Pulmonary Disorders in PregnancyDr. Coloma; 2/22/2012

Respiratory Physiology Hormonal changes in pregnancy affect the upper

respiratory tract and airway mucosa o Hyperemia, mucosal edema, hypersecretion and

increased mucosal friability Estrogen is probably responsible for producing tissue

edema, capillary congestion and hyperplasia of mucus glands

Anatomic changes in pregnancy The diaphragm is displaced cephalad by as much as 4 cm The A-P and transverse diameter of the thorax increases

chest wall circumference enlarges Diaphragm excursion greater than in non-pregnant

Pulmonary Function in pregnancy Decreased

o Functional residual capacity, 10-20% by termo Residual volumeo Expiratory reserve volumeo Peak expiratory flow rateo Total lung capacity

Unchangedo RRo Vital capacityo Lung compliance

Increasedo Tidal volumeo Airway conductanceo Total pulmonary resistance

**No difference in pulmonary function between singleton and twin pregnancies

Ventilation Minute ventilation increases significantly reaching 20-40%

above baseline at term Alveolar ventilation increases by 50-70% Because of…

o Enhanced respiratory drive due to high serum progesterone level

o Compensated respiratory alkalosiso Low expiratory reserve volume

Oxygen Delivery Maternal arteriovenous oxygen difference is decreased

o Increased tidal volume delivers more oxygen than required

o Increased total hemoglobin and oxygen carrying capacity (Bohr effect) during normal pregnancy

Arterial Blood Gases Physiological hyperventilation results in respiratory

alkalosis Compensatory renal excretion of bicarbonate Reduced pC02 from maternal hyperventilation aids CO2

(waste) transfer from the fetus to the mother while facilitating oxygen release to the fetus

“Physiologic Dyspnea” Increased awareness of desire to breathe Can occur early in pregnancy Does not interfere with daily activities Actual exercise tolerance not greatly affected

Increase progesterone levels probably is the most important mechanism

Mechanical impediment of the gravid uterus often blamed

It is important to distinguish the physiologic dyspnea from disorders complicating pregnancy

The presence of other symptoms and signs of cardiopulmonary disease indicates a possible pathologic nature of dyspnea and the patient should further be evaluated

ASTHMA in pregnancy Chronic inflammatory airway disorder with major

hereditary component Environmental stimulant can trigger reversible airway

obstruction Airway obstruction are due to bronchial smooth muscle

contraction, vascular congestion, mucosal edema and tenacious mucus

Pregnancy outcome in Asthma Clinical features of asthma during pregnancy are the same

as those in non-pregnant women Unless there is severe disease, pregnancy outcomes are

generally excellent According to a study by Gluck et al: 1/3 improved, 1/3

unchanged, 1/3 clearly worsened Increased morbidity linked with progressively more severe

disease, poor control or botho Preterm delivery, preeclampsia, abruptio

placenta, LBW, miscarriages, CS delivery

Status Asthmaticus Life threatening complication

o Muscle fatigue, respiratory arresto Pneumothorax, pneumomediastinumo Acute cor pulmonaleo Arrhythmias

Maternal and perinatal mortality significantly increased when mechanical ventilation is required

Fetal Effects of Asthma Response to maternal hypoxemia

o Decreased umbilical blood flowo Increased systemic and pulmonary vascular

resistanceo Decreased CO fetal growth restriction

Fetal response is an indicator of maternal status

Fetal outcome Physician and patients should not inappropriately avoid

the use of effective pharmacotherapy because of concerns for fetal effects of drugs

Clinical Course Mild wheezing to severe bronchoconstriction Can be intermittent to persistent (mild, moderate, severe) Symptoms

o Nocturnal awakeningo Interference with normal activity

Short acting beta-agonist for symptoms Assess lung function

Clinical Evaluation Subjective severity of asthma does not frequently

correlate with objective measures of airway function or evaluation

PE is also an inaccurate predictor of severity

Useful clinical signs Labored breathing Tachycardia Pulsus paradoxus Prolonged expiration Use of accessory muscle Central cyanosis and altered consciousness are sign of

potentially fatal attack

Pulmonary function testing Should be routine in management of acute and chronic

asthma Best measure of severity

o FEV1 less than 1 L or <20% of predicted value o Peak expiratory flow rate

Woman determines her own baseline when asymptomatic (personal best), to compare with values when symptomatic

Ideally… FEV1 >80% of predicted PEFR predicted values 380-550 L/min Therapeutic adjustments based on woman’s personal best

Therapy1. Avoidance and control of asthma triggers

a. Including allergy, URTI, sinusitis, exercise, aspirin, NSAIDs

b. Irritants (tobacco smoke , chemical fumes, humidity, emotional upset)

c. F-series prostaglandins , ergonovined. GERD

i. Due to relaxation of LES2. Medications during pregnancy

a. Poorly controlled asthma is potentially more dangerous for the fetus than medication

i. Teratogenic period at 4-10 weeks after LMP

b. Medications are added in a sequential fashion with few differences from the non-pregnant patient

