Respiratory distress is a life-threatening condition that frequently necessitates admission to the intensive care unit (ICU). It is characterized by inadequate oxygenation and/or ventilation, leading to hypoxemia and hypercapnia. ^[1] The management of respiratory distress often involves the use of non-invasive ventilation (NIV) strategies to avoid the complications associated with invasive mechanical ventilation, such as ventilator-associated pneumonia and barotrauma. ^[2] Among the various NIV modalities, high-flow nasal oxygen (HFNO) and continuous positive airway pressure (CPAP) are commonly used. ^[3]

Respiratory distress in critically ill patients remains a significant challenge in intensive care settings. Non-invasive ventilation strategies such as High-Flow Nasal Oxygen (HFNO) and Continuous Positive Airway Pressure (CPAP) have been widely adopted to reduce intubation rates and improve patient outcomes. ^[4] Endotracheal intubation is associated with complications, including ventilator-associated pneumonia, sedation-related risks, and prolonged ICU stay. Hence, avoiding invasive mechanical ventilation using effective non-invasive techniques is of paramount importance. ^[5]

HFNO delivers humidified oxygen at high flow rates (up to 60 L/min), providing low levels of positive end-expiratory pressure (PEEP) and reducing inspiratory effort. CPAP, on the other hand, delivers a constant positive airway pressure, recruiting collapsed alveoli and improving oxygenation. ^[6] While both modalities offer benefits, there is ongoing debate regarding their relative effectiveness in preventing intubation in ICU patients with acute respiratory distress. ^[7]

Studies like the FLORALI trial demonstrated that HFNO reduced intubation rates compared to standard oxygen therapy but was not significantly superior to CPAP in severe cases. ^[8] CPAP, widely used in conditions like cardiogenic pulmonary edema, has been shown to provide better airway pressure support, reducing the need for intubation in moderate-to-severe hypoxemia. ^[9]

Several studies have compared the efficacy of HFNO and CPAP in various clinical settings, including acute respiratory failure, post-extubation respiratory support, and pre-oxygenation for intubation. ^[10] However, the evidence regarding their comparative effectiveness in preventing intubation in patients with respiratory distress in the ICU remains inconclusive. Some studies suggest that HFNO may be more effective in reducing the need for intubation, while others have found no significant difference between the two modalities. ^[11]

This study aims to compare HFNO and CPAP in ICU patients with respiratory distress to determine their relative efficacy in preventing intubation, assessing patient outcomes, safety, and tolerance levels.

This was a prospective, randomized controlled study conducted in Respiratory Intensive Care Unit (RICU),Government Medical College, Sangareddy. The study population included adult patients admitted with acute respiratory distress requiring non-invasive ventilation.

Inclusion Criteria

• Age >18 years
• Acute respiratory failure with PaO₂/FiO₂ ratio <300
• Respiratory distress requiring non-invasive support
• No contraindications to HFNO or CPAP

Exclusion Criteria

• Immediate need for intubation
• Hemodynamic instability (MAP <65 mmHg)
• Severe acidosis (pH <7.25)
• Facial deformities preventing CPAP mask fitting
• Do-not-intubate orders

Patients were randomized in a 1:1 ratio to receive either HFNO or CPAP using a computer-generated random sequence. The HFNO group received oxygen at a flow rate of 50-60 L/min with a FiO2 adjusted to maintain SpO2 ≥ 92%. The CPAP group received a constant pressure of 8-10 cm H2O with a FiO2 adjusted to maintain SpO2 ≥ 92%.

Data on demographic characteristics, clinical parameters, and outcomes were collected prospectively. The primary outcome was the rate of intubation within 72 hours of initiation of therapy. Secondary outcomes included 28-day mortality, ICU length of stay, and the incidence of complications such as nasal bridge ulceration, pneumothorax, and ventilator-associated pneumonia.

Statistical Analysis

Data were analyzed using SPSS version 25. Continuous variables were compared using the Student’s t-test or Mann-Whitney U test, as appropriate. Categorical variables were compared using the chi-square test or Fisher’s exact test. A p-value < 0.05 was considered statistically significant.

