Effect of cardiogenic oscillations on gas mixing during tracheal insufflation of oxygen

Influence of apneic oxygenation on cardiorespiratory system homeostasis

PURPOSE

The aim of this study was to elucidate the magnitude of variations in oxygenation indices and the pattern of hemodynamic changes in response to the net effect of tracheal apneic oxygenation (AO) with a view to define the safe time limit of its application.

METHODS

After obtaining Animal Research Ethics Committee approval, AO was applied in 12 piglets for 40 min. Arterial (a) and mixed venous (v) blood samples for oxygen (O2) and carbon dioxide (CO2) tension (PaO2/PvO2, PaCO2/PvCO2), O2 saturation (SaO2/SvO2), pHa, base excess (BEa), and bicarbonate (HCO3a) determination and for alveolar O2 tension (PAO2), PaO2/FiO2 and PaO2/PAO2 ratio, arterial-mixed venous O2 content (AVDO2), and O2 extraction ratio (O2ER) estimation were collected on anesthesia induction, 10, 20, 30, and 40 min during AO and 10 and 20 min after reconnection to the ventilator. Concomitant hemodynamic data were obtained.

RESULTS

Besides PvO2 and PAO2, AO adversely influenced PaO2 (248-113 mmHg), PaCO2 (35-145 mmHg), PvCO2, PaO2/FiO2, and PaO2/PAO2 in a time-depended fashion, whereas SvO2, AVDO2, and O2ER were minimally affected. P(a - v)CO2 was reversed throughout AO. Acid-base status derangement, consisting of HCO3a elevation, BEa widening, and acidemia (pH 6.9) maximized 40 min after AO. During AO, heart rate, systemic and pulmonary circulation pressures, and cardiac output were progressively elevated, whereas systemic vascular resistance was reduced. All the studied parameters reverted almost to baseline within the 20-min period of ventilator reconnection.

CONCLUSION

Tracheal AO for 40 min ensures acceptable blood oxygenation, promotes notable hypercapnic acidosis, and consequent transient hemodynamic alterations, which are almost completely reversible after reconnection to the ventilator.

"Ventilatory alternans": a left-right alternation of inspiratory airflow in humans

In a study visualizing ventilation with hyperpolarized (3)He magnetic resonance imaging (MRI) in elite breath hold divers, the dynamic MRI images in one subject exhibited an apparent alternation of the image intensity between left and right lung. We hypothesized that the alternation resulted from alternating variations in inspiratory flow rate to left and right lungs. Analysis showed that the alternation was not due to random uncorrelated temporal fluctuations of intensity (p<0.001). The frequency of alternation was approximately 56 min(-1), suggesting a cardiac origin. Similar alternation of ventilation was confirmed retrospectively in 4 of 6 additional subjects. These observations are consistent with previous studies showing cardiogenic mixing of gas in the lung. We speculate that cardiogenic pendelluft, possibly from ballistic lateral motion of the beating heart, could cause alternating variations of inspiratory flow to the lungs.

Transtracheal oxygen delivery

Tracheal insufflation of oxygen has at least three major uses for chronic oxygen supplementation through a percutaneous catheter, it is an adjunctive measure to enhance gas exchange during mechanical ventilation, and it provides an emergency therapy for oxygen delivery with upper airway obstruction. In this article the mechanisms of gas exchange and techniques of oxygen delivery are described for each of these major uses.

Combination of tracheal gas insufflation and airway pressure release ventilation

STUDY OBJECTIVE

We hypothesized that the continuous gas flow administration delivered through an insufflation catheter positioned above the carina during airway pressure release ventilation (APRV) would facilitate carbon dioxide (CO2) elimination, resulting in normocarbia with a substantially reduced peak airway pressure (Paw). To test this hypothesis, we compared intermittent positive pressure ventilation (IPPV), tracheal gas insufflation (TGI), APRV, and combined TGI and APRV (TGI + APRV).

DESIGN

Animal study with random application of four ventilatory modes in a canine restrictive-thorax model with and without pulmonary edema.

SETTING

Research laboratory at Kumamoto (Japan) University School of Medicine.

SUBJECTS

Six mongrel dogs.

INTERVENTIONS

Application of four ventilatory modes (IPPV, TGI, APRV, and TGI + APRV).

