A simple case of.. Acute severe asthma MasterclassIC Schiermonnikoog 2017
Case (1) Female, 27 - G1P0 (26 weeks) PMH - several admissions for severe acute asthma (no MV) Progressive dyspnea for 1 week Admitted to another hospital with acute severe asthma Despite MV and various bronchodilators progressive respiratory acidosis transfer to Radboudumc
Physiology of pregnancy Increase in cardiac output (both heart rate and stroke volume). In third trimester gravid uterus may compress the vena cava in supine position Increase in minute ventilation (mainly tidal volume) with compensated respiratory alkalosis Fall in FRC without a change in FEV1 or FEV1/FVC ratio Increased GFR and plasma volume combined with albumin and gastric motility may decrease medication levels
Asthma and pregnancy Preeclampsia Placenta and placental abruption Obstetric hemorrhage Increased risk of unplanned emergency cesarean delivery Worse outcome
Important considerations Permissive hypoxia may not be safe A normal PaCO2 is abnormal (during pregnancy normally compensated respiratory alkalosis - PaCO2 28-32 mm Hg) NPPV may increase the risk of aspiration Delivery of the fetus had only moderate improvement in respiratory function during mechanical ventilation
Increased intubation risk Pregnancy related airway hyperemia Increased risk for aspiration Precipitous development of hypoxemia Increase in airway resistance
Critical Care Fellow asks the 1 st question Is it true that permissive hypercapnia is contraindicated in pregnancy because of vasoconstriction of the placental vessels?
Case (2) Admission Hb 7.6, WBC 16.4, potassium 5.6 ph 6.89, PaCO2 25.3 kpa, PaO2 9.6, HCO3 35.6, BE -2.4 Tv 400 ml, RR 6/min, I:E 1:5, FiO2 50%, PEEPe 0 (Ppeak 59 cmh2o, Pplat 29 cmh2o, PEEPi 21, VEI 22 ml/kg IBW)
Medical treatment β-agonist bronchodilator with continuous delivery (salbutamol 10-15 mg/h) - iv salbutamol 0.1 μg/kg/min Systemic corticosteroids (methylprednisolone iv 120-160 mg/day in 4 divided doses for 48 hrs with tapering as the patient improves) Magnesium sulfate iv (2 gram over 20 minutes) followed by continuous infusion with serum level monitoring Muscular paralysis
Mechanical ventilation Restore adequate oxygenation (and ph?) Minimize air-trapping to prevent hypotension/barotrauma Early involvement of obstetrician (fetal monitoring) Buy time
Critical Care Fellow asks the 2 nd question Oxygenation is probably sufficient but I am not certain about the level of hypercapnia and the degree of hyperinflation. How would you improve ventilator settings?
Contribution of different MV factors to PEEPi generation N = 186 - controlled mechanical ventilation Independent factors Flow limitation (+) Major effect P < 0.001 τ = RRS CRS TE / τrs (-) (< 1.85) Moderate effect P < 0.001 BMI (+) (> 26 kg/m 2 ) Small effect 0,007 RRS (-) (> 15 cmh2o/l/s) Small effect 0,01 12 Flow limitation VENTILAB group investigators Natalini G. Respir Care 2016;61:134-141
Controlled MV = Pplat = PEEPTOT CRS = Volume / (Pplat - PEEPTOT) Rrs = (Pmax - Pplat)/Flowinsp τ = RRS CRS
Treatment Treat flow limitation - bronchodilators and sitting position Increase TE / τrs (> 2) Effect of Tv less important
Hypercapnia? CO2 transfer from fetal to maternal circulation is gradientdependent Fetal acidosis reduces oxygenation of fetal hemoglobin Fetal (respiratory) acidosis without hypoxia is better tolerated than fetal metabolic acidosis due to hypoxia
Extracorporeal CO2 removal Blood flow 400 ml/min - sweep gas O2 10 l/min
First 24 hours 7,2 ph PEEPi VEI 22 VEI 20 VEI 13 VEI 15 30 7,1 7 6,9 20 10 PEEPi 6,8 6,7 12.00 14.00 16.00 18.00 20.00 22.00 24.00 02.00 04.00 06.00 08.00 10.00 12.00 Tidal volume 400 ml and PEEPe 0 0
Critical Care Fellow asks the 3 d question Can you explain how a blood flow of only 400 ml can actually result in a substantial decrease in arterial carbondioxide levels?
