Pregnancy: Respiratory Physiology

Anatomy and Physiology in Pregnancy

• Respiratory physiology is altered during pregnancy.
• Lower ribs flare out, increasing the subcostal angle and transverse chest diameter.
• The diaphragm rises approximately 4 cm.
• Progesterone stimulates respiratory centers, which can cause hyperventilation and dyspnea.
• Hyperventilation leads to decreased alveolar tension and PCO2, resulting in respiratory alkalosis compensated by decreased plasma bicarbonate.

Respiratory Function Terminology

• Functional residual capacity is the lung volume at the end of a normal exhalation.
• Vital capacity refers to the volume of air expired with maximal inspiration.
• Tidal volume is the air volume moving in and out of the lungs during normal, quiet breathing.
• Closing capacity refers to the lung volume at which small airways begin to close.
• Dead space indicates the anatomic area where gas exchange does not occur.

Pathophysiology

• Respiratory infections, asthma, and cystic fibrosis can obstruct the airway and alveoli.
• Obstruction prevents CO2 clearance, leading to hypercarbia.
• Obstructive pulmonary disease may result in inadequate oxygen intake.
• Hypoxia is a significant threat to the fetus since the maternal-fetal placental unit relies on passive oxygen uptake.
• The fetus grows in a lower PO2 environment compared to the mother.

General Signs and Symptoms of Respiratory Distress

• Dyspnea
• Leukocytosis
• Cough
• Fever
• Sudden onset of chills
• Chest pain, including pleuritic pain
• Bronchial breath sounds
• Purulent sputum
• Chest dullness
• Rales, crackles
• Egophony, whispered pectoriloquy

Acute Nasopharyngitis in Pregnant Women

• Acute nasopharyngitis, or the common cold, is more severe during pregnancy.
• Estrogen stimulation can increase nasal congestion in pregnant women.
• Recommend simple cold remedies:
  • Get extra rest and sleep, consume a diet high in vitamin C.
  • Take acetaminophen (Tylenol) every 4 hours for aches and pains, but do not exceed 3,000 mg/day.
  • Avoid acetylsalicylic acid (Aspirin) during pregnancy.
  • Use a room humidifier or medicated vapor rub to loosen nasal secretions.
  • Apply cool or warm compresses to relieve sinus headaches.

Influenza in Pregnant Women

• Influenza, caused by type A, B, or C viruses, spreads epidemically with symptoms like high fever, extreme prostration, aching pains, and sore throat.
• Studies suggest a possible link between influenza during pregnancy and schizophrenia in children.
• Treatment includes antipyretics like acetaminophen.
• Oseltamivir (Tamiflu), a pregnancy category C antiviral, should be administered immediately if needed.
• Influenza vaccines made from inert viruses are safe for pregnant women.

Pneumonia in Pregnant Women

• Pneumonia is a lung tissue invasion caused by organisms such as Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae.
• An inflammatory response in the lung alveoli causes a flood of exudate composed of red blood cells, fibrin, and polymorphonuclear leukocytes.
• This inflammation confines bacteria or viruses but can block breathing space.
• Extreme fluid collection reduces oxygen for both the woman and fetus.
• Therapy consists of antibiotics and possibly oxygen.
• Ventilation support may be needed in severe cases.
• Pneumonia is linked to fetal growth restriction and preterm birth due to oxygen deficiency.
• Oxygen should be administered if pneumonia is present during labor.

Asthma in Pregnant Women

• Asthma is characterized by reversible airflow obstruction, airway hyperreactivity, and airway inflammation triggered by allergens.
• Inhaled allergens cause an immediate release of bioactive mediators like histamine and leukotrienes.
• Asthma leads to constriction of bronchial smooth muscle, mucosal inflammation and swelling, and thick bronchial secretions, causing difficulty breathing.
• Asthma can lead to preterm birth or fetal growth restriction if a significant attack occurs during pregnancy.
• Well-managed asthma is less of a threat.
• Asthma may improve due to high corticosteroid levels.
• Regularly used medications safety should be discussed with a healthcare provider.

Intrapartum Nursing Interventions for Asthmatic Pregnant Women

• Continue routine asthma medications.
• Assess peak expiratory flow rate (PEFR) at admission and every 4 to 12 hours.
• Maintain maternal oxygenation by pulse oximetry greater than 95%.
• Maintain hydration during labor.
• Monitor fetal wellbeing.
• Fentanyl is a preferred analgesic; avoid meperidine (Demerol) or morphine as they release histamine.
• Lumbar anesthesia is preferred for cesarean delivery to reduce oxygen consumption and ventilation.

Tuberculosis (TB) in Pregnant Women

• TB involves lung tissue invasion by Mycobacterium tuberculosis.
• Macrophages and T lymphocytes confine the bacillus, leading to fibrosis, calcification, and scar tissue formation.
• Antibodies from this infection cause a positive response to the Mantoux test (PPD).
• Symptoms of TB include chronic cough, weight loss, hemoptysis, low-grade fever, extreme fatigue, and night sweats.
• Women in high-risk areas should undergo skin testing at their first prenatal visit.
• A positive reaction means that there has been an exposure to TB and so confirmation requires a safe chest X-ray (lead-shielded abdomen) or sputum culture.

