High-flow nasal cannula: impact on oxygenation and ventilation in an acute lung injury model

Abstract

Introduction: High-flow nasal cannula therapy (HFNC) has been shown to be more effective than continuous positive airway pressure (CPAP) in reducing intubations and ventilator days. HFNC likely provides mechanisms to support respiratory efficiency beyond application of distending pressure. We reason that HFNC washout of nasopharyngeal dead space impacts CO(2) removal along with oxygenation. The aim of this study was to demonstrate the flow dependence of CO(2) reduction and improved oxygenation during HFNC and the dependence on leak around the nasal prongs.

Materials and methods: Neonatal piglets (n=13; 2-6 kg) were injured with IV oleic acid and supported with HFNC at 2 through 8 L/min. High and low leak around the nasal prongs was accomplished by using single and double prong cannulae, respectively. Measurement of hemodynamic, respiratory and blood gas parameters were made at each setting following 10 min for physiologic equilibration. Tracheal pressures were recorded by transmural catheters.

Results: With HFNC, CO(2) trended downward in a flow-dependent manner independent of leak. Oxygenation and tracheal pressures increased in a flow-dependent manner with the greatest effect during double prong. At 8 L/min, tracheal pressures did not exceed 6 ± 1 cmH(2) O.

Conclusions: HFNC improves gas exchange in a flow-dependent manner; double prong had greater impact on O(2;) single prong had greater impact on CO(2) elimination.

Copyright © 2010 Wiley-Liss, Inc.

Figures

Figure 1. Baseline and Injury

Gas exchange alterations following oleic acid injury. Left panel; change in arterial PCO2, baseline vs. injury. Right panel; change in A-a gradient baseline vs. injury. N=13; p <0.01

Figure 2. Real-time Tracheal Pressures

Typical tracing of real time tracheal pressure as recorded using a water-filled catheter at SP 2 lpm.

Figure 3. Tracheal Pressures

Summarized data for tracheal pressures during CPAP; r2=0.99;p=0.02 (left panel). Tracheal pressures for high (r2=0.81;p=0.04) and low leak conditions (r2=0.82;p=0.04) (right panel).

Figure 4. Partial Pressure Carbon Dioxide

Effects of incremental increases in CPAP on PCO r2 2 =0.5;p=0.5(left panel). Effects of incremental increases in HFNC flow rate on PCO (low 2 2 leak r =0.92;p<0.01; low leak r2=0.7;p=0.07) (right panel).

Figure 5. Partial Pressure Oxygen

Effects of incremental increases in CPAP on PO2 (left panel). Effects of incremental increases in HFNC flow rate on O2 in low leak condition (r2=0.85;p=0.03) (top right panel). Effects of incremental increases in HFNC flow rate on O2 in high leak condition (bottom right panel).