Respiratory Flashcards
respiratory physiology in pregnancy
Increase in O2 demand
Ventilation increases by 40% (physiological hyperventilation)
- No change in vital capacity or RR
- Women breathe more deeply, increasing their tidal volume from 500 –> 700ml, –> increased inspiratory capacity
Maternal hyperventilation –> higher pO2 and lower CO2 level with compensatory fall in serum bicarbonate (resp alkalosis)
- This pO2/CO2 gradient facilitates efficient gas exchange between the mother and fetus
Diaphragmatic elevation and increased intra-abdominal pressure results in a decrease of the residual lung volume –> decrease in total lung capacity of 200ml
However, an increase in diaphragmatic excursion and use of accessory muscles means that the vital capacity remains unaltered
Impact asthma on pregnancy
Severity of asthma - more likely to have deterioration in pregnancy
Deterioration usually due to stopping medications (fear of impact on pregnancy)
Severe poorly controlled asthma with hypoxaemia a/w:
- FGR
- PTB
- Admission to NICU
Management of asthma
Counsel asthma unlikely to affect pregnancy
- Maintaining good control will minimise risks
Emphasis on good control to minimise risks
Check inhaler technique
- Encourage spacer
Smoking cessation
General lifestyle advice
Should have home peak flow monitor and tailored management plan if symptoms
Flu vaccine
Avoid triggers
May not be appropriate for low dose aspirin or NSAIDs
Encourage breastfeeding - some risk reduces atopy in baby
Pharmacological management
of asthma
Mild asthma - beta 2 agonist inhaler (salbutamol) prn
If using reliever >3x/week, then commence regular steroid preventer (beclomethasone inhaler)
If still using regular reliever, then add a LABA (long-acting beta 2 agonist, salmeterol)
3rd line leukotrien (montelukast)
Oral steroids for flares
Asthma in labour
Rare because produce steroids
If on oral steroids for >2/52, need IV hydrocortisone in labour
Early epidural to prevent need for GA
Carboprost can cause bronchospasm - therefore avoid
Aetiology and incidence of CF
Autosomal recessive
Multisystem disorder –> deranged chloride transport
Dysfunction of exocrine glands with abnormal mucous production
Carrier: 1 in 25
Incidence: 1 in 2500 live births
Management principles of CF
Maintain adequate nutrition
Consider effect on lung function
Risk of congestive cardiac failure
Management of diabetes
Counsel of chance of baby having CF
Pre-conception counselling
with CF
Genotype of woman and partner should be established
- If no paternal testing, given carrier frequency of 1 in 25, 2-3% risk of child having CF
Genetic testing options:
- IVF with PIGD
○ Rate of success 33% per cycle
- Amniocentesis / CVS
- IVF pregnancy with donor egg/sperm
Antenatal care of CF woman
Relatively little data on outcomes
Increased risk of PTB and IUGR
Higher risk of mortality c.f. normal women
- But mortality not increased compared to age matched non-pregnant CF women
Lung function is strongest predictor of outcome
- FEV1 >60% for pregnancy
Provide psychosocial support
- High chance of 1 parent family at some point
Optimise lung function
Continue prophylactic antibiotics
- Usually flucloxacillin and tobramycin
Inhaled corticosteroids and mucolytics continue
Regular PT
Optimise nutrition
- Fat soluble vitamins and NG / enteral feeds
- High dose folic acid
Anaesthetic review
Pathogenesis of smoking in pregnancy
Smoking potentially disrupts the implantation process and interfering with the transformation of the uterine spiral arteries
Studies show thickening of the villous membrane of the placenta in smokers, lessening the ability of the placenta to function
Nicotine also impairs amnio acid transport across the placenta
44% reduced chance of live birth per IVF cycle if smoke
Incidence of smoking in NZ/AU
Australia: 1 in 10
NZ: 1 in 8
44% of Aboriginal and Torres Strait Islander
22% of Maori women
Smokers in pregnancy more likely to be younger and live in areas of SE disadvantage
Obstetric complications of smoking in pregnancy
Reduced fertility
Ectopic pregnancy
Fetal abnormalities - e.g. cleft lip and palate
Miscarriage
Placental complications
- Praevia (RR 1.36), abruption (2-fold increase)
PPROM (preterm prelabour)
Premature birth (2-fold increase)
FGR
Low birthweight
Stillbirth
VTE risk
Anaesthetic risks and respiratory complications
One study found that women that stopped smoking <15/40 were at no greater risk of adverse outcomes than non-smokers
Of pregnancies that are complicated by severe PET, smoking is a/w increased rates of perinatal mortality, placental abruption and SGA
Child and adult complications of maternal smoking
SUDI
Respiratory disease
ENT and other infections
Childhood cancers
Nicotine dependence
Nicotine replacement therapy in pregnancy
Behavioural counselling first line
Safest to give up smoking without NRT, but NRT is safer than continuing to smoke
Lozenge and gum preferred
Patches - Deliver a stronger flow of nicotine than other preparations
- If they are used, they should only be used in the daytime and removed at night to avoid continuous fetal exposure to nicotine
Suggested that as nicotine metabolised 30% more quickly in pregnancy
Management of smokers in pregnancy
Ask about it at every visit
Offer cessation support
Other household members should be supported to quit as well
Culturally appropriate care
Continue services PP and 70% will resume smoking
