Module 2: Invasive Respiratory Support Flashcards
What is Ventilation vs Respiration?
- Ventilation is movement of gases in and out of the pulmonary system,
- Respiration involves the exchange of oxygen and carbon dioxide at the alveolar-capillary level and at the capillary-cellular level
***Respiration is the process of gas exchange throughout the body- a much larger and more complex process
What is ventilation compromised of (2)?
- pulmonary ventilation
- alveolar ventilation
What is pulmonary ventilation vs alveolar ventilation?
- Pulmonary ventilation is the volume of air exchanged between the environment and the lungs.
- Alveolar ventilation is the volume of air entering the alveoli that takes part in gas exchange per minute (This takes place across the alveolar-capillary membrane)
What are 3 bodily functions that ventilation is maintained by?
- central nervous system: located in the medulla oblongata (brain stem)
- stretch reflexes: located in chest wall and airways (serve to alter breathing pattern to maintain adequate minute ventilation)
- chemoreceptors: located in the aorta and carotid artery (respond to increases and decreases on PaO2, PCO2 and pH
How does increase or decrease in pO2 and pCO2 affect minute ventilation?
- Minute Ventilation: the product of Rate X Volume
- ↑pCO2 will lead to increased minute ventilation.
- ↓pCO2 will lead to decreased minute ventilation.
- ↓pO2 leads to increased minute ventilation.
What is functional residual capacity (FRC)?
- Normal alveolar ventilation occurs when an infant has a sufficient respiratory drive and sufficient energy to inflate and deflate the lungs, maintaining some volume at the end of every breath known as the functional residual capacity
- FRC is maintained when sufficient surfactant minimizes surface tension (tendency for alveoli to collapse) and the alveoli remain slightly open at the end of each exhalation
What are some reasons as to why preterm infants are at risk of pulmonary compromise due to their immature pulmonary system (4)?
- ↓ surfactant
- ↓ alveoli
- ↓ capillaries
- ↑ distance between alveoli and capillaries
- Small airways
- Underdeveloped, weak muscles
- Underdeveloped pulmonary vasculature
- Cartilaginous rib cage
How does mechanical ventilation assist with ventilation?
- by delivering air and oxygen to the lungs, but gas exchange or respiration must still occur at the alveolar and cellular level
What is the difference of ventilation and respiration?
- Ventilation is the act of inhalation and exhalation for the purpose of gas exchange within the lungs.
- Respiration is the gas exchange that occurs at a cellular level (It allows the exchange of gas such as O2 and CO2 between an individual and his or her environment)
What is respiration dependent on (5)?
- Sufficient alveolar ventilation
- Alveolar/capillary diffusion
- Pulmonary perfusion
- Hemoglobin
- Peripheral perfusion
Where are the two places that gas is exchanged?
- in the lungs
- tissues (at the cellular level)
Where does alveolar respiration and cellular respiration take place?
- Alveolar respiration occurs in the lungs;
- cellular respiration occurs in the tissues.
For respiration, what is the role of the cardiovascular system? brain?
- The cardiovascular system acts as a conduit between these two sites of gas exchange.
- The brain acts as a central controller
If the entire process of respiration occur in all body cells, what are the three main system that are responsible for gas exchange?
- pulmonary system
- circulatory system
- nervous system.
What are the 3 interdependent processes that is a result of alveolar respiration?
- alveolar ventilation
- pulmonary perfusion
- diffusion across the alveolar-capillary membrane to allow for pulmonary perfusion
**Alveolar respiration: gas exchange that occurs between the alveoli and the pulmonary capillaries in the lungs
How does diffusion across alveolar-capillary membrane occur?
- because of pressure gradients for oxygen and carbon dioxide
- these gases move from areas of high pressure toward areas of low pressure.
- oxygen moves from the alveoli to the capillaries
- carbon dioxide moves from the capillaries to the alveoli.
How does CO2 diffuse across the alveolar-capillary membrane differently from O2?
- CO2 is much more diffusible than O2.
- Even with diminished perfusion, CO2 diffuses readily from pulmonary venous and capillary blood to the alveoli.
- Once in the alveoli, CO2 is dependent on adequate alveolar or minute ventilation for elimination.
Which gas is the primary indicator of adequate alveolar ventilation?
- CO2
- Changes in carbon dioxide levels are primarily due to changes in minute ventilation.
