Oxygen Therapy
Faisal Malmstrom,
Critical Care Department
SKMC
Carl Wilhelm Scheele
Priestly and Lavoisier
ABC
 Air goes in and out, blood goes round
and round.
Any variation on this is a bad thing.
Airway obstruction needs to be
addressed immediately
Respiratory failure
 Type 1 (hypoxemic)
Saturation < 90%. PaO2 <60 mm Hg
 Type 2 (hypercapnic)
PCO2>50 mmHg, pH<7.35
Definitions
 Hypoxemia
 Hypoxia
Hypoxemia
 Low alveolar oxygen tension
(ambient, hypoventilation)
 Ventilation-perfusion mismatch
 Right to left shunt (venous admixture)
intracardiac
extracardiac
 Impaired oxygen diffusion (uncommon)
Alveolar gases
V/Q mismatch
 Ventilated but not perfused: increased
dead space ventilation, VT=VD+VA
VD= VD equipment + VD anatomic + VD physiologic
 Perfused but not ventilated: shunt
>20% Shunt fraction, minimal
improvement with increased FiO2
Hypoxia
 Hypoxemic Hypoxia
 Anaemic Hypoxia
 Stagnant Hypoxia ( distributive or low
CO)
 Histotoxic Hypoxia
VDO2= CO x Hb x SAT/100 x 1.34ml/gHb+
(PaO2 x 0.003mlO2/100ml/mmHg)
Symptoms of Hypoxemia
and Hypoxia





Dyspnea, tachypnea. Hyperventilation
+/- Cyanosis ( Hb, perfusion) >15g/l
Impaired mental performance----coma
Seizures, permanent brain injury
Tachycardia/Hypertension –
Hypotension/Bradycardia( 30 mmHg)
 Lactic acidosis
Indications for Oxygen
therapy
 Cardiac and respiratory arrest
 Hypoxemia ( pO2 < 58.5 mmHg,
Sat<90%)
 Hypotension ( Systolic BP < 100 mmHg)
 Low Cardiac Output and Metabolic
Acidosis ( bicarbonate <18 mmol/l)
 Respiratory distress ( RR>24/minute)
American College of Chest Physicians and NHLBI
Treatment I
 Empiric oxygen treatment
Cardiac/ respiratory arrest
Hypotension
Respiratory Distress
Trauma
GCS decrease from any cause
Postoperative
Treatment II
 Verify hypoxemia
Pulse oximetry
ABG’s
 Start Oxygen treatment.
 Treatment goal ( sat level)
 Administration mode, flow, when to stop
The oxyhaemoglobin dissociation curve showing the relation between partial pressure of oxygen
and haemoglobin saturation
Currie, G. P et al. BMJ 2006;333:34-36
Copyright ©2006 BMJ Publishing Group Ltd.
Charting Oxygen treatment
Dodd, M E et al. BMJ 2000;321:864-865
Copyright ©2000 BMJ Publishing Group Ltd.
Bad medicine
To withhold Oxygen out of fear of
hypercarbic ventilatory failure is poor
practice
Identify patients at risk (COPD)
Use Venturi masks 0.24 -0.28 ---- FiO2.
ABG’s/ O2-sat to direct therapy
Support ventilation (BiPAP, intubation)
Oxygen Hazards
 Fire ( airway fires)
 Tissue toxicity, pulmonary and retina
 Decreased hypoxemic drive and
increased VD in COPD.
 Seizures (hyperbaric)
 Mucosal damage due to lack of humidity
Oxygen administration
 Low flow systems
 High Flow systems (HFOE)
Nasal Prongs
Bateman, N T et al. BMJ 1998;317:798-801
Copyright ©1998 BMJ Publishing Group Ltd.
Face Mask (“Hudson”)
Non-rebreather
Venturi Mask
Venturi valve
Bateman, N T et al. BMJ 1998;317:798-801
Copyright ©1998 BMJ Publishing Group Ltd.
Long term oxygen therapy prolongs survival in hypoxaemic patients with COPD when used for
&ge;15 hours/day. (Results from the nocturnal oxygen therapy trial (NOTT) and the MRC trial)
Currie, G. P et al. BMJ 2006;333:34-36
Copyright ©2006 BMJ Publishing Group Ltd.
Take home message
 Acute empiric oxygen treatment is ok but hypoxemia
should be verified with pulse oximetry and /or ABG’s
when situation more stable.
 Oxygen is a drug and should be ordered as such:
mode of administration, flow rate, FiO2 (venturi),
treatment goal, monitoring, when to stop.
 Never withhold oxygen out of fear of possible
hypercarbia
 Avoid overzealous treatment- Adequate saturation for
the patient. COPD 88-90%