Table 1: Distribution of 1Baseline Characteristics

In table 1, The CPAP group is slightly older on average (60.0 years) compared to the HFNO group (56.0 years). The HFNO group has a higher percentage of males (68.0%) compared to the CPAP group (50.0%). Higher BMI in the CPAP group (33.3 vs. 24.4), though not significant, may indicate a trend where obese patients were more likely to require CPAP due to increased airway resistance and obesity-related hypoventilation. Smoking history was significantly higher in the CPAP group (65% vs. 37%, p=0.05). The CPAP group has a higher percentage of patients with hypertension (69.0%) compared to the HFNO group (50.0%). The HFNO group has a higher percentage of patients with diabetes (58.0%) compared to the CPAP group (43.0%).

Table 2: Respiratory Parameters

In table 2, The CPAP group has a higher average PaO₂/FiO₂ ratio (247.4) compared to the HFNO group (152.3), suggesting that CPAP may provide better oxygenation support. The CPAP group has a slightly higher respiratory rate (34.0 breaths/min) compared to the HFNO group (30.0 breaths/min). Both groups are within the normal range, but the HFNO group has a slightly higher pH (7.39) compared to the CPAP group (7.37). The CPAP group has a higher average PaCO₂ (49.0 mmHg) compared to the HFNO group (44.0 mmHg). The CPAP group has a higher average lactate level (2.2 mmol/L) compared to the HFNO group (1.1 mmol/L).

Table 3: Distribution of Primary Outcome

Both groups have similar intubation rates, with the HFNO group slightly higher (38%) compared to the CPAP group (36%). The p-value = 0.056 is borderline significant. It is very close to the conventional threshold of 0.05 but does not quite reach it.

Table 4: Distribution of Secondary Outcomes

A trend toward higher mortality in the HFNO group (44.0% vs. 37.0%, p = 0.057) was observed, but the difference is not statistically significant. The HFNO group had a longer average ICU stay (14.7 days vs. 8.9 days), but the difference is not statistically significant (p = 0.154).

Table 5: Complications among patients

In table 5, Nasal Bridge Ulceration was 24% of HFNO patients experienced nasal bridge ulceration compared to 17% in the CPAP group. Pneumothorax occurred in 11% of HFNO patients vs. 7% of CPAP patients. The p-value (0.132) indicates that this difference is also not statistically significant. A common ICU-associated complication, VAP was observed in 21% of HFNO patients compared to 23% in CPAP patients. The p-value (0.39) confirms that this difference is not statistically significant.

Table 6: Distribution of Subgroup Analysis

In table 6, Mild Hypoxemia (PaO₂/FiO₂ 200-300): HFNO was used more frequently (59% vs. 39%), possibly because it is more comfortable and well-tolerated in mild-moderate hypoxemia. Moderate Hypoxemia (PaO₂/FiO₂ 100-200): Both HFNO and CPAP were used equally, indicating no clear preference for one over the other in this category. Severe Hypoxemia (PaO₂/FiO₂ <100): Both groups had an equal proportion (71%), suggesting that HFNO and CPAP were considered interchangeable for severe cases

Our results align with several recent studies. A multicenter randomized controlled trial by Duan et al. found that CPAP reduced the risk of meeting intubation criteria compared to HFNO in patients with acute hypoxemic respiratory failure. ^[12] Similarly, Mirunalini et al. reported that CPAP significantly decreased intubation rates and prolonged invasive mechanical ventilation-free periods in COVID-19 patients with hypoxic respiratory failure. ^[13]

Furthermore, the RECOVERY-RS trial demonstrated that an initial strategy of CPAP significantly reduced the risk of tracheal intubation or mortality compared with conventional oxygen therapy. ^[14]

In current study both groups have similar intubation rates, with the HFNO group slightly higher (38%) compared to the CPAP group (36%). The p-value = 0.056 is borderline significant. It is very close to the conventional threshold of 0.05 but does not quite reach it.Our findings indicate that the intubation rate was comparable between the HFNO and CPAP groups. This aligns with previous studies, such as the FLORALI trial by Frat et al. (2015), which showed that HFNO reduced intubation rates compared to conventional oxygen therapy but was not superior to non-invasive ventilation (NIV) in preventing intubation. ^[15] However, our study suggests that CPAP may offer a slight advantage in patients with more severe hypoxemia (PaO₂/FiO₂ < 200).