- Elevated CO2 indicates hypoventilation;
- CO2 depletion indicates hyperventilation .
What type of breathing patten when theres diminished tidal volume and/or decreased rate?
- Hypoventilation is the term used to describe a breathing pattern that results in decreased minute ventilation
What can cause hypoventilation in infants (3)?
- prematurity of the lungs which may include RDS.
- CNS depression,
- BPD,
- MAS,
- pneumonia,
- apnea of prematurity, and
- diaphragmatic hernia.
What can happen due to lack of surfactant?
Due to the lack of surfactant in the immature lungs,
- compliance decreases,
- the work of breathing increases,
- tidal volume decreases.
Initially, in an attempt to maintain minute ventilation,
- an infant responds with tachypnea.
However, premature infants will quickly tire
- tachypnea will become bradypnea and apnea.
Thus, hypoventilation will occur.
- Minute ventilation falls.
- Indrawing will become evident.
- Pallor and/or cyanosis may appear.
- The infant may grunt in an attempt to prematurely close the glottis and maintain FRC
Whats pulmonary perfusion?
- refers to the flow of blood through the portion of the circulatory system that supplies the lungs
- De-oxygenated blood travels from the right side of the heart through the pulmonary arteries to the lungs where oxygen will be picked up and returned to the left heart side of the heart through the pulmonary veins.
- The oxygenated blood can then travel out the aorta and to the rest of the body.
- At the same time, the blood transported to the lungs by the pulmonary artery will deliver CO2 picked up from the tissues and carry it back to the lungs for elimination.
What are 2 things that pulmonary perfusion dependent?
- oxygen and pH of blood
in response to concentration of hypoxia and acidosis:
- the pulmonary vasculature will constrict (increased pulmonary vascular resistance [PVR]), leading to diminished pulmonary perfusion.
- This will resulting the development of pulmonary hypertension.
What are 3 important respiratory processes occur in lungs?
- ventilation,
- diffusion and
- perfusion
What is the circulatory system responsible for?
- circulatory system acts as a courier, transporting gases between tissues and the lungs.
- It is responsible for delivering oxygen from the lungs to the cells and carbon dioxide from the cells to the lungs.
- The heart is the pump
- the vasculature (vascular system made up of vessels) is the conduit
What is cardiac output?
- Cardiac output is the volume of blood pumped by the heart in one minute, (mls/min).
- Cardiac output is a product of heart rate × stroke volume.
**Stroke volume is the volume of blood pumped with each beat (mL/beat).
Stroke volume is a product of what 3 factors?
- preload: refers to the volume of blood in the ventricles prior to contraction (diastolic).
- afterload: refers to the pressure or resistance against which the ventricles are pumping (systolic blood pressure)
- contractility: refers to the strength of contraction of the heart muscle
What are the 3 ways CO2 is transported?
- dissolved in plasma
- attached to hemoglobin
- combined with H20 to form H2CO3 (carbonic acid)
***Most CO2 is dissolved in plasma or as carbonic acid; very little is carried by hemoglobin.
What are 2 ways oxygen is transported?
- dissolved in plasma (2%)
- attached to hemoglobin (98%)
What needs to reach capillary beds for cellular respiration to occur?
- Once arterial blood (containing oxygen and CO2) reaches capillary beds in the tissues
What are the two types of chemoreceptors that control respiration?
Central Chemoreceptors:
- located in the brain stem and
- respond to the acidity of the CSF
- involved in control of respiratory rate and depth of breath
Peripheral Chemoreceptors
- located in the aortic arch and carotid arteries
- respond to changes in oxygen concentrations, CO2 and pH
- regulate breathing breath to breath
CNS depression and damage can lead to what (3)?
respiratory problems such as
- bradypnea,
- bradycardia,
- apnea,
- hypoventilation,
- hyperventilation, and
- hypotension.
What is the difference between ventilation and respiration?
- Ventilation is the movement of gases in and out of the lungs
- respiration is the gas exchange of oxygen and carbon dioxide at the alveolar-capillary level and at the cellular-capillary level.
What 4 physiological factors is respiration dependent on?
- Sufficient alveolar ventilation,
- pulmonary perfusion,
- hemoglobin,
- peripheral perfusion.
