Module 2: Resp Ax (Ventilation) Flashcards
what does ventilation play a critical role in?
CO2 clearance, determining arterial O2 saturation, and O2 supply
what is the main respiratory muscle?
diaphragm and then intercostal muscles
what is the tissue in the lungs?
elastic tissue. parietal pleura line thoracic wall and upper portion of diaphragm; visceral pleura line outside of each lung
type 1 alveolar cells
- comprise 90% of alveolar wall, susceptible to injury, and are main structural cells
type 2 alveolar cells
double the number of type 1 cells; produce surfactant; and can divide into type 1 and 2 cells when lung tissue is damaged
what is the most sensitive region of the respiratory tract?
carina; triggers cough reflex
what is the role of surfactant?
increases lung compliance, prevents alveolar collapse, and decreases alveolar surface tension
ventilation assessment
- main determinants = RR and tidal volume which define minute ventilation
- RR and Vt are influenced by WOB
- WOB is influenced by lung compliance, a/w resistance and respiratory muscle function
ventilation
movement of air in and out of the lungs
what is one way to determine effectiveness of ventilation?
measuring PaCO2
what are ax cues that can indicate an increase in PaCO2 levels (hypercapnia/hypercarbia)?
- increased RR
- shallow breaths
- SOB/dyspnea
- headaches, dizziness, confusion, decreased LOC
- respiratory acidosis
ax cues for respiratory muscle function
- medical hx, course of illness
- nutrition status
- prolonged ventilator dependence
- neuro conditions
- increased WOB leading to fatigue
compliance
measure of distensibility of a tissue
what is internal compliance?
how easily the alveoli/lung tissue can be stretched
what happens if internal compliance is decreased?
that means lungs are stiff, and trying to inflate poorly compliant lungs require more pressure and physical effort increasing WOB
what happens if internal compliance is increased?
lungs are easily stretched and require less pressure, so WOB is decreased
what is the effect of resp infections on internal compliance?
they reduce internal compliance b/c accumulation of fluid and thick mucus in alveoli makes it harder for lungs to expand and fill with air
ax cues for internal compliance
- medical hx (COPD, pulmonary fibrosis, interstitial lung disease)
- chest xray (consolidation, atelectasis)
- secretions
- crackles on auscultation
what is external compliance?
the ability of the lungs to fully inflate and the diaphragm and chest wall to expand and contract
ax cues for external compliance
- medical hx (trauma, rib #s, chest burns)
- anything inhibiting diaphragm expansion (obesity, ascites, pregnancy, bowel obstruction, rib or spinal deformities)
- pneumo/hemothorax
- pleural effusion
- pain with breathing/coughing
normal WOB is _____ of total body expenditure
<2%
what can airway resistance be influenced by?
diameter of airway/artificial airway (the narrower the diameter, the greater the resistance therefore causing increased WOB)
ax cues for airway resistance
- wheezes/stridor
- presence of bronchospasm
- medical hx
- a/w obstruction (anaphylaxis, tumors)
- artificial airways
- thick, copious secretions
work of breathing
amount of effort required to breathe
what three factors impact WOB?
1) force required to expand lungs
2) pressure required to overcome elastic recoil of lungs
3) resistance generated by airways
when does WOB increase?
with any condition that impairs resp muscles, decreases lung compliance, or increases a/w resistance
ax cues for increased WOB
- nasal flaring
- accessory muscle use
- chest retractions
tidal volume
volume of air that is inhaled and exhaled in a single breath during normal quiet breathing (mL)
why is tidal volume important?
its a factor in determining overall efficiency of ventilation
what is the equation for minute ventilation
minute ventilation (L/min) = tidal volume (mL) x RR (breaths/min)
what is the primary compensatory mechanism in tidal volume?
a change in RR to maintain volume of air moving in and out per minute
minute ventilation
amount of air inhaled and exhaled from the lungs in one minute determined by RR and tV
what might directly impact tidal volume?
- age, body size
- resp muscle strength
- resp disease, condition
- meds
- LOC
- mechanical ventilation
ax cues for tidal volume
- observed depth of respirations
- directly measured volumes through mechanical ventilation
vital capacity
max volume (amount) of air that can be expired after a max inhalation (deep breath); reflects max lung capacity
why is vital capacity important?
part of criteria used for determining if a pt can be weaned from ventilatory support
what is a normal VC measurement? how can you obtain a measurement?
~3-5L. using settings on a ventilator (usually done by RT), or by coughing
what is the most accurate way to determine vital capacity?
spirometry
what factors directly impact vital capacity
- resp muscle fx
- internal/external compliance concerns
- age related anatomic changes
ax cues for vital capacity
- ability to cough
- pulm fx tests/spirometry
- measurement via mechanical ventilator
functional residual capacity
volume of air left in lungs at the end of normal exhalation; used in determining compliance
what does FRC do?
allows air to flow easily into lungs during inhalation; helps prevent collapse of small airways and alveoli at the end of expiration
how do conditions like atelectasis and ARDS affect FRC?
lead to alveolar collapse and loss of FRC = decreased compliance, increased WOB and impaired ventilation
what factors directly impact FRC?
- age
- disease (COPD, asthma)
- body position (decreased FRC in supine)
- abdominal pressure
- alveolar collapse (consolidation, ARDS, atelectasis decrease FRC and vol of air in lungs)
