2. Respiratory Changes Oxygen consumption increase 25-35%  100% in labor Minute ventilation ↑ in excess of CO2 mainly due to increased TV not RR  tachypnea is considered abnormal sign Increased incidence of atelectaisis

3. ABG Changes PO2PCO2pH HCO3 Non preg 98407.40 24-31 Preg, seated 101287.45 18-21 Preg, supine 95287.45 18-21

4. Causes of Acute Hypoxia Preeclampsia / Eclampsia & HELLP Hemorrhage with massive transfusion Amniotic fluid & Air embolism Pneumonia Pulmonary edema ( cardiogenic + tocolytic )

5. Anticipated Intubation Risks Airway  edema & hyperemia potential need of small ETT Aspiration  delayed gastric emptying &relaxed GE sphincter Limited reserve  High VO2 & decreased FRC

6. Asthma & Pregnancy Variable course 33% no change 35% worsening 28% improvement. Interpretation of PaCO2 in light of physiologic changes  pre existing respiratory alkalosis CXR with shielded abdomen is safe when needed Poorly controlled asthma during pregnancy has adverse outcome on fetus

7. Asthma & Pregnancy Treatment strategy is the same for non pregnant  Inhaled bronchodilator  systemic steroid Theophyline should be reduced in 2 nd & 3 rd TM  lower protein binding and higher free drug In prolonged systemic steroid use  stress dose should be given peripartum

8. NIPPV In Pregnancy 4 patients with acute chest syndrome (complication of sickle cell anemia) Acute Hypoxemia PaO2/FIO2 < 200 Received PSV in addition to standard Rx of Acute chest syndrome None required intubation, ICU stay was shorter than matched cases who were intubated Al Ansari Annals of Thoracic Medicine 2007

9. ARDS & Mechanical Ventilation Low tidal volume ventilation study excluded pregnant  Hypercapnia harm on fetus Airway pressure might be high due to the compression of gravid uterus & not necessarily related to lung disease

10. VTE & Pregnancy Incidence 0.5-1% Highest cause of mortality 1-30% 2 risk factors Hypercoagulopathy  hormonal mediated Stasis ( compressive effect of gravid uterus) Most common site Lt Ileo-femoral vein  US a less sensitive test than in non pregnant Radiation dose of venography is <500 mcGY (very small risk in case of high clinical suspicion)

11. VTE & Pregnancy D-dimer can be high up to four fold in normal pregnancy  can not be used Morse Thromb Haemost 2004 Fetal radiation exposure of CXR + V/Q & CTA  <5000 mcGy This is 100 to 200 times < dose thought to produce a significant risk of fetal anomalies.

12. Utility Of VQ Scan 113 pregnant with suspected PE had VQ scan 73% had normal scan 24% non diagnostic test  VQ utility is much higher than non pregnant No Rx given for both groups No evidence of VTE in follow up of 20 months even in the non diagnostic No evidence of radiation effect on fetal outcome Chan Archive of Int Med 2002

13. VTE RX During pregnancy either UFH IV for few days then replace by LMWH or start with LMWH May need larger bolus of UFH IF LMWH to be used monitoring with level of anti Xa Comadin can be used between GA 13 w till mid 3 rd TM The 7 th ACCP Guidelines 2004

14. Risk Of Stroke & Venous Thrombosis Retrospective review of Us delivery registry 1 500 000 chart reviewed Estimated stroke risk 13.1/100 000 IC venous thrombosis11.6 /100 000 Predisposing factors  C section HTN electrolytes & Acid base disturbances Odds Ratio >3 Lanska Stroke 2000