eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Critical Care

Acidosis, Respiratory: Differential Diagnoses & Workup

Author: Margaret A Priestley, MD, Assistant Professor of Clinical Anesthesiology and Critical Care, University of Pennsylvania School of Medicine; Clinical Director, Pediatric Intensive Care Unit, The Children's Hospital of Philadelphia
Coauthor(s): Ronald Litman, DO, Associate Professor of Anesthesiology and Pediatrics, University of Pennsylvania School of Medicine
Contributor Information and Disclosures

Updated: Jan 5, 2009

Differential Diagnoses

Alkalosis, Metabolic
Empyema
Alveolar Proteinosis
Goodpasture Syndrome
Asphyxiating Thoracic Dystrophy (Jeune Syndrome)
Hantavirus Pulmonary Syndrome
Aspiration Syndromes
Head Trauma
Asthma
Hemosiderosis
Atelectasis, Pulmonary
Hemothorax
Bronchiectasis
Histoplasmosis
Bronchiolitis
Human Immunodeficiency Virus Infection
Bronchitis, Acute and Chronic
Mycoplasma Infections
Bronchopulmonary Dysplasia
Near Drowning
Congenital Diaphragmatic Hernia
Neonatal Resuscitation
Congenital Stridor
Respiratory Distress Syndrome
Croup
Cystic Adenomatoid Malformation
Cystic Fibrosis

Workup

Laboratory Studies

  • ABG analysis
    • The ABG is diagnostic of a respiratory acidosis.
    • The serum HCO3 - level and pH can be helpful in distinguishing acute hypercapnia from chronic hypercapnia. If the pH is greater than 7.45, elevated PaCO2 may compensate for metabolic alkalosis and not a primary process.
  • Tests for acute respiratory acidosis
    • pH decreases 0.08 for every 10-mm Hg increase in PaCO2.
    • HCO3 - increases by 1 mEq/L for every 10-mm Hg increase in PaCO2.
    • If PaCO2 increases acutely to 80 mm Hg, the pH is 7.12 and the HCO3 - value is 28 mEq/L.
  • Tests for chronic respiratory acidosis
    • pH decreases 0.03 for every 10-mm Hg increase in PaCO2.
    • HCO3 - concentration equals 24 mmol/L ± 4 for every 10-mm Hg increase in PaCO2 greater than 40 mm Hg.
    • For example, if the PaCO2 is 80 mm Hg, the pH is 7.28, and the HCO3 - value is 40 mEq/L ± 4.
  • Evaluation of HCO3 - resorption
    • The HCO3 - -resorption process is efficient.
    • If a patient with chronic hypercapnia has a pH of more than 7.20, a superimposed acute on chronic respiratory acidosis or concomitant metabolic acidosis is most likely occurring as well.
  • Toxicology screen for narcotics, benzodiazepines, alcohol, or tricyclic antidepressants if indicated
  • Electrolyte assessment for abnormalities associated with muscle weakness (eg, hypophosphatemia, hypokalemia, hypomagnesemia, hypocalcemia)

Imaging Studies

  • Chest radiography findings may help in the diagnosis.
  • CT scanning of the chest is indicated if the history and physical findings suggest primary pulmonary disease.
  • CT angiography may be indicated to rule out pulmonary embolus.
  • CT scanning or MRI of the brain is indicated if the history and physical findings suggest signs of an intracranial process.
  • MRI of the spine may be indicated by the history and physical findings.

Other Tests

  • Pulmonary function tests, including spirometry if the child can cooperate
  • Electromyelography (EMG), if indicated to evaluate neuromuscular disease
  • Polysomnography, or sleep study, to evaluate for obstructive or central sleep apnea, if indicated

More on Acidosis, Respiratory

Overview: Acidosis, Respiratory
Differential Diagnoses & Workup: Acidosis, Respiratory
Treatment & Medication: Acidosis, Respiratory
Follow-up: Acidosis, Respiratory
References
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References

  1. Epstein SK, Singh N. Respiratory acidosis. Respir Care. Apr 2001;46(4):366-83. [Medline].

  2. Ramamoorthy C, Tabbutt S, Kurth CD, et al. Effects of inspired hypoxic and hypercapnic gas mixtures on cerebral oxygen saturation in neonates with univentricular heart defects. Anesthesiology. Feb 2002;96(2):283-8. [Medline].

  3. Goldstein B, Shannon DC, Todres ID. Supercarbia in children: clinical course and outcome. Crit Care Med. Feb 1990;18(2):166-8. [Medline].

  4. Makhoul IR, Bar-Joseph G, Blazer S, et al. Intratracheal pulmonary ventilation in premature infants and children with intractable hypercapnia. ASAIO J. Jan-Feb 1998;44(1):82-8. [Medline].

