Respiratory Physiology: Tissue Inertia

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Questions and Answers

What does an AST/ALT ratio greater than 1 indicate?

Normal liver function

Wilson & Alcoholic liver disease (correct)

Hepatic injury

Cholestatic disease

What does a bilirubin level increase in urine typically indicate?

Increased conjugated bilirubin (correct)

Increased unconjugated bilirubin

Hemolytic anemia

Normal liver function

Which of the following accurately describes the role of albumin in liver function evaluation?

Reflects acute changes in synthetic function

Long half-life limits its usefulness in acute situations (correct)

Elevated levels indicate liver regrowth

Short half-life makes it a reliable early indicator

What is true regarding AFP levels greater than 1000 ng/mL?

Common in patients with Hepatocellular Carcinoma (HCC) Signup and view all the answers

What is the effect of body position on ventilation distribution in the lungs?

In the upright position, ventilation is greater in dependent (basal) regions than in apical regions. Signup and view all the answers

What occurs in Zone I of the West zones in the lung during the respiratory cycle?

No perfusion occurs, resulting in dead space. Signup and view all the answers

How does aging affect closing capacity (CC) and functional residual capacity (FRC)?

CC increases, leading to decreased oxygenation. Signup and view all the answers

What is the primary factor determining ventilation distribution at high airflow rates?

Resistance within the airways. Signup and view all the answers

What happens to functional residual capacity (FRC) in a supine 70-year-old patient?

FRC decreases by about 1L due to continuous airway closure. Signup and view all the answers

What is the effect of anesthesia on airway resistance (RAW)?

RAW generally increases during anesthesia. Signup and view all the answers

In what scenario does diffusion, rather than convection, occur in the lungs?

In the respiratory bronchioles and alveoli. Signup and view all the answers

What factor does NOT influence the distribution of ventilation in the lungs?

Type of anesthesia administered. Signup and view all the answers

What condition is associated with an increased risk of developing atelectasis during anesthesia?

Obesity (BMI > 40) Signup and view all the answers

How does the application of PEEP affect pulmonary shunt and flow during ventilation?

Increases shunt and decreases flow to non-dependent regions Signup and view all the answers

Which factor does NOT contribute to an increase in atelectasis?

Older age Signup and view all the answers

What is the relationship between age and the V/Q mismatch during anesthesia?

V/Q mismatch increases with age Signup and view all the answers

During which type of lung recruitment maneuver is pressure typically applied?

40 cm H2O for 7-8 seconds Signup and view all the answers

What commonly contributes to hypoxemia other than hypoventilation?

Impaired diffusion Signup and view all the answers

What observation is true for infants compared to adults regarding atelectasis?

Infants have more atelectasis than adults Signup and view all the answers

What occurs in regions of the lung that have a R→L shunt?

No ventilation to the collapsed region Signup and view all the answers

What is the primary difference between explicit and implicit memory inhibition at lower concentrations of inhalational anesthetics?

Explicit memory becomes impossible to recall, while implicit memory does not. Signup and view all the answers

Which receptors are primarily responsible for the sedative effect of inhalational anesthetics like N2O and Xenon?

K2P channels Signup and view all the answers

What is required for the activation of NMDA receptors?

Both presynaptic agonist stimulation and postsynaptic depolarization Signup and view all the answers

Which GABA subunit is associated with the sedative and amnesic effects of benzodiazepines?

GABA α1 subunit Signup and view all the answers

What mechanism primarily inhibits excitatory postsynaptic depolarization through non-NMDA receptors?

Presynaptic mechanism primarily blocking a voltage-dependent process Signup and view all the answers

What is the main pathophysiologic event associated with widespread inflammation and increased permeability?

Neuroimmune interaction Signup and view all the answers

What is the effect of an epidural block on postoperative ileus?

It decreases ileus duration by 36 hours. Signup and view all the answers

Which fibers are involved in the visceral innervation that can amplify symptoms in a 'vicious cycle'?

Myelinated A-δ fibers and unmyelinated C fibers Signup and view all the answers

What is the role of sympathetic innervation in the functions of the GI tract?

Increases GI vasoconstriction and decreases motility Signup and view all the answers

Which statement about visceral pain blocks is correct?

Only sympathetic nerves are blocked. Signup and view all the answers

Which nerve is primarily responsible for parasympathetic innervation of the upper GI organs?