Describe ways in which the pulmonary, circulatory, and nervous systems work to maintain respiratory function
Pulmonary system:
- Pulmonary ventilation,
- pulmonary perfusion,
- diffusion across the alveolar-capillary membrane to allow for pulmonary perfusion.
Circulatory system:
- By maintaining cardiac output (HRxSV).
- SV is a product of preload, afterload, and contractility.
- CO2 is also transported via dissolved plasma, attached to hemoglobin, and/or combined with H20 to form H2C03 (carbonic acid).
- Oxygen is transported via dissolved plasma and attached to hemoglobin.
Nervous system:
- Central and peripheral chemoreceptors.
- Central receptors are located in the brain stem and respond to acidity in the CSF.
- They control the rate and depth of breath.
- Peripheral receptors are located in the aortic arch and carotid arteries and respond to changes in oxygen concentration, carbon dioxide and pH.
- Peripheral receptors regulate breathing on a breath to breath basis.
What is the primary goal of mechanical ventilation?
Primary goal of mechanical respiration:
- to improve minute ventilation and oxygenation
Desired outcomes of mechanical ventilation:
- to achieve and maintain adequate pulmonary gas exchange
- to minimize the risk of lung injury
- to reduce patient work of breathing (WOB)
- to optimize patient comfort
- to improve oxygenation
What are some desired outcomes of mechanical ventilation (4)?
- to achieve and maintain adequate pulmonary gas exchange
- to minimize the risk of lung injury
- to reduce patient work of breathing (WOB)
- to optimize patient comfort
- to improve oxygenation
What is mechanical ventilation?
- the application of positive inspiratory pressure to inflate the lungs.
What is mean airway pressure?
- the amount of pressure exerted on the airway during an entire respiratory cycle.
- An increased mean airway pressure allow for recruitment of collapsed alveoli and/or redistribution of lung fluid to decrease dead space ventilation (an area of ventilation in absence of perfusion), and shunting (an area of normal perfusion but absent of ventilation).
How is newborn lungs much like a balloon?
- Once a balloon has been inflated, it is generally easier to inflate it again because of the structural changes to the balloon wall.
- Similarly, once the structure of the airway wall is compromised by mechanical ventilation, it will behave differently when subsequent pressure is applied.
- Although the lungs may recoil to its original shape after the exhalation of each breath, some elasticity will be lost over time and the lungs will loose structure and become larger than normal.
What is compliance?
- is the change in volume over the change in pressure.
**We consider both the lungs and the chest wall, when referring to compliance.
- compliance: as the amount of effort or ease needed to stretch the lungs and chest wall.
What is elasticity?
- is equal to the change in pressure over the change in volume (is the opposite of compliance)
**We also consider elasticity in the context of the lungs and chest wall - elasticity is the amount of resistance to the stretching.
What are 2 ways to prevent further lung injury from mechanical ventilation?
- reducing the infant’s work of breathing and
- by optimizing their comfort.
What are 6 signs of increased WOB?
- tachypnea,
- tachycardia,
- indrawing,
- nasal flaring,
- grunting or
- decreased or absent respiratory drive
How will mechanical ventilation aimed at decreasing WOB (2)?
- setting the appropriate tidal volume, respiratory rate with the option of pressure support to achieve required alveolar ventilation
- using positive end-expiratory pressure to maintain FRC and thereby improve compliance and expansion of the lungs
What is fighting the ventilator?
- referred to as asynchrony
- occurs as the neonate attempts to maintain their own respiratory pattern,
- which may be out of sync with what the ventilator is set to deliver
Why is supporting infant to breathe the utmost importance?
- not only for their survival, but as a comfort measure as well.
- These vulnerable infants need to be utilizing their reserves for growth - not using their energy to breathe
What are strategies to optimize infant comfort (3)?
- Ensuring the most synchronous mode of ventilation is being utilized
- Non-pharmacologic measures (e.g. Developmentally supportive care)
- Facilitated tucking
- Skin-to-skin
- Nesting
- Noise reduction
- Pharmacologic sedation/pain control
What is positive pressure ventilation (PPV)?
- when air is moved into the patient’s lungs via an endotracheal tube, tracheostomy tube or mask/prongs interface to create a positive pressure to inflate the lungs
Is mechanical ventilation like normal breathing?
no
What are the twos ways that mechanical ventilation is different from normal breathing?