How do we explain ph after 12 hours Before After Before After ph 7.07 7.09 7.15 7.80 PvCO2 19.8 17.0 15.4 2.2 PvO2 7.4 7.1 5.5 73.4 Filter dysfunction
ECCO2R in acute severe asthma Rescue therapy in giant pneumomediastinum causing tamponade ( in stead of surgical decompression) using ultra protective MV Unsafe mechanical ventilation or severe hypercapnic acidosis to prevent pulmonary barotrauma Jones MG. Am J Respir Crit Care Med 2013;187:e5-e6 Pavot A. Medicine 2017;96:41
Case series N = 16-50.5 ± 10.6 years 13 vv-ecls and 3 va-ecls Hours on ECLS 300 ± 119 Mortality 0% No complications Di Lascio. Perfusion 2017;32:157-163
ECLS/ECCO2-R Only 1 case with acute severe asthma during pregnancy (5 weeks duration) - successful Steinack C. J Asthma 2017;54:84-88
Case (3) Slow improvement ECCO2-R stop Day 4 Day 4 Day 5 Day 5 Day 5 Day 5 Start PSV
Critical Care Fellow asks the 4 th question I have heard different opinions on the use of external PEEP during controlled MV. What is the latest update on its effect on hyperinflation?
Case (4) Day 5 10.00 stop ECCO2-R Day 5 12.00 start PSV with PEEPe 5 Day 5 Day 6 Day 6 Day 7 Day 7 Day 8
PS 8 - PEEP 4 PEEPi = 11-3 = 8 cmh2o - 2 = 6 cm H2O
Dynamic PEEPi 5 9 6 12
Static PEEPi 7 7 12 0 8 9 9
Case (5) Day 8 10.00 extubation Day 10 transfer to general ward
Question 1 & 2 Is it true that permissive hypercapnia is contraindicated in pregnancy because of vasoconstriction of the placental vessels? I have heard different opinions on the use of external PEEP during controlled MV. What is the latest update on its effect on hyperinflation?
Question 3 & 4 Can you explain how a blood flow of only 400 ml can actually result in a substantial decrease in arterial carbondioxide levels? I have heard different opinions on the use of external PEEP during controlled MV. What is the latest update on its effect on hyperinflation?
At term 600-700 ml/min
Maternal oxygenation Maternal Umbilical vein Umbilical artery 500 375 N = 34, caesarian section 439 PaO2 (mmhg) 250 125 135 255 0 29,2 18,1 39,3 27,5 36,4 32.7% 65.4% 99.7% FiO2 during operation (%) 22 Rorke MJ. Anaesthesia 1968;23:585-596
Effect of hypercapnia on umbilical vein oxygenation Pig sows 400 PaO2 (mmhg) 300 200 100 111,5 314,4 292,6 258,3 125,2 0 67,4 54,7 48,2 26,1 31,5 Air O2 100% O2 100% + CO2 6% O2 100% + CO2 50% Air + CO2 5% Hypercapnia improves umbilical vein oxygen pressure Hanka R. J Physiol 1975;247:447-460
Effect of hypercapnia on uterine blood flow Addition of 5% CO2 PaCO2 72.3 Stop Hanka R. J Physiol 1975;247:447-460
End-inspiratory volume above FRC (VEI) Start apnea Lungvolume N = 9 FRC Inspiration/Expiration Pplat tidal volume Pplat - PEEPi Tv VTrap End-inspiratory volume above FRC (Vei) Tuxen DV. Am Rev Respir Dis 1987;136:872-879
Complications during mechanical ventilation Geen Hypotension Barotrauma Hypotension + barotrauma 18% Threshold Complication < threshold (%) Complication > threshold (%) P-value 9% 23% 50% Pplat 20 cm H2O 40% 58% > 0.10 Vei 1.4 L 0% 65% 0.03 Vei 20 ml/kg 14% 63% 0.06 In follow-up study (N = 10) the authors showed that use of Vei to guide MV can prevent these complications N = 22 Tuxen DV. Am Rev Respir Dis 1992;146:1136-1142 Williams TJ. Am Rev Respir Dis 1992;146:607-615
Calculation of VEI Volume Crs = Tv / (Pplat - PEEPtot) Compliance VEI = Trapped volume + Tv VEI VEI = Crs Pplat Tv VEI = Tv Pplat Pplat - PEEPtot Trapped volume PEEPtot Pplat Pressure
VEI measurement VCV Inspiratory hold + switch to PSV VCV 45 seconds
An example 20 Male, 31 COPD IV - exacerbation Waiting list LTx Tv 450 - RR 12 - I:E =1:4 VEI (ml/kg) 15 10 5 PaCO2 11.5 kpa 0 VEI (C) VEI (V) VEI (GS)
CO2 production Glucose + O2 Energy + CO2 ± 200 ml/min v-aco2 difference = 40 ml per liter blood CO of ± 5L/min necessary to remove CO2 load
Mixed venous blood contains 52 ml CO2 / 100 ml
Conclusion We only need to clear 400 ml of blood of the complete CO2 content to balance VCO2 Because in contrast to alveoli the sweep gas contains no CO2, the gradient is sufficient to remove a major portion of CO2 in a single pass
The best combination of flow rate and surface area Pigs (N=7) VCO2 200-280 ml/min - increased dead space Use blood flow rate of 1000 ml a surface area 0.8 m 2 and sweep gas of ± 6 l/min Karagiannidis C. Intensive Care Med Exp 2017;5:34
Yeo HJ. Crit Care 2017;21:297 ECMO for acute severe asthma N = 272 (ELSO registry) Survivors Non-Survivors Mean duration ECMO 176.4 hrs 16,5% Canulation-site hemorrhage 13,6% Death due to hemorrhage 1,5% 83,5% Survival associated with: age, bleeding, post- ECMO driving pressure
Older studies show increase of VEI 2 FRC (L) PEEPi (cm H2O) 10 1,5 8 FRC (L) 1 6 4 PEEPi (cm H2O) 0,5 2 N = 10 0 PEEP 1.3 ± 0.3 PEEP 6.3 ± 0.3 PEEP 10.5 ± 0.3 PEEP 16.1 ± 0.3 Guerin C. Am J Respir Crit Care Med 1997;155:1949-1956 0
External PEEP PEEPi Manual abdominal compression External PEEP Flow limitation 10 8 No flow limitation 14 8
Does PEEPe reduces hyperinflation in controlled ventilation? N = 100 - Controlled MV - PEEPi 7 ± 2 mmhg PEEPe 80% PEEPtot 9 ± 2 mmhg Complete High Low Increase < 50% of applied PEEP Only small percentage with no/small increase in hyperinflation 46% 21% 33% No additional hyperinflation with expiratory flow limitation and low RR PEEP absorber Natalini G. Ann Intensive Care 2016;6:53
Complete PEEP absorber predicted by.. Flow limitation Low respiratory rate } AUC 0.87 PEEP 5 9 7 12 13 12 12
Caramez MP. Crit Care Med 2005;33:1519-1528 Paradoxical Biphasic Classic
10 Sticky airway closure PEEP 8 Hysteresis 8 PEEP 8 8 PEEP 8 6 Increasing stiffness airway 10 2 PEEP 8 8 3 Increased radial tension 10 8 Flow retarder Bernoulli principe PEEP 8