Chronic kidney disease (CKD) leads to poor exercise tolerance, vascular dysfunction, and reduced quality of life. This randomized controlled trial will compare intermittent hypoxic training (IHT) with traditional aerobic training in patients with CKD stages 3-4.

A total of 60 participants aged 40-65 years will be recruited and randomized into three groups. Interventions will last 12 weeks, with three 30-minute supervised sessions per week. Outcome measures include exercise tolerance (6-Minute Walk Test), cardiovascular parameters (blood pressure, heart rate recovery), kidney function (serum creatinine, eGFR), fatigue (Fatigue Severity Scale), and quality of life (KDQOL-36)

Chronic kidney disease (CKD) stage 3 is characterized by reduced exercise capacity, muscle weakness, and increased cardiovascular risk, which negatively impact quality of life. Exercise interventions have shown benefits in improving functional outcomes, but traditional aerobic training may be limited due to comorbidities and reduced physiological reserve. Intermittent hypoxic training (IHT) improves oxygen utilization, cardiovascular adaptation, and mitochondrial function. Specialized hypoxicator devices are costly and not widely available, so practical alternatives such as hypoventilation training and breathing restriction masks may provide comparable benefits.

Study Objective:

To evaluate the effects of hypoventilation training and breathing restriction mask training on exercise tolerance, cardiovascular function, kidney function, fatigue, and quality of life in CKD stage 3 patients.

Study Design:

Randomized controlled trial including 60 patients with CKD stage 3, aged 40-65 years, recruited from outpatient clinics at Aboker Hospital and Pharos University. Participants will be screened for eligibility through medical history, vital signs, and laboratory tests (serum creatinine, eGFR, hemoglobin, electrolytes).

Interventions:

Group A - Hypoventilation Training:

Moderate-intensity aerobic exercise on a cycle ergometer (40-60% HR reserve)

Intermittent breath-holding: 5-10 seconds every 1-2 minutes

Continuous monitoring of SpO₂, heart rate, and blood pressure

Group B - Breathing Restriction Mask Training:

Same aerobic protocol as Group A

Participants wear an adjustable resistance mask to simulate hypoxia

Mask set to induce mild hypoxemia (SpO₂ ≥85%)

Continuous monitoring of SpO₂, heart rate, and blood pressure

Group C - Control Group:

Same aerobic exercise protocol under normal breathing conditions

Moderate intensity (40-60% HR reserve)

Periodic monitoring of vital signs for safety

Intervention Duration:

12 weeks, 3 supervised sessions per week, 30 minutes per session

Outcome Measures:

Primary Outcome:

Exercise tolerance assessed via 6-Minute Walk Test (6MWT) at baseline and post-intervention

Secondary Outcomes:

Fatigue: Fatigue Severity Scale (FSS), self-reported, 9 items, 7-point Likert scale

Quality of Life: KDQOL-36, disease-specific questionnaire covering physical/mental health, symptoms, effects, and burden of CKD

Cardiovascular Assessment: Blood pressure (SBP, DBP) and Heart Rate Recovery (HRR = HR_peak - HR_1min)

Kidney Function: Serum creatinine and eGFR (CKD-EPI/MDRD

Inclusion Criteria:Adults (40-65 years) diagnosed with CKD stages 3a,b

• Medically stable and cleared for exercise

Exclusion Criteria:

• Uncontrolled hypertension
• Severe cardiac arrhythmias
• Recent hospitalization (<3 months)

cardiovascular disese unstable

Both men and women are eligible; no gender restriction

This study will compare the effects of intermittent hypoxic training (IHT) versus traditional aerobic training (TAT) on exercise tolerance and vascular health in patients with chronic kidney disease (CKD) stages 2-4. Participants will be randomized into two intervention groups and undergo supervised exercise sessions over a 12-week period. Primary outcomes include peak oxygen uptake (V̇O₂peak) and endothelial function (flow-mediated dilation), while secondary outcomes include arterial stiffness, 6-minute walk distance, and quality of life measures. Safety and adherence will be closely monitored throughout the study. Data will be analyzed to determine the comparative efficacy of IHT and TAT in improving functional and vascular health in this population

Masking Description: Outcome assessors and data analysts will be blinded to group allocation; participants and trainers cannot be blinded due to the nature of the intervention