Respiratory failure laboratory findings

Jump to navigation Jump to search

Respiratory failure Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Respiratory Failure from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Study of Choice

History and Symptoms

Physical Examination

Laboratory Findings

Chest X Ray

Electrocardiogram

CT

MRI

Echocardiography and ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical therapy

Oxygen therapy

Mechanical ventilation

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Respiratory failure laboratory findings On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Respiratory failure laboratory findings

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Respiratory failure laboratory findings

CDC on Respiratory failure laboratory findings

Respiratory failure laboratory findings in the news

Blogs on Respiratory failure laboratory findings

Directions to Hospitals Treating Type page name here

Risk calculators and risk factors for Respiratory failure laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hadeel Maksoud M.D.[2]

Overview

Laboratory findings consistent with the diagnosis of respiratory failure include abnormal bicarbonate, oxygen, phosphate, and magnesium levels.

Tests of Oxygenation

PaO2/FiO2 ratio (PF ratio)
<math>{P/F\ ratio} = \left (\frac{PaO_2}{Fi0_2}\right) \times 100</math>
  • Normal is 500
  • ARDS is < 200

This measure is easier to calculate. Comparative studies suggest it correlates better with pulmonary shunts than does the A-a gradient.[1][2][3]

Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO2D)
<math>\mbox{A-a gradient} = {PAO_2}\ -\ {PaO_2}</math>
<math>{PAO_2} = {Fi0_2} *\left ({760 - 47}\right) \ -\ \frac{PaCO_2}{0.8}</math>
  • Normal is < 10 mm Hg

The A-a gradient is harder to calculate, but accounts for changes in respiration as measured by the partial pressure of carbon dioxide. However, this calculation relies on the respiratory quotient being constant in the prediction of alveolar CO2 When compared to the PF ratio, the A-a gradient is found to correlate less well with pulmonary shunting.[1][2][3]

Among outpatients with possible pulmonary embolism, the A-a gradient may be a better test.[4]

An online calculator for the A-a gradient is at http://www.mdcalc.com/aagrad.

Other Laboratory Findings

References

  1. 1.0 1.1 Covelli HD, Nessan VJ, Tuttle WK (1983). "Oxygen derived variables in acute respiratory failure". Crit. Care Med. 11 (8): 646–9. PMID 6409506.
  2. 2.0 2.1 El-Khatib MF, Jamaleddine GW (2004). "A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery". Chest. 125 (2): 592–6. PMID 14769743.
  3. 3.0 3.1 Cane RD, Shapiro BA, Templin R, Walther K (1988). "Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients". Crit. Care Med. 16 (12): 1243–5. PMID 3191742.
  4. McFarlane MJ, Imperiale TF (1994). "Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism". Am. J. Med. 96 (1): 57–62. PMID 8304364.
  5. O'Driscoll BR, Howard LS, Earis J, Mak V (June 2017). "BTS guideline for oxygen use in adults in healthcare and emergency settings". Thorax. 72 (Suppl 1): ii1–ii90. doi:10.1136/thoraxjnl-2016-209729. PMID 28507176.
  6. Celli BR, MacNee W (June 2004). "Standards for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper". Eur. Respir. J. 23 (6): 932–46. PMID 15219010.

Template:WH Template:WS