MEASUREMENTS AND RESULTS

TGI + APRV facilitated CO2 elimination. The peak Paw was significantly lower during TGI + APRV than during IPPV (nonpulmonary edema model; 15 +/- 4 vs 28 +/- 9 cm H2O; p < 0.05; pulmonary edema model: 20 +/- 4 vs 34 +/- 10 cm H2O; p < 0.05). Normocarbia was observed in both models. Neither TGI nor APRV alone maintained normocarbia.

CONCLUSION

The combined use of TGI and APRV is a more effective method of maintaining normocarbia with reduced peak Paw than either IPPV or APRV alone.

Transfer of gas from the acinus during continuous flow and intermittent positive pressure ventilation

We used a technique of measuring Xenon133 washout (XeW) from the alveolar space to evaluate transfer of gas from the acinus (Mackenzie et al., J. Appl. Physiol. 68: 2013-2018, 1990) during 2 min of apnea, 2 min of tracheal insufflation with oxygen (TRIO) and 90 sec of intermittent positive pressure ventilation (IPPV) in 6 anesthetized and paralyzed dogs. Xenon133 dissolved in saline was injected into an occluded acinar region through a pulmonary artery catheter, and XeW was measured by gamma scintillation scanning. With this technique, XeW during apnea represents the contribution of cardiogenic oscillations in regional flow. The XeW rate constant (min-1 +/- SE) was 0.37 +/- 0.03 during apnea. This was not different (P > 0.05) with TRIO (0.29 +/- 0.04). With IPPV, the rate constant increased to 3.49 +/- 0.39, faster than with either apnea or TRIO (P < 0.001). We conclude that: (1) TRIO does not increase convective gas transfer from the acini compared to apnea; and (2) transfer of gas out of the acini due to cardiogenic oscillations is a very small portion of the total gas eliminated during IPPV.

Cardiopulmonary resuscitation without intermittent positive pressure ventilation

The purpose of this study was to examine whether tracheal insufflation of oxygen (TRIO) could be used as a substitute for intermittent positive pressure ventilation (IPPV) during cardiopulmonary resuscitation (CPR) in dogs with orotracheal intubation. Twenty-seven anesthetized, paralyzed and intubated dogs were used. The tip of the insufflation catheter was placed 1 cm distal to the top of the endotracheal tube. The effects of TRIO at a flow rate of 10 l/min with or without a continuous positive airway pressure (CPAP) of 5 cmH2O during external cardiac compressions were compared with those managed under the standard CPR. During CPR, TRIO without CPAP maintained adequate gas exchange. Peak airway pressures in the TRIO groups were significantly lower than that in the standard CPR group. No significant differences were observed in arterial, pulmonary artery and diastolic right atrial pressures during CPR among the three groups. However, the coronary perfusion pressures in the TRIO group with CPAP always tended to be low during CPR. The present study suggests that TRIO without CPAP should be a promising substitute for IPPV during CPR when IPPV is not feasible.

Gas exchange by intratracheal insufflation in a ventilatory failure dog model

Respiratory insufficiency patients who need only partial ventilatory support are, nevertheless, intubated and connected to a respirator. In search of a partial respiratory assistance method we evaluated the gas exchange, mechanisms, and hemodynamic effects of intratracheal insufflation (ITI) via a narrow (0.2-cm) catheter. The effects of flow rate (0.05-0.2 liter/min per kg), catheter tip position (carina, bronchus, and trachea), and superimposed chest vibration at 22 Hz were studied in seven anesthetized and partially paralyzed dogs. ITI in the carina induced CO2 removal (VCO2) of 48 +/- 16 ml/min in the periods between breaths, which was 39% of the control VCO2. CO2 removal rates between breaths with ITI in a bronchus and in the trachea were 63 and 28% of control, respectively (P < 0.05). ITI at 0.15-0.2 liter/min per kg augmented total VCO2 by > 50% over control (P < 0.05) and decreased PaCO2 by 10% (P < 0.05) despite a 28% fall in VE and 32% lower work of breathing (P < 0.05). Adding vibration to ITI at 0.15 liter/min per kg induced VCO2 of 162 +/- 34 ml/min, which was significantly greater than control, while PaCO2 fell from 69 +/- 24 to 47 +/- 6 mmHg (P < 0.05), despite complete cessation of spontaneous breathing. ITI with or without vibration did not cause any hemodynamic changes, except for a fall in the shunt fraction from 14.6 +/- 9.9% to 5.8 +/- 2.8% with vibration. Thus, ITI at low flow rates can support respiration with no hemodynamic side effects. Adding chest vibration further enhances gas exchange and can provide total ventilation.