Guidelines for Chronic Asthma1. Patient education – effect on pregnancy and general

management2. Avoidance or control of environmental precipitating

factors3. Objective assessment of pulmonary function and fetal well

being4. Pharmacologic therapy to provide baseline control and

treat exacerbations

Step Therapy Medical Management of Asthma during Pregnancy

Mild Intermittent Asthmao No daily medications, inhaled beta agonist as

needed Mild Persistent Asthma

o Preferred: low dose inhaled CSo Alternative: Cromolyn, leukotriene receptor

antagonist, or theophylline (serum level: 5-12 mcg/mL)

Moderate Persistent Asthmao Preferred: low dose inhaled CS and long acting

beta agonist or medium dose inhaled CS or medium dose inhaled CS and long acting beta agonist

o Alternative: low dose or (if needed) medium dose inhaled CS and either leukotriene receptor antagonist or theophylline (serum level 5-12 mcg/mL)

Severe persistent asthmao Preferred: High dose inhaled CS and long acting

beta agonist and (if needed) oral CSo Alternative: High dose inhaled CS and

theophylline and oral CS if needed

Leukotriene receptor antagonists

Not effective for acute disease Used with inhaled steroids to minimize dosing No widespread experience with use in pregnant women

Theophylline Might be used as a third line agent after beta agonist

therapy and inhaled steroids Extensive experience

Does not appear to cause developmental risk Has limited use in acute exacerbation

Acute Asthma Exacerbation Beta agonist with or without ipratropium via a metered

dose inhaler with a spacer or in nebulized form Systemic CS Oxygen to maintain pO2 >60 mmHg and preferably

normal, the O2 saturation at or above 95% to ensure fetal well being

IV hydration FEV1 or PEFR

o Continuous pulse oximetry and EFM Lowered threshold for hospitalization in pregnant Aggressive management of asthma exacerbation is

recommended because of greater risk to the fetus from untreated asthma

Non-responders EARLY INTUBATION for worsening respiratory status

despite aggressive treatment Indications for MECHANICAL VENTILATION

o Fatigueo CO2 retentiono Hypoxemia

PNEUMONIA in Pregnancy Infrequent, yet, serious complication

o Most frequent cause of non-obstetric infectiono 3rd most frequent cause of indirect obstetric

death Can occur at any time during gestation

o In the 3rd trimester it is associated with preterm labor

Causes significant fetal complicationso Hypoxia and acidosis poorly tolerated by fetus

Bacteriology Virtually any infectious agent can cause pneumonia in a

pregnant patient S. pneumonia is the most common Other etiologic agents

o M. pneumoniao H. influenzaeo Influenza and other viruses

Clinical features Preceding URTI Cough, fever, dyspnea and chills Delay in recognition might lead to development of

complications such as respiratory failure or empyema

Diagnosis CXR is essential for diagnosis Tests to identify specific pathogen are optional

Management Hospitalize pregnant women with radiologically proven

pneumonia MONOTHERAPY with macrolide: azithromycin,

clarithromycin, erythromycin Severe disease admit to ICU

o ARDS commono Mechanical ventilation may be neededo Respiratory fluoroquinolones: Levofloxacino Or Beta Lactam + Macrolide: Amoxicillin or Co-

amoxiclav, Cefuroxime or Ceftriaxone

Clinical improvement in 48-72 hours:o Fever lyseso Pleural effusion develops in 20%

Radiographic abnormalities may take 6 weeks to resolve Persistent fever requires follow up radiograph

Criteria for severe CAP RR >30/min PaO/FiO 250 below Confusion or disorientation Uremia Leukopenia 4,000 below Thrombocytopenia 100,000 below Hypothermia Hypotension requiring aggressive fluid resuscitation

Pregnancy outcome 0.8% maternal mortality rate 7% required intubation and mechanical ventilation 1/3 of cases PROM, preterm delivery, LBW

Prevention Pneumococcal vaccine recommended for:

o Immunocompromisedo Significant smoking history o Diabetes, cardiac, pulmonary or renal diseaseo Asplenia

Severe pneumonitis Life threatening

o Influenza pneumoniao Varicella pneumonia

TUBERCULOSIS in pregnancy Mycobacterium tuberculosis granulomatous pulmonary

reaction 90% disease contained, dormant for lung In immunocompromised or with other disease, reactivated

to clinical disease

Clinical features Cough with minimal sputum production Low grade fever Hemoptysis Weight loss Extrapulmonary TB in immunocompromised Infiltrative patterns on chest radiograph AFB bacilli in sputum of 2/3 of culture positive patients

High risk TB1. Healthcare workers2. Contact with infectious patient3. Working or living in homeless shelters4. Alcoholics5. Illicit drug users6. Detainees and prisoners7. HIV infected

Skin Testing A 5 tuberculin units of purified protein derivative P No further evaluation if negative Positive skin test of 5 mm or more requires CXR

Skin Testing B Very high risk 5 mm

o HIV positive, abnormal CXR, recent contact with active case

High risk 10 mm

o Foreign-born, drug users, HIV negative, low income population, with medical conditions that increase risk for TB

No risk factors 15 mm

Treatment DOTS Quadruple regimen for active infection

o HRZEo + pyridoxine 25 mg daily to reduce hepatic

toxicity Monotherapy with INH for latent infection Breastfeeding not prohibited during therapy

Neonatal TB Transplacental Aspiration of infected secretions at delivery Congenital TB: hepatosplenomegaly, respiratory distress,

fever and lymphadenopathy Unlikely if mother treated before delivery or sputum

negative Newborn is susceptible (50%) so isolate from mother with

active disease