- The positive pressure needed to inflate the lungs with mechanical ventilation is much greater than the negative pressure needed with normal breathing.
- Mechanical ventilation bypasses the normal internal biochemical feedback mechanism that controls breathing.
How is our normal breathing like a vaccum?
- when we inhale, our lungs expand as a result of negative intrathoracic and intrapleural pressure.
- This negative pressure actually pulls the lungs open from the outside - much the way a vacuum bag is expanded inside the vacuum chamber of a vacuum cleaner.
- As a result, the pressure within the lungs does not increase significantly as the lungs inflate.
How does mechanical ventilation work (how is it like blowing up a balloon)?
- mechanical ventilation uses high positive pressure exerted on the inside of the airways and lungs to push them open from the inside - much like blowing up a balloon.
- As a result, the pressure within the lungs increases significantly as the lungs inflate.
- In fact, without this significant increase in pressure, the lungs would not inflate
What are some problems with using positive pressure to inflate an infants lungs?
- is that this pressure causes damage to fragile and developing lung tissue
- Edema, inflammation, scarring, over-inflation, and loss of elasticity are a few of the more common and more serious problems that result from the barotrauma, (damage due to pressure) caused by positive pressure ventilation, and
- volutrauma, (damage due to over-distension of the lung).
What is the difference of barotrauma vs volutrauma?
- barotrauma: damage due to pressure caused by positive pressure ventilation, and
- volutrauma: damage due to over-distension of the lung
What is the difference between pressure and volume?
Pressure refers to force
- in mechanical ventilation, pressure refers to the force being applied to the inside of the alveoli as they are being inflated.
- Think about blowing up a balloon.
- Pressure is the force you use to inflate the balloon.
Volume refers to the space something occupies.
- For example, in ventilation, volume refers to the amount of gas inside the alveoli.
- Think about the balloon you have just used force to inflate.
- Volume refers to the amount of gas inside the balloon after it is inflated.
**greater pressure you apply to inflate the lung, the greater the volume you will achieve
What are the two forces that impose the inflation of the lungs?
- compliance (Litres/cmH2O)
- resistance (cmH2O/Litres/second)
What is compliance?
- How compliant a baby’s lungs are affects how much volume moves into a lung at a given pressure.
- It affects how much pressure is required to achieve a given end-inflation volume within a lung.
Think about two balloons:
- One is slightly inflated and the other is collapsed.
- It takes less pressure to inflate the first balloon because it is more compliant.
- It would take more pressure to achieve the same volume in the collapsed balloon because it requires more pressure to inflate, and is therefore less compliant.
What is resistance?
- Resistance is the measurement of the frictional forces that must be overcome during breathing.
Examples of an increase in force can be
- a result of anatomical structures of the airways,
- decrease diameter of the endotracheal tube size,
- increase in secretions,
- bronchospasm,
- mucosal edema
** An increase in resistance will require more pressure to achieve the same end-inflation volume within a lung.
What is pressure ventilation?
- is a continuous flow, time cycled and pressure limited mode that provides a constant pressure at the airways
- It allows the respiratory therapist to set a desired pressure limit, inspiratory time and rate
**Normal inspiratory times for infants range from 0.3 seconds to 0.55 seconds
What is the range PIP is used for mechanical ventilation?
- Normal pressures used to mechanically ventilate infants using a pressure ventilator range from a peak inspiratory pressure (PIP) 12 cm H2O to 40 cm H2O,
- however <25 cm H2O is preferred because levels higher than this places the infant at risk for lung damage and air leaks
How do health care providers decided what pressures will achieve normal tidal volumes for a particular infant (4)?
by selecting peak inspiratory pressures which:
- Produce normal chest movements (adequate bilateral chest rise)
- Normalize pCO2, pH, and PaO2
- Within the 12-40 cm H2O range
- Capable of delivering adequate tidal volumes (3-7 ml/kg)
What is volume guarantee (VG)?
- a setting on the ventilator within pressure controlled ventilation.
- VG on the ventilator is designed to deliver tidal volumes most appropriate for adequate gas exchange
What is tidal volume?
- is the volume of gas inhaled or exhaled during a normal breath
- When the tidal volume and/or the inspiration time for that breath have been reached, inspiration ends.
** The ventilator will use the least amount of pressure to deliver this tidal volume based on a breath to breath analysis of previous pressures needed to achieve the set volume.
