Use of Nasal Pressure to Assess Inspiratory Effort Under Different Oxygen Treatments

Patients in the intensive care unit (ICU) often require different modalities of oxygen therapy to maintain adequate oxygenation.Common oxygen therapy modalities include nasal cannula oxygen, face mask oxygen and high flow nasal cannula oxygen (HFNC).These modalities of oxygen therapy not only affect the patient's oxygenation status, but may also influence nasal and esophageal pressures by altering the upper airway pressure gradient, which in turn affects respiratory mechanics and patient comfort.

Esophageal pressure fluctuations (ΔPes), as a reflection of mean transpulmonary pressure during unassisted voluntary breathing, provide an important basis for assessing inspiratory effort.However, esophageal manometry still faces many challenges for its bedside implementation in clinical practice, especially in unstable patients with respiratory distress and severely impaired gas exchange.Notably, the COVID-19 pandemic has led to a significant increase in the number of patients with acute respiratory failure, who often require condition-specific oxygen therapy of varying severity and are mostly treated outside the ICU.Given that such patients are at high risk of deterioration, it is particularly important to continuously monitor their inspiratory effort.

nasal pressure is an important physiological indicator for assessing upper airway resistance and airflow dynamics characteristics, whereas esophageal pressure is a key parameter that directly reflects intrathoracic pressure and respiratory effort.Previous studies have shown that there may be a physiological correlation between intranasal pressure and oesophageal pressure, and that this correlation may be influenced by a variety of factors, including airflow velocity, oxygen concentration, and the dynamics of upper airway resistance.Earlier physiological studies by comparing oesophageal pressure fluctuations (ΔPes) with nasal pressure fluctuations (ΔPnose) fluctuations found that when inspiratory effort was increased, there was no significant phase difference between these pressure waveforms.In addition, it was observed that there was a significant correlation between ΔPes and airway pressure fluctuations (ΔPaw) obtained by airway occlusion manoeuvres during inspiratory effort testing.However, although these findings provide important clues for understanding respiratory mechanics, studies on the correlation between nasal pressure and esophageal pressure under different oxygen therapy conditions are still relatively limited, especially lacking data support from prospective physiological studies.Therefore, further systematic studies are needed in the future to investigate in depth the effects of different oxygen therapy parameters (e.g., flow rate, humidity, and temperature, etc.) on the relationship between nasal pressure and esophageal pressure, so as to provide more precise guidance for clinical practice.