Respiratory System III Flashcards
What is a restrictive pulmonary disease characterized by?
A decreased TLC by %20 or more from predicted
What happens during pulmonary edema?
- fluid backs up into interstitial space is usually cleared by the lymphatic system
- if it becomes too much for the lymphatic system, the fluid builds up in the interstitial spaces around airways and blood vessels and can eventually start to leak into the alveoli
- -fluid in alveoli impacts diffusion and can lead to a shunt; can also interfere with surfactant function and impair lung inflation
How does heart disease cause pulmonary edema?
myocardial infarction/hypertensie left ventricular failure –> increase left atrial pressure –> increase pressure in pulmonary vein –> increase Pcap –> increased fluid flux across endothelium
What else, aside from a heart condition, can cause increased Pcap?
excessive saline/plasma/blood infusions
How is pulmonary edema due to increased Pcap self-limiting?
as fluid leaks out, the proteins in the capillary become concentration and oncotic pressure increases –> fluid gets pulled back into capillary
How does increase capillary permeability occur and how does it contribute to pulmonary edema?
inhaled or circulating toxins –> integrity of endothelial barrier is destroyed –> proteins leak into interstitial space –>capillary oncotic pressure decreases –> fluid leaks into interstitial space (NOT SELF LIMITING, VERY DANGEROUS)
What are the symptoms of pulmonary edema?
- dyspnea
- cough (nonproductive in early stages, pink foam in advanced stages)
- cyanosis
How does pulmonary edema affect pulmonary function?
- PV curve is shifted downward and to the right
- resistant to flow through airways increases (fluid surrounds airways and isolates them from retractive forces of parenchyma)
- TLC, VC, and FRC decrease
How does pulmonary edema affect blood gases?
- If only interstitial edema is present: little change in PaO2 despite increase in barrier to diffusion
- If alveolar edema is present: decrease in PaO2 (due to shunt); PaCO2 remains normal/drops because ventilation increases due to low PaO2 or stimulation of lung receptors by high transpulmonary pressures (stiffer lung –> greater pressures for ventilation)
What causes idiopathic pulmonary fibrosis (diffuse interstitial pulmonary fibrosis)?
an immunological reaction due to some kind of toxic insult to lungs causes non-uniform thickening of the interstitium of the alveolar walls
Describe the pathogenesis of idiopathic pulmonary fibrosis.
inflammatory response –> infiltration with lymphocytes and plasma cells –> fibroblast lay down collagen (scarring)
Who is most affected by idiopathic pulmonary fibrosis?
middle-aged to older adults; genetic component
What are the symptoms of idiopathic pulmonary fibrosis?
- dyspnea, especially upon exercise
- rapid shallow breathing
- unproductive cough
- disease often progresses to respiratory failure
How is idiopathic pulmonary fibrosis treated?
currently there is not treatment
How does idiopathic pulmonary fibrosis affect pulmonary function?
- TLC, VC, and FRC decrease
- airway caliber is normal, FEV1/FVC are high
- PV curve shifts downward and to the right
- increased collagen/scarring reduces distensibility of the lung
How does idiopathic pulmonary fibrosis affect gas exchange?
- PaO2 is reduced - mild at rest (results from V/Q mismatch), more severe upon exercise (diffusion impairment)
- PaCO2 is low due to increased ventilation due to low PaO2
How do diseases of the chest wall and neuromuscular disease affect lung volumes?
increased stiffness in the chest wall or inability of respiratory muscles to contract strongly (either due to nerve or muscle damage) can decrease lung volume
What are the epidemiological stats for obesity?
- prevalence has doubled over the last 2 decades
- 30% of Americans are obese, another 35% are overweight
- increasing prevalence in children
- increasing prevalence worldwide
- abdominal fat is the greatest problem
How does obesity affect pulmonary mechanics?
- FRC decreases due to increased chest wall stiffness
- TLC is normal but RV may increase due to airway closure
- compliance of lung is reduce
- increased pulmonary resistance (Raw) and decreased Gaw (lung volume)
- increased airway responsiveness
How is Gaw related to Raw?
Gaw = 1/Raw
How does breathing compare between normal and obese individuals?
obese patients breath at a lower tidal volume and higher frequency to reduce the work of breathing
How does obesity affect blood gases?
PaO2: usually low due to low lung volume and airway obstruction (shunt)
PaCO2: usually normal; VE increases to maintain normal PaCO2
Does obesity increase incidence of asthma or COPD?
asthma: increased incidence/prevalence; worsens with weight gain
COPD: emphysema patients are usually lean but chronic bronchitis is associated with obesity
What happens during sleep apnea?
muscles relax during sleep –> tongue and soft palate fall back against throat –> obstruction –> hypoxemia –> arousal (can occur as many as 50 times/hr
What are the outcomes of sleep apnea?
- excessive daytime sleepiness
- headaches upon awakening
- depression
- hypertension
- cardiovascular disease
- stroke
How does obesity aggravate/contribute to sleep apnea?
fat deposition in the soft palate, uvula, neck area, and pharynx lead to increased risk of obstruction
What is obesity hypoventilation syndrome (Pickwickian syndrome)?
blunting of chemoreceptor sensitivity leads to hypoventilation when awake
How does obesity contribute to pulmonary hypertension?
airway closure –> low PAO2 levels –> constriction of pulmonary arterioles (hypoxic pulmonary vasoconstriction)
*may also increase interstitial edema, promoting airway obstruction
