Chapter 23 Part 2: Restrictive Lung Disorder Notes

Muscular Dystrophy

• Part two of chapter 23, restrictive lung disorders, slide 113.

• Muscular dystrophies are X-linked recessive disorders.

• Duchenne's is the most severe form.

• Dystrophin provides structural support to the sarcolemma of skeletal muscle cells.

• In Duchenne's, there isn't enough dystrophin produced.

• In other muscular dystrophies, the dystrophin is abnormal.

• The inflammatory process begins, and muscles are replaced by fat.

• This can affect the diaphragm, leading to restrictive lung disease.

Guillain-Barré Syndrome (GBS)

• Slide 115

• Presentation: Progressive weakness starts in the legs then ascends to the arms.

• Severe cases can result in inability to use muscles, potentially requiring intubation and mechanical ventilation.

• Cause: Demyelination of peripheral nerves.

• Often linked to a prior viral or bacterial infection four to six weeks prior.

• Zika virus infections have a statistically significant link to GBS.

• Mortality rate: $3\%$$$3\%$$, a high mortality rate.

• Most patients spontaneously resolve, but some experience lifelong debilitation.

Myasthenia Gravis

• Slide 117

• Autoimmune disease and hypersensitivity reaction

• Neuromuscular junction: Neurons signal skeletal muscles to contract.

• Acetylcholine, a neurotransmitter, is released by the neuron, crosses the synapse, and binds to acetylcholine receptors on the sarcolemma.

• Myasthenia Gravis: Immunoglobulins bind to postsynaptic acetylcholine receptors at the neuromuscular junction.

• This acts as a competitive inhibitor, preventing acetylcholine from binding and the muscle from contracting.

• Hypersensitivity reaction leads to destruction of acetylcholine receptors and the sarcolemma.

• This can affect the diaphragm, leading to respiratory failure.

Chest Wall Deformities

• Slide 120

• Scoliosis, lordosis, kyphosis, kyphoscoliosis, etc.

• These conditions can start with vertebral deviations that can be caught during physical exams.

• Restrictive Lung Disorder: Deformities compromise the thoracic volume, limiting lung expansion and full breaths.

Ankylosing Spondylitis

• Slide 128

• Not considered important for this lecture.

Flail Chest

• Slide 135

• Two or more rib fractures at distant sites.

• The rib cage is no longer an anchor for the external intercostals.

• This impairs the ability to expand the lungs and bring air in, causing restrictive lung disorder.

• Internal intercostals are used to force air out of the lungs.

• Flail chest also impairs internal intercostals.

Obesity

• Slide 139

• Approximately $45\%$$$45\%$$-$46\%$$$46\%$$ of the US population and nearly $50\%$$$50\%$$ of people in New Mexico suffer from obesity.

• Obesity increases risk for many diseases.

• Definition: BMI for men greater than $20\%$$$20\%$$, and for women, greater than $25\%$$$25\%$$.

• People with a BMI greater than $30$$$30$$ have a dramatically increased likelihood of mortality.

• High BMI driven by muscle.

Leptin and Ghrelin

• Slide 140

• Leptin triggers satiation or feeling full.

• Ghrelin stimulates appetite.

• The body can override default presets.

Pickwickian Syndrome and Sleep Apnea

• Sleep apnea often occurs in obese individuals due to fat deposits in the neck, which can occlude the airway during sleep.

• Manifestations of Obesity:

  • Somnolence, daytime sleepiness

  • Shortness of breath

  • Polycythemia (extra tissue requires extra oxygen and waste delivery, leading to extra blood cell production)

  • Cor pulmonale

  • Impotence (often a result of cardiovascular issues, which are common in obese individuals)

  • Urinary incontinence

• Disorders of obesity include decreased chest wall compliance.

Weight Loss

• Cutting 300 calories a day results in a pound of weight loss per week.

• Weight loss should occur through exercise and diet.

• Gastric bypass is not advocated.

Pneumonia

• Slide 147

• Pneumonia involves a microbe or re-aspirated gastric content acting as an infectious agent in the alveoli and interstitium.

• This triggers an inflammatory response, attacking the infected tissue.

• Inflammatory cells invade the alveolar walls, producing exudate.

• Bacterial pneumonia: Exudate fills the alveolar spaces, leading to consolidation.

• This makes it difficult to cough, reduces surface area for gas exchange, and causes pulmonary infiltrates.

• Untreated pneumonia can be fatal.

• Viral pneumonia: Viruses do not generate exudates.

• Walking pneumonia: A negotiated compromise where the patient is sent home rather than being hospitalized.

• Auscultation reveals crackles and wheezing.

• Symptoms: Chills, fever, cough; pain that discourages coughing.

• Pulmonary infiltrates (white shadowing) indicate fluid in the parenchyma or alveoli, which is a medical emergency.

• WBC count greater than 15,000 suggests acute bacterial pneumonia.

• Antibiotics should only be given if it's bacterial.

• If unknown, give broad-spectrum antibiotics; if known, medicate the specific bacteria.

SARS and COVID-19

• Slide 161

• COVID-19 is a SARS coronavirus two virus.

• Mode of transmission: Respiratory droplets; requires hand washing and masks.

• Older individuals have a greater likelihood of death and problems.

• Median incubation: 4-6 days, up to 14 days for COVID-19.

• Mortality rate for SARS 1: Approximately $10\%$$$10\%$$, but up to $50\%$$$50\%$$ for those older than 60.

Tuberculosis (TB)

• Slide 167

• Mycobacterium tuberculosis is extremely prevalent and deadly.

• Estimated that one third of the world is infected, with 10-12 million in America.

• Mortality rate is high if untreated (greater than $50\%$$$50\%$$.

• Multi-drug cocktails are used to combat antibacterial resistance.

• High-risk patients: Elderly in crowded conditions, slums, prisons, immigrants.

• TB immunization can sometimes give a positive TB test

• Those who have had a previous TB infection are also at a higher risk.

• TB is spread by droplets, similar to SARS coronaviruses.

• Mycobacterium loves vertebra and lung tissue.

• It can stay dormant for years (30-40 years).

• It destroys lung tissue via caseous necrosis, forming cysts (Ghon complex).

• Type 4 hypersensitivity (T-cell mediated) is involved.

• A TB test with induration indicates antibodies towards TB.

• Symptoms: Low-grade fever, persistent cough with hemoptysis, night sweats, weight loss.

• Rales (crackles) are heard early on in the apices of the lungs.

• Definitive diagnosis: Sputum culture (three consecutive early morning specimens) to check for the bacillus.

• Nodules (Ghon complexes) are found in the apices and posterior segments of the lung.

• Treatment: Triple drug cocktail for 9-12 months.

• Skipping medications can lead to antibiotic resistance, which is a death sentence.