Therapeutic Management of TB

• Isoniazid
• Ethambutol
• Rifampicin

TB Therapeutic Management Considerations

• Adequate calcium is needed to prevent tuberculosis pockets from breaking down in the lungs.
• Wait 1 to 2 years after infection inactivity before conceiving.
• Lung shape changes due to pressure from the uterus can break open recently calcified pockets.
• Increased pressure during labor can break open pockets.
• Recent inactive TB may become active postpartum when the lung returns to its vertical position.
• TB is spread to the infant postpartum rather than through the placenta.
• a negative sputum culture rules out active tuberculosis.

Tuberculosis treatment

• Treatment involves continuing tuberculosis medications while breastfeeding because it is safe for the infant.
• Absence of active disease with less than 2 years converted PPD is treated with 300mg/day of isoniazid after the 1st trimester and continuing for 6 -9 months.
• Women younger than 35 years with an unknown duration of positive PPD result should receive 300mg/day of isoniazid for 6-9 months postpartum.
• Women older than 35 years do not receive isoniazid unless they have active disease.
• Women with active disease in pregnancy are treated immediately with isoniazid(INH) 300 mg, combined with rifampicin(RIF) 600 mg and ethambutol 1 gram daily for 2 months then followed by INH and RIF for an additional 7 months.
• Pyridoxine(Vitamin B6) 50 mg/day is an essential supplement to reduce hepatotoxicity while taking INH.

Chronic Obstructive Pulmonary Disease (COPD) in Pregnant Women

• COPD is an airway constriction primarily associated with long-term cigarette smoking.
• The condition is now seen more in pregnancy as women are waiting until age 35-40 years old to have children.
• Constrictive air disease limits oxygen supply, leading to fetal growth restriction and preterm birth.
• Women may require additional rest and supplemental oxygen.
• Sleep apnea may be mitigated with continuous positive airway pressure (CPAP) at night.
• A cesarean birth may be recommended due to shortness of breath during pushing.

Cystic Fibrosis in Pregnant Women

• Cystic fibrosis is a recessively inherited disorder causing dysfunction of the exocrine glands.
• Mucus secretions become so viscid that normal lung and pancreatic functions are compromised.
• Men with cystic fibrosis are subfertile due to thick semen.
• Women are subfertile due to viscid cervical mucus.
• Reproductive technologies such as alternative insemination or in vitro fertilization may be necessary.
• Symptoms include chronic respiratory infection, overinflation of the lungs, and difficulty digesting fat and protein.
• Poor pulmonary function leads to inadequate oxygen for the fetus, growth restriction, preterm labor, and perinatal death.
• Fetal testing can identify disease with chorionic villi sampling, amniocentesis, or chromosome 7 identification, with screening routinely done after birth.
• Therapy supplements pancreatic enzymes with pancrelipase (Pancrease).
• Bronchodilator or antibiotic is used to reduce pulmonary symptoms while consulting with healthcare providers.
• Daily chest physiotherapy is necessary to reduce lung secretions, requiring monitoring and care during labor to prevent dehydration.

Anaphylactoid Syndrome of Pregnancy Signs

• Anaphylactoid syndrome of pregnancy (ASP), previously called amniotic fluid embolism, is a sudden cardiovascular and respiratory collapse during labor.
• ASP involves inflammation, and an anaphylactic-like reaction following entry of amniotic fluid into the maternal circulation.
• ASP causes release of cytokines, which lead to dysfunction of events, including blood clotting and inflammation.
• Acute onset causes unexpect rapid onset dyspnea as well as facial erythema.
• Acute onset may present with cough, and cyanosis.
• Acute onset may present with chest pain, seizures, and restlessness.
• Acute onset, acute onset of pulmonary edema.
• Acute onset of circulatory collapse, and can cause coagulation.

Diagnostic Testing for Respiratory Compromise

• CBC
• Sputum Culture
• Oxygenation by pulse oximetry
• Chest radiograph with abdominal shield
• Arterial blood gases when oxygen saturation remains less than 95%
• Pulmonary function tests

Arterial Blood Gases

• ABG anaylsis is a blood test that measures oxygen and carbon dioxide, as well as blood pH,
• Pregant pH is 7.40-7.46, and non-pregnant pH is 7.35-7.45
• Pregnant P02 is 80-106mm Hg, and non-pregnant P02 is 75-100mm Hg
• pregnant Pco2 is 26-32mm HG, and non-pregnant Pco2 is 35-45mm HG
• Pregnant HC03 is 18-22mEq/L, and non-pregnant HC03 is 22-26mEq/L

Fetal Effects of Respiratory Disorders

• Hypoxemia is the greatest fetal threat from respiratory emergencies.
• Chronic respiratory diseases can result in uteroplacental insufficiency, intrauterine growth restriction, and prematurity.
• Respiratory emergencies, such as pulmonary embolism or anaphylactoid syndrome can require emergency cesarean delivery.
• Fetal brain is vulnerable to hypoxia and respiratory acidosis and may suffer from irreversible brain damage or death.

Nursing Interventions for Respiratory Infections

1. Discuss the risk of respiratory infections with the woman and her family.
2. Encourage early treatment of URTI.
3. Encourage healthy behaviors.
4. Respond immediately to sings, reports, sputum and so on.
5. use antibitiocs. 6.Have a baseline function studies done.
6. Seek referrals from pulmonary specialists. 8.Use nebulizers as needed.
7. educate women on detection and prevention of preterm labor

Critical Care Interventions for Respiratory Emergencies

1. Prevent hypoxia.
2. Provide resuscitation.
3. Provide venilation and oxygenation.
4. Position patient.
5. IV access.
6. Monitor vitals.
7. Pulse oximetry.
8. Chest radiograph.
9. arterial blood gas levels. 10.Assess fetal status.