Vagus nerve Signup and view all the answers

Which section of the GI tract is NOT innervated by the vagus nerve?

Descending colon Signup and view all the answers

Study Notes

Ventilation and Inertia

Tissue inertia is most pronounced during rapid ventilations.
Pleural pressure (PPL) gradient contributes to a less negative PPL at the lung base compared to the apex, affecting ventilation dynamics.
A 1 cm vertical expansion leads to a PPL increase of 0.3 cm H2O, lessened but not negated by weightlessness.
Ventilation distribution shifts with body position; the apex has greater PPL but lower compliance during inspiration, leading to reduced aeration compared to basal regions.

Ventilation Distribution by Flow Rates

At low flow (rest), ventilation distribution is compliant, favoring the base over the apex.
High airflow leads to resistance-determined distribution where base equals apex.

Closing Capacity and Age

Closing Capacity (CC) is defined as the sum of Residual Volume (RV) and Closing Volume (CV); it remains unchanged with body position.
Aging is associated with increased CC and Functional Residual Capacity (FRC), linked to decreased oxygenation.
Airway closure occurs at FRC = CC, decreasing in upright individuals over age 65 and supine individuals over age 45.
COPD and airway edema further increase CC, leading to common closure issues.

Pulmonary Blood Flow and Zones

Blood flow (Q̇) is higher at the lung base than the apex due to hydrostatic pressure variations.
West's zones describe lung perfusion:
- Zone I: No perfusion; alveolar pressure (PALV) exceeds pulmonary arterial pressure (PPA).
- Zone II: Intermittent perfusion; PPA exceeds PALV during systole.
- Zone III: Continuous perfusion throughout the respiratory cycle, unaffected by gravity.
- Zone IV: Reduced perfusion due to extra-alveolar vessel compression.

Anesthesia Effects on Lung Function

Anesthesia increases airway resistance (RAW) and decreases FRC by approximately 20%.
Static compliance of the total respiratory system is significantly reduced during anesthesia.
Atelectasis occurs in 90% of anesthetized patients, often evident even prior to surgery.
High body mass index (BMI) and increasing FiO2 correlate with greater atelectasis incidence.
Oxygenation impairment is primarily due to atelectasis and airway closure.

Preventive Measures for Atelectasis

Use of PEEP around 7 cm H2O can help reverse hypoxemia, but the effect is not proportional.
Recruitment maneuvers entail high-pressure breaths to re-open collapsed alveoli.
Increased FiO2 is associated with improved oxygenation post-operatively, particularly with gas resorption.

V/Q Mismatch and Gas Exchange Impairment

At the apex, ventilation exceeds blood flow (V > Q), while at the base, blood flow exceeds ventilation (Q > V).
Anesthesia exacerbates shunting and V/Q mismatch, particularly in older populations.
V/Q mismatches arise from preexisting lung disease, hypoventilation, and impaired diffusion.

Visceral Innervation and Autonomic Functions

Visceral innervation comprises myelinated A-δ fibers and unmyelinated C fibers, influencing autonomic control.
Sympathetic innervation to upper GI organs occurs from T5-L2, while parasympathetic control is mediated via the Vagus nerve.
Lower GI organ innervation occurs from T9-L3 through pelvic nerves influencing motility and autonomic vasoregulation.

Hepatic Function and Enzymatic Markers

The AST/ALT ratio is key in determining hepatic injury severity; values > 1 suggest conditions like Wilson's or alcoholic liver disease.
Bilirubin measurements indicate acute liver disease when conjugated forms are elevated; hemolysis causes both conjugated and unconjugated elevations.
In liver disease, pre-albumin serves better than albumin to reflect protein nutrition status.

Sedation and Anesthetic Interactions

The effects of inhalation anesthetics (IA) on memory include inhibiting explicit recall due to hippocampal impairment.
Sedation observed from N2O and Xenon relates to antagonism of NMDA receptors.
Structural interactions between anesthetic agents and neural receptors involve various binding dynamics, crucial for both sedative and anesthetic action.

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Description

Explore the concepts of tissue inertia and pleural pressure gradients as they relate to respiratory physiology. This quiz covers how ventilation distribution changes with body position and how factors like compliance affect aeration levels in different lung regions. Test your understanding of these essential physiological principles.