Regional Ventilation During High Flow Nasal Cannula and Conventional Nasal Cannula in Patients With Hypoxia

Regional Ventilation During High Flow Nasal Cannula and Conventional Nasal Cannula in Patients With Hypoxia

Comparison of Regional Ventilation Pattern During High Flow Nasal Cannula Between Conventional Low Flow System Nasal Cannula in Patients With Mild to Moderate Hypoxia

High-flow nasal cannula (HFNC) that uses heated and humidified oxygen was recently introduced for bedside care. It has been shown to be associated with reduced risks of tracheal intubation rates and mortality in adult hypoxic patients. The mechanisms of the effects of HFNC are thought to be related to the favorable effects of the heated and humidified gas, the high-flow rate used to minimize the entrainment of room air, and an increase in the ventilation efficiency, including the elimination of nasopharyngeal dead space, positive end-expiratory pressure (PEEP) effects, and improvements in paradoxical abdominal movement. Regarding the effects on lung volume, global ventilation in the lungs increases during HFNC, which is thought to attribute to PEEP effects. However, how regional ventilation is affected during HFNC in comparison with conventional NC remains unknown. Because PEEP in mechanically ventilated patients improves the regional homogeneity of ventilation, investigators postulated that HFNC via PEEP effects would result in more homogeneous regional distributions in the ventilation changes. Investigators therefore assessed global and regional ventilation in patients with hypoxia receiving care via HFNC using electric impedance tomography and compared these results with conventional nasal cannula.

Patients in "HFNC first" receive oxygen therapy using HFNC in ahead of conventional nasal cannula oxygen therapy. After 20 minutes of HFNC therapy, patients receive conventional nasal cannula oxygen therapy.

Patients in "LFS first" receive oxygen therapy using conventional nasal cannula in ahead of HFNC therapy. After 20 minutes of conventional nasal cannula oxygen therapy, patients receive HFNC oxygen therapy.

Inclusion Criteria: Age >20 years Subjective dyspnea in room air SaO2< 90% in room air Oxygen requirement for nasal cannula < 6 L/m Exclusion Criteria: Unstable vital signs SBP <90 mmHg DBP < 60 mmHg Heart rate > 120 bpm Respiratory rate > 30 bpm Persistent dyspnea under oxygen therapy using NC Severe hypoxia PaO2/FiO2< 200 mmHg Unable to cooperate Delirium Reduced cognitive function

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