates is integral to proper care.
• This chapter will look at the next several
  components of an organism, with focus on how
  ventilations are controlled and oxygen
  transported.

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Physiology

• Regulation of Ventilation
• Breathing is primarily involuntarily controlled
• Feedback to the brain on breathing status
  provided by
• Chemoreceptors
• Lung receptors

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Physiology (contd)

• Regulation of Ventilation
• Chemoreceptors
• Central chemoreceptors are located in the
  medulla.
• Monitor CO2 in arterial blood and pH of CSF.

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Physiology (contd)

• Regulation of Ventilation
• Chemoreceptors
• Peripheral chemoreceptors are located in the
  aortic arch and carotid bodies.
• More specific to changes in oxygen levels.

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Physiology (contd)

• Regulation of Ventilation
• Lung receptors
• Irritant receptors
• Stretch receptors
• J-receptors

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Figure 8-1 Respiration is controlled by the
autonomic nervous system. Receptors within the
body measure oxygen, carbon dioxide, and hydrogen
ions and send signals to the brain to adjust the
rate and depth of respirations.
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Physiology (contd)

• Regulation of Ventilation
• Hypercapnic drive
• The normal impetus to breathe is the level of CO2
  in arterial blood.
• Hypoxic drive
• This occurs when oxygen levels become the impetus
  to breathe.

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Physiology (contd)

• Ventilation/Perfusion Ratio (V/Q Ratio)
• Describes the relationship between the amount of
  ventilation and perfusion the lung receives.
• Ideally the ratio would be 1, but it is not.
• All etiologies of respiratory distress can be
  defined in terms of ventilation or perfusion
  deficits.

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Physiology (contd)

• Ventilation/Perfusion Ratio (V/Q Ratio)
• Pressure imbalances
• Perfusion of blood through the alveoli capillary
  bed can be influenced by capillary driving
  pressure or the air pressure within the lung.

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Figure 8-2 Perfusion of the pulmonary
capillaries is affected by pressure within the
alveoli and pressure within the capillaries.
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Physiology (contd)

• Ventilation/Perfusion Ratio (V/Q Ratio)
• Ventilatory disturbances
• Conditions that result in wasted ventilation
  through the lungs.
• The correction is to enhance alveolar ventilation.

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Physiology (contd)

• Ventilation/Perfusion Ratio (V/Q Ratio)
• Perfusion disturbances
• Conditions that result in wasted perfusion
  through the lungs.
• The correction is to enhance lung perfusion.

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Physiology (contd)

• Transport of O2 and CO2 in the Blood
• Oxygen transport
• 9798.5 is attached to hemoglobin
• 1.53 is dissolved in plasma

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Physiology (contd)

• Transport of O2 and CO2 in the Blood
• Carbon dioxide transport
• 70 bound in the form of bicarbonate
• 23 attached to hemoglobin
• 7 dissolved in plasma

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Figure 8-3 hemoglobin and dissolved in plasma.
Carbon dioxide is transported in the blood in
three ways as bicarbonate, attached to
hemoglobin, and dissolved in plasma.
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Physiology (contd)

• Alveolar/Capillary Gas Exchange
• Gas exchange in the lungs
• Venous blood is low in O2 and high in CO2.
• Alveolar gas is high in O2 and low in CO2.
• When the RBC passes by the alveoli, the gases
  flow down their partial pressure gradients.

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Overview of ventilation and perfusion
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Case Study

• You are alerted to respond to a local freeway
  rest stop for a patient with respiratory
  distress. Upon your arrival, you find the patient
  sitting in the lobby of the rest stop bathroom
  facility, looking scared. As you approach, he
  says to you, I was just driving. I dont know
  what happened.

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Case Study (contd)

• Scene Size-Up
• 62-year-old male patient
• BSI precautions are taken
• NOI is respiratory distress
• There is only one patient
• There are no barriers to extrication from this
  location to the ambulance

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Case Study (contd)

• What is the basic disturbance in blood chemistry
  that can cause respiratory distress?
• The patient's dyspnea points to a problem with
  what body system?
• What precautions for your safety should you take?

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Case Study (contd)

• Primary Assessment Findings
• Patient responsive to verbal stimuli, AOx3
• Airway patent, no foreign bodies or fluid
• No objective indications of dyspnea present,
  patient speaks in full sentences

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Case Study (contd)

• Primary Assessment Findings
• Respiratory rate is 22 times/minute
• Peripheral pulse is present, skin is warm and dry

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Case Study (contd)

• Is this patient a high or low priority? Why?
• What care should be provided immediately?
• What information must the body's chemoreceptors
  be telling the brainstem in order for the
  respirations to be rapid?

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Case Study (contd)

• Medical History
• Patient has a history of high blood pressure and
  clots in my lungs
• Medications
• I take a blood pressure reducer. It's in my
  travel bag in my car
• Allergies
• Aspirin

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Case Study (contd)

• Pertinent Secondary Assessment Findings
• Pupils reactive to light, airway patent
• Breath sounds clear bilaterally with no accessory
  muscle use
• Pulse oximeter reads 94 on room air

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Case Study (contd)

• Pertinent Secondary Assessment Findings
• Muscle tone is noted to all extremities
• Patient denies any history of trauma
• Skin normal
• B/P 160/88, Pulse 108, Respirations 22

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Case Study (contd)

• En route to the hospital, the patient states that
  he was driving to his daughter's home, and that
  he'd been driving for 11 hours straight, stopping
  only for fuel.
• How might this information be beneficial to
  understanding the patient's presentation?

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Case Study (contd)

• Will you change your treatment based on
  information you have now learned?
• Why is the patient's enhanced ventilation effort
  not really helping his oxygenation status?

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Case Study (contd)

• Care provided
• High-flow oxygen via nonrebreather mask
• Place the patient in a position of comfort
• Initiate Paramedic intercept prior to departure
  or en route
• Verbally reassure patient en route and provide
  reassessment

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Case Study (contd)

• Explain how oxygen therapy may help improve the
  patient's condition.
• Given this patient's presentation, medical
  history, and physical exam findings, is he likely
  using the hypercapnic or hypoxic drive to control
  respirations?

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Summary

• Consistent with other chapters in this section,
  understanding the cellular level of functioning
  will assist the Advanced EMT not only in
  interpreting the patient's problem, but also
  managing it more efficiently.
• If the cells are not being provided oxygen
  delivery and carbon dioxide removal, cells will
  die and the patient can easily die.