Efficacy of tracheal insufflation of oxygen during oleic acid-induced pulmonary edema

STUDY OBJECTIVES

To determine whether tracheal insufflation of oxygen (TRIO) might be useful in field resuscitation of casualties with lung dysfunction.

DESIGN

Physiological measurements of cardiac and respiratory function were compared before and after oleic acid lung injury.

SETTING AND PARTICIPANTS

Beagles were studied in a laboratory.

INTERVENTIONS

Oleic acid (0.06 mL/kg) was injected over four minutes into the central venous port of a pulmonary artery catheter. Measurements were made during 30 minutes of TRIO before and after acute lung injury.

MEASUREMENTS

Hemodynamic and respiratory measurements, including intravascular pressures, heart rate, cardiac output, blood gases, respiratory system compliance, and O2 consumption were recorded during conventional mechanical ventilation and TRIO.

RESULTS

Before acute lung injury, PaO2 (mean +/- SD) increased (P less than .05) from 96 +/- 7.4 (13 +/- 1.0 kPa) during conventional mechanical ventilation to 360 +/- 123 mm Hg (48 +/- 16.4 kPa) after TRIO. PaCO2 (mean +/- SD) increased (P less than .05) from 39.5 +/- 1.1 (5.3 +/- 0.1 kPa) to 102 +/- 27.4 mm Hg (13.6 +/- 3.6 kPa). Arterial and mixed venous pH values decreased in proportion to PCO2. After acute lung injury, compliance decreased. PAO2 decreased (P less than .05) to 58 +/- 8.4 mm Hg (7.7 +/- 1.1 kPa) during conventional mechanical ventilation and increased (P less than .05) to 84 +/- 19.6 mm Hg (11.2 +/- 2.6 kPa) after 30 minutes of TRIO.

CONCLUSION

Despite poor gas exchange after acute lung injury, TRIO maintained adequate oxygenation and may be useful for emergency ventilation even when pulmonary edema complicates resuscitation.

Respiration by tracheal insufflation of oxygen (TRIO) at high flow rates in apneic dogs

Tracheal insufflation of oxygen (TRIO) is a technique in which oxygen is introduced into the trachea at a constant flow rate via a catheter advanced to the level of the carina. We studied the effects of flow rates (0.5, 1.0, 1.5 and 2.0 l.kg(-1).min(-1)) on arterial blood gases during TRIO in 6 apneic dogs. The constant flow was administered through the tip of a catheter (I.D. 2.0 mm) advanced to a site of 1 cm above the carina. After 30 min of TRIO, the mean Pa(CO)(2) at the flow rates of 0.5, 1.0, 1.5 and 2.0 l.kg(-1).min(-1) were 88 +/- 20, 76 +/- 20, 64 +/- 23 and 52 +/- 18 mmHg, respectively. CO(2) elimination increased as the flow rates increased from 0.5 to 2.0 l.kg(-1).min(-1). Based on the above study, we examined the effects of TRIO at a flow rate of 3 l.kg(-1).min(-1) in another 5 apneic dogs. TRIO, at a flow rate of 3 l.kg(-1).min(-1), was able to maintain normocarbia over 4 hr. The mean Pa(O)(2) and Pa(CO)(2) at 4.0 hr were 465 +/- 77 and 41 +/- 4 mmHg. Although the mechanism of pulmonary gas exchange during TRIO is unclear, our study is the first to document that normocarbia can be maintained by high-flow TRIO in apneic dots.

Transtracheal O2 insufflation (TOI) as an alternative method of ventilation during cardiopulmonary resuscitation

We examined the efficiency of continuous transtracheal O2 insufflation (TOI) as a method of ventilation during cardiopulmonary resuscitation (CPR) in a canine model. The tip of the insufflation catheter was placed 1 cm above the carina. The effects of TOI at flow rates of 0.2, 0.5, and 1.0 l/kg per min during and after CPR were examined in dogs with induced ventricular fibrillation. During CPR, adequate oxygenation and ventilation were maintained with TOI at flow rates of 0.5 and 1.0 l/kg per min, but not at 0.2 l/kg per min. After CPR, TOI was adequate to maintain oxygenation, but not ventilation. TOI alone did not prevent post-CPR hypercarbia in successfully resuscitated animals. Still, this study suggests that TOI might be useful as a temporary measure for emergency ventilation during CPR, especially in situations such as upper airway abnormalities, when mask ventilation or endotracheal intubation is not feasible.