Intermittent Positive Pressure Ventilation

Question 1

Intermittent Positive Pressure Ventilation (IPPV)

Answer 1

IPPV refers to the application of higher than ambient airway pressures during inspiration and/or exhalation in order to improve respiratory function

Question 2

Indications

Answer 2

• Cardio - Respiratory Arrest
• Acute Respiratory Failure requiring ventilatory support
• CHF - Pulmonary Edema

Question 3

Contraindications

Answer 3

• Caution in patients with poor lung compliance e.g emphysema, asthma

Question 4

Principles

Answer 4

• Normal breathing is a process of negative pressure ventilation
• Gas is moved into the tracheobronchial tree by displacement of the diaphragm and the chest wall is expanded; in doing so, negative intrapleural pressure is created and the lungs are expanded, creating a pressure gradient from the oropharynx to the alveoli and thus initiating air movement into the lungs
• Air is then moved out of the tracheobronchial tree when the diaphragm and chest wall are relaxed and the lungs are passively deflated as the pressure gradient from the environment to the lungs is reversed

Question 5

When positive pressure is applied to the respiratory system, either continuously or at end expiration, a host of physiologic changes occur. The bulk of these changes occur in the cardiopulmonary system

Answer 5

• In some pts w/ left ventricular dysfunction, positive pressure may actually IMPROVE cardiac output
• this occurs by several mechanisms:
  1. Pts w/ elevated filling pressures may bave a decresase in end-diastolic volume and improve cardiac performance as the diastolic volume moves to a better position on the Starling curve

2. Cardiac function may improve as coronary arterial oxygen content increases
3. Positive intrathoracic pressure can cause a decrease in ventricular afterload, therby enhancing cardicac performance

Question 6

Key points

Answer 6

• In the OBTUNDED pt or cardiac arrest, ventilations are delivered slowly (1.5 to 2.0s)
• In the CONSCIOUS pt, attempt to match the pt’s spontaneous rate and rhythm

Question 7

Key point - Emphasis is placed on the SLOW delivery of ventilations to minimize high airway pressure

Answer 7

• LOW airway pressure reduces the likelihood of excessive esophageal opening pressure contributing to gastric inflation and its consequences
• Ventilations must be kept down to 8-10/min - in the past we oftened ventilated much more frequently than that, and the result can be markedly reduced blood flow
• It is extremely important (and adequate) to ventilate w. about 400-600cc at no more than 10/min