CRITICAL CARE: RESPIRATORY
EXAM TWO STUDY GUIDE
MECHANICS OF VENTILATION
Ventilation is the movement of air in and out of the airway (alveoli).
Ventilation requires movement of the walls of the thoracic cage and of its
floor, the diaphragm.
When the chest capacity increases-----air enters the trachea-----bronchi-----
bronchioles-----alveoli-----
then inflates the lungs.
When the chest and diaphragm return to their previous position -----the lungs
recoil and force air out of the bronchi and trachea.
Inspiration occurs in the first 1/3 of the respiratory cycle-----requires energy
Expiration occurs in the latter two thirds of the respiratory cycle-----require
very little energy (passive)
Air Pressure Variances are a part of the mechanics of ventilation. Air flows
from a region of higher pressure to a region of lower pressure.
Air Resistance
Resistance is determined by the radius or size of the airway through which
the air is flowing as well as lung volume and airflow velocity. Any process
that affects the bronchioles diameter or width affects airway resistance. With
increased resistance, greater than normal respiratory effort is required to
achieve normal levels of ventilation.
MECHANICS OF DIFFUSION
Pulmonary Diffusion is the process of which oxygen and carbon dioxide are
exchanged from areas of higher concentrations to areas of lower
concentration at the air-blood interface. The alveolar-capillary membrane is
ideal for diffusion because of its thinness and large surface area. Oxygen and
carbon dioxide travel across the alveolar capillary membrane without
difficulty because of the difference in gas concentration in the alveoli and
capillaries.
, Pulmonary Perfusion is the actual blood flow through the pulmonary
vasculature. Perfusion is the exchange of o2 and CO2 between the RBCs and
the body tissues. It is influenced by alveolar pressure. The pulmonary
capillaries are sandwiched between adjacent alveoli.
If alveoli pressure is high-----capillaries are squeezed.
Pulmonary artery pressure, gravity and alveolar pressure determine the
patterns of perfusion. In lung disease these factors vary, and the perfusion of
the lung may become abnormal.
VENTILATION-PERFUSION IMBALANCES
Adequate gas exchange depends on an adequate ventilation-perfusion (V/Q)
ratio. In different areas of the lung the ratio varies.
Airway blockage, local changes in compliance(elasticity), and gravity
may alter ventilation.
Pulmonary artery pressure, alveolar pressure or gravity may alter
perfusion.
V/Q imbalances causes shunting of blood, resulting in hypoxia
Shunting of blood id the main cause of hypoxia after abdominal or
thoracic surgery. Also, in must types of respiratory failure.
When the shunting of blood exceeds 20% severe hypoxia develops.
DIAGNOSTIC ASSESSMENTS:
COMPREHENSIVE RESPIRATORY H & P ASSESSMENT
The health history initially focuses on the patients’ presenting problems and
associated symptoms.
Onset, location, duration, character, aggravating, alleviating factors,
radiation (if relevant) and timing of the presenting problem.
How do these factors impact the patients ADL’s, work and family
activities and quality of life?
The nurse must also explore non-pulmonary disease when evaluating
symptoms.
The physical examination includes the patient’s appearance (skin color,
clubbing of fingernails), inspection of the upper and lower respiratory airway
structures. Also, the observation of the breathing pattern and rate.
PULMONARY FUNCTION TEST (PFT’S)
Determine lung function and breathing difficulties.
EXAM TWO STUDY GUIDE
MECHANICS OF VENTILATION
Ventilation is the movement of air in and out of the airway (alveoli).
Ventilation requires movement of the walls of the thoracic cage and of its
floor, the diaphragm.
When the chest capacity increases-----air enters the trachea-----bronchi-----
bronchioles-----alveoli-----
then inflates the lungs.
When the chest and diaphragm return to their previous position -----the lungs
recoil and force air out of the bronchi and trachea.
Inspiration occurs in the first 1/3 of the respiratory cycle-----requires energy
Expiration occurs in the latter two thirds of the respiratory cycle-----require
very little energy (passive)
Air Pressure Variances are a part of the mechanics of ventilation. Air flows
from a region of higher pressure to a region of lower pressure.
Air Resistance
Resistance is determined by the radius or size of the airway through which
the air is flowing as well as lung volume and airflow velocity. Any process
that affects the bronchioles diameter or width affects airway resistance. With
increased resistance, greater than normal respiratory effort is required to
achieve normal levels of ventilation.
MECHANICS OF DIFFUSION
Pulmonary Diffusion is the process of which oxygen and carbon dioxide are
exchanged from areas of higher concentrations to areas of lower
concentration at the air-blood interface. The alveolar-capillary membrane is
ideal for diffusion because of its thinness and large surface area. Oxygen and
carbon dioxide travel across the alveolar capillary membrane without
difficulty because of the difference in gas concentration in the alveoli and
capillaries.
, Pulmonary Perfusion is the actual blood flow through the pulmonary
vasculature. Perfusion is the exchange of o2 and CO2 between the RBCs and
the body tissues. It is influenced by alveolar pressure. The pulmonary
capillaries are sandwiched between adjacent alveoli.
If alveoli pressure is high-----capillaries are squeezed.
Pulmonary artery pressure, gravity and alveolar pressure determine the
patterns of perfusion. In lung disease these factors vary, and the perfusion of
the lung may become abnormal.
VENTILATION-PERFUSION IMBALANCES
Adequate gas exchange depends on an adequate ventilation-perfusion (V/Q)
ratio. In different areas of the lung the ratio varies.
Airway blockage, local changes in compliance(elasticity), and gravity
may alter ventilation.
Pulmonary artery pressure, alveolar pressure or gravity may alter
perfusion.
V/Q imbalances causes shunting of blood, resulting in hypoxia
Shunting of blood id the main cause of hypoxia after abdominal or
thoracic surgery. Also, in must types of respiratory failure.
When the shunting of blood exceeds 20% severe hypoxia develops.
DIAGNOSTIC ASSESSMENTS:
COMPREHENSIVE RESPIRATORY H & P ASSESSMENT
The health history initially focuses on the patients’ presenting problems and
associated symptoms.
Onset, location, duration, character, aggravating, alleviating factors,
radiation (if relevant) and timing of the presenting problem.
How do these factors impact the patients ADL’s, work and family
activities and quality of life?
The nurse must also explore non-pulmonary disease when evaluating
symptoms.
The physical examination includes the patient’s appearance (skin color,
clubbing of fingernails), inspection of the upper and lower respiratory airway
structures. Also, the observation of the breathing pattern and rate.
PULMONARY FUNCTION TEST (PFT’S)
Determine lung function and breathing difficulties.
