Effects of Short-term 28% and 100% Oxygen on Paco2 and Peak Expiratory Flow Rate in Acute Asthma

A Randomized Trial

      Study objective

      We conducted the first randomized controlled study to assess the effects of short-term 28% and 100% oxygen on Paco2 and peak expiratory flow rate (PEFR) in patients with acute severe asthma.

      Patients and interventions

      Seventy-four patients (mean age, 37.9 ± 9.7 years [± SD]; PEFR, 41.0 ± 12.1% of predicted) from two emergency departments were randomized to receive 28% or 100% oxygen during 20 min.


      The administration of 100% oxygen significantly increases Paco2 (p = 0.03) and decreases PEFR (p = 0.001) as compared with administration of 28% oxygen. Paco2 before and during oxygen administration correlated significantly (p = 0.001) in both groups. Patients breathing 28% oxygen experienced a Paco2 fall; on the contrary, patients who received 100% oxygen showed an increase in Paco2, particularly those with Paco2 before oxygen treatment > 40 mm Hg.


      This study confirmed previous observations that oxygen dose should be variable and based on achieving and maintaining target arterial oxygen saturation measured by pulse oximetry ≥ 92% rather than on prescribing predetermined concentrations or flow rates of inspired oxygen.

      Key words


      CI (confidence interval), PEFR (peak expiratory flow rate), Spo2 (pulse oximetric saturation), V˙/ Q˙ (ventilation/perfusion)
      To read this article in full you will need to make a payment


      Subscribe to CHEST
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Molfino NA
        • Nannini LJ
        • Martelli AN
        • et al.
        Respiratory arrest in near-fatal asthma.
        N Engl J Med. 1991; 324: 285-288
        • Molfino NA
        Near-fatal asthma.
        in: Hall JB Corbridge T Rodrigo C Acute asthma: assessment and management. McGraw-Hill, New York, NY2000: 29-47
        • National Asthma Education and Prevention Program
        Expert panel report 2: Guidelines for the diagnosis and management of asthma. National Institutes of Health, Bethesda, MD1997 (publication No. 55–4051)
      1. British guidelines on asthma management 1995: review and position statement.
        Thorax. 1997; 53: S1-S24
      2. Canadian asthma consensus report. Management of patients with asthma in the emergency department and in hospital.
        Can Med Assoc J. 1999; 161: S53-S59
        • Rodriguez-Roisin R
        Acute severe asthma: pathophysiology and pathobiology of gas exchange abnormalities.
        Eur Respir J. 1997; 10: 1359-1371
        • Rodriguez-Roisin R
        Gas exchange in acute asthma.
        in: Hall JB Corbridge T Rodrigo C Acute asthma: assessment and management. McGraw-Hill, New York, NY2000: 83-103
        • British Thoracic Society and others
        Guidelines for the management of asthma: management of acute asthma.
        Thorax. 2003; 58: i32-i50
        • Scottish Intercollegiate Guidelines Network
        Emergency management of acute asthma: a national clinical guideline. Scottish Intercollegiate Guidelines Network, Edinburgh, Scotland1999 (Sign Publication No. 38)
        • Inwald D
        • Roland M
        • Kuitert S
        • et al.
        Oxygen treatment for acute severe asthma.
        BMJ. 2001; 323: 98-100
        • Werner HA
        Status asthmaticus in children: a review.
        Chest. 2001; 119: 1913-1929
        • Chien JW
        • Ciufo R
        • Novak R
        • et al.
        Uncontrolled oxygen administration and respiratory failure in acute asthma.
        Chest. 2000; 117: 728-733
        • FitzGerald M
        Extracts from “clinical evidence”: acute asthma.
        BMJ. 2001; 323: 841-845
        • Thomson AJ
        • Webb DJ
        • Maxwell SR
        Oxygen therapy in acute medical care: the potential dangers of hyperoxia need to be recognised.
        BMJ. 2002; 321: 1406-1407
      3. NHLBI/WHO work shop report. Global strategy for asthma management and prevention. National Institutes of Health, Bethesda, MD2002 (Publication No. 02–3659)
        • American Thoracic Society
        Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease (COPD) and asthma.
        Am Rev Respir Dis. 1987; 136: 225-244
        • Rodrigo C
        • Rodrigo G
        Therapeutic response patterns to high and cumulative doses of salbutamol in acute severe asthma.
        Chest. 1998; 113: 593-598
        • Rodrigo GJ
        • Rodrigo C
        The role of anticholinergics in acute asthma treatment: an evidence-based evaluation.
        Chest. 2002; 121: 1977-1987
        • McFadden ER
        • Kiser R
        • deGroot WJ
        Acute bronchial asthma: relations between clinical and physiologic manifestations.
        N Engl J Med. 1973; 288: 221-225
        • Altman DG
        • Machin D
        • Bryant TN
        • et al.
        Statistics with confidence. BMJ Books, Bristol, UK2000
        • Lenfant C
        Arterial-alveolar difference in Pco2during air and oxygen breathing.
        J Appl Physiol. 1966; 21: 1356-1362
        • Rodriguez-Roisin R
        • Ballester E
        • Torres A
        • et al.
        Mechanisms of abnormal gas exchange in patients with status asthmaticus needing mechanical ventilation.
        Am Rev Respir Dis. 1989; 139: 732-739
        • Ballester E
        • Reyes R
        • Roca J
        • et al.
        Ventilation-perfusion mismatching in acute severe asthma: effects of salbutamol and 100% oxygen.
        Thorax. 1989; 44: 258-267
        • Tai E
        • Read J
        Arterial-blood gas tension in asthma.
        Lancet. 1967; 1: 644-646
        • McFadden ER
        • Lyons H
        Arterial blood gas tension in asthma.
        N Engl J Med. 1968; 278: 1027-1032
        • Carruthers DM
        • Harrison BDW
        Arterial blood gas analysis or oxygen saturation in the assessment of acute asthma?.
        Thorax. 1995; 50: 186-188
        • Rodrigo GJ
        Oxygen treatment for acute severe asthma: oxygen saturation may help identify patients in need of intensive management [letter].
        BMJ. 2001; 323: 1069