The Use of PEEP (or CPAP) in CHF

The Use of PEEP (or CPAP) in CHF

CASE

A 69-year old male is brought into your department in acute respiratory distress. He is breathing 56 times per minute, using all of his accessory muscles of respiration. His skin is cold and moist. His BP is 188/110, with sinus tachycardia at a rate of 152/minute. His S02 = 70% per pulse-oximeter. He has bilateral inspiratory crackles in all lung fields and his wife states he has been “battling heart failure” for several years.

RESULTS:

  • pH = 7.21
  • paC02 = 54 mmHg
  • pa02 = 81 mmHg
  • Sa02 = .69

EVALUATION

Pump failure induced acute pulmonary edema with severe masked hypoxemia and early respiratory failure.

INITIAL CLINICAL GOAL

To improve oxygenation and respiratory function. (restoration of functional residual capacity {FRC} improve alveolar filling and improve pulmonary compliance.)

INITIAL TREATMENT

  1. Begin CPAP via facemask at +5 cmH20 at an FIO2 of 40%. A very modest reduction in work of breathing noted.
  2. CPAP increased to 10 cmH20.

The respiratory frequency dropped to 32/minute; S02 – increased to 88%; BP – 144/88 and the skin color has gone from cyanosis to pale with no cyanosis. The skin has become less diaphoretic and his work of breathing improved.

REPEAT ABG

  • pH = 7.40
  • PaCO2 = 31 mmHg
  • Pa02 = 188 mmHg
  • Sa02 = .92
  • FI02 - .40

DISCUSSION

Patients presenting with cardiogenic acute pulmonary edema (congestive heart failure) are experiencing several acute derangements of their pulmonary function caused by fluid being forced through the alveolar capillary membrane and into the interstitial spaces. The lungs lose compliance, the FRC reduced and there is a substantial reduction of alveolar capillary membrane required for adequate gas exchange. The reduction of the alveolar volume is worsened during expiration. Some patients experience respiratory acidosis due to the inability to maintain adequate minute volume due to the shift of the compliance curve. By addressing these issues using carefully titrated end-expiratory pressure, a significant amount of overall stabilization takes place. The substantive therapy often includes reopening coronary arterial circulation; and inotropic support.

CAUTIONS

  1. DO NOT elect to use CPAP by facemask if the patient cannot protect their own airway.
  2. Begin emergency mask CPAP in patients that are tachypneic. (patients who are not breathing fast may not be candidates for end-pressure).
  3. Monitor patient responses and if the CPAP causes signs of perfusion and/or respiratory function to worsen (respiratory frequency increases), discontinue the CPAP and consider the need for intubation and controlled ventilation.
  4. When vasodilator and inotropic drugs are in play, remember to reduce the CPAP levels are the underlying pathophysiology is corrected.