The Effects of Obesity on the Cardiopulmonary System: Implications for Critical Care Nursing

Kim Garrett, RN, MS, CNP; Kathy Lauer, RN, PhD; Beth-Anne Christopher, RN, MS

Disclosures

Prog Cardiovasc Nurs. 2004;19(4) 

In This Article

Obesity-Related Pathophysiology of the Pulmonary System

Pulmonary complications of obesity present significant risks to the critically ill individual. Duration of mechanical ventilation and weaning times were found[12] to be significantly longer for these patients, as well as oxygen requirements during hospitalization.

Deposition of adipose tissue in the abdomen, on the diaphragm, and in intercostal muscles impairs respiratory system function and decreases lung expansion. These alterations, along with the increased weight of excess adipose tissue on the chest wall, lead to decreased functional residual capacity, expiratory reserve volume, forced expiratory reserve volume, and minute ventilation.[15,21] Vital capacity and total lung volume generally remain in the normal range but may be reduced by ≥ 30% in a severely obese individual. Multiple factors such as abnormal chest wall resistance, abnormal diaphragmatic position, increased airway resistance, and/or the need to eliminate higher daily levels of carbon dioxide contribute to an increased breathing effort.[15] Because of alveolar collapse and airway closure at the lung bases, obese individuals have widened alveolar-arterial oxygen gradients and ventilation-perfusion mismatching. Arterial hypoxemia associated with the ventilation-perfusion abnormality puts the obese individual at increased risk for sudden death.[15]

Obese individuals are also at increased risk of developing OSAS and/or OHS. These syndromes lead to chronic hypoxia, hypercapnia, and sleep fragmentation, which ultimately results in hypoventilation, episodic hypoapnea, apnea, and arousal from sleep. These problems, when combined with the increased work of breathing in inefficient and fatigued respiratory muscles, hamper the ability of the severely obese individual to recover from periods of apnea due to hyperventilation, which leads to worsening arterial blood gas abnormalities. A vicious cycle develops wherein chronic hypoxemia and hypercarbia further exacerbate the condition.[22]

Clinically, these individuals exhibit daytime sleepiness, fatigue, irritability, and personality changes associated with the chronic sleep deprivation and nocturnal oxyhemoglobin desaturation, which puts them at increased risk for arrhythmias, including tachy-brady syndrome, atrial fibrillation, sinus arrest, and second-degree heart blocks.[22]

Gastroesophageal reflux disease is also common in the obese individual,[23] which occurs because obese individuals have higher volumes of gastric fluid and increased intraabdominal pressures, which predispose them to an increased incidence of aspiration. The incidence of developing postoperative pulmonary complications is double that of nonobese individuals.[16,24] In addition, thoracic and upper abdominal incisions may exacerbate pulmonary dysfunction.[15]

Obesity complicates nursing care and the assessment of cardiac and pulmonary function. Nursing care of the obese individual should be aimed at obtaining accurate measurements, optimizing function, and preventing complications.

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