Sussan Soltani Mohammadi.MD CPAP- BIPAP Sussan Soltani Mohammadi.MD Assistant professor Shariati Hospital

Positive Airway Pressure Therapy: Application of higher than ambient airway pressure during inspiration and/or exhalation to improve respiratory function

Positive pressure applied during inspiration → PPV. Positive pressure applied during exhalation → PEEP.

Positive pressure applied during spontaneous breathing to maintain an elevated baseline airway pressure → CPAP

Difference between PEEP and CPAP: PEEP → elevated baseline pressure during mechanical ventilation (during separate mode). CPAP → elevated baseline pressure during spontaneous breathing.

BIPAP: Bilevel positive airway pressure→ is an intermittent CPAP or CPAP with release Occasionally described as Airway Pressure Release Ventilation (APRV)

This mode was developed during the late 1980s using the principle of CPAP. Allow the clinician to set the two CPAP levels → pressure high at inspiratory time and pressure low or release pressure at expiratory time

In BIPAP clinician set not only the pressure but also the time spent at each level. Time high or inspiration and time low or expiration. When the patient is breathimng spontaneously, transition of pressure from higher to lower → tidal movement of gas and subsequent CO2 elimination.

The short expiratory time ( time at the low pressure) prevents complete exhalation and maintains alveolar distention .

When PP is applied to the respiratory system (continuously or at end expiration) → physiologic changes occur → cardio respiratory system.

Pulmonary effect Redistribution of extra vascular water → improve oxygenation, lungs compliance and vent/perfusion matching. ↑ FRC → increase volume of patent alveoli at lower levels of PEEP and inflation of previously collapsed alveoli → alveolar recruitment at higher levels of peep.

Cardiovascular effects ↓CO by three mechanism: ↓ venous return RV dysfunction (ppv increase PVR → increase RV afterload) ↑pulmonary pressure → ↑ RVEDV →left ward shift of interventricular septum →LV distensibility ↓

Technical application Invasively: Endotracheal tube Tracheostomy tube 2) Non invasively: Mask: Nasal, Oronasal, Full face mask Nasal pillow

The basic equipments required are: 1) Ventilator 2) Ventilator tubing 3) An interface connecting the system to the patient

CPAP: Commonly is delivered by a tight fitting mask With a continuous gas-flow rate (15-30 lit/min at a specific FIO2) A reservoir bag, a one way valve, a humidifier and an expiratory pressure valve

patients can not tolerate mask due to claustrophobia aerophagia or hemodynamic instability → endotracheal intubation

Indications Respiratory insufficiency has not yet progress to true respiratory failure with dyspnea , use of accessory muscle 2) Ph < 7.35 , PaCo2 > 45 mmHg , RR > 25

3)Treatment of atelectasis (especially postoperative) 4) Post extubation stridor: Immediately → reintubation 30 min or later → is the result of laryngeal edema → CPAP

6)Exaxerbation of COPD ,asthma 5) Accelerate the weaning of ventilatory support 6)Exaxerbation of COPD ,asthma 7) Hypoventilation syndromes (obesity, obstructive sleep apnea syndrome)

8) Do not intubate patients (who have refused intubation) 9) Acute cause of respiratory insufficiency who require a short period of ventilatory support until underlying problem can be treated (pulmonary edema , ARDS , pneumonia , chest trauma ).

Contraindications Cardiopulmonary arrest or sever hemodynamic instability ,life threatening dysrhythmia 2) Apnea or need for immediate intubation 3) Facial burns , trauma or surgery

6) Sever ill patient with multi organ dysfunction 4) Uncontrolled vomiting or sever GIB and need for airway protection (risk of aspiration) 5) Uncooperative patient (extreme anxiety) 6) Sever ill patient with multi organ dysfunction

Ventilators Most studies have used pressure cycle ventilator however volume-cycle ventilator has been used successfully. Patients tolerate P.C.Ventilator better. Risk of barotrauma and degree of air leak are less than with V.C.Ventilator.

Types of ventilators have ranged from standard ICU type ventilator to portable ones designed for CPAP or NIPPV. Use of portable pressure-cycle ventilator in ICU provides high FIO2 levels and lack of alarm or monitors.

Monitoring For leaks around the mask Amount of ventilation , ABG (PaO2) Physical exam of the patient for synchrony with mechanical ventilation

patient comfort Presence or absence of stress responses (tachycardia , tachypnea) Degree of accessory muscle use at the bedside

Unsuccessful treatment Rapid shallow breathing Continues accessory muscle use Paradoxical abdominal respiration

Successful treatment Conversion of rapid shallow breathing →slower deeper pattern Exhaled tidal vol ≥ 5-6 ml/kg RR≤ 20 ↓CO2 Improvement of respiratory parameter usually occurs within the first hours.

Factors necessitating intubation 1)Major factors: Respiratory arrest Respiratory pause with gasping or reduced consciousness Agitation requiring sedation Bradycardia with ↓ consciousness Hemodynamic instability (SBP < 70)

2) Minor factors: RR>35(or > than admission) PH< 7.30 (or < than admission) PaO2< 60 mmHg Increasing encephalopathy

Presence of one major factor at any time or two minor factors after 1 hour of NIV should lead to intubation

Complications Pressure necrosis over the bridge of the nose Nasal ,sinus or ear pain at initiation of NIPPV (start at low pressure and slowly rise it) Nasal congestion and dryness Oral dryness

Eye dryness and iritation Pneumothorax (rare but may occur at high pressure especially in bullous lung disease) Aspiration especially with full face mask Gastric insufflation(25% may need NG tube)

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