Mortality rates were similar in both groups, consistent with meta-analyses (e.g., Rochwerg et al., 2019) that found no significant mortality benefit of HFNO over CPAP or NIV in acute respiratory failure. ^[16] This suggests that both modalities are viable in managing respiratory distress, but the choice of therapy should consider patient tolerance, availability, and clinical response.

In this study a trend toward higher mortality in the HFNO group (44.0% vs. 37.0%, p = 0.057) was observed, but the difference is not statistically significant. The HFNO group had a longer average ICU stay (14.7 days vs. 8.9 days), but the difference is not statistically significant (p = 0.154). This result aligns with studies such as the study by Hernandez et al. (2016), which found similar ICU stay durations for patients managed with HFNO versus CPAP post-extubation. ^[17]

In this study Nasal Bridge Ulceration was 24% of HFNO patients experienced nasal bridge ulceration compared to 17% in the CPAP group. Pneumothorax occurred in 11% of HFNO patients vs. 7% of CPAP patients. The p-value (0.132) indicates that this difference is also not statistically significant. A common ICU-associated complication, VAP was observed in 21% of HFNO patients compared to 23% in CPAP patients. The p-value (0.39) confirms that this difference is not statistically significant.

CPAP use was associated with a higher incidence of nasal bridge ulceration, a well-documented adverse effect of mask-based non-invasive ventilation. Conversely, pneumothorax and ventilator-associated pneumonia (VAP) rates were comparable, which is consistent with existing literature indicating that non-invasive strategies generally reduce these complications compared to invasive mechanical ventilation. ^[18]

In our study HFNO was used more frequently (59% vs. 39%), possibly because it is more comfortable and well-tolerated in mild-moderate hypoxemia. Moderate Hypoxemia (PaO₂/FiO₂ 100-200): Both HFNO and CPAP were used equally, indicating no clear preference for one over the other in this category. Severe Hypoxemia (PaO₂/FiO₂ <100): Both groups had an equal proportion (71%), suggesting that HFNO and CPAP were considered interchangeable for severe cases.

In patients with a PaO₂/FiO₂ ratio between 100-200, CPAP showed a slight trend toward lower intubation rates. This supports previous findings that CPAP may be more effective in moderate-to-severe hypoxemia by maintaining alveolar recruitment and improving oxygenation. In contrast, in milder cases (PaO₂/FiO₂ > 200), HFNO performed similarly to CPAP, likely due to better patient comfort and secretion clearance. ^[19]

Limitations: The sample size was relatively small, which may limit the generalizability of our findings. Additionally, the study was conducted at a single tertiary care teaching hospital, potentially introducing selection bias. Future multicenter studies with larger sample sizes are warranted to validate our findings and provide more definitive conclusions.

Both HFNO and CPAP are effective strategies for managing acute respiratory failure. The choice of therapy should be individualized based on disease severity, patient comfort, and clinical response. CPAP may be more beneficial in patients with moderate to severe hypoxemia, while HFNO may be better tolerated in less severe cases. our study suggests that CPAP may be more effective than HFNO in reducing the need for intubation and improving certain clinical outcomes in patients with acute respiratory distress. However, the choice between CPAP and HFNO should be individualized, considering patient-specific factors, potential complications, and resource availability. Further research is needed to establish clear guidelines for the optimal use of non-invasive respiratory support modalities in various clinical scenarios. HFNO can also be used as an alternative to CPAP because it has better patient tolerance than CPAP

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