My 75 year old patient has an arterial oxygen tension (Pa02) less than 90 mmHg on room air. Does age affect PaO2?

Short answer: Yes! Most studies of blood gas concentrations have demonstrated a decrease in oxygen tension with age.1

Earlier studies have demonstrated a linear decrease in oxygen tension based on observations that included relatively small number of patients over the age of 60. 1 More recently, however, in a study of 532 consecutive patients admitted for elective surgery without overt cardiac, pulmonary, or metabolic disease, obesity or smoking, the mean PaO2 differed by age group as follows:

  • <30 years: 98.4 mmHg
  • 30-50 years: 88.7 mmHg
  • 51-70 years: 81.0 mmHg
  • >70 years: 76.5 mmHg

After age 70 years, decline in Pa02 may slow down or actually reverse, likely related to the “survival of the fittest” in more advanced years. 1,2 Some have suggested accepting a PaO2 80-85 mmHg as normal for subjects > 65 years of age. 3

The decrease in PaO2 with age is a result of increased heterogeneity of ventilation/perfusion ratio, especially reduced ventilation in the dependent parts of the lung. 3 Aging is also associated with a decrease in chest wall compliance, muscle (including the diaphragm) strength, forced expiratory volume in 1 second (FEV1), vital capacity, and diffusing capacity of carbon monoxide (DLC0)/alveolar volume.  

In addition, aging is associated with a reduction in response to hypoxia and hypercarbia, making older patients particularly vulnerable to complications from  heart failure and pneumonia4, especially in the current Covid-19 era.

Bonus Pearl: Did you know that poor response to hypoxic or hypercarbic states in the elderly is likely related to an age-related decline in efferent neural output to respiratory muscles?4

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References

  1. Blom H, Mulder M, Verwej W. Arterial oxygen tension and saturation in hospital patients: effect of age and activity. BMJ 1988;297:720-2. Doi:10.1136/bmj.297.6650.720 https://www.bmj.com/content/297/6650/720   
  2. Delclaux B, Orcel B, Housset B, et al. Arterial blood gases in elderly persons with chronic obstructive pulmonary disease (COPD). Eur Respir J 1994;7:856-61. https://www.researchgate.net/publication/15147788_Arterial_blood_gases_in_elderly_persons_with_chronic_obstructive_pulmonary_disease_COPD
  3. Janssens JP, Pache JC, Nicod LP. Physiological changes in respiratory function associated with ageing. Eur Respir J 1999;13:197-205. https://www.researchgate.net/publication/12689073_Physiological_changes_in_respiratory_function_associated_with_ageing
  4. Sharma G, Goodwin J. Effect of aging on respiratory system physiology and immunology. Clin Interventions in Aging 2006;1:253-60. https://pubmed.ncbi.nlm.nih.gov/18046878/

 

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

 

My 75 year old patient has an arterial oxygen tension (Pa02) less than 90 mmHg on room air. Does age affect PaO2?

My patient with cirrhosis has a large right sided pleural effusion with only a small amount of ascites. Could this effusion still be related to his cirrhosis?

Yes! Although we often associate pleural effusions in patients with cirrhosis with the presence of large ascites, some patients present with hepatic hydrothorax even in the absence of significant ascites.1-3  

In fact, in a study involving 77 patients with hepatic hydrothorax, 49% had minimal or small and 9% had no detectable ascites!1  Interestingly, nearly three-quarters of patients in this study had right sided pleural effusion with 10% having bilateral and 17% having left sided effusion only. Hepatic hydrothorax without ascites as the first sign of liver cirrhosis has also been reported.2

Although the mechanism(s) behind hepatic hydrothorax is not fully clear, the passage of peritoneal fluid into the pleural cavity through defects in the tendinous portion of the diaphragm assisted by negative intrathoracic pressure during inspiration is commonly favored. 1-3  

Supportive evidence includes a number of studies involving intraperitoneal injection of air, dyes or technetium 99 m-sulfur colloid that have demonstrated the trans-diaphragmatic flow of ascites into the pleural cavity. 1-4  In the absence of ascites, a complete equilibrium between the amount of ascites produced and its flow into and reabsorption by the pleural cavity is assumed.1,2

Bonus Pearl: Did you know that although most patients with hepatic hydrothorax have a transudative pleural effusion according to Light’s criteria, 1 study showed that 18% of patients may meet the Light’s criteria for an exudative effusion? 5,6

 

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References

  1. Badillo R, Rockey DC. Hepatic hydrothorax: Clinical features, management, and outcomes in 77 patients and review of the literature. Medicine 2014;93:135-142. https://www.ncbi.nlm.nih.gov/pubmed/24797168
  2. Kim JS, Kim CW, Nam HS, et al. Hepatic hydrothorax without ascites as the first sign of liver cirrhosis. Respirology Case Reports 2016;4:16-18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4722098/
  3. Rubinstein D, McInnes IE, Dudley FJ. Hepatic hydrothorax in the absence of clinical ascites: diagnosis and management. Gastroenterology 1985;88:188-91. https://www.ncbi.nlm.nih.gov/pubmed/3964765
  4. Holt KA, Oliviera E, Rohatgi PK. Hepatic hydrothorax demonstration by Tc-99 sulfur colloid ascites scan. Clin Nucl Med 1999;24:609. https://www.ncbi.nlm.nih.gov/pubmed/10439187 
  5. Light RW. New treatment for hepatic hydrothorax? Ann Am Thorac Soc 2016;13:773-74. https://www.atsjournals.org/doi/full/10.1513/AnnalsATS.201603-223ED
  6. Bielsa S, Porcel JM, Castellote J, et al. Solving the Light’s criteria misclassification rate of cardiac and hepatic transudates. Respirology 2012;17”721-726. https://www.ncbi.nlm.nih.gov/pubmed/22372660
My patient with cirrhosis has a large right sided pleural effusion with only a small amount of ascites. Could this effusion still be related to his cirrhosis?

How should I interpret an isolated elevated hemidiaphragm on chest x-ray?

In hospitalized patients, an elevated hemidiaphragm on chest x-ray is not a rare finding and is frequently asymptomatic. It has many potential causes, including lobar collapse or surgical resection of the lung, diaphragmatic eventration, distention of stomach or colon, or phrenic nerve paralysis (1).  

Among patients with a paralyzed hemidiaphragm, damage to the phrenic nerve caused by surgery (e.g. cardiac), mediastinal tumors, cervical spine pathology, diabetes, autoimmune (e.g. vasculitis) and infectious causes (e.g. herpes zoster and polio viruses) are often cited as potential causes; most may be idiopathic, however (1,2,3).

Chest x-ray has a high negative predictive value (93%) but a poor positive predictive value for diagnosis of hemidiaphragm paralysis (1).  When in doubt, the fluoroscopic “sniff” test should be used for confirmation.  

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1. Chetta A, Rehman AK, Moxham J, et al. Chest radiography cannot predict diaphragm function. Resp Med 2005;99:39-44

2. Curtis J, Nawarawong W, Walls J, et al. Elevated hemidiaphragm after cardiac operations: incidence, prognosis, and relationship to the use of topical ice slush. Annals of Thoracic Surgery 1989;48:764-8.

3. Crausman RS, Summerhill EM, McCool FD. Idiopathic diaphragmatic paralysis: Bell’s palsy of the diaphragm? Lung 2009;187:153-157.

Contributed by Ethan Balgley, Harvard Medical Student

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

How should I interpret an isolated elevated hemidiaphragm on chest x-ray?