  5. Laffey JG, O'Croinin D, McLoughlin P, Kavanagh BP. Permissive hypercapnia--role in protective lung ventilatory strategies. Intensive Care Med. Mar 2004;30(3):347-56. [Medline].

  6. ARDS Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med. 2000;342:1301-8. [Medline].

  7. Annane D, Orlikowski D, Chevret S, Chevrolet JC, Raphael JC. Nocturnal mechanical ventilation for chronic hypoventilation in patients with neuromuscular and chest wall disorders. Cochrane Database Syst Rev. 2007;(4):CD001941. [Medline].

  8. Brian JE. Carbon dioxide and the cerebral circulation. Anesthesiology. May 1998;88(5):1365-86. [Medline].

  9. Halpern P, Raskin Y, Sorkine P, Oganezov A. Exposure to extremely high concentrations of carbon dioxide: a clinical description of a mass casualty incident. Ann Emerg Med. Feb 2004;43(2):196-9. [Medline].

  10. Kiely DG, Cargill RI, Lipworth BJ. Effects of hypercapnia on hemodynamic, inotropic, lusitropic, and electrophysiologic indices in humans. Chest. May 1996;109(5):1215-21. [Medline].

  11. Low JM, Gin T, Lee TW, Fung K. Effect of respiratory acidosis and alkalosis on plasma catecholamine concentrations in anaesthetized man. Clin Sci (Lond). Jan 1993;84(1):69-72. [Medline].

  12. Mas A, Saura P, Joseph D, et al. Effect of acute moderate changes in PaCO2 on global hemodynamics and gastric perfusion. Crit Care Med. Feb 2000;28(2):360-5. [Medline].

  13. Mazzeo AT, Spada A, Pratico C, et al. Hypercapnia: what is the limit in paediatric patients? A case of near-fatal asthma successfully treated by multipharmacological approach. Paediatr Anaesth. Jul 2004;14(7):596-603. [Medline].

  14. Thome UH, Carlo WA. Permissive hypercapnia. Semin Neonatol. Oct 2002;7(5):409-19. [Medline].

  15. Vavilala MS, Lee LA, Lam AM. Cerebral blood flow and vascular physiology. Anesthesiol Clin North America. Jun 2002;20(2):247-64. [Medline].

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Further Reading

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Keywords

respiratory acidosis, carbon dioxide acidosis, CO2 acidosis, acute respiratory acidosis, chronic respiratory acidosis, hypercapnia, hypercarbia, supercarbia, acidemia, blood pH, acid-base balance, pCO2, minute ventilation, bicarbonate, hypercapnic acidosis, arterial partial pressure of carbon dioxide, hypoxemia, PaCO2, depressed central respiratory drive, acute paralysis of the respiratory muscles, acute parenchymal lung and airway diseases, increased dead space, wasted ventilation, scoliosis, pulmonary vasoconstriction, supraventricular arrhythmias, hypoplastic left heart syndrome, hypercapnic encephalopathy, myasthenia gravis, bronchopulmonary dysplasia, asthma, emphysema, encephalitis, meningitis

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Contributor Information and Disclosures

Author

Margaret A Priestley, MD, Assistant Professor of Clinical Anesthesiology and Critical Care, University of Pennsylvania School of Medicine; Clinical Director, Pediatric Intensive Care Unit, The Children's Hospital of Philadelphia
Margaret A Priestley, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Ronald Litman, DO, Associate Professor of Anesthesiology and Pediatrics, University of Pennsylvania School of Medicine
Ronald Litman, DO is a member of the following medical societies: American Academy of Pediatrics, American Society of Anesthesiologists, and Society for Pediatric Anesthesia
Disclosure: Nothing to disclose.

Medical Editor

G Patricia Cantwell, MD, Associate Clinical Professor, Department of Pediatrics, University of Miami; Director of Pediatric Critical Care Medicine, Miller School of Medicine, Jackson Children's Hospital
G Patricia Cantwell, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, American Heart Association, American Trauma Society, National Association of EMS Physicians, Society of Critical Care Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Barry J Evans, MD, Assistant Professor of Pediatrics, Temple University Medical School; Director of Pediatric Critical Care and Pulmonology, Associate Chair for Pediatric Education, Temple University Children's Medical Center
Barry J Evans, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

CME Editor

Mary E Cataletto, MD, Associate Director, Division of Pediatric Pulmonology, Winthrop University Hospital; Professor of Clinical Pediatrics, State University of New York at Stony Brook; Director of Children's Sleep Services, Winthrop University Hospital
Mary E Cataletto, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Chest Physicians
Disclosure: Shering Plough Pharmaceuticals Honoraria Consulting

Chief Editor

Timothy E Corden, MD, Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin
Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, and Wisconsin Medical Society
Disclosure: Nothing to disclose.

 
 
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