Simon Baudouin Senior Lecturer in Critical Care University of Newcastle

 Conventional definitions ◦ Type 1 PaO 2 < 8 kPa on air ◦ Type 2 PaO 2 6 kPa  Not helpful! ◦ Ultimately all severely ill patients become hypercapnic without intervention  Acute  Chronic  Acute on chronic  Reach ITU v intubate in EAU

 Hypoxaemia – V/Q mismatch & shunt  Hypercapnia ◦ Hypoventilation ◦ Increase in deadspace ventilation ◦ V/Q mismatch

 Uk National COPD audit 2003; Thorax 2006;61:  234 UK acute hospitals  40 consecutive acute COPD admissions  7259 patients  90 day readmission rate 31.4%!

 16-47% hypercapnia  Half will need ventilatory support - Plant et al, Thorax, 2000; 55: year survey in Leeds  983 admissions  2.2% ICU admissions  73% hospital mortality in ICU admissions 70 NIV patients/year/250,000 population

 Explanation of hypoxaemia and hypercapnia  Multiple inert gas elimination Broad V/Q distribution  Hypercapnia = ventilation to under-perfused units  Hypoxaemia = shunting  Respiratory muscle fatigue?  Altered central drive?

 Hypoxaemia is usually correctable with low flow O 2  The optimal target SaO 2 is unknown > 90% - O 2 dissociation curve > 85% (ARDS net)  One small study (n = 36) 6.6hPa v 9.0 hPa -no difference (underpowered)  High flow O 2 will worsen Hypercapnia  Change to controlled O 2 will reduce PaCO 2

 pH < or = 7.35 Mortality %

Randomised controlled trials in NIV Early use of non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentre, randomised, controlled trial. Plant et al. Lancet, 2000; 355: UK Hospitals n = 236 Mortality p = 0.05 Intubation p = 0.02

BMJ 2003;326: Typical UK hospital will avoid 3-9 ICU admissions/year Save £12, ,000

“The use of non-invasive positive pressure ventilation in the emergency department”  RCT  6/12 study  NIV vs. conventional support  87 screened -34 “immediate” intubation -27 entered -11 conventional -16 NIV Wood. Chest, 1998; 113:

Time to intubation Standard 4.8 hrs NIV 26.0 hrs NIV in A&E

Should all patients receive NIV in a critical care area? No RCTs Majority of trials are in Critical Care areas Plant

 Recommendations of the COAD and NIV Standards of Care sub-committees of the British Thoracic Society, RCP & Modernisation Agency  Every acute admissions unit should have an NIV service

-Failure rate 7-50% -delay intubation  Acidosis  APACHE II -Indications for HDU admission  For intubation if NIV fails  Initial pH 7.25 or less  Worsening pH on NIV

 Patient choice  Failure of NIV  Usually obvious clinically ◦ Fatigued “awful looking” patient ◦ Worsening hypercapnia and LOC ◦ A&E arrest/peri-arrest situation

 Patient/ventilator interactions  Weaning  Tracheostomy  Nutrition  The “unweanable” patient

 Rapid trial of extubation (onto NIV)  Early tracheostomy  Regular Sedation cessation  Weaning protocols  A little progress every day!

 N=43 (most with COAD  failed wean for 3 days  Shorter ICU & hospital LOS  Less need for tracheostomy 90 day survival Am J Respir Crit Care Med 2003;168:70-6

 COPD admissions will increase  NIV is effective in both survival and prevention of intubation  Outcome of ventilation in COPD is no worse than in other conditions  Patient choice and informed decisions

 Previously fit 24 year old women  First pregnancy  No problems until week 35  “Cough and cold”  “Shivery”  Increasingly breathless over 24 hours  Brought to maternity ward by husband  Clearly very unwell  SaO2 air 79%  RR 35/min  Crackles ++  Foetus alive  Critical Care outreach called

Early corticosteroids in severe influenza A/H1N1 pneumonia and acute respiratory distress syndrome. Am J Respir Crit Care Med May 1;183(9):  French national registry – no benefit; possible early harm European SICM database Cox analysis no benefit from steroids

 Critical Care obstetric intensivist  Separate the two patients  Foetus is viable  Ventilation for the Mother is inevitable  Experience from other units  Urgent Caesarean section  Ventilated with Critical Care ventilator during section  Healthy girl delivered  Mother transferred to critical care unit

 Substitute for the respiratory muscle pump  Complex multi- functional machines  Efficacy established during polio epidemics 1960s  Led to development of modern, centralised critical care services

 Broncho- pulmonary dysplasia  Well + Tierney rats ventilated with peak airway pressures 45 cm H 2 O developed pulmonary oedema  Carlton Lung overexpansion increases lymph flow in lambs Lymph flow ml/Kg

Mortality at 180 days Protection 31.0% Conventional 39.8% P = 0.007

Normal lung Partial collapse/floodingComplete collapse recruitable

5 cm PEEP

 N = 1000  60 day mortality  Liberal v conservative fluid

 Improved oxygenation  Increased ventilator free days  No increase in shock or dialysis

N = 549 How much PEEP? Higher versus lower PEEP in patients with ARDS New Engl J Med 2004;351: Lower PEEP = 8 cm H 2 O Higher PEEP = 13 cm H 2 O

 Often improves oxygenation  Proposed mechanisms -recruitment of dorsal collapsed lung units -improved respiratory mechanics -increased secretion drainage -decreased injury from mechanical forces

Prone positioning in ARDS N=304 N=791

 Initial improvement in PaO2/SaO2 to 90%  Gradual fall to SaO2 84%  CXR – no mechanical cause

 Rescue = desperation  Rescue = no high grade evidence  Rescue = risks as well as possible benefits ◦ Oscillator ventilation ◦ ECMO

 Rate 60 – 100 bpm  TV below anatomic deadspace  Alveoalar derecruitment & overdistention limited

Large, multi-centre RCT Conventional v high frequency ventilation Complete recruitment 2012 Over 800 patients

ECMO

Outcome in 1 ECMO centre (Glenfields) Protocolised care Experienced experts Average outcome in 92 conventional centres 11 referral centres Non protocolised care Variable experience Variable clinical cover/team

 Hypoxaemia is the greatest immediate threat  Severe oxygen induced hypercapnia is rare  Oxygen induced hypercapnia only occurs in chronic respiratory failure  Previously well patients with hypercapnia are severely ill  Hypercapnia does not equate to COPD