TRANSITION SERIES
Topics for the Advanced EMT
CHAPTER
8
Regulation of Ventilation,
Ventilation/Perfusion
Ratio, and Transport
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.
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.
Physiology
• Regulation of Ventilation
– Breathing is primarily involuntarily
controlled
– Feedback to the brain on breathing
status provided by:
 Chemoreceptors
 Lung receptors
Physiology (cont’d)
• Regulation of Ventilation
– Chemoreceptors
 Central chemoreceptors are located in
the medulla.
 Monitor CO2 in arterial blood and pH of
CSF.
Physiology (cont’d)
• Regulation of Ventilation
– Chemoreceptors
 Peripheral chemoreceptors are located in
the aortic arch and carotid bodies.
 More specific to changes in oxygen
levels.
Physiology (cont’d)
• Regulation of Ventilation
– Lung receptors
 Irritant receptors
 Stretch receptors
 J-receptors
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.
Physiology (cont’d)
• 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.
Physiology (cont’d)
• 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.
Physiology (cont’d)
• 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.
Figure 8-2 Perfusion of the pulmonary capillaries is affected by pressure within the alveoli and pressure within
the capillaries.
Physiology (cont’d)
• Ventilation/Perfusion Ratio (V/Q Ratio)
– Ventilatory disturbances
 Conditions that result in wasted
ventilation through the lungs.
 The correction is to enhance alveolar
ventilation.
Physiology (cont’d)
• Ventilation/Perfusion Ratio (V/Q Ratio)
– Perfusion disturbances
 Conditions that result in wasted perfusion
through the lungs.
 The correction is to enhance lung
perfusion.
Physiology (cont’d)
• Transport of O2 and CO2 in the Blood
– Oxygen transport
 97%–98.5% is attached to hemoglobin
 1.5%–3% is dissolved in plasma
Physiology (cont’d)
• 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
hemoglobin and dissolved in plasma. Carbon dioxide is transported
in the blood in three ways: as bicarbonate, attached to hemoglobin, and
dissolved in plasma.
Figure 8-3
Physiology (cont’d)
• 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.
Overview of ventilation and perfusion
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 don‘t
know what happened.”
Case Study (cont’d)
• 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
Case Study (cont’d)
• 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?
Case Study (cont’d)
• Primary Assessment Findings
– Patient responsive to verbal stimuli,
A&Ox3
– Airway patent, no foreign bodies or fluid
– No objective indications of dyspnea
present, patient speaks in full sentences
Case Study (cont’d)
• Primary Assessment Findings
– Respiratory rate is 22 times/minute
– Peripheral pulse is present, skin is warm
and dry
Case Study (cont’d)
• 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?
Case Study (cont’d)
• 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
Case Study (cont’d)
• 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
Case Study (cont’d)
• 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
Case Study (cont’d)
• 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?
Case Study (cont’d)
• 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?
Case Study (cont’d)
• 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
Case Study (cont’d)
• 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?
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.