The "2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" increased the focus on methods to ensure that high-quality cardiopulmonary resus...

Cardiopulmonary resuscitation quality: Improving cardiac resuscitation outcomes both inside and outside the hospital: A consensus statement from the American heart association

Context:This translational research initiative focused on the physiology of cardiopulmonary resuscitation (CPR) initiated by a clinical observation of consistent hyperventilation by professional rescuers in out-of-hospital cardiac arrest. This observation generated scientific hypotheses that could o

Death by hyperventilation: a common and life-threatening problem during cardiopulmonary resuscitation.

In 10 patients with severe, acute respiratory failure we studied the effects of positive end-expiratory pressure when intermittent positive pressure ventilation (IPPV) with inspired oxygen (F(IO2)) up to 0.5 failed to maintain arterial oxygen tension (P(aO2)) above 70 torr.Positive end-expiratory pressures (PEEP) of 0, 5, 10, and 15 cm H(2)O were applied for 30-min periods each and in random order. Blood gas exchange, lung volumes, compliance, and hemodynamics were studied at each level of PEEP. P(aO2) (F(IO2) = 1.0) rose linearly with elevation of PEEP, the mean increase being from 152 to 347 torr, or 13 torr/cm H(2)O PEEP. Mean functional residual capacity (FRC) was 1.48+/-0.78 liters at zero PEEP (i.e., IPPV) and the increase was essentially linear, reaching 2.37 liters at 15 cm H(2)O PEEP. P(aO2) and FRC showed a close correlation. Total and lung static compliance were greater during ventilation with high than with low levels of PEEP. The increase in P(aO2) correlated with the specific lung compliance. Dynamic lung compliance decreased progressively with rising levels of PEEP except for an increase with 5 and 10 cm H(2)O PEEP in patients with initial values of 0.06 liter/cm H(2)O or higher. Cardiac index fell in some patients and rose in others and there was no correlation of mean cardiac index, systemic blood pressure, or peripheral vascular resistance with level of PEEP. The most probable explanation for the effect of PEEP on P(aO2) and compliance is recruitment of gas exchange airspaces and prevention of terminal airway closure.

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Ventilation with end-expiratory pressure in acute lung disease

Effect of Mechanical Ventilation and Airway Pressures on Circulation and Blood Gas Exchange The ventilatory pattern is defined by: the inspiratory and expiratory flow rates and pressures, including...

Acute respiratory failure in the adult

In young, healthy people the alveolar–arterial PO2 difference (A-aDO2) is small at rest, but frequently increases during exercise. Previously, investigators have focused on ventilation/perfusion mismatch and diffusion abnormalities to explain the impairment in gas exchange, as significant physiological intra-pulmonary shunt has not been found. The aim of this study was to use a non-gas exchange method to determine if anatomical intra-pulmonary (I-P) shunts develop during exercise, and, if so, whether there is a relationship between shunt and increased A-aDO2. Healthy male participants performed graded upright cycling to 90% VO2max while pulmonary arterial (PAP) and pulmonary artery wedge pressures were measured. Blood samples were obtained from the radial artery, cardiac output (Q) was calculated by the direct Fick method and I-P shunt was determined by administering agitated saline during continuous 2-D echocardiography. A-aDO2 progressively increased with exercise and was related to Q (r = 0.86) and PAP (r = 0.75). No evidence of I-P shunt was found at rest in the upright position; however, 7 of 8 subjects developed I-P shunts during exercise. In these subjects, point bi-serial correlations indicated that I-P shunts were related to the increased A-aDO2 (r = 0.68), Q (r = 0.76) and PAP (r = 0.73). During exercise, intra-pulmonary shunt always occurred when A-aDO2 exceeded 12 mmHg and Q was greater than 24 l min−1. These results indicate that anatomical I-P shunts develop during exercise and we suggest that shunt recruitment may contribute to the widened A-aDO2 during exercise.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.2004.069302

Intra-pulmonary shunt and pulmonary gas exchange during exercise in humans

SUMMARY The effects of altering end-expiratory inflation pressure were studied in mechanically ventilated dogs in the normo-, hypo- and hypervolaemic state. The mean fall in cardiac output resulting from an increase in end-expiratory pressure was smaller in the hypervolaemic group than in the other two groups. A positive end-expiratory pressure increased the mean deadspace/tidal volume ratio in all groups. A negative end-expiratory pressure increased venous admixture, particularly in the over-transfused animals, but the increase was not significant in the hypovolaemic group. A negative end-expiratory pressure did not affect deadspace/tidal volume ratio.

The effects of variations in end-expiratory inflation pressure on cardiorespiratory function in normo-, hypo and hypervolaemic dogs

SUMMARY Changes in cardiorespiratory function resulting from haemorrhage and overtransfusion were measured in forty-seven dogs during controlled ventilation. In the animals bled to a mean arterial pressure of 70 mm Hg there were significant reductions in arterial Pco2, carbon dioxide output and oxygen consumption, cardiac output and total venous admixture. In the animals transfused to a mean central venous pressure of 15 mm Hg there was a significant fall in total thoracic compliance and arterial Po3 and significant increases in the alveolar-arterial Po3, difference and carbon dioxide output.

The cardiorespiratory effects of haemorrhage and overtransfusion in dogs

The effects of variations in end-expiratory inflation pressure on cardiorespiratory function in normo-, hypo- and hypervolaemic dogs

SUMMARY The effects of changes in applied positive pressure waveform during inspiration were studied in anaesthetized dogs mechanically ventilated with air in the normo-, hypo- and hypervolaemic states. Four waveforms were used (sine, square, late peak and early peak flow patterns), these being delivered from a specially constructed ventilator which behaved as a volume preset machine in the inspiratory phase. Controlled ventilation was performed at a constant frequency of 20 respirations per minute at a fixed inspiratory: expiratory ratio of 1:2. None of the waveforms used was found to produce significant changes in cardiorespiratory function within any of the three states of blood volume.

The effects of variations of inspiratory flow waveform on cardiorespiratory function during controlled ventilation in normo-, hypo- and hypervolaemic dogs

SUMMARY Changes in cardiorespiratory function resulting from the use of three different inspiratory: expiratory ratios (1:2, 0.5:2.5, and 2:1) have been studied in normo-, hypo- and hypervolaemic dogs. Deadspace/tidal volume ratio increased slightly with the 0.5:2.5 ratio in all the states of blood volume but the changes were not statistically significant. There was a significant increase in arterial-alveolar Pco 2 difference on the 0.5:2.5 ratio in the hypervolaemic state and there was a significant reduction in the Pco 2 difference with the 2:1 ratio in the normovolaemic state. There was a significant reduction in arterial Po 2 and a significant increase in venous admixture on the 0.5:2.5 ratio in the hypervolaemic state. Cardiac output was reduced after haemorrhage and increased after overtransfusion but there were no significant changes resulting from changes in the I: E ratio within each state of blood volume.

The effects of variations in inspiratory: expiratory ratio on cardiorespiratory function during controlled ventilation in normo-, hypo- and hypervolaemic dogs

W.E.I. Finlay

Papers

The effects of variations in end-expiratory inflation pressure on cardiorespiratory function in normo-, hypo and hypervolaemic dogs

The cardiorespiratory effects of haemorrhage and overtransfusion in dogs

The effects of variations in end-expiratory inflation pressure on cardiorespiratory function in normo-, hypo- and hypervolaemic dogs

The effects of variations of inspiratory flow waveform on cardiorespiratory function during controlled ventilation in normo-, hypo- and hypervolaemic dogs

The effects of variations in inspiratory: expiratory ratio on cardiorespiratory function during controlled ventilation in normo-, hypo- and hypervolaemic dogs