Volume Capnography in the Intensive Care Unit: Potential Clinical Applications.

Volume capnography provides a noninvasive, continuous display of the fractional concentration or partial pressure of carbon dioxide (Pco2) versus exhaled volume. Derived measurements and calculations are influenced by changes in both ventilation and perfusion and are therefore useful for assessing both respiratory and cardiovascular function. This article provides an evidence-based review of several potential uses of volume capnography in the intensive care unit: 1) monitoring the effectiveness of ventilation by using end-tidal Pco2 as a surrogate for arterial Pco2, 2) assessing volume responsiveness, 3) measuring cardiac output, 4) determining prognosis in patients with the acute respiratory distress syndrome, 5) optimizing alveolar recruitment, and 6) excluding pulmonary embolism. Studies performed during the past few decades have clearly shown that volume capnography can provide important prognostic information in patients with acute respiratory distress syndrome and that end-tidal Pco2 should not be used to estimate or even to monitor the direction of change in the arterial Pco2 in mechanically ventilated intensive care unit patients. Unfortunately, few conclusions can be made from studies evaluating other potential applications. Of these, the most promising are the noninvasive measurement of cardiac output and optimization of alveolar recruitment in patients with acute respiratory distress syndrome and in mechanically ventilated, morbidly obese patients.

Volume Capnography in the Intensive Care Unit: Physiological Principles, Measurements, and Calculations.

Volume capnography provides a noninvasive and continuous display of the fractional concentration or partial pressure of expired carbon dioxide versus exhaled volume. Derived measurements and calculations include the end-tidal, mean alveolar, and mixed expired carbon dioxide partial pressure (Pco2); the volume of CO2 exhaled per breath and per minute; the airway, alveolar, and physiologic dead space volume; the physiologic dead space to tidal volume ratio; and expired minute ventilation, dead space ventilation, and alveolar ventilation. Thus, volume capnography provides a wealth of information about both respiratory and cardiovascular function, and it has many potential applications in critically ill patients. The effective use of volume capnography, however, requires a thorough understanding of its underlying physiological principles and the meaning and significance of derived measurements and calculations.

Isolation of Aspergillus in three 2009 H1N1 influenza patients.

OBJECTIVES: To describe the association of Aspergillus with influenza. DESIGN/SETTING/SAMPLE: Three case reports of ICU patients with influenza complicated by the isolation of Aspergillus species are described and a review of the literature on the topic was performed. CONCLUSIONS: Severe influenza cases can be complicated by Aspergillus infection.

The impact of right ventricular dysfunction on the prognosis and therapy of normotensive patients with pulmonary embolism.

The prognosis and optimal therapy of patients with pulmonary embolism (PE) are strongly influenced by the presence or absence of associated hemodynamic derangements. Patients with normal systemic arterial pressure have a relatively low risk of recurrent PE and death when treated promptly with therapeutic anticoagulation. Those who present with hypotension, shock, or cardiac arrest, however, have a much higher mortality rate and often receive thrombolytic therapy. Recent evidence indicates that the presence of right ventricular (RV) dysfunction identifies a subgroup of normotensive patients with a much more guarded prognosis who may benefit from more intensive therapy with thrombolytic agents. This article reviews our current understanding of the pathophysiology and diagnosis of RV dysfunction and its impact on the prognosis and therapy of normotensive patients with PE.