Heliox Improves Hemodynamics in Ventilated Patients w/COPD
Objective: To test the hypothesis that, compared with air-oxygen, heliox would improve cardiac performance in mechanically ventilated patients with severe chronic obstructive pulmonary disease and systolic pressure variations > 15 mm Hg and to determine clinical variables associated with favorable hemodynamic responses to heliox.
Design: A prospective interventional study.
Setting: Medical and respiratory intensive care units at a university-affiliated tertiary medical center.
Patients: Twenty-five consecutive mechanically ventilated patients with severe chronic obstructive pulmonary disease and acute respiratory failure who had systolic pressure variations > 15 mm Hg.
Interventions: Respiratory and hemodynamic measurements were taken at the following time with the same ventilator setting: a) baseline; b) after 30 mins with heliox; and c) 30 mins after return to air-oxygen.
Measurements and Main Results: Heliox ventilation decreased intrinsic positive end-expiratory pressure (air-oxygen vs. heliox [mean ± sd] 13 ± 4 cm H₂O vs. 5 ± 2 cm H₂O, p < .05), trapped lung volume (air-oxygen vs. heliox 362 ± 67 mL vs. 174 ± 86 mL, p < .05), and respiratory changes in systolic pressure variations (




PP) (air-oxygen vs. heliox 29 ± 5% vs. 13 ± 7%, p < .05). In the ten patients with pulmonary arterial catheters, heliox decreased mean pulmonary arterial pressure, right atrial pressure, and pulmonary arterial occlusion pressure and increased cardiac index. Preheliox



PP correlated with the magnitude of reduction in intrinsic positive end-expiratory pressure during heliox ventilation. Age, preheliox Paco ₂, and ratio of forced expiratory volume at first second to forced vital capacity correlated inversely, whereas preheliox



PP correlated positively with increases in cardiac index.
Conclusions: Heliox may be a useful adjunct therapy in patients with severe chronic obstructive pulmonary disease during acute respiratory failure who have persistent intrinsic positive end-expiratory pressure-induced hemodynamic changes despite ventilator management.


Patients with chronic obstructive pulmonary disease (COPD) who suffer from acute respiratory failure frequently develop air trapping and intrinsic positive end-expiratory pressure (PEEPi) during positive pressure ventilation. The presence of PEEPi may adversely affect lung mechanics, increase work of breathing, and worsen gas exchange and hemodynamics. Clinically, PEEPi may be reduced by relieving bronchospasm, lengthening expiratory time, and lowering tidal volume (Vt) while allowing permissive hypercapnea. During the acute stage, however, these strategies may not be feasible or effective because the patient's respiratory drive is strong, which increases respiratory rate, and the effects of bronchodilators and steroids have not been maximized.

Helium-oxygen mixture (heliox, HeO₂) has a gas density lower than air-oxygen mixture and may reduce resistance to the turbulent flow across the constricted segments of the airways. Heliox has been used successfully as an adjunct therapy in acute exacerbation of asthma and upper airway obstruction. Heliox reduced PEEPi but did not improve hemodynamics in mechanically ventilated COPD patients who were intubated for various medical and surgical reasons. Heliox reduced work of breathing in intubated COPD patients during the T-piece weaning trial. The combination of heliox with noninvasive ventilation improved patient comfort and gas exchange.

In this study, we hypothesized that heliox would improve cardiac performance in COPD patients who had PEEPi-associated hemodynamic effects. We recruited 25 patients with severe COPD who were mechanically ventilated for acute respiratory failure. All subjects had systolic pressure variations (equivalent to pulsus paradoxicus in spontaneously breathing patients) > 15 mm Hg but no systemic hypotension. We also determined clinical variables associated with favorable hemodynamic responses to